Thanks, David, that's good information.

English is not my first language, and I don't understand what "sabins" mean, but is the conclusion that all three do a good job absorbing LF and that the Lenrd's has a bit of an advantage on the other two constructions? I could be very wrong. :)
Sabins are a unit of measure, but knowing any more than that is not necessary to interpret the graphs. To me, it looks like MegaLENRDs and SuperChunks perform closely, with StudioTips Corner Absorber - the design most like what you contemplate making - absorbing less at all frequencies. So yes, SSC is more effective than what you're planning. Apparently, the additional material "in the corner" is exactly what makes them more effective. So yes it will cost more. But even then, it's still pretty darn cheap - if you're "buying right." I just ordered 2" Owens Corning 703 plain (unfaced) 24" x 48" for $.65/SF. That's $5.20 per panel with 12 per pack being $62.40.

When you view those graphs on the studiotips site, just remember that those are normalized and for linear foot of corner - not for square foot of absorbtion. That said, the SuperChunk has almost 100% more square footage than the LENRD.

Now, if it were done per square foot of surface area, you'd see that the SuperChunk will outperform the LENRD. I'd bet at least 1 beer that below 60Hz (in the real world) that the chunk would pull away even further from the other 2.

Thanks for clearing that up, pepar.

Both the MegaLenrd and the Superchunk seem to outperform the type of bass trap I'm planning on building. That's unfortunate, and I might have to reconsider my plans. Since I don't live in USA, I wont be able to buy these OC 703 that seem very popular to use as bass trap materiale. What other materiale is recommended - glass, fiber rockwool?

I'm glad that there are people with experience and knowledge about acoustic treatment on the Internet. I would otherwise be lost. ;)

Thanks for clearing that up, pepar.

Both the MegaLenrd and the Superchunk seem to outperform the type of bass trap I'm planning on building. That's unfortunate, and I might have to reconsider my plans. Since I don't live in USA, I wont be able to buy these OC 703 that seem very popular to use as bass trap materiale. What other materiale is recommended - glass, fiber rockwool?

I'm glad that there are people with experience and knowledge about acoustic treatment on the Internet. I would otherwise be lost. ;)
Something to put this into context is that if you now have NO bass traps, adding almost anything will help. Owens Corning fiberglass products are sold internationally. Where do you live?

pepar:
You have a good point, and putting some bass traps in the corners is a good idea wether I use the most effective construction or not. My problem is that I'm a bit afraid that making the wrong decisions would actually make the room even more unsuited for movie soundtracks. I'm not expecting my HT to sound like a million dollar theater, but I know there are things I can do for a moderate price. The first step was treating the ceiling, sidewalls and rear wall with acoustic panels, and I'm very pleased with the result. I probably should've started with bass traps since LF is the biggest problem in small rooms, but it's definitely next on my to do list.

I live in Norway, and I would have to pay a lot in taxes, and of course shipping and handling.

pepar:
You have a good point, and putting some bass traps in the corners is a good idea wether I use the most effective construction or not. My problem is that I'm a bit afraid that making the wrong decisions would actually make the room even more unsuited for movie soundtracks. I'm not expecting my HT to sound like a million dollar theater, but I know there are things I can do for a moderate price. The first step was treating the ceiling, sidewalls and rear wall with acoustic panels, and I'm very pleased with the result. I probably should've started with bass traps since LF is the biggest problem in small rooms, but it's definitely next on my to do list.

I live in Norway, and I would have to pay a lot in taxes, and of course shipping and handling.
The materials we've been discussing are specifically made for thermal and acoustical insulation and isolation, much of it in the HVAC trade (Heating, Ventilation and Air Conditioning). If they are building commercial buildings in Norway with heating and/or cooling systems, then there are contractors installing this stuff. If there are contractors installing it, then odds are there are distributors selling it to them. I must admit complete ignorance of the Norwegian construction industry and perhaps my assumptions are bogus. Have you searched the equivalent of our "yellow pages" telephone directory?

In Europe in general, I think you'd probably want to look toward mineral wool (rockwool). That seems to be more readily available there.

Bookhouseboy, did you notice a difference in your sound after treating your first reflection points?

While skimming through http://www.bobgolds.com/AbsorptionCoefficients.htm, I noticed 705 has LOWER absoportion numbers than 703, yet everyone suggests 705 over 703 for bass traps.

Can anyone shed a little light on this?


Also, I was wondering what would be the effects of alternating 703 and 705 sheets in a Chunk style trap. Anyone care to guess?

While skimming through http://www.bobgolds.com/AbsorptionCoefficients.htm, I noticed 705 has LOWER absoportion numbers than 703, yet everyone suggests 705 over 703 for bass traps.

Can anyone shed a little light on this?
I saw the same data and simply went with the 703. The traps on StudioTips seem to be made with it as well, as are many other commercially available traps I looked at before deciding to stick with DIY..

There seems to be a lot of talk about which is better on low end, but I think everyone would agree that either way you go it is going to help.

Glenn

Yes, Kevin12586, I did notice an improvement. The first thing that struck me was a better separation of instruments and sound effects. It's like the soundstage is clearer. The second thing I noticed was a better upper mid bass. The panels that I use don't absorb very low, but I guess cleaning up in the high frequencies does have an effect on mid bass. I also feel that the sound is much more pleasent and less "hard" than before. I can play at higher volumes without the treble being too aggressive.

pepar:
The rockwool panels I'm refering to are used in the industry, and are specially made for acoustical treatment, so I'm sure they'll do a good job as bass traps, as well as being safe.

I've decided to go on with my plans. Is 6" thickness enough, or should I use 8"?

Thanks Bookhouseboy, I will be putting up panels in the next few weeks and I enjoy reading about other people's improvement; it makes me look forward to my improvement once I put up my treatment.

Yes, Kevin12586, I did notice an improvement. The first thing that struck me was a better separation of instruments and sound effects. It's like the soundstage is clearer. The second thing I noticed was a better upper mid bass. The panels that I use don't absorb very low, but I guess cleaning up in the high frequencies does have an effect on mid bass. I also feel that the sound is much more pleasent and less "hard" than before. I can play at higher volumes without the treble being too aggressive.
Covering my FRP's with 2" OC SelectSound Black (see my link), including ceiling, L&R front walls and rear wall, made the same improvements; cleaned everything up, better front imaging, widened soundstage and better surround field/mains integration. And the fattening of the upper bass frequencies. Of course, I've since learned - by running some tests - that my fat upper bass is W-A-Y too fat, which is one of the main reasons I'm now working on bass traps.

Covering my FRP's with 2" OC SelectSound Black (see my link), including ceiling, L&R front walls and rear wall, made the same improvements; cleaned everything up, better front imaging, widened soundstage and better surround field/mains integration. And the fattening of the upper bass frequencies. Of course, I've since learned - by running some tests - that my fat upper bass is W-A-Y too fat, which is one of the main reasons I'm now working on bass traps.

Wow pepar, I didn't realize you didn't have bass traps yet. When you get them up, can you let us know and tell us of your overall impression?

Stima,

> While skimming through http://www.bobgolds.com/AbsorptionCoefficients.htm, I noticed 705 has LOWER absoportion numbers than 703, yet everyone suggests 705 over 703 for bass traps. Can anyone shed a little light on this? <

One problem with that data like is it goes no lower than 125 Hz, so you can't see what happens at 60 Hz and 80 Hz. Another problem is the material was resting on the floor when it was tested in the lab, and that will damp any potential membrane behavior from the panel itself. A thick, dense panel of rigid fiberglass mounted off the wall or straddling a corner has a resonance all its own, and that could account for the increased absorption I have measured when comparing 705 to 703. Here's that comparison:

www.ethanwiner.com/density/density.html

Also, a lot of pro studio designers use 705 because it is mechanically more stable and easier to cut clean edges etc. However, lower density rigid fiberglass approaches the same performance when it's thicker. That is, when 2 inches thick 705 is definitely better than 703 for bass frequencies, but at 6 inches thick or more the disparity is much less.

--Ethan

Ethan,

Do you know of any data utilizing the "chunk" method?

As with your tests, any test with the chunk method would raise questions such as alternating material densities and FSK placement\existance.

kevin12586:
I'm sure you'll be happy with treating the first reflection points. Good luck!

pepar:
Good to hear that I'm not imagining the improvements. Before I install the bass traps, I'm gonna do a measurement in the lower frequencies to see how the graph changes after the traps are in place. I'm inspired by this link: http://www.sbrjournal.net/currentissue/articles/acoustics/Acoustics.htm


Ethan Winer:
If you have the time, could you give me some advice?
Your articles on room acoustics are great, but since my English is only ok, and my math skills likewise, I would be grateful for a little help.

The room is rectangular (20 x 13,5 feet) except for a 6,5 feet wide and 2 feet deep "outgrowth" in the left, front corner of the room. I'm planning to use five, one for each corner, bass traps similiar to the panels in your test. I'm gonna make them out of Rockwool acoustic panels, and I was planning to use 6" or 8" thickness and stack them from floor to ceiling like you did in your test, but after reading your conlcusion, I wonder if I maybe should go for a higher number of traps. What do you recommend? I'm new to acoustics, so please use as simple language as possible. ;)

I am sure Ethan will chime in but the more area you can cover the better it will work, instead of thickness. Now I believe this is comparing 8 4' panels will work better then 4 8' panels- this is only to a point-Bass trapping needs 4 or more inchs so spreading around 1" panels in your room is not going to do the job for the low end.


Glenn

>Good to hear that I'm not imagining the improvements. Before I install the bass traps, I'm gonna do a measurement in the lower frequencies to see how the graph changes after the traps are in place. I'm inspired by this link: http://www.sbrjournal.net/currentis...s/Acoustics.htm<

Hats off to Ryan on that.. Great job!

Glenn

Wow pepar, I didn't realize you didn't have bass traps yet. When you get them up, can you let us know and tell us of your overall impression?
Sure will, and will chronical it on my HT website. I will try to take some measurements before and after. As long as DIY projects like this take me, another day or two for taking proper measurements shouldn't make any difference. :)

Thanks for taking the time to answer my question, myfipie.

I've used 1" panels (which works fine for frequencies above 500hz, if the lab numbers don't lie) for the first reflection points, but I'll use at least 2 x 3" panels for the bass traps. The panels are 2 feet wide and 4,7 feet long. Putting as many as eight or more traps that big in my HT is going to be a problem, but I guess compromising is not an option if you want to get the best out of your surround system.

I got the link from one of your earlier posts, and it was really interesting and inspiring to see the results Ryan got with his bass traps. It would be awesome to see my graph go from bumpy to near flat. He did use the BFD to flatten the last peaks, but I would be overly happy with anything even close to his graph.

Stima:

I noticed 705 has LOWER absoportion numbers than 703, yet everyone suggests 705 over 703 for bass traps
I don't.
Do not use 705 for superchunks.
Optimal for a superchunk might be 701 as a face, and then 34" diagonal 703 behind it -- but it might depend on the room what's 'optimal'.

Depth is more effective at lower frequencies than more density -- and too much density simply means the sound won't go far enough into the material to be absorbed. Around a meter deep I'd consider using fluffy fiberglass pink instead of anything rigid.

You might want to play around with Chris Whealy's Porous Absorber Calculator.
http://www.bobgolds.com/whealy.com/acoustics/Porous.html
IR-761 lists several materials and their Rayls
R11 3.5" 89mm fluffy fiberglass pink batt is 4800 mks rayls/m
Rockwool RWA45 (flow resistivity = 16,500 Rayls/m),
rockwool at 83mm, 98kg/m^3, 58800 mks rayls/m

Stima:

Do not use 705 for superchunks.
Optimal for a superchunk might be 701 as a face, and then 34" diagonal 703 behind it ...Depth is more effective at lower frequencies than more density...


You might want to play around with Chris Whealy's Porous Absorber Calculator.



Currently, I had planned to do the 24" chunks with alternating 703 and 705 with a face of 703 (FSK facing out) to maximize materials on hand. If I needed more surface area, I could remove some 705 and put spaces in the columns hidden by the GOM. (I had planned to leave the FSK on the sheets because the membrane is at an extreme angle to the sound source. (180 +/- 30deg.)

So to prove to myself this setup is not best (as you suggest), I downloaded and ran the calculator. I did a search via Google to try and find a rayls/m for 703 and 705, and found an old NASA document quoting 14000 for 701, 27000 for 703 and nothing for 705. I would guess the number would almost double to 54000 for 705 given it doubled from 701 to 703. Also the numbers don't give any reference to FSK material...which we know affects absorption. Since it's missing on all materials, I could also guess the effect would be similar across the board. That being the case, if someone knows the rayls/m value of FSK, I would appreciate it to get a better feel for the true absorption of each product.

While playing around, I still found at 4", the 705 had better lower end absorption compared to the 703. Not by much after 60hz, but it did extend quite a bit lower.

Now, to put your 703 over 705 to the test, I went to 8" and 12". (Using the 24" pieces for superchunk would give a maximum depth of 12") Since there was no way to get a true reading for the superchunks method in the calculator, I could only look at differences between 4", 8" and 12". The difference was VERY apparent as the material got thicker. At 12" the 703 became the better trap than the 705 and MUCH MUCH better than either at 4".

All this to say, according to your calculator, given a choice between 703 and 705, when going above 4", the better choice is in fact the 703. (As you stated in your reply. :cool: )

However, since there really is very little empirical data for various methods of chunk formation, I will probably have to resort to multiple in-home tests to figure which is best. :o

However, since there really is very little empirical data for various methods of chunk formation, I will probably have to resort to multiple in-home tests to figure which is best. :o
We look forward to your test results.

Books,

> after reading your conlcusion, I wonder if I maybe should go for a higher number of traps. <

Yes, more traps = better bass. Always.

--Ethan

Books,

> after reading your conlcusion, I wonder if I maybe should go for a higher number of traps. <

Yes, more traps = better bass. Always.

--Ethan
At what point do all those traps begin to negatively impact mids and highs?

pepar

At what point do all those traps begin to negatively impact mids and highs?
If you have too many of them, then
a) you have to turn your speakers up to the point of distortion
b) you can overabsorb at higher frequencies, resulting in a less than pleasing room (aka anechoic)
c) the more absobers you put into a room there's a diminishing returns for absorbtion
d) more absorbers in the room may reduce the bass absorbtion average per square foot of absorber (i.e. you get a lot more HF absorbtion, but much less than the advertised bass absorbtion -- this isn't 'lying' manufacturers, it's just that the room is significantly different than the measured room).

Pepar,

> At what point do all those traps begin to negatively impact mids and highs? <

Great question. The answer depends on what sort of bass traps they are. For absorbers that affect mostly the bass range - say, up to 300 Hz or so - you should be able to put in as many as you want with no ill affect. However, this would not be the case with plain rigid fiberglass or acoustic foam. Traps made of those materials will absorb the entire range more or less evenly, so there's a very real risk of overdamping a room at mid and high frequencies with too many traps.

Stop me if you've heard this before: :D

I have 38 traps in my 25 by 16 living room home theater, and the reverb time is very uniform (good thing) across the entire range, down to about 50 Hz. The room is absolutely not too dead sounding, and the bass is very tight and even all around the room. But the key is the trap design - my traps have a very specific and intentional curve of absorption versus frequency to avoid making a room too dead.

--Ethan

Stima:

Currently, I had planned to do the 24" chunks with alternating 703 and 705 with a face of 703 (FSK facing out)It's not a studiotips superchunk if you've got FSK anywhere. It's an experiment.

I did a search via Google to try and find a rayls/m for 703 and 705, and found an old NASA document quoting 14000 for 701, 27000 for 703 and nothing for 705.I think I know the one you mean.

Also the numbers don't give any reference to FSK material
Rayls is flow resistivity.
FSK is air tight so its flow resistivity is "infinity rayls/m"
The calculator is for porous absorbers, and FSK is not what I'd call porous.

While playing around, I still found at 4", the 705 had better lower end absorption compared to the 703. Not by much after 60hz, but it did extend quite a bit lower.Yep. Try it again at 24" thick. (EDIT: you did! see below)
Did you try multiple angles of incidence?
0.003% (i.e. 0.00003 multiplyer) of the sound goes straight into an absorber. Most of it is diffuse sound.
Here's an example of the effect in the first post of http://forum.studiotips.com/viewtopic.php?t=2254


Since there was no way to get a true reading for the superchunks method in the calculator True. It's in a corner and separated from other things, whereas the calculator assumes it's infinite surface area.

I could only look at differences between 4", 8" and 12". The difference was VERY apparent as the material got thicker. At 12" the 703 became the better trap than the 705 and MUCH MUCH better than either at 4".Yep

All this to say, according to your calculator, given a choice between 703 and 705, when going above 4", the better choice is in fact the 703. (As you stated in your reply. )Yep. It's not MY calculator. It's Chris Whealy's. (He had a temporary hosting company problem, so I'm hosting his website on mine for a month or so.)

However, since there really is very little empirical data for various methods of chunk formationPersonnally I'd just trust the acousticians who discovered it. And remember that corner chunks are probably incompatable with DE style absorbtion.
I will probably have to resort to multiple in-home tests to figure which is best.I gave that a try once. I don't have any conclusions, nor a lot of confidence in my results, but here's what I did.
http://www.bobgolds.com/CornerTrap/20040627/home.htm
http://www.bobgolds.com/CornerTrap/20040627/table.htm
http://www.bobgolds.com/CornerTrap/20040627/compare.htm

And remember that corner chunks are probably incompatable with DE style absorbtion.

:eek: WHAT!?!? Why is this? Do the corner chunks generally push the room past optimum absorption? If this is the case, can it be countered by using one sheet with FSK as a face for the chunk? (FSK facing into room.)

Stima:

My thinking (without measurements, so take this with a grain of salt) on corner absorbers vs DE Style absorbtion is that
a) DE style is (front wall fully absorbed, carpet, side walls and rear wall 50% thin absorbtion on lower half of walls, porous absorbtion in soffets and membrane absorbtion in columns, leather seats)
b) studiotips corner absorbers require space around them to work as predicted. (edge effect - read Eric Desart's PlayingWithBaffles.doc)

So, if you put studiotips corner absorbers in the front vertical corners, they'd be touching the fully absorbed front wall. Simiarly on the rear vertical corners they'd be touching the lower 50% absorbed walls. This ruins the edge-effect LF absorbtion boost.
The DE soffets are separated from this wall of absorbtion, so they may already be corner trap-ish (ceiling/wall corner).

It's not that DE style treatment absorbtion turns corner traps into thin HF traps, but just that corner traps change. I'm not sure how significant the change would be.

FSK doesn't change any of my concerns.
I'd use FSK if I were overabsorbed in HF -- and for nothing else.
I'd try to design a room without FSK.

I define "DE Style" as above, includes DIY.
I define "DE Designed" to include about a hundred other criteria done by Dennis's company, including ray tracing of the sound.

I believe that Ethan Winer's "I have 38 traps in my 25 by 16 living room home theater," doesn't suffer from this, because his traps are placed with space between them (bare gypsum/drywall), and not against a 16'x8' wall of absorbtion.

Stima:

My thinking (without measurements, so take this with a grain of salt) on corner absorbers vs DE Style absorbtion is that
a) DE style is (front wall fully absorbed, carpet, side walls and rear wall 50% thin absorbtion on lower half of walls, porous absorbtion in soffets and membrane absorbtion in columns, leather seats)
b) studiotips corner absorbers require space around them to work as predicted. (edge effect - read Eric Desart's PlayingWithBaffles.doc)

So, if you put studiotips corner absorbers in the front vertical corners, they'd be touching the fully absorbed front wall. Simiarly on the rear vertical corners they'd be touching the lower 50% absorbed walls. This ruins the edge-effect LF absorbtion boost.
[Mr. Bill]Oooh, nooo![/Mr. Bill] My front - behind a false wall - is lined with 2" J-M Linacoustic. Front ceiling has a 4'x8'x2" OC SelectSound panel. L&R front walls a 4'x4' OC SelectSound Panel. Rear wall a 2'x8' of same. Thin carpet all around up to chair rail. Wood floors. Plaster walls and ceiling. Six LaZBoys. Room 13'x21'x8' (nominal-slightly canted walls and ceiling). My plan is (was?) to place 24" face SSCs both corners and ceiling/wall behind false wall and ceiling/wall in rear, and maybe 4' SSCs above 4'x4' L&R panels. I "assumed" the ones lying against the Linacoustic would be enhanced by it. Your post seems to be telling me not only won't it be enhanced, it will be less effective. Right?

Books,

> after reading your conlcusion, I wonder if I maybe should go for a higher number of traps. <

Yes, more traps = better bass. Always.

--Ethan

That's the straight forward answer I was looking for. Thanks.

Well, since the panels I'm gonna use DO absorb high frequencies, I think I'll start with five traps and see if they do the job with the bass response. If they don't, I'll just add a couple of traps. I don't want to over absorb the highs and mids, so this is the best approach.

Ethan:
Your HT is only a little bigger than mine, and you have 38 traps!? I must say that I'm impressed, because I can't see how I would fit a number close to 38 in my HT.

They must be all over the place!

pepar:

Studiotips superchunks work best isolated. If you have no other treatment in the room, superchunks are perfect.

Putting them up against a bunch of other absorbtion reduces the edge effect boost, but
a) they're still deep absorbtion (good)
b) they're still in corners (all modes active in tri-corners, good)

Bookhouseboy

There's a picture of what I think is Ethan's HT on the bottom left of this page
http://www.realtraps.com/placing_mt.htm
There's 16 out of 38 shown in that picture.

Bookhouseboy

There's a picture of what I think is Ethan's HT on the bottom left of this page
http://www.realtraps.com/placing_mt.htm
There's 16 out of 38 shown in that picture.
Yea, my wife would go for that . . . if she were blind. :)

(No offense, Ethan!)

pepar:

Studiotips superchunks work best isolated. If you have no other treatment in the room, superchunks are perfect.

Putting them up against a bunch of other absorbtion reduces the edge effect boost, but
a) they're still deep absorbtion (good)
b) they're still in corners (all modes active in tri-corners, good)
<sigh>Thank you.

Thanks for the link, BasementBob.

That actully doesn't look half bad considering the amount of traps. The color and finish matches the walls and ceiling, so I think it looks pretty good. But If I were to sell the house, I would probably take them out before showing the room to the potentional buyers. ;)

Bob:

> I believe that Ethan Winer's "I have 38 traps in my 25 by 16 living room home theater," doesn't suffer from this, because his traps are placed with space between them (bare gypsum/drywall), and not against a 16'x8' wall of absorbtion. <

I don't understand how a bass trap is affected at mid/high frequencies depending on what else the traps are touching. Or is that not what you meant?

As I explained above, the reason I can have 38 traps and not overdamp the room is because the traps are designed to be semi-reflective on their front surface. They do absorb mids and highs through the rear surface, and when mounted across a corner or spaced off the wall a fair amount of sound gets to the rear. But the balance in my room is ideal, and I have the R+D data to prove it. :D I really wish you lived closer to me so you could come by for a visit!

Book:

> I can't see how I would fit a number close to 38 in my HT. They must be all over the place! <

Actually they're not intrusive at all once you're in the room. Most are in corners, and only six are at the first reflection points (including the rear surrounds). Believe it or not, this Thursday I'm replacing seven of them with larger traps from our new line we'll announce at the HES show next month.

pepar:

> Yea, my wife would go for that . . . if she were blind. :) (No offense, Ethan!) <

None taken. I'm lucky to have a wife who also appreciates great sound. So she and I both benefit!

--Ethan

Bob:

> I believe that Ethan Winer's "I have 38 traps in my 25 by 16 living room home theater," doesn't suffer from this, because his traps are placed with space between them (bare gypsum/drywall), and not against a 16'x8' wall of absorbtion. <

I don't understand how a bass trap is affected at mid/high frequencies depending on what else the traps are touching. Or is that not what you meant?

As I explained above, the reason I can have 38 traps and not overdamp the room is because the traps are designed to be semi-reflective on their front surface. They do absorb mids and highs through the rear surface, and when mounted across a corner or spaced off the wall a fair amount of sound gets to the rear. But the balance in my room is ideal, and I have the R+D data to prove it. :D I really wish you lived closer to me so you could come by for a visit!

Book:

> I can't see how I would fit a number close to 38 in my HT. They must be all over the place! <

Actually they're not intrusive at all once you're in the room. Most are in corners, and only six are at the first reflection points (including the rear surrounds). Believe it or not, this Thursday I'm replacing seven of them with larger traps from our new line we'll announce at the HES show next month.

pepar:

> Yea, my wife would go for that . . . if she were blind. :) (No offense, Ethan!) <

None taken. I'm lucky to have a wife who also appreciates great sound. So she and I both benefit!

--Ethan

I think it is great you have so many traps, but really you don't need that many, not to say it will not help with everyone you put in but you do start to get to a point of diminishing returns. My own room I have 13 bass traps and I know that the first 8 made the BIGGEST difference.

Glenn

Glenn,

> really you don't need that many ... the first 8 made the BIGGEST difference. <


Absolutely, and I didn't mean to imply otherwise. No sense scaring people! :eek: In most cases the first four make the biggest improvement. But man oh man, those last 34 really add the crowning touch. :D

--Ethan

So Ethan,

In your opinion, will the "chunk" style bass trap work when placed against mid\hf freq absorption?

More to the point: Do you have any opinion or testing to show the affects of chunk style traps when used in a theater treated using via Dennis Erskine style of absorption? (Full front and side walls up to 1st reflection, then 50% remaining walls.)

NO OFFENSE BOB! Just always like to get more of a consensus opinion. ;)

What is the best software to measure RT60 ?? I have read a fww places on this thread that it can be bought off the shelf. What are the majority of folks using here ?

What is the best software to measure RT60 ?? I have read a fww places on this thread that it can be bought off the shelf. What are the majority of folks using here ?
That's true, but it can also be free (http://www.hometheatershack.com/roomeq/).

Ethan:
I don't understand how a bass trap is affected at mid/high frequencies depending on what else the traps are touching. Or is that not what you meant?
I think that's backwards.

The edge effect quote that I'm most fond of is
from: Proceedings of Noise Con 90, David A. Nelson, P.E., INCE Bd. Cert
The discontinuity in the wave field at the edge of the specimen create a diffraction effect that warps the sound field to make the specimen appear as much as a quarter-wavelength larger in each direction. This increases the sound absorption coefficient to such a degree that it often exceeds the theoretical limit of 1.00.

So, to re-write what you wrote
- A bass trap is NOT affected at high frequencies by what else the traps are touching.
- A bass trap is affected at low frequencies by what else the traps are touching.

But those two lines are also misleading.
The quote by David A. Nelson is much more predictive, and is the best definition of "edge effect" that I've seen.
For example, it's not so much that "touching" is the criteria, but rather proximity relative to wavelength.

Certainly an absorber's contribution to the change in the sound of the room is dependant on the contents of the room. That includes how the absorber is placed (corner, spacing from the wall, proximity to other absorbers, sound paths, etc), and how much absorbtion is in the room (moving from 5% room-surfaces coverage to 15% coverage will have a dramatic effect, whereas moving from 85% coverage to 95% coverage won't be perceptable, even though it's the same volume-and-surface of additional absorbtion product).

Just looking at your HT I can see lots of reasons why you could have a good RT60. I'd bet you have a good sweet spot too. I'm not so sure you have a good sweet area (which DE Designs do).

The edge effect quote that I'm most fond of is:

"The discontinuity in the wave field at the edge of the specimen create a diffraction effect that warps the sound field to make the specimen appear as much as a quarter-wavelength larger in each direction. This increases the sound absorption coefficient to such a degree that it often exceeds the theoretical limit of 1.00."

Should I seek therapy if that makes perfect sense? :)

Stima,

> Do you have any opinion or testing to show the affects of chunk style traps when used in a theater treated using via Dennis Erskine style of absorption? <

I don't see what one has to do with the other. If you put a bass trap in a wall-wall corner, I can't see how it matters what other mid/high absorption is on the walls either nearby or far away.

--Ethan

Bob,

> I think that's backwards. <

Wouldn't be the first time! :eek:

> The edge effect quote that I'm most fond of is <

Oh, edge effect. To me that could either be diffraction (probably irrelevant at 80 Hz) or having a panel's edge surface exposed which simply increases the total surface area. I'm not sure which of these your examples relate to.

> So, to re-write what you wrote <

You're really losing me now. The reason my traps don't absorb mids and highs as much as bass is simply because the entire front surface has a plastic membrane behind the fabric. The membrane reflects mids and highs, but bass passes right through. This is a pretty simple concept!

> it's not so much that "touching" is the criteria, but rather proximity relative to wavelength. <

I'd have to see hard evidence that placing a sheet of one-inch 703 somewhere in proximity to a much thicker bass trap affects anything at low frequencies.

> That includes how the absorber is placed (corner, spacing from the wall, proximity to other absorbers, sound paths, etc) <

If a bass trap absorbs more or less near a corner or not near a corner, that has everything to do with how bass "collects" in corners and nothing to do with what (I thought) you've been talking about.

> Just looking at your HT I can see lots of reasons why you could have a good RT60. I'd bet you have a good sweet spot too. I'm not so sure you have a good sweet area (which DE Designs do). <

I can't imagine on what you base that. Please do explain. As you know, I'm not a fan of using 1-inch material anywhere in a room except perhaps at the first reflection points. But even then 3 inches is better because it gives that much more bass trapping.

I have a fabulous response pretty much everywhere in the room. Yes, the low end changes somewhat around the room. That's about impossible to avoid. And at mid and high frequencies the only thing that changes is due to loudspeaker directionality. So if I stand up there's a bit less high end than seated and perfectly on axis. But the Reflection Free Zone is very large, and will soon be even larger when I put some "better shaped" panels there in a few days.

--Ethan

But man oh man, those last 34 really add the crowning touch. :D

--Ethan

That had me laughing out loud. The first four traps were most important, but the last 34 did the finishing touch. :p

Ethan:

To me that could either be diffraction (probably irrelevant at 80 Hz)Nope.
There's data from Cath. Univ. Leuven showing as much as a 160% boost due to edge effect at 80hz.

having a panel's edge surface exposed which simply increases the total surface area.Nope.
All "edges" have to have length.
But the above quote is true for "edges" that have no area.
A 2'x4'x4" absorber placed on the floor has an edge length of 12', and an edge surface area of 4 ft^2. (Your Number's Game stuff)
A 24" diagonal corner trap in an 8' vertical corner has an edge length of 20', and an edge surface area of 0 (zero) ft^2.
In both cases it's irrelivent for the edge effect how big the edge surface area is.
Only the location of the edge, and the surface area of the sample, and the proximity to other samples.

Ethan:
Do you have any more pictures of your room on the www than the one that I found? (front, sides)

Stima,

> Do you have any opinion or testing to show the affects of chunk style traps when used in a theater treated using via Dennis Erskine style of absorption? <

I don't see what one has to do with the other. If you put a bass trap in a wall-wall corner, I can't see how it matters what other mid/high absorption is on the walls either nearby or far away.

--Ethan


Hmmmm....now I have two differing opinions on bass traps next to Mid\HF absorption.

Taking a step back, I had assumed the added benefit of chunk style was both the increased volume and surface area of the trap. However, thinking about that...with two of the three sides of the triangle in very close proximity to walls....I begin to wonder if the surface area has anything to do with the increased performance.

Further pondering...I start to agree with Ethan in wondering why the material next to a trap effects the attributes OF the trap.

I wonder what DE's thoughts are on this subject. :confused:

*EDIT* Ahh...so it's NOT the surface area...but the EDGE area! Nothing like posting while someone is posting. :p

Stima:

I don't know how corner traps will perform when placed between and against walls full of absorbtion. I just think it'll be different than any corner measurement data we have.

I remember looking for diagonal corner traps in Dennis' gallaries once, but didn't find any. So I guessed he solved the same problem (bass absorbtion) in another way, a way that combined well with other acoustical/asthetical issues for the listeners.
http://www.designcinema.com/galleries.html
You could search for Dennis's posts on corner traps in the archives.

so it's NOT the surface area...but the EDGE area!It's not the area at all. It's the proximity of the edges. If they're touching there's no edge at all. Corner traps should behave as predicted if the separation to the nearest absorber is greater than 1/4 wavelength.

[/QUOTE]Hmmmm....now I have two differing opinions on bass traps next to Mid\HF absorption.[QUOTE]

After countless hours of reading, I have a high level of respect for the opinions of both Ethan and Bob. :)

I have planned on doing a DE style treatment with some sort of bass trapping. I have been considering "chunk style".(and still am)

What are the opinions of a Jon Risch DIY bass trap(I guess thats the proper name) found here (http://www.geocities.com/jonrisch/basstrap.htm) ?
Or these (http://teresaudio.com/haven/traps/traps.html) ?

I was thinking of putting them behind a false wall in the L&R corners. Maybe stack them two high.

Question for everyone. I am thoroughly enjoying my new HT and have tried to follow a lot of the great advise in this thread. One issue though. I used to listen to music in Pure Direct on my receiver (Yamaha RX-V2600 with Axiom M80 speakers) and in my untreated living room it sounded fantastic. I have regular plain ol'walls of course and wood flooring with a rug so it is a pretty live room. In my theater it sounds too muddy and compressed in Pure Direct. My back wall is dead with 1" linacousic and I also have carpet and I'm sure that's why. Is this a compromise I will have to live with if I primarily want it to sound good for movies? I am currently listening to music in 7 channel stereo on the Yamaha and it sounds wonderful, but I do miss that Pure Direct a little. Any thoughts???

Bob,

> There's data from Cath. Univ. Leuven showing as much as a 160% boost due to edge effect at 80hz. <

I have to think we're talking about different things. But I'm always willing to change my mind in the face of compelling evidence. Can you post or email me that data?

> A 2'x4'x4" absorber placed on the floor has an edge length of 12', and an edge surface area of 4 ft^2. (Your Number's Game stuff) <

Right - a 2' by 4' panel that's 4 inches thick has 50 percent more surface area from the exposed edges.

> A 24" diagonal corner trap in an 8' vertical corner has an edge length of 20', and an edge surface area of 0 (zero) ft^2. <

It depends if the edges are sticking out from the wall, as is typical with a plain panel, or is set into the wall a la superchunks or by beveling the edges. Which do you mean?

> Only the location of the edge, and the surface area of the sample, and the proximity to other samples. <

I can see how for a severe angle of incidence a wall full of 1-inch 703 could be considered to "extend" the surface of a bass trap mounted across a corner. That is, a 2' by 4' panel 1 inch thick could be considered as a 24 inch thick panel 1 inch by 48 inches. But in practice I can't see how this is relevant. If it were relevant, test data for 1-inch rigid fiberglass would show a meaningful amount of absorption at 80 Hz. Which it doesn't.

> Do you have any more pictures of your room on the www than the one that I found? <

Very soon I'm going to make a video version of my "How to set up a room" article. So that will show much more of the room in context. My partner Doug is coming by tonight to help me install some new products we'll announce at HES June 1. As soon as that's done I'll make the video.

--Ethan

Jon,

> In my theater it sounds too muddy and compressed in Pure Direct. <

If I understand your question, "Pure Direct" and whatever other receiver brands call the same feature has nothing to do with room acoustics or muddiness. My receiver has two stereo modes - one with the tone controls enabled (though mine are always left flat), and a "direct" mode that bypasses the tone controls. Either way, when listening to stereo content in a stereo mode, it should be equivalent to using an old-style stereo receiver. Versus the various "enhanced" modes that engage the center and surround speakers and optionally add reverb and ambience effects.

> My back wall is dead with 1" linacousic and I also have carpet <

That's a sure recipe for muddy sound because it absorbs a lot at high frequencies, but does nothing for the low mids and bass. So the room is too dead yet boomy at the same time.

> Is this a compromise I will have to live with if I primarily want it to sound good for movies? <

Not at all! The solution is to treat your room in a more appropriate manner.

--Ethan

Jon,

> In my theater it sounds too muddy and compressed in Pure Direct. <

If I understand your question, "Pure Direct" and whatever other receiver brands call the same feature has nothing to do with room acoustics or muddiness. My receiver has two stereo modes - one with the tone controls enabled (though mine are always left flat), and a "direct" mode that bypasses the tone controls. Either way, when listening to stereo content in a stereo mode, it should be equivalent to using an old-style stereo receiver. Versus the various "enhanced" modes that engage the center and surround speakers and optionally add reverb and ambience effects.

> My back wall is dead with 1" linacousic and I also have carpet <

That's a sure recipe for muddy sound because it absorbs a lot at high frequencies, but does nothing for the low mids and bass. So the room is too dead yet boomy at the same time.

> Is this a compromise I will have to live with if I primarily want it to sound good for movies? <

Not at all! The solution is to treat your room in a more appropriate manner.

--Ethan

I thought I did that??? I also have a very large bass trap in the front corner and am planning on additional ones. They will actually be broadband absorbers in the corners. I am making sure to leave it pretty live with a good portion of the walls untreated. I am just targeting the first reflestion points and I don't have those up yet. Those will just target the higher frequencies though since they are 1" thick material. It doesn't sound boomy at all now for music or movies. My living room is completely untreated yet direct sounds better in there. Movies sound excellent in the theater IMO, much better than the living room so the treatments I implemented have been very positive in that regard. My receivers "direct mode" bypasses all processing. Stereo modes enable them, but mine are left pretty flat as well.

Hmm, I was set on buying 6" rockwool acoustic panels to use as bass traps in the five corners of my HT, but the representative for the company recommended to start with 2" panels and then add an extra panel if I didn't get the results I wanted. The first reflection points on the left and right wall, ceiling and some of the rear wall is treated with 1" panels that absorbs down to 500hz. He meant that using 6" panels as bass traps could make the room to dead.

So should I listen to his advice, or should I go for my initial plan?

I know I'm asking questions about things that are elementary, but I just want to make sure before ordering the panels. Please be overbearing. :)

Jon,

> I also have a very large bass trap in the front corner <

One bass trap is not enough. Ever. Unless it's 10 by 15 feet. :D

--Ethan

Boy (doesn't anyone use names here?),

> the representative for the company recommended to start with 2" panels <

For bass trapping? Yikes.

> He meant that using 6" panels as bass traps could make the room to dead. <

Listen to us, not him. Really. This is a big problem I see all the time. Just because someone sells acoustic materials doesn't mean they automatically know how best to use them.

> Please be overbearing. <

Always glad to oblige!

--Ethan

Ethan,

"Boy (doesn't anyone use names here?)"

I know my nick is kinda long, so just use Boy for short.

"Listen to us, not him. Really. This is a big problem I see all the time. Just because someone sells acoustic materials doesn't mean they automatically know how best to use them."

Yeah, I was thinking that when I spoke to him. I'm ordering twelve 6" panels tomorrow. I can't wait to do a frequency measurement after installing the traps.

"Always glad to oblige!"

Thanks. It's a great thing when professionals take their time to answer questions from beginners on the Internet, wether the subject is gardening or rocket science. It makes me believe in the more positive aspects of the Internet, such as communicating with people from all over the world and sharing useful information.

Jon,

> I also have a very large bass trap in the front corner <

One bass trap is not enough. Ever. Unless it's 10 by 15 feet. :D

--Ethan

I do realize that, but that is just a start. It is 14" X 22" X 8'. I will put one more in the other corner and probably two more in the back corners as well. Do you think this will "brighten' up my music any????

I'd agree. For bass control, 2" is basically worthless unless you have a TON of it. To straddle corners, you'll want AT LEAST 4" - 6" is better if you want to get some bass control.

Bryan

I'd agree. For bass control, 2" is basically worthless unless you have a TON of it. To straddle corners, you'll want AT LEAST 4" - 6" is better if you want to get some bass control.

Bryan

I'm glad to hear that 6" is a good number. Is it ambitious to think that 6" rockwool panels will absorb as low as 50-60 hz? I know it depends on placement and so forth, but I would like to know the general effect these kind of corner traps have.

Is it realistic to expect 6" of mineral wool to absorb down to 50-60hz? Not at all. Is it unrealistic to expect it to have a 1.0 absorbtion coefficient at 50hz? Yeah - probably. It'll still do a good job though.

IMO, 50hz is getting down toward the bottom of what you can effectively deal with via velocity absorbers (unless you have the luxury of building some 2-3' deep absorber recesses in the corner of your room - which some people do). You can still have some effect below that but not of the magnitude that you can above it.

I agree with Bryan. Bass traps with help down to 40hz, but remember I am using the word "help" not solve.

Glenn

Thanks for the information guys. It's comforting to know that the traps will have a positive effect on the lowest frequencies. I'm not expecting a perfect frequency response, but I'm hoping for a good starting point. The biggest problem in my HT is a terrible dip around 30hz, but I'm gonna buy another sub that I'm sure will cure this problem. I guess HT is a never ending hobby.

I've now ordered 12 x 6" panels, and I'll post results when they are finished, if that's of interest.

Jon,

> It is 14" X 22" X 8'. I will put one more in the other corner and probably two more in the back corners as well. Do you think this will "brighten' up my music any???? <

In my opinion, a 22 by 14 foot room needs at least 8 bass traps, and even twice that is not too many. I wouldn't say it will brighten up your room per se because bass traps are supposed to affect mainly the bass range. Some bass traps absorb the full range, and that type might take you in the wrong direction. But generally speaking, once the bass is tamed the mids and highs by contrast will improve.

--Ethan

Books,

> It's a great thing when professionals take their time to answer questions from beginners on the Internet <

Thanks, I'm trying. I've been doing this since long before the Internet, when the MIDI forum at CompuServe was the main audio online gathering place. And I was helping even before that, when books and print magazines were the main form of spreading information. It can only help everyone, and I've benefited plenty myself from others who were kind enough to share what they know.

--Ethan

bpape
IMO, 50hz is getting down toward the bottom of what you can effectively deal with via velocity absorbers (unless you have the luxury of building some 2-3' deep absorber recesses in the corner of your room - which some people do). I'm considering doing my entire front wall with 2.5' of fluffy. Haven't worked it out yet though. I note that I've NEVER seen a HT like that.

bpape
I'm considering doing my entire front wall with 2.5' of fluffy. Haven't worked it out yet though.
FYI (http://peparsplace.com/html/3.html)

pepar:
As near as I can tell from your link, you have 1" of linacoustic there (including a nice speaker cutout).
I'm talking about having 30" of fluffy fiberglass pink.

Jon,



In my opinion, a 22 by 14 foot room needs at least 8 bass traps, and even twice that is not too many. I wouldn't say it will brighten up your room per se because bass traps are supposed to affect mainly the bass range. Some bass traps absorb the full range, and that type might take you in the wrong direction. But generally speaking, once the bass is tamed the mids and highs by contrast will improve.

--Ethan

If we are supposed to put one bass trap per corner in a room, how do we fit 8 in a square room? Are you saying to treat other areas besides corners with bass trapping?

pepar:
As near as I can tell from your link, you have 1" of linacoustic there (including a nice speaker cutout).
I'm talking about having 30" of fluffy fiberglass pink.
Well, it's 2", but I thought your post said "2.5". 30" - whoaaa!

If we are supposed to put one bass trap per corner in a room, how do we fit 8 in a square room? Are you saying to treat other areas besides corners with bass trapping?
I had the same concerns and am going the StudioTips SuperChunk route with the 24" stack face. I have a novel idea to mount and cover them. I do not have a Taj Mahal, but I still have aesthetic concerns. Realistically, I am a few weeks away from completion, but I will try to take (meaningful) before and after measurements.

If we are supposed to put one bass trap per corner in a room, how do we fit 8 in a square room? Are you saying to treat other areas besides corners with bass trapping?

I do know corners can also mean where wall and ceiling meet, not just 2 walls. I need to find a good way to implement more traps and still have the room look nice. Thanks Ethan for your help. I think part of my issue may be the speakers are too close to the back wall and thus can't breath. My description of the sound was "muddy", but I don't think that is entirely accurate. Restricted may be a better term. I'll try to move them out (if there is room) and see if that helps.

Help,
After treating my room with 3, 2x4x8' 3-4" thick panels, 2 in the front and one corner wall in the rear. 5 wall panels, 3, 2x4x4' 3-4" thick on the right wall, 2 on the rear wall, and 2 covering 36" square windows on the rear wall also. I use 703 on the walls, 3" from the wall, and in the windows, and 705 in the corners.
I have peaks from fq. 28 to 40 to 95 db. The nulls are 75 db between 80 and 90, and fq. 225 to 250 are from 75 to 65 db.
Prior to treatment, the peak from 28 to 40 was only 87. The nulls at fq. 75 to 90 were 65 db, 100 to 120 to 67 db, and 180 to 200 were 73 db.
I mixed the wall panels, two with the paper to the front, bass, and two others with the paper to the rear, one had no paper, front or back.
The room which was live and has toned down and it does take more amp. too get the same loudness from the speakers, but I don't see how I could've increased the peak in lower bass.
Placing the sub in the front left position did help some, but it is not practical because it would be in a walk way. The sub. is behind the sofa and against the rear wall. The room is app. 17x25, but a curtain separates the listening and viewing area from another part of the room at 14'. Listening area is 17x14', setting at 14' from the speakers.
I do have pictures of the room, but don't know how post them on this site. I have read Ethans material and this thread. Thanks if you can help.

Jon & Kevin,

> corners can also mean where wall and ceiling meet, not just 2 walls. <

Exactly.

> I think part of my issue may be the speakers are too close to the back wall and thus can't breath. <

Animals need to breath, but I don't know that loudspeakers do. :D

Seriously, this issue is called SBIR - Speaker/Boundary Interference Response, which describes a series of predictable peaks and nulls whose frequencies are determined by the distances to nearby rigid boundaries. There's also "LBIR" which is the same thing but related to the Listener's (the "L" in "LBIR") distance to a nearby boundary.

I once measured the response at the listening position for a number of distances between the speakers and the front wall behind them. I started with the speakers flat against the wall, then moved them out from the wall in six inch increments. Some distances definitely gave a better low frequency response than others, and this is a worthy experiment if you have a way to measure the LF response. But I'll also tell you that when I put the speakers back against the wall and brought in eight bass traps, that made the response far better than even the best wall-speaker spacing gave. And of course adding traps also reduces ringing which is just as important as a flat response.

--Ethan

Jon & Kevin,

> corners can also mean where wall and ceiling meet, not just 2 walls. <

Exactly.

> I think part of my issue may be the speakers are too close to the back wall and thus can't breath. <

Animals need to breath, but I don't know that loudspeakers do. :D

Seriously, this issue is called SBIR - Speaker/Boundary Interference Response, which describes a series of predictable peaks and nulls whose frequencies are determined by the distances to nearby rigid boundaries. There's also "LBIR" which is the same thing but related to the Listener's (the "L" in "LBIR") distance to a nearby boundary.

I once measured the response at the listening position for a number of distances between the speakers and the front wall behind them. I started with the speakers flat against the wall, then moved them out from the wall in six inch increments. Some distances definitely gave a better low frequency response than others, and this is a worthy experiment if you have a way to measure the LF response. But I'll also tell you that when I put the speakers back against the wall and brought in eight bass traps, that made the response far better than even the best wall-speaker spacing gave. And of course adding traps also reduces ringing which is just as important as a flat response.

--Ethan

That's interesting. I think I'll wait to get my additional traps in and than mess with it. I did move the speakers out about 4" and the bass did improve, but my speakers are flanked on the outsides by a wall on one side of the room and my AV rack on the other. Nothing I can do about that unless I go with an acoustical transparent screen and that's not in the plans. 2 channel stereo sounds wonderful now because the crossover kicks in at 80Hz and my SW takes care of the lows. No more tweaking until the additional traps are in.

That's interesting. I think I'll wait to get my additional traps in and than mess with it. I did move the speakers out about 4" and the bass did improve, but my speakers are flanked on the outsides by a wall on one side of the room and my AV rack on the other. Nothing I can do about that unless I go with an acoustical transparent screen and that's not in the plans. 2 channel stereo sounds wonderful now because the crossover kicks in at 80Hz and my SW takes care of the lows. No more tweaking until the additional traps are in.
Yes, at some point practical and aesthetic concerns trump ideal speaker/sub placement. At that point, treatments and EQ are all that's left to employ.

I've got a slightly odd situation I'm hoping I can get some advice on.

I live in a loft, with some rooms carved out of it. None of the walls go to the ceiling, so think overgrown cubicles. The ceiling is 12' high, the walls go to about 8.5'.

I'm enclosing a shot of the floorplan for the theater (a bad scan). As you can see, it's a somewhat odd shape (being in NYC real estate is always a compromise). The distance from the back of the couch to the screen is about 13'. It's all worked out quite nicely, but I'm sure it would be even better if I could cut down on a bit of the liveness. We've put carpet down which helped quite a bit, but I'm wondering what the best method to tame the remaining reverb is.

Any suggestions?

I've got a slightly odd situation I'm hoping I can get some advice on.

I live in a loft, with some rooms carved out of it. None of the walls go to the ceiling, so think overgrown cubicles. The ceiling is 12' high, the walls go to about 8.5'.

I'm enclosing a shot of the floorplan for the theater (a bad scan). As you can see, it's a somewhat odd shape (being in NYC real estate is always a compromise). The distance from the back of the couch to the screen is about 13'. It's all worked out quite nicely, but I'm sure it would be even better if I could cut down on a bit of the liveness. We've put carpet down which helped quite a bit, but I'm wondering what the best method to tame the remaining reverb is.

Any suggestions?
None of the walls going to the ceiling sounds like the entire loft area outside of your theater is the culprit. If so, treatment is needed there.

No, the reverb is definitely more evident in the theater. Anywhere else in the apartment you don't hear it. Probably because there are enough soft surfaces (furniture, lots of books in shelves, etc.). In the theater it's very spare, really just the screen and the couch. I had a setup in the same location before the walls went up and reverb wasn't much of an issue because things were so open. With the new walls the inside of the theater is a much more "live" space.

No, the reverb is definitely more evident in the theater. Anywhere else in the apartment you don't hear it. Probably because there are enough soft surfaces (furniture, lots of books in shelves, etc.). In the theater it's very spare, really just the screen and the couch. I had a setup in the same location before the walls went up and reverb wasn't much of an issue because things were so open. With the new walls the inside of the theater is a much more "live" space.


Then you have solved your own problem! ;) If the walls have screwed up your sound field...which it appears you now have 1st reflections to deal with when before you didn't....you now need to treat those walls with some absorption. Find your first reflection points using the simple light and mirror trick. Once you find them, threat those areas with absorption panels. This should do the trick.

Thanks Stima, I figured it would be something like that but wanted to check with the collective brain and make sure that there was nothing else I was missing there. I'm guessing I should be able to do it with a few panels on each side and behind the speakers.

Thanks Stima, I figured it would be something like that but wanted to check with the collective brain and make sure that there was nothing else I was missing there. I'm guessing I should be able to do it with a few panels on each side and behind the speakers.
You should also consider the ceiling, floor and, many times overlooked, the back wall.

Can someone tell me about why you have to be able to breathe through the cloth to use it?

I just built some panels, 2 bass traps and 3 panels that will hang on the walls to absorb some of the mids/highs.

The cloth I used I couldn't blow through - but I used it anyways. Did I waste my time? All the cloth I found I could blow through I could see through to some extent and since the panels are supposed to be black I wanted them black. (Err I mean wife wanted them black:D)

If you can't breathe through it much at all, you'll change the absorbtion characteristics as the fabric will act somewhat like a membrane. For the mid/high reflection absorbers, this is a non-starter.

A good quality fabric like GOM will still appear black but is easy to blow through. If you need more 'blackness', you an put a layer of dyed muslin or burlap behind it to add some more darkness without restricting the airflow.

Bryan

Can someone tell me about why you have to be able to breathe through the cloth to use it?

I just built some panels, 2 bass traps and 3 panels that will hang on the walls to absorb some of the mids/highs.

The cloth I used I couldn't blow through - but I used it anyways. Did I waste my time? All the cloth I found I could blow through I could see through to some extent and since the panels are supposed to be black I wanted them black. (Err I mean wife wanted them black:D)
Bryan's nailed it; if you can't breathe through it, air molecules don't pass through it, and if air molecules don't pass through it, sound waves won't pass through it.

Jon & Kevin,

> corners can also mean where wall and ceiling meet, not just 2 walls. <

Exactly.


--Ethan

If you had to choose, and you are limited with how many panels you can install, which would be a better solution:

1. Treat all tri corners (where wall/wall/ceiling meet) with bass trapping?

2. Treat some tri corners and some wall/ceiling corners with bass trapping?

If #2, how to determine which tri corners and which wall/ceiling corners to treat. I was all set to just treat all my tri corners until I read this statement and now I am unsure.

I am buying 20-2'x4' panels and I have to treat my open basement with those. This includes hitting the first reflection points from my front speakers on the side walls, putting panels on my screen wall, bass trapping in all tri corners (unless I am told otherwise) putting a panel in the staircase due to the 2 parallel walls (the basement space is completely open so sound in the theater should be affected by the sound heading up the staircase) and depending on how many panels I have left, treat the ceiling for FRP.

Here (http://www.avsforum.com/avs-vb/attachment.php?attachmentid=55445) is the layout of my basement.

If #2, how to determine which tri corners and which wall/ceiling corners to treat. I was all set to just treat all my tri corners until I read this statement and now I am unsure.
[/URL] is the layout of my basement.


I looked at your layout to see what the room dimentions are and it isn't clear. You show a side wall that is offset and split? The reason I'm asking is that it is my understanding that when you are deciding which walls/corners to treat (other than first and second reflection points) you should go with the walls causing the most problems with the sound. You can use a "mode" calculator to tell you which walls are causing the most problems due to the size of the room.

I'm sure one of the other guys can give you detailed instructions on how to go about this much better than I can.

All of the dimensions are on the drawing (except for the far right wall which is 31'9"). As for the offset, use the inner portion, the outer portion is just where the concrete wall is in reference to my drywall.

Where can I find this 'mode' calculator that you mention?

If you had to choose, and you are limited with how many panels you can install, which would be a better solution:

1. Treat all tri corners (where wall/wall/ceiling meet) with bass trapping?

2. Treat some tri corners and some wall/ceiling corners with bass trapping?

If #2, how to determine which tri corners and which wall/ceiling corners to treat. I was all set to just treat all my tri corners until I read this statement and now I am unsure.

I am buying 20-2'x4' panels and I have to treat my open basement with those. This includes hitting the first reflection points from my front speakers on the side walls, putting panels on my screen wall, bass trapping in all tri corners (unless I am told otherwise) putting a panel in the staircase due to the 2 parallel walls (the basement space is completely open so sound in the theater should be affected by the sound heading up the staircase) and depending on how many panels I have left, treat the ceiling for FRP.

Here (http://www.avsforum.com/avs-vb/attachment.php?attachmentid=55445) is the layout of my basement.

To do the job right I would start with bass traps floor to ceiling in the front corners and then focus on ceiling to wall or floor to wall corners.

Glenn

To do the job right I would start with bass traps floor to ceiling in the front corners and then focus on ceiling to wall or floor to wall corners.

Glenn

So I should start with bass traps in the front corners then the wall/ceiling corners? So not 'all' the tri-corners need to be addressed since I am limited?

If you look at the plans, the red lines running from left to right are support beams that run across the ceiling, they are about 6" in height and form a tri-corner when they reach a wall, I was planning to put bass traps there as well, do you agree?

Counting the tri-corners that are formed by the support beams, how many tri-corners would you recommend be treated?

All of the dimensions are on the drawing (except for the far right wall which is 31'9"). As for the offset, use the inner portion, the outer portion is just where the concrete wall is in reference to my drywall.

Where can I find this 'mode' calculator that you mention?
It doesn't show ceiling height, unless it's there and I missed it.

Kevin,

> If you had to choose, and you are limited with how many panels you can install, which would be a better solution: <

That drawing doesn't show where the speakers and listener will be, so it's impossible to say what traps will be best where. But even if you had included that on the drawing, it's still impossible to predict. As Glenn said, for bass trapping you treat as many corners as possible, especially in the front, using rigid fiberglass at least four inches thick.

--Ethan

Bryan's nailed it; if you can't breathe through it, air molecules don't pass through it, and if air molecules don't pass through it, sound waves won't pass through it.

Well - don't take this the wrong way - but it sounds like conventional wisdom. Considering the work and $$$ it will take me to redo my absorbers I want to make sure this is accurate.

I guess what I'm saying is, are you certain this is true?

Certainly I could put up a wall of this cloth and hold a conversation through it.

Any tests been done on this type of thing?

Bryan's nailed it; if you can't breathe through it, air molecules don't pass through it, and if air molecules don't pass through it, sound waves won't pass through it.
Air molecules don't need to pass through it. They just need to vibrate it to transmit sound waves.

Regards,
Terry

Well - don't take this the wrong way - but it sounds like conventional wisdom. Considering the work and $$$ it will take me to redo my absorbers I want to make sure this is accurate.

I guess what I'm saying is, are you certain this is true?

Certainly I could put up a wall of this cloth and hold a conversation through it.

Any tests been done on this type of thing?
And don't you take this the wrong way either. Before you spent the $$$ and did all the work, did you research building absorbers?

To use your example, the metric is not that you can carry on a conversation through it, but that your voices sounds the same with the cloth between you and the other conversant as they do without.

Air molecules don't need to pass through it. They just need to vibrate it to transmit sound waves.

Regards,
Terry
Wouldn't the air molecules need to be touching each other to pass the energy along losslessly? Otherwise the cloth gets involved in the transaction and then it's characteristics come into play.

And don't you take this the wrong way either. Before you spent the $$$ and did all the work, did you research building absorbers?

To use your example, the metric is not that you can carry on a conversation through it, but that your voices sounds the same with the cloth between you and the other conversant as they do without.

Don't worry I'm not sensative at all. I did lots of research and everything I read said I should buy cloth I could blow through. I just didn't. :D

I haven't yet hung them up on the wall and now I'm having second doubts about my decision to use a cloth weave I couldn't blow through.

I'm simply trying to find an accurate answer to my question - by someone who knows based on fact and data not conventional wisdom. If you're the guy who knows - then you're the guy. I'm just the guy asking questions!

If I have to go back to the store, spend a couple bucks, and redo the coverings - so be it. I'm just trying to avoid it.

But based on your logic - are you saying the voice would sound the same through a cloth wall I could breath through? :p

It doesn't show ceiling height, unless it's there and I missed it.

Sorry, the ceiling is 7.5' high, I didn't realize you wanted that dimension as well.


That drawing doesn't show where the speakers and listener will be, so it's impossible to say what traps will be best where. But even if you had included that on the drawing, it's still impossible to predict. As Glenn said, for bass trapping you treat as many corners as possible, especially in the front, using rigid fiberglass at least four inches thick.

The left speaker is 6" off the left wall, the center will be located above the screen and the right speaker is parallel to the left. Both left/rights speakers are 2 feet from the front wall. The center is in a window well on the front wall. The front row of seats is 12' from the front wall and 10' from the front speakers.

I understand it is impossible to predict and thank you for your help. Based on what everyone has stated, this is what I am now going to do, please let me know if anyone sees any problems with this:

1. Add bass trapping, at least 4" thick, to all tri-corners (including where the support beams meet the walls to form a tri-corner)
2. Add bass trapping to the front wall, where the wall and ceiling meet
3. Treat all first reflection points for all 3 front speakers from each seat in the theater with 2" panels
4. Treat the front wall with 2" panels
5. Treat behind the screen with 2" panels
6. Put 1 panel in the staircase on one of the 2 parallel walls
7. If I have panels left, treat the FRP on the ceiling

If I have missed anything, please let me know.

Thanks

But based on your logic - are you saying the voice would sound the same through a cloth wall I could breath through? :p
No, while you can blow through acoustically transparent cloth, I'd bet that not all cloth that can be blown through is acoustically transparent. I don't know where to find acoustical data on cloth not being sold as specifically having some partticular usage for that purpose. I imagine others here could though . . .

No, while you can blow through acoustically transparent cloth, I'd bet that not all cloth that can be blown through is acoustically transparent. I don't know where to find acoustical data on cloth not being sold as specifically having some partticular usage for that purpose. I imagine others here could though . . .

Good point.

I await the experts who will tell me I should have just gotten the right cloth the first time around - or not.

MUCHO:

If you can easily breath through it, then it's acoustically transparent, and the acoustical properties of whatever you put behind it will be the final acoustical properties of it in the room.

But that doesn't mean that you MUST use a covering that you can breath through.

I can't easily breath through the fabric of my shirt, so it will change the absorbtion of the fiberglass behind it if that fabric were used as a cover. Bass will probably still go through it as if it wasn't there. But some frequencies will be reflected some amount. Who knows how much.

Putting a thin light air-tight covering over the fiberglass, such as SaranWrap, will reflect just a bit of highs.

Putting a heavier material, such as a heavy velour curtain, will reflect more frequencies -- but may absorb some on its own too. It might even be six of one and half a dozen of the other.

A heavier still material, such as leather, as you might have on a couch, will reflect sound all the way down to the mid frequences.

Heavier still material, such as drywall, will reflect sound all the way down to the bass frequencies. A 'wall' like this will still absorb something -- but it's so BAD an absorber that it's called a reflector.


Variations on this theme are actually quite useful.
For example, if your RT60 is too low in the HF, but just fine in the LF, you can cover some of your absorbers with something reflective to increase the HF RT60 without changing the LF RT60, such as the FRK or foil etc.
Similarly, if you've got a cloth couch, you can buy a leather couch.

And the knowledge of what happens when you cover things is also useful.
For example, your first reflection point absorbers you probably want to catch all the MF to HF sound (to improve stereo imaging) -- so a cover that's acoustically transparent to take maximum HF use of the absorber fiberglass would be a good thing.

Realistically, if the material is breathable easily or even relatively easily, it will work fine for covering treatments and can be considered transparent for that purpose.

For purposes of putting cloth in front of a speaker, that's a whole different story. Even some relatively breathable fabrics - some even by Guilford - are not suitable for this use as they tend to absorb extreme high frequencies by as much as 10db in some cases.

Realistically, if the material is breathable easily or even relatively easily, it will work fine for covering treatments and can be considered transparent for that purpose.

For purposes of putting cloth in front of a speaker, that's a whole different story. Even some relatively breathable fabrics - some even by Guilford - are not suitable for this use as they tend to absorb extreme high frequencies by as much as 10db in some cases.

10db???? Is this a guess or do you have data to back that up? That just seems like a lot for a piece of fabric. I guess high frequencies only dogs can hear could be possible. :D

Glenn

10db???? Is this a guess or do you have data to back that up? That just seems like a lot for a piece of fabric. I guess high frequencies only dogs can hear could be possible. :D

Glenn
Naugahyde? :D

Realistically, if the material is breathable easily or even relatively easily, it will work fine for covering treatments and can be considered transparent for that purpose.

For purposes of putting cloth in front of a speaker, that's a whole different story. Even some relatively breathable fabrics - some even by Guilford - are not suitable for this use as they tend to absorb extreme high frequencies by as much as 10db in some cases.

Bryan,

In the Guillford fabric line, I found the FR series material to be somewhat coarse and extremely low on the WAF (at least for covering wall treatments). We ordered up a bunch of other samples and settled on several colors from their Anchorage line (can't remember the style number). The material is much smoother, seems "breathable" and meets the WAF. I'm not sure the blow through test helped me determine if this material was suitable to cover the wall treatments. Have you used any of the GOM lines other than the FR701 series?

This has also got me looking at the decision to use something like speaker grill cloth for the front screen wall instead of Black FR701 GOM.

Thoughts?

Regards,

BillMac

Sorry, the ceiling is 7.5' high, I didn't realize you wanted that dimension as well.




The left speaker is 6" off the left wall, the center will be located above the screen and the right speaker is parallel to the left. Both left/rights speakers are 2 feet from the front wall. The center is in a window well on the front wall. The front row of seats is 12' from the front wall and 10' from the front speakers.

I understand it is impossible to predict and thank you for your help. Based on what everyone has stated, this is what I am now going to do, please let me know if anyone sees any problems with this:

1. Add bass trapping, at least 4" thick, to all tri-corners (including where the support beams meet the walls to form a tri-corner)
2. Add bass trapping to the front wall, where the wall and ceiling meet
3. Treat all first reflection points for all 3 front speakers from each seat in the theater with 2" panels
4. Treat the front wall with 2" panels
5. Treat behind the screen with 2" panels
6. Put 1 panel in the staircase on one of the 2 parallel walls
7. If I have panels left, treat the FRP on the ceiling

If I have missed anything, please let me know.

Thanks

No one has any opinions on my plans? At least tell me if this sounds sufficient or if you would make any changes to my plans........all help is appeciated

Thanks for all the info guys. Really appriciate it. For now I guess I'll take the lazy mans way and go with what I got :D

I have a question about first reflection points. In my basement, the left wall is 6" from the left speaker and 9' from the right speaker, the right wall is 21' from the right speaker and 30' from the left speaker.

Because of the extreme difference in distance distance from the right wall to the listening position, does the right wall need to be treated as well? I ask because I am assuming it will take longer for sound to bounce off the right wall and reach the listener than the left wall, and by the time the sound has reached the listener the brain has already processed what has happened. Am I mistaken?

I have a question about first reflection points. In my basement, the left wall is 6" from the left speaker and 9' from the right speaker, the right wall is 21' from the right speaker and 30' from the left speaker.

Because of the extreme difference in distance distance from the right wall to the listening position, does the right wall need to be treated as well? I ask because I am assuming it will take longer for sound to bounce off the right wall and reach the listener than the left wall, and by the time the sound has reached the listener the brain has already processed what has happened. Am I mistaken?
If I were you (and without further ado), I'd treat all first reflection points - ceiling, front L&R walls, floor AND back wall) and then add bass traps in the front. And THEN I'd make some acoustical measurements to see if I needed more traps and/or some diffusion. That's what I'd do . . . :)

I have a question about first reflection points. In my basement, the left wall is 6" from the left speaker and 9' from the right speaker, the right wall is 21' from the right speaker and 30' from the left speaker.

Because of the extreme difference in distance distance from the right wall to the listening position, does the right wall need to be treated as well? I ask because I am assuming it will take longer for sound to bounce off the right wall and reach the listener than the left wall, and by the time the sound has reached the listener the brain has already processed what has happened. Am I mistaken?
If the difference between the direct speaker-to-ear distance and the billiard-shot distance reflecting off the wall is greater than around 15', you are OK. The reflection does not get integrated into the direct sound, and your front sound stage is undisturbed.

Regards,
Terry

If the difference between the direct speaker-to-ear distance and the billiard-shot distance reflecting off the wall is greater than around 15', you are OK. The reflection does not get integrated into the direct sound, and your front sound stage is undisturbed.

Regards,
Terry
Still, with all that space, he may still need to put some absorption on that wall, right?

Still, with all that space, he may still need to put some absorption on that wall, right?
Sure. Depends upon the reverberation times of the room, but typical home theaters need lots of wideband absorption.

- Terry

Terry,

> typical home theaters need lots of wideband absorption. <

Oh sure, it's okay when you say it!

http://www.ethanwiner.com/emoticons/rofl3dbig.gif

--Ethan

Terry,

> typical home theaters need lots of wideband absorption. <

Oh sure, it's okay when you say it!

http://www.ethanwiner.com/emoticons/rofl3dbig.gif

--Ethan
I just measure reverb times and adjust them, using acoustical treatment, to where they should be! :)

- Terry

I just measure reverb times and adjust them, using acoustical treatment, to where they should be! :)

- Terry

Glad to see you are coming around to the right way of thinking... :p :D I am just kidding Terry don't flame me..

Glenn

Bill,

IIRC, the Anchorage is one of the worst acoustical performers in the Guilford line. However, most of that issue is due to HF attenuation. For walls in front of soft broadband absorbtion it should be fine - just don't put it in front of speakers.

Bryan

Right! That's what I figured. Thanks.

Still, with all that space, he may still need to put some absorption on that wall, right?

So it would be best to treat the far wall.

Thanks, I think I FINALLY have a plan to acoustically treat my theater :)

So it would be best to treat the far wall.

Thanks, I think I FINALLY have a plan to acoustically treat my theater :)
I'm not sure there's a consensus on treating that wall or if there is, that there's consensus on why. It seems likely you'll need more broadband absorption than what the "other" first reflection point absorbers will provide, but Terry's point of the wall being so far away so as not to cause an "early" reflection is a good one.

I recommend that you should get some acoustical testing software, a decent microphone and take some measurements. If that sounds daunting, bear in mind that it's pretty much the only way to know what you really need beyond those first reflection points. And it's not really that daunting once you get into it.

Any advice on good acoustical testing software?

Any advice on good acoustical testing software?
Room EQ Wizard (http://www.hometheatershack.com/roomeq/) is a good one, and it's free. And I use the calibrated mic from ETF Acoustics (http://www.etfacoustic.com/micpreamp.html) which is excellent, but far from free. Perhaps someone else here can point you to a lesser expensive mic that will still do the job.

New to this but there is great info from everyone.

I have a question of the "Front Wall"

I have an existing wall from previous owner that is insulated. I have built and Wall inside of that and that is where I am at.

I have read many things on the "Front Wall" and that it should be "Dead"

My question is this (2 fold) (More concerned with "in room" acoustics then sound transmission thorughout the rest of the house.

To make the wall better for acoustics should I:

a. Fill with 3.5 inch "acoustical Cotton Bats that I have, ,put a layer of 1" Linacoustic over the whole thing including the face of the studs. Then cover the wall with GOM?

or


b. Fill with 3.5 inch "Acoustical cotton bats that I have, then Drywall, then 1" Linacoustic, Then GOM.


c. do "a" or "b" on the bottom half of the wall only.

Not sure if "a" will make the wall or room too dead.

Need a little expert advice.

thank you,

:)

You may need to clarify what you are trying to do here.

Where do you want your front speakers to be located? In front of the new wall, mounted flush in the wall, behind the wall\screen like at a theater?

actually the speakers will be in front of the new wall or attached to the new wall.

there is not enough depth to put the speakers into the wall.

basically the original wall was crooked and done rather poorly, in has drywall on it and standard insulation behind it.

We built a new wall 1" decoupled from the original wall just to level it out and make it square. It is open for whatever I need to do acoustically.

hope that helps.

Basically, my question is since there is an existing wall with Drywall on it. Can I fill the new wall with insulation and cover with GOM? or do I need to Drywall the new wall on the side facing the viewing area? (then have to treat that)

thank you for your help.

To make the wall better for acoustics should I:

a. Fill with 3.5 inch "acoustical Cotton Bats that I have, ,put a layer of 1" Linacoustic over the whole thing including the face of the studs. Then cover the wall with GOM?

or

b. Fill with 3.5 inch "Acoustical cotton bats that I have, then Drywall, then 1" Linacoustic, Then GOM.

"a" will give you some pretty good bass absorption on the front wall. "b" won't. It depends on what the room needs. But extra bass absorption is generally a very desirable thing, especially since you can add it invisibly and with little trouble or expense.

Regards,
Terry

My question is this (2 fold) (More concerned with "in room" acoustics then sound transmission thorughout the rest of the house.

To make the wall better for acoustics should I:

a. Fill with 3.5 inch "acoustical Cotton Bats that I have, ,put a layer of 1" Linacoustic over the whole thing including the face of the studs. Then cover the wall with GOM?

or


b. Fill with 3.5 inch "Acoustical cotton bats that I have, then Drywall, then 1" Linacoustic, Then GOM.



:)

I'm no expert but after long time researching my HT build this is what I picked up.

You mentioned that acoustics is the issue and not sound insulation. When you are using option b its for sound insulation purposes. You are basically building a double wall which will be very good for sound insulation. Is the wall in question common to the rest of the house?

The way you should look at the issue is how much sound insulation do you need.

If you don't need the sound insulation help from the additional layer of drywall then go with option a. You will then in effect have started your acoustical treatments. But you, still need to figure out what the optimal combination of depth of cotton bats plus linacoustics would be for your room.

Cheers,

Exipnos

thank you guys for your help.

My room is 14 x 18 x 8

Front wall is the double wall.

Original wall is attached to the frame of the house, the wall I added is not, except where the RSIC clips meet.

When Left wall and Right walls are Linacoustic 1" floor to ceiling about 4 feet out. Both side walls the rest of the 14 feet are Linacoustic 44 inches from floor and dry wall the rest of the way. (plan on using acoustical panels where needed above 44 inches)

back wall is the same as the sides. but may us some diffusers on that if needed.

I will have bass traps 18" diag. floor to ceiling on front wall in both corners, and the back wall a bass trap from the floor up to 44" (Chair Rail Height) in both corners. Then a small bass trap in the upper corners of back wall. (Functional and cosmetic)

I have carpet with 3/8 pad on floor.

Have not thought much about the ceiling yet, there is currently a drop ceiling 2 inches from joist. might have to use some first reflection panel across the ceiling after i get things fired up.

Am I on the right path??

In order to help balance things a bit better, use the drop ceiling to your advantage. Plan on filling the gap above the drop with fluffy insulation as well as the joist cavities. This will broaden the absorbtion othe drop ceiling.

thank you guys for your help.

My room is 14 x 18 x 8

Front wall is the double wall.

Original wall is attached to the frame of the house, the wall I added is not, except where the RSIC clips meet.

When Left wall and Right walls are Linacoustic 1" floor to ceiling about 4 feet out. Both side walls the rest of the 14 feet are Linacoustic 44 inches from floor and dry wall the rest of the way. (plan on using acoustical panels where needed above 44 inches)

back wall is the same as the sides. but may us some diffusers on that if needed.

I will have bass traps 18" diag. floor to ceiling on front wall in both corners, and the back wall a bass trap from the floor up to 44" (Chair Rail Height) in both corners. Then a small bass trap in the upper corners of back wall. (Functional and cosmetic)

I have carpet with 3/8 pad on floor.

Have not thought much about the ceiling yet, there is currently a drop ceiling 2 inches from joist. might have to use some first reflection panel across the ceiling after i get things fired up.

Am I on the right path??

wow sounds like you have really thought through your room acoustics, hats off to you sir. As Bryan said the fluffy fiberglass above the drop ceiling works great.

Glenn

"a" will give you some pretty good bass absorption on the front wall. "b" won't. It depends on what the room needs. But extra bass absorption is generally a very desirable thing, especially since you can add it invisibly and with little trouble or expense.

Regards,
Terry
Kermie: My room is 13 x 21 x 8 and it needs a LOT of absorption in the 100Hz-300Hx range. I'd imagine your room will be pretty much the same.

wow sounds like you have really thought through your room acoustics, hats off to you sir. As Bryan said the fluffy fiberglass above the drop ceiling works great.

Glenn


Thanks to about 2 months of reading this sight prior to starting. There are some great minds on here. I do not have an unlimited budget so I am just doing what I can with what I have.

Great idea about the ceiling. It should not cost much so I will put that on the list.


As far as the "absorption in the 100Hz-300Hx range" what is the best way to go about that. "Acoustical Panels"?


I have a friend that sets up for a local band and he has some good knowledge of sound but he won't be around until July. He said he would come over with some of his computer equipment to help with the location and panels.

Hopefully I will be at that point by then. A few hours here and there, you can't get much done.....lol.

Thanks to about 2 months of reading this sight prior to starting. There are some great minds on here. I do not have an unlimited budget so I am just doing what I can with what I have.
The DIY route, after lots of reading - here and everywhere you can find, can produce near-pro results. Certainly results that will have your friends' jaws dropping. And not cost a lot of money. If you can source the raw material and build your own panels, traps, etc., you can spend but a fraction of what some have in their theaters.

Great idea about the ceiling. It should not cost much . . .
Precisely!

As far as the "absorption in the 100Hz-300Hx range" what is the best way to go about that. "Acoustical Panels"?
Bass traps (http://forum.studiotips.com/viewforum.php?f=8).

I have a friend that sets up for a local band and he has some good knowledge of sound but he won't be around until July. He said he would come over with some of his computer equipment to help with the location and panels.
Excellent! As close as the "great minds" here can get to diagnosing and prescribing for your theater from their keyboards, acoustical testing IN THE ROOM is quite necessary for your theater to be all it can be. And a laptop with a modest amount invested in software and hardware is an economical way to pull the room together acoustically.

>As far as the "absorption in the 100Hz-300Hx range" what is the best way to go about that. "Acoustical Panels"?<

I would recommend either 2 ways, 4" (or 6") rigid fiberglass panels staddling corners or super chunks in the corners. With super chunks we have tested in a lab and have found them very effective even at 50hz.

Glenn

Glenn

I have a metal 6 panel fire-proof door at the back of my theater, about 28' from the front wall, should this door be treated?

I have a metal 6 panel fire-proof door at the back of my theater, about 28' from the front wall, should this door be treated?
What are the walls? Probably, it should be treated however it would be treated if it were a wall - first reflection point and/or as part of an overall absorption/diffusion strategy.

sorry if this has already been asked and answered but I havent' come across..

With all this fiberglass packed on all outsides of the room walls, aren't you all concerned about the health hazards? If yes, what care are you taking?


thanks
sri

sorry if this has already been asked and answered but I havent' come across..

With all this fiberglass packed on all outsides of the room walls, aren't you all concerned about the health hazards? If yes, what care are you taking?
Is this a general question, or asked specifically of one member? All of my fiberglass panels are covered with fabric, I vacuum them every now and then, and our house has a few ion breeze filters.

What are the walls? Probably, it should be treated however it would be treated if it were a wall - first reflection point and/or as part of an overall absorption/diffusion strategy.


The walls are sheetrock with the first reflection points going to be treated. I will be treating the front wall so now I am looking at the back wall. I will be adding a bar to the rear of my theater, is treatment still recommended back there?

The walls are sheetrock with the first reflection points going to be treated. I will be treating the front wall so now I am looking at the back wall. I will be adding a bar to the rear of my theater, is treatment still recommended back there?
Well, the back wall is one of the first reflection points (though distance may make it moot). Some go for absorption, others for diffusion. A bar may be diffusive by itself, while bar patrons would be absorptive - and absorbing. :) Barring using some sophisticated room modeling software, just built the darn thing and *then* use some simple and relatively inexpensive testing software/hardware to determine what you need beyond first reflection points. Just don't make the bar concave.

Just my $.03.

As usual, thanks Pepar :)

If you're out of room (or WAF) and need to deal more with the 100-300Hz range, simply modding your reflection absorbers from 1" to 2" and potentially from 703 to acoustical cotton will provide excellent additional absorbtion in that range without any more loss of wall or floor space.

Is HF comb filtering on acoustically transparent screens due to interference from reflections between the speaker face and the screen, or is it due to the screen attenuating different HFs by different levels? I'm wondering what, if any, benefits would be had by treating the speaker face with absorpative material.

Is HF comb filtering on acoustically transparent screens due to interference from reflections between the speaker face and the screen, or is it due to the screen attenuating different HFs by different levels? I'm wondering what, if any, benefits would be had by treating the speaker face with absorpative material.
The comb filtering is from the sound reflecting from the back of the screen to the face of the speaker and back out through the screen - out of phase, of course, with the direct sound. If you click on my link and navigate to pg 14, you'll see the recommended (by THX) acoustical treatment to minimize the comb filtering. This is present only with microperfed screens; the cloth screens seem to not have the issue. But then, they are at most, only approaching unity gain, where a Stewart, for example, can have gain. Mine is a microperfed Stewart Firehawk, a 1.3-ish screen. Perfing cuts gain by 11%, but that's still a nice gain.

This is present only with microperfed screens; the cloth screens seem to not have the issue.

Actually, this is not the case even for the highly touted SR products. It can be heard and can be measured. Both Tony Grimani and I have measured and demonstrated this.

Actually, this is not the case even for the highly touted SR products. It can be heard and can be measured. Both Tony Grimani and I have measured and demonstrated this.
:eek: You mean their advertising is false???!!!

edit: Perhaps John Dahl's quote is most accurate; "No screen we’ve tested to date matches the acoustical transparency . . "

"No screen we’ve tested to date matches the acoustical transparency . . "

...that should be extended to include light transparency as well. :)

So Dennis (or anyone else), how effective is placing absorpsion on a speaker face in reducing comb filtering of AT screens? Does it all but eliminate it? Or are the reflective properties of the tweeters and woofers enough to keep a significant portion of the comb filtering intact?

There's been some discussion about it, starting here (http://www.avsforum.com/avs-vb/showthread.php?t=640385&page=62&pp=30). Unfortunately, you'll have to weed through some cleverly disguised flames and insults (fluff and sarcasm).

So Dennis (or anyone else), how effective is placing absorpsion on a speaker face in reducing comb filtering of AT screens? Does it all but eliminate it? Or are the reflective properties of the tweeters and woofers enough to keep a significant portion of the comb filtering intact?

There's been some discussion about it, starting here (http://www.avsforum.com/avs-vb/showthread.php?t=640385&page=62&pp=30). Unfortunately, you'll have to weed through some cleverly disguised flames and insults (fluff and sarcasm).
The mask and treatment of the cavity behind the speaker mitigates the comb filtering, and the 1/3 octave EQ shapes the sound to compensate for the loss due to getting sound through the little holes, but try as I might, I cannot get the center spkr's sound identical to the L & R spkrs.

Having said that, dialog issuing forth from the actor's mouths is a wonderful thing and I don't think I will ever have any other setup than the center channel behind the screen.

Just my $.03.

sri777 :

With all this fiberglass packed on all outsides of the room walls, aren't you all concerned about the health hazards? If yes, what care are you taking?

from: http://www.recording.org/ftopict-21013.html

Folks,

People have heard all kinds of stories about fiberglass and it's hazzards. It has been stated:

I mean that cutting fiberglass can be a bit of a health hazard because the fibers, which are a known carcinogen, are released into the air and can be inhaled. Studies have shown that glass fibers from a stationary piece of rigid fiberboard will not be released into the air in significant numbers, especially when the board is covered in fabric, but you should definitely wear gloves and some type of facemask when cutting 705. I'm pretty sure that a paper mask will be enough, but you should definitely double check me on this before you start.

OK,

There have been more than a few questions/statements regarding health issue relating to fiberglass in the past few weeks - and tis time to maybe put the "myths" to rest.

It was reported in the late 80's early 90's about the possibility of fiberglass being a possible carcinogen - and many claims from various sources since then that it actually is.

However the following comes directly from the American Lung Association:

Direct contact with fiberglass materials or exposure to airborne fiberglass dust may irritate the skin, eyes, nose and throat. Fiberglass can cause itching due to mechanical irritation from the fibers. This is not an allergic reaction to the material. Breathing fibers may irritate the airways resulting in coughing and a scratchy throat. Some people are sensitive to the fibers, while others are not. Fiberglass insulation packages display cancer warning labels. These labels are required by the U.S. Occupational Safety and Health Administration (OSHA) based on determinations made by the International Agency for Research on Cancer (IARC) and the National Toxicology Program (NTP).

1994- NTP listed fiberglass as "reasonably anticipated to be a human carcinogen" based on animal data.

1998- The American Conference of Govern- mental Industrial Hygienists reviewed the available literature and concluded glass wool to be "carcinogenic in experimental animals at a relatively high dose, by route(s) of administra- tion, at site(s), of histologic type(s) or by mechanism(s) that are not considered relevant to worker exposures".

1999- OSHA and the manufacturers volunta- rily agreed on ways to control workplace exposures to avoid irritation. As a result, OSHA has stated that it does not intend to regulate exposure to fiberglass insulation. The voluntary agreement, known as the Health & Safety Partnership Program includes a recom- mended exposure level of 1.0 fiber per cubic centimeter (f/cc) based on an 8-hour workday and provides comprehensive work practices.

2000- The National Academy of Sciences (NAS) reported that epidemiological studies of glass fiber manufacturing workers indicate "glass fibers do not appear to increase the risk of respiratory system cancer". The NAS supported the exposure limit of 1.0 f/cc that has been the industry recommendation since the early 1990s.

2001- The IARC working group revised their previous classification of glass wool being a possible carcinogen. It is currently considered not classifiable as a human carcinogen. Studies done in the past 15 years since the previous report was released, do not provide enough evidence to link this material to any cancer risk.

Here is the link if you wish to check it out yourself:

http://www.lungusa.org/site/pp.asp?c=dvLUK9O0E&b=35439

In addition i would point out that the American Cancer Society does not even take the time to reference fiberglass.

The advice given above - protecting both your body and lungs from this product - that makes sense - but the claim that the product is a known carcinogen is not recognized by any government agency of any country that i know.

The only claims I know that support the cancer myth are made by fringe groups not recognized by any govt or medical agencies that i am aware of. Apparently without any hard scientific backup to support the claims.

Be safe - be smart - but don't be afraid.........

Sincerely,

Rod

but try as I might, I cannot get the center spkr's sound identical to the L & R spkrs.


This can be as a result of any number of issues. First on the diagnostic list is to perform a nearfield RTA of each speaker to determine how much, if any, of the difference is directly related to speaker design, rather than placement (and often you'll find a broken speaker!). Second would be to plot the RTA of the center channel speaker, move the L or R into the same position as the center, measure its RTA and overlay on the original plot. Any differences would be as a result of speaker position.

The fact that one speaker is mounted differently (with respect to the listener) with respect to height, orientation, proximity to boundaries, or angle will change the timbre of the speaker.

Solutions include baffle mounting each speaker to minimize differences or placing all three speakers behind the screen. Regardless of any manufacturer's, or third party party's, claims no screen is 100% acoustically transparent (and, in some cases while measured differences exist, audible differrences do not).

This can be as a result of any number of issues. First on the diagnostic list is to perform a nearfield RTA of each speaker to determine how much, if any, of the difference is directly related to speaker design, rather than placement (and often you'll find a broken speaker!).
The speakers are identical. (M&K S-150's and S-150AC)

Second would be to plot the RTA of the center channel speaker, move the L or R into the same position as the center, measure its RTA and overlay on the original plot. Any differences would be as a result of speaker position.
You're probably onto something here because the left sounds a bit different from the right on the pre/pro's pink noise. However, all spkrs are Omnimounted to the wall and can't easily be swapped around.

The fact that one speaker is mounted differently (with respect to the listener) with respect to height, orientation, proximity to boundaries, or angle will change the timbre of the speaker.
Another good one, Dennis, and one that never occurred to me. The L&R are level with each other, but while the center spkr is less than one "spkr height" higher than the other two, it is nonethelsss higher. I got lazy when I mounted them and even had to flip it upside down to get it where it is (and use the original mounting location). As part of an upgrade involving bass traps, I plan on lowering all of the speakers and placing them on the same plane.

Solutions include baffle mounting each speaker to minimize differences or placing all three speakers behind the screen. Regardless of any manufacturer's, or third party party's, claims no screen is 100% acoustically transparent (and, in some cases while measured differences exist, audible differrences do not).
Only the center is behind the screen now and it's not practical to mount L&R behind the screen. Everything sounds fine during use though a hard left to hard right pan can be a bit distracting . . to me . . . but no one else.

With the center speaker being higher, it is firing downward and the sound strikes the screen at an angle. I think that may be contributing to the different timbre and reducing that angle of incidence - or eliminating it - may make my EQ'ing job easier. When "viewed" off axis, a circle is an ellipse (with less area). I'm reasoning that the ellipses are restricting the sound much more than the circles. Does that sound logical?

Talk about being lucky. A couple of weeks ago, I went to Joan Fabrics to price out fabric to wrap my panels. I found some acousticallytransparentt fabric for $5.99/yd on sale. They told me based on my panel sizes I would need about 17-20 yards to do what I needed. I decided to wait and shop around a little more.

This week, my wife tells me that Rag Tag had a 'store closing' sign and was trying to get ride of everything, she said that they had fabric, but she was unsure what type I needed. So today we went there and I was able to find some acoustically transparent fabric again, a little difficult with the store being in shambles, and also finding the right color (black). The first fabric I found they only had about 10 yds left, but I noticed they had some more black fabric behind the counter and to my surprise, it was just what I needed. I gave the salesperson the dimensions of my panels and was told I would need about 22 yards. I asked her to check how much was on the roll, and of course it was 1 yard short. So I told her I would take all of it and I also bought 3 yards of the one I originally found.

Oh, by the way, the best part of the story.........the fabric was on sale for $1.00/yd :D

When I reminded my wife how much we almost spent a few weeks ago, she smiled 'almost' as much as I did. :D

Solutions include baffle mounting each speaker to minimize differences.

Dennis, don't you suggest placing the fiberglass on the baffle wall rather than the front of the speaker?.

I can not remember a recommendation to cover the speaker face with fiberglass when I attended THX training.

I would think that would contribute to the difference in sound between treated and non treated speakers.

Dennis, don't you suggest placing the fiberglass on the baffle wall rather than the front of the speaker?.

I can not remember a recommendation to cover the speaker face with fiberglass when I attended THX training.

I would think that would contribute to the difference in sound between treated and non treated speakers.
I occasionally correspond with John Dahl on my home theater project and he is always at the ready to provide assistance. Here is one of his replies re center speaker behind a perfed screen:

"Jeff,

What you’re probably hearing is not so much screen attenuation which can be corrected with EQ, rather you’re hearing comb filtering which cannot be corrected with EQ. Two things to do. 1. Make sure that there is at least 6” space between the front face of the speaker and the back of the screen (10” is a bit better). 2. Put a couple of inches of (black color) acoustic absorption material on the front of the speaker with cut outs only for the drivers. This should clean things up considerably. For EQ you want a first order filter hinged at 6KHz. Rolling gradually up from 6KHz to +2dB at 20K.

You’ve probably done this but be sure you’re using broadband (20-20K) pink when you EQ but the internal band limited (500-2K) pink to set the levels. The levels MUST be set accurately before you do a listening test.

Whatever you do pink noise will reveal some differences. To reassure yourself that you’ve done a good thing play program material through each channel in turn. I doubt you’ll be able to hear any differences attributable to the screen and not to room interactions.

Let me know how it works out.

Best regards,

John Dahl
Technical Product Marketing Manager
THX Ltd.

Would 4" - 6" thick rockwool or rigid fiberglass placed underneath my couches provide meaningful bass trapping? I know corners are best, etc., but if that isn't an option for asthetics, how effective would locating these under sofas?

> Would 4" - 6" thick rockwool or rigid fiberglass placed underneath my couches provide meaningful bass trapping? <

Possibly a tiny bit, but probably not enough to matter.

--Ethan

Would 4" - 6" thick rockwool or rigid fiberglass placed underneath my couches provide meaningful bass trapping? I know corners are best, etc., but if that isn't an option for asthetics, how effective would locating these under sofas?
For bass traps, especially <100Hz, it really is "looks good" or "works good." :( Unless you have the luxury of designing a theater from scratch - in a fairly large empty space.

Would 4" - 6" thick rockwool or rigid fiberglass placed underneath my couches provide meaningful bass trapping? I know corners are best, etc., but if that isn't an option for asthetics, how effective would locating these under sofas?

Have you thought about building a super chunk in the corner? You can put a false wall in front of it and it looks pretty nice.

Glenn

I'm currently setting up new speakers+sub in an ongoing diy home theater project in my living room. After reading through a lot of this thread I think i have a good idea about how to go about treating the room but I have some questions specific to the awkward room design. For one thing, there's a giant un-centered window covering about 40% of the front wall. Does sound generally pass through a window or is it a source of reflection? I mention the window isn't centered because if I push my speakers out as wide as I'd like them one of them is backed by wall while the other is still behind window. I was thinking I could build extentions to the frame of my screen hanging from the ceiling to put absorbtion material behind both speakers. good idea or no?

Also, the house is supported on blocks with wood floors. I'm planning on getting a big throw rug for the front of the room to handle first reflections from the l/c/r but bass seems to stay in the room longer than it should (standing wave?) like my head is inside a speaker cabinet. Are there ways to bass trap via floor modification? I can do some corner and maybe a few wood traps on the wall but if there's a way to stop the floor from shaking so much maybe that would be a good first step? I have plenty of crawlspace and willingness to fight the snakes for it:P

Thanks in advance!

I'm currently setting up new speakers+sub in an ongoing diy home theater project in my living room. After reading through a lot of this thread I think i have a good idea about how to go about treating the room but I have some questions specific to the awkward room design. For one thing, there's a giant un-centered window covering about 40% of the front wall. Does sound generally pass through a window or is it a source of reflection?
The window will most likely reflect sound as uniformly as it passes light.

Also, the house is supported on blocks with wood floors. I'm planning on getting a big throw rug for the front of the room to handle first reflections from the l/c/r but bass seems to stay in the room longer than it should (standing wave?) like my head is inside a speaker cabinet. Are there ways to bass trap via floor modification? I can do some corner and maybe a few wood traps on the wall but if there's a way to stop the floor from shaking so much maybe that would be a good first step? I have plenty of crawlspace and willingness to fight the snakes for it.
The floor *is* trapping when it's shaking. Whatever freequency or frequencies makes it vibate is/are being absorbed. It's the frequencies that are not shaking the floor that are not being trapped and are, most likely, the source of your "head in a speaker cabinet" sensation. Need to know more about your room and it's construction to go further.

When I hang my 2'x4' panels vertically on the wall, approximately how far off the ground should they be placed? I know that it depends on the locations of my speakers (I have floorstanders and my center is mounted close to the ceiling pointed down), and of course they have to be mounted so that all FPR from all speakers hit each panel.

I have 2 rows of seats, with the second row on a 12" high riser, and I would prefer to have all my panels mounted level across the room so all/any help would be greatly appreciated.

When I hang my 2'x4' panels vertically on the wall, approximately how far off the ground should they be placed? I know that it depends on the locations of my speakers (I have floorstanders and my center is mounted close to the ceiling pointed down), and of course they have to be mounted so that all FPR from all speakers hit each panel.

I have 2 rows of seats, with the second row on a 12" high riser, and I would prefer to have all my panels mounted level across the room so all/any help would be greatly appreciated.
It entirely depends on the locations of the speakers and the audience. If you can do the mirror trick, do it. If not, you need to visualize what the path of each speaker's sound is to each seat. Angle of incidence = angle of reflection. Think bank shots in pool. I know aesthetics are important, but it just shouldn't figure into this equation.

The window will most likely reflect sound as uniformly as it passes light.
Glass will reflect higher frequencies and pass lower ones. Where that transition is will depend on the thickness of the glass.

Kal

Glass will reflect higher frequencies and pass lower ones. Where that transition is will depend on the thickness of the glass.

Kal
Thanks for "revising and extending" my comment.

Kevin,

In general, in most settings, if you mount the panels starting a 2' from the floor and extending to 6' up (assuming 2'x4' panels), you'll cover it. It offers enough vertical coverage for low or high speakers, risers, etc.

Bryan

Thanks Bryan, that is the advice I was looking for, now I just need to get my chairs so I can find the actual spots on the wall for my panels :)

Thanks Bryan, that is the advice I was looking for, now I just need to get my chairs so I can find the actual spots on the wall for my panels :)
Ceiling and back wall are first reflection points, too. IN my theater, "doing" the back wall made a huge difference.

I have the panels to treat the ceiling, so that is no problem, but I don't have anymore for the rear wall. I am not going to buy a 10 panel bundle, for only a few panels. When I am done, I will have all FRP on one wall treated for all seats (the second wall is over 25' away and decided to leave that alone; no decision either way was made when I asked about it in this thread), bass traps in all corners and 2 ceiling to wall corners, ceiling treated for the front row but not for the 2nd row (I hardly have guests over so if I am going to sacrifice I figured I would do it here).

Maybe in the future I will get more panels and add to the above but considering I had no treatment whatsoever to now having a considerable amount, even though I had to sacrifice in a few places, is good for me.

By the way, last night, just having my FRP panels leaning on the walls, until I get my chairs to put them in their permanent positions, I heard such a great difference that it put a smile on my face. I am far from an audiophile so I won't attempt to describe whether I heard a difference in the mids or highs, but the ability to hear panning from one side of the theater to the next was AMAZING compared to how it was pre-treatment. I clearly heard voices coming from the center of my screen and effects happening in either the left or right speakers. That alone was worth all the effort and money spent, I can't wait until they are up on the walls and I put the FRP on the ceiling. :D

I have the panels to treat the ceiling, so that is no problem, but I don't have anymore for the rear wall. I am not going to buy a 10 panel bundle, for only a few panels. When I am done, I will have all FRP on one wall treated for all seats (the second wall is over 25' away and decided to leave that alone; no decision either way was made when I asked about it in this thread), bass traps in all corners and 2 ceiling to wall corners, ceiling treated for the front row but not for the 2nd row (I hardly have guests over so if I am going to sacrifice I figured I would do it here).

Maybe in the future I will get more panels and add to the above but considering I had no treatment whatsoever to now having a considerable amount, even though I had to sacrifice in a few places, is good for me.

By the way, last night, just having my FRP panels leaning on the walls, until I get my chairs to put them in their permanent positions, I heard such a great difference that it put a smile on my face. I am far from an audiophile so I won't attempt to describe whether I heard a difference in the mids or highs, but the ability to hear panning from one side of the theater to the next was AMAZING compared to how it was pre-treatment. I clearly heard voices coming from the center of my screen and effects happening in either the left or right speakers. That alone was worth all the effort and money spent, I can't wait until they are up on the walls and I put the FRP on the ceiling. :D
Please let us know how big a smile you have when everything's in place! I'm especially interested in hearing your comments on the bass traps.

Unfortunately, I won't be getting my chairs for 4-6 weeks (I just ordered them), but I should have the bass traps up in a few weeks and I will let you know.

Have you put up your bass traps yet pepar?

Unfortunately, I won't be getting my chairs for 4-6 weeks (I just ordered them), but I should have the bass traps up in a few weeks and I will let you know.

Have you put up your bass traps yet pepar?
No, I haven't. I've gotten bogged down in home maintenance/repairs/upgrades and guests who just have to watch a movie. That's part of my interest in your comments after completing your installation.

I did buy an electric knife on ebay, though, and hope to rip the front of my theater apart next week and start stuffing it with 'glass chunks.

Well I finally got the room finished and the screen hung all to find out I am very UNDER impressed by the rooms sounds.

Using RoomEQ wizard confirms what my ears are telling me.

Between the two HUGE humps at 100hz and 6khz, there is SERIOUS comb filtering with or without my screen. Turning off the sub(s) does NOTHING to help the bump at 100hz. Running a room mode calculator found at www.RealTraps.com shows there is a mode right at 100hz. I have NO idea why there is such a huge bump at 6khz and a dip at 1khz. The only thing I can think of is my use of all Klipsch speakers. I have KLF-15's for the front, KLF-C7 for a center, and 4x KSP-S6's for surrounds.


So, anyone have any ideas on where to start? I have already tried putting 8, 4"x2'x4' OC705 (also tried left over OC703) panels in the front and back, but they only helped mildly.

I can include screen shots of the full frequency response and\or waterfall response of the bass end.

Stima:

Please:
a) start your own thread
b) 3D room dimensions and layout (a drawing or photos would be nice), including doors, windows, speakers, and listener and measurement positions.
c) What's in the room - chairs, carpet, absorbers, diffusers, strange shapes, etc
d) the RoomEQ shots
e) Have you tried single speaker near field measurements to see if there is a defective speaker?
f) What is a KLF-15 ? (I know what a KLF-C7 is)
g) Do you have your receiver's bass management turned on, and is it working (everything lower than 80hz going to a sub). Is it set to 100hz instead of 80hz?
h) Have you tried moving the sub into a null ?
i) Can you describe "UNDER impressed by the rooms sounds" in more detail. What didn't you like? In my case, for example, people are always talking about how great Master And Commander sounds with the cannons -- and they're not impressive at my place.

I did start my own thread...no one must of seen it. I mistakenly put it in the game room\media room area. :rolleyes: I will start one in this area and post back with the info. ;)

I did start my own thread...no one must of seen it. I mistakenly put it in the game room\media room area. :rolleyes: I will start one in this area and post back with the info. ;)
Maybe just post a link directly to the new thread so that those interested members on this thread can jump directly to it to follow your situation.

*EDIT* Corrected link :rolleyes:

Direct link to my thread: http://www.avsforum.com/avs-vb/showthread.php?p=7964198#post7964198

Any and all help will be welcomed. :cool:

Direct link to my thread: http://www.avsforum.com/avs-vb/newreply.php?do=newreply&noquote=1&p=7964198

Any and all help will be welcomed. :cool:
That link leads to a "post reply" screen to your thread . . .

Hi-

Well... after making my first purchase towards this project 6 months ago :eek: I finally had the time (where the wife and kids were gone) to make my first "superchunk" style, corner, bass trap.

I used
3 - pieces of a JM equivalent to OC703, 2" thick.
1 - FRK panel.
3 - 48"x1" dowels (from HD)
1 - 2'x2' 1/4" hardboard panel (from HD)
6 - screws
about 2 yards of speaker cloth from Joanns Fabrics

You can check out the superchunk info here (http://forum.studiotips.com/viewtopic.php?t=535) . I used the 24" pattern on the 3 pieces of fiberglass, and also added the full panel of FRK in front of that. To cut the triangles I used a straight-edge to score the panel with a utility knife, first lightly, then a little deeper. This created an internal channel for the $10 electric carving knife that I used to make the final cut. By the way, this method of scoring then cutting works really well. The internal channel guides the carving knife to the point where you could literally make the cut with little concentration.

The frame is made from the hardboard panes cut a little shorter than in half, diagonally. I used a hand saw because I don't own many power tools. The triangle was estimated using a dry-fit of the 1" dowel, the triangular fiberglass, and the 2" of the FRK.

The bolt of speaker cloth at Joanns was wide enough to use a straight peice of fabric.

No pics (yet) because my wife has the digital camera... sorry.

I'll try to measure the FR at a later date. I want to make a few more panel first.

...just excited to share...

Hi-

Well... after making my first purchase towards this project 6 months ago :eek: I finally had the time (where the wife and kids were gone) to make my first "superchunk" style, corner, bass trap.

I used
3 - pieces of a JM equivalent to OC703, 2" thick.
1 - FRK panel.
3 - 48"x1" dowels (from HD)
1 - 2'x2' 1/4" hardboard panel (from HD)
6 - screws
about 2 yards of speaker cloth from Joanns Fabrics

You can check out the superchunk info here (http://forum.studiotips.com/viewtopic.php?t=535) . I used the 24" pattern on the 3 pieces of fiberglass, and also added the full panel of FRK in front of that. To cut the triangles I used a straight-edge to score the panel with a utility knife, first lightly, then a little deeper. This created an internal channel for the $10 electric carving knife that I used to make the final cut. By the way, this method of scoring then cutting works really well. The internal channel guides the carving knife to the point where you could literally make the cut with little concentration.

The frame is made from the hardboard panes cut a little shorter than in half, diagonally. I used a hand saw because I don't own many power tools. The triangle was estimated using a dry-fit of the 1" dowel, the triangular fiberglass, and the 2" of the FRK.

The bolt of speaker cloth at Joanns was wide enough to use a straight peice of fabric.

No pics (yet) because my wife has the digital camera... sorry.

I'll try to measure the FR at a later date. I want to make a few more panel first.

...just excited to share...
And it is appreciated, too! Especially by me, as I have the materials, right down to the ebay-bought electric carving knife, to install SSCs behind my false wall. Pics, FR measurements, whatever you can post, will all be appreciated as well.

Thanks!

For those of you that didn't notice this thread in the subwoofer section, here is a thread that I started before I installed any treatments and after I installed some bass traps around my basement. If you go to post 53 of this thread (http://www.avsforum.com/avs-vb/showthread.php?t=689817) you will see what I did and my frequency response before and after.

Let me know what you think.

Acoustical Treatments question

what is the cheapest way to achive desired acoustics in a home theater?

Okay... here are a few shots from the second trap I made. Since this one was a little smaller than the first, I used 3/4" dowels. There are a few more shots in my gallery.

Empty Frame:
http://gallery.avsforum.com/data/507/medium/cornertrap_99_Small_.JPG

Laying in the wedges:
http://gallery.avsforum.com/data/507/medium/cornertrap_99_10_Small_.JPG

Getting ready for the final stretch and staple...
http://gallery.avsforum.com/data/507/medium/cornertrap_99_12_Small_.JPG

Finished product:
http://gallery.avsforum.com/data/507/medium/cornertrap_99_13_Small_.JPG

The dowel that goes in the corner is peppered with staples... it ain't pretty but it works.

Here are some shots of the beefier panel I made. In this case I put another piece of 2'x4'x2" FRK in front of the wedges and made the top and bottom panels a little larger. It came out very nice, imho. So nice, my wife said it looked good without me asking her opinion! :D

http://gallery.avsforum.com/data/507/medium/cornertrap_99_1_Small_.JPG

...and a view on the top...
http://gallery.avsforum.com/data/507/medium/cornertrap_99_5_Small_.JPG

It's better to have a filled tringular cavity than a hollow one?

Here are some shots of the beefier panel I made. In this case I put another piece of 2'x4'x2" FRK in front of the wedges and made the top and bottom panels a little larger. It came out very nice, imho. So nice, my wife said it looked good without me asking her opinion! :D
Very nice indeed, Tweakophyte. Will you be posting any measurements?

It's better to have a filled tringular cavity than a hollow one?
Hi GetGray, here's a very helpful site (http://forum.studiotips.com/viewforum.php?f=8) for acoustical treatments, including comparisons of different designs. I believe it is where Tweakophyte got his design/ideas.

Hi-

It will be a while before I can have a measurement session. It will only be FR... sorry.

Hi-

It will be a while before I can have a measurement session. It will only be FR... sorry.
How does it sound? :)

Hi-

I started a break-out thread here (http://www.avsforum.com/avs-vb/showthread.php?t=700442) because...
I made a short video of me doing my cuts, here. (http://video.google.com/videoplay?docid=3067566258802658704) Please note I could not find my mask, so that is part of an old t-shirt :) covering my face. Also, since I filmed this myself, my technique is not perfect. Really I just wanted to show how easy this stuff is to work with so you people on the fence can just go do it.
:D

How does it sound? :)

:) I'd love to give you a complete a/b, but that will be a while. I want to do some first-reflection treatment (6 more 2'x4' panels to make) and it will be a while before I can do some critical listening. I also will want to re-calibrate and re-eq the room with the treatments (I'll save the current curve for a potential, future a/b with and without the treatements.)

That said, I did do a little listening. There is a Chemical Brothers track that has a series of long, reverse bass sweeps. These sweeps are very revealing of the FR response of the room. They then go into a deep, musical bass beat which, in the worst of set-ups could sound obviously late (i.e. lots of smear and delay). I did notice it being tighter and smoother, but again, without an a/b session it could all be in my head ;)

Hi-

I started a break-out thread here (http://www.avsforum.com/avs-vb/showthread.php?t=700442) because...
I made a short video of me doing my cuts, here. (http://video.google.com/videoplay?docid=3067566258802658704) Please note I could not find my mask, so that is part of an old t-shirt :) covering my face. Also, since I filmed this myself, my technique is not perfect. Really I just wanted to show how easy this stuff is to work with so you people on the fence can just go do it.
:D
EXCELLENT!! Very informative!

Razor knife and an electric carving knife did make me wonder if it would turn into a self-amputation video . . . :D

Just got done using a very sharp fishing knife to cut 12 pieces of OC 703 into 17" x 17" x 24" superchunks. This will be enough to fill the 8ft void from my corners on both sides of the screen, ceiling to stage. I did like the video Tweak :) , however I found it easier to cut everything on a board on top of some saw horses. ;) It was easier on the back....

Tonight I'll be working on the framing to hold the chunks from falling over which will be covered with some nice black felt. Then onto some reflection point treatments.

I did like the video Tweak :) , however I found it easier to cut everything on a board on top of some saw horses. ;) It was easier on the back....


See... you missed my point. I wanted to show everyone what you could do with no tools, just a carving knife and an old T-shirt. :p

Just got done using a very sharp fishing knife to cut 12 pieces of OC 703 into 17" x 17" x 24" superchunks. This will be enough to fill the 8ft void from my corners on both sides of the screen, ceiling to stage. I did like the video Tweak :) , however I found it easier to cut everything on a board on top of some saw horses. ;) It was easier on the back....

Tonight I'll be working on the framing to hold the chunks from falling over which will be covered with some nice black felt. Then onto some reflection point treatments.
Make sure you check the acoustical properties of the felt. If it's not acoustically transparent (at mid to higher frequencies) it will be reflective. You may want that, but you should be aware of its effect before applying.

These are used for rear corner bass traps. I most likely will not use the felt when I work on my reflection treatments. BPape and Ethan did not see a problem with using this felt for corner bass traps. Besides, you can see light through the material, and it also passes the breath test. Low frequencies should not be an issue.

These are used for rear corner bass traps. I most likely will not use the felt when I work on my reflection treatments. BPape and Ethan did not see a problem with using this felt for corner bass traps. Besides, you can see light through the material, and it also passes the breath test. Low frequencies should not be an issue.
Sounds like you've already researched and addressed that issue then.

Ok, here's a couple of dumb questions for you all... Does a Insul-Shield type product have a surface that can be painted after it is installed? And rather than putting filler above it to even out the wall could I just place some moulding above it to separte it visually from the area above? The moulding might look like it is a little high on the wall but it seems like it would be easier than the other methods I've seen mentioned...

No - don't paint it - you'll mess up the absorbtive properties.

As far as not doing the wall tops and just covering the bottom - sure, you can do that.

Bryan

So then do the Insul-Shield type products come in different colors? I've also seen fabric panels, do those do basically the same thing as the Insul-Shield?

Insul-shield is not a room finish...it is a room treatment. Insul-shield is either installed behind fabric or wrapped in fabric.

GoM Fabric colour charts (pictures of the fabric's weave)
http://www.silentsource.com/gom_index.html
http://www.getridofnoise.com/FabritecColorChart.html

Hello guys :)

I got a question for the pros here. I made 1 of 8 little bass traps thats going up across the ceiling/front wall. They are 1 ft chunks that are 5 1/2'' thick. Im just wondering if Im wasting my time by making these?

http://i40.photobucket.com/albums/e220/titch--/Home%20Theater/basstrap-1.jpg

thx

Hello guys :)

I got a question for the pros here. I made 1 of 8 little bass traps thats going up across the ceiling/front wall. They are 1 ft chunks that are 5 1/2'' thick. Im just wondering if Im wasting my time by making these?

thx
this size will not have any effect at the low end - maybe not even into subwoofer frequencies.

Well, if you make enough of them, you'll get enough square footage to make some difference. The problem is that each one isn't that much surface area and they're not terribly thick.

Hey, they're better than nothing for sure - depending on what's inside and how they're constructed.

Bryan

I just finished my 8ft high 17" x 17" x 24" superchunk bass traps for the rear corners next to my HT Screen. I used OC 703 and built some frames out of 1" x 2" pine that I covered with black felt. Thanks to Bryan P. for all his advice.

http://img.photobucket.com/albums/v396/sirquack/LeftSuperchunkframe.jpg

http://img.photobucket.com/albums/v396/sirquack/Superchunksstacked.jpg

http://img.photobucket.com/albums/v396/sirquack/LeftSuperchunk.jpg

Below is a before/after graph, what do you all think. I think overall, there is some good improvement. I do notice a difference when I listen to music now, only with these 2 traps. :)

http://img.photobucket.com/albums/v396/sirquack/SuperchunkBA.gif

I plan to do some more bass traps asap, and then maybe look at some first reflection treatments. The room is about 30ft x 31ft overall, however, the HT portion is set back in one corner about 6ft, so really it is kinda L shaped. The back wall where the screen resides is 15ft wide and sits back 6ft to make it more private. After that 6ft, it opens up into the larger room. I also have 9ft ceilings.

I just finished my 8ft high 17" x 17" x 24" superchunk bass traps for the rear corners next to my HT Screen. I used OC 703 and built some frames out of 1" x 2" pine that I covered with black felt. Thanks to Bryan P. for all his advice.
Below is a before/after graph, what do you all think. I think overall, there is some good improvement. I do notice a difference when I listen to music now, only with these 2 traps. :)

I plan to do some more bass traps asap, and then maybe look at some first reflection treatments. The room is about 30ft x 31ft overall, however, the HT portion is set back in one corner about 6ft, so really it is kinda L shaped. The back wall where the screen resides is 15ft wide and sits back 6ft to make it more private. After that 6ft, it opens up into the larger room. I also have 9ft ceilings.
That's GREAT that your 24" face SSCs are absorbing below 80Hz, and especially below 50Hz. My plan is to build the 24" face version, but I was concerned that it would be necessary to build 'em with the full 34" face in the Studiotips design to get to the lower frequencies.

And excellent job aesthetically as well! Thanks for the post!

I guess I should of said that I already have 2 bass traps in my front corners, from floor to ceiling. I just wanted maximum coverage of the corners of my room. So I thought I would try and put something up by the ceiling/front wall as well.

These traps are made of some very dence/heavy fiberglass that I found, never seen anything like it before.

thx

Sirquack:

By any chance are your FL and FR speakers about 2' from the side wall and about 14" from the front wall (measured from center of tweater)?

Where in the room was that measurement taken?

SQ:

You Rock!

Sirquack:

By any chance are your FL and FR speakers about 2' from the side wall and about 14" from the front wall (measured from center of tweater)?

Where in the room was that measurement taken?
Beside the pictures showing that to be - roughly - the case, I get the impression that something in the FR charts told you this. Right?

Thanks Scott :)

Hi Bob! Off the top of my head the mains are about 22-23" from the front wall (the Axioms are 15" deep) and are about 26" from the side walls. I also have them toed in a bit, maybe to far? I saw on Ethan Winers website he has a picture where all the speakers point right at the prime listening position. I've never toed my mains in this much. Even if my Axioms are facing straight forward, the soundstage is great.

In both situations the SPL meter was placed on a tripod in my center recliner, exactly where my ears would be. This is also exactly 38% back from the front wall.

This is an old picture that does not include the above bass traps, in addition, the center channel is now mounted up further on the wall right below the screen.

http://img.photobucket.com/albums/v396/sirquack/Sideview.jpg

That's GREAT that your 24" face SSCs are absorbing below 80Hz, and especially below 50Hz. My plan is to build the 24" face version, but I was concerned that it would be necessary to build 'em with the full 34" face in the Studiotips design to get to the lower frequencies.

And excellent job aesthetically as well! Thanks for the post!

If you can fit a 34" one in your room then go for it. We built a prototype and found it to be HUGE! But if you have the space then go for it.

Glenn

If you can fit a 34" one in your room then go for it. We built a prototype and found it to be HUGE! But if you have the space then go for it.

Glenn
Even behind my false wall the 34" faced SSC would be a problem as it would encroach upon speaker mounts and even the false wall itself. If I ever build another house though . . .

It's better to have a filled tringular cavity than a hollow one?

A hollow one is definitely not as effective as a filled one. My concern is that if you're filling the entire cavity, the density of the fiberglass is less critical, and using a solid 703 superchunk style trap appears wasteful. A less dense product for starters is more "inviting" to moving air particles. It will reflect less sound. Energy conversion to heat through friction won't be as efficient as 703 or 705, but if you have enough fiberglass depth it will eventually happen deeper in the bowels of interstitial spaces. So if you place a 1 inch or 2 inch 703 FSK panel (with 45 degree miter cut sides) against a corner, floor to ceiling, and just stuff the cavity behind with fluffy R-38 insulation, you'd have an equally well performing bass trap. And it will cost a fraction of a solid 703 superchunk trap.
Tumara Baap

. . . So if you place a 1 inch or 2 inch 703 FSK panel (with 45 degree miter cut sides) against a corner, floor to ceiling, and just stuff the cavity behind with fluffy R-38 insulation, you'd have an equally well performing bass trap. And it will cost a fraction of a solid 703 superchunk trap.
Tumara Baap
You're right about the cost, but I'd want to see data on the "equally well performing" part vis-a-vis 703.

You're right about the cost, but I'd want to see data on the "equally well performing" part vis-a-vis 703.

Sorry, I was too casual in my choice of words. I meant something along the lines of "respectable performance" or "acceptable performance", or "for all practical purposes, very effective performance." As a matter of fact if one could shift some of the cost advantage to treating a greater surface area, any superchunk 703 superiority would be further negated, and maybe even trumped.
I don't know how the hard numbers would pan out of one versus the other. However, Ethan Winer has done tests juggling a number of variables, such as fiberglass density, surface area, and panel depth. The take home point was that beyond a certain depth of 8 inches or so, density of fiberglass makes a piddling difference to performance.

Tumara Baap

Sorry, I was too casual in my choice of words. I meant something along the lines of "respectable performance" or "acceptable performance", or "for all practical purposes, very effective performance." As a matter of fact if one could shift some of the cost advantage to treating a greater surface area, any superchunk 703 superiority would be further negated, and maybe even trumped.
I don't know how the hard numbers would pan out of one versus the other. However, Ethan Winer has done tests juggling a number of variables, such as fiberglass density, surface area, and panel depth. The take home point was that beyond a certain depth of 8 inches or so, density of fiberglass makes a piddling difference to performance.

Tumara Baap
If I hear you correctly - if finances make the choice between doing it as you suggest and not doing it at all, definitely choose the former. A large majority have nothing, so it would be a great improvement.

I thought I would update the above drawing to give you all a better idea of what the room looks like. Keep in mind this is not to scale. :)

Since I have completed my Superchunk Traps on the front wall, my next plans are to build some column traps to go in the rear corners.

I would also like to put some bass traps where the walls/ceiling meet in the HT area above where I'm thinking about putting some 1st reflection treatments. Also, I eventually might put some 1st reflection on the ceiling locations.

As you can see, there is a 10" bulk head dropped along the entire width of the room, I might be able to put some smaller bass traps up in the corner facing the screen?

What do you all think?

http://img.photobucket.com/albums/v396/sirquack/htroom4.jpg

Also, I have a few questions for using 703 for 1st Reflection Treatments:

1) First of all, am I correct in saying I want to leave some space behind the 703 and the wall, within the frame I build?

2) Also, do I want to use the FRK(scrim) on the side facing the room, or use regular 703 with no facing?

3) For those wall/ceiling treatments do most people use 2" thick or double up and use 4" thick 703?

Thanks in advance, Randy

...
Also, I have a few questions for using 703 for 1st Reflection Treatments:

1) First of all, am I correct in saying I want to leave some space behind the 703 and the wall, within the frame I build?

2) Also, do I want to use the FRK(scrim) on the side facing the room, or use regular 703 with no facing?

3) For those wall/ceiling treatments do most people use 2" thick or double up and use 4" thick 703?

Thanks in advance, Randy
For the treatment of first reflections:

1. There is no need to leave any space.
2. Don't face the FRK side towards the room.
3. A 2" thickness is enough.

- Terry

As Terry said you don't have to leave a space, but if you do it will pick up not only a little more low end (which all rooms need) but will also pick up more high end due to sound coming in from the sides also. If you do space it you don't want to have any facing on the back of the panel.

Glenn

Thanks guys,

Glenn, one question. When looking at the pictures of your 244's on the Audioholics review, it appears your spacing is built into the framing, however, I don't see any holes that would allow sound to come in from the sides? Are you saying the high end is traveling through the wood framing? Now when I look at the RealTraps design, it appears they have a slotted hole design around the perimeter of the frame, which appears to be aluminum?

Thanks, Randy

http://img.photobucket.com/albums/v396/sirquack/htroom4.jpg

Looking at this, is it important to have a bass trap in the bottom right hand corner (by your fridge) even thourgh it is 31 feet away.

Just looking for some expert advice. I have a similar set up....

thanks

Hey Kermie, BPape on this forum had told me once this might be a good idea. I'm still looking for suggestions as this is a very large room. I've noticed with my Axiom EP500 Sub, that this opposite corner seems to have a lot of low bass.

Thanks guys,

Glenn, one question. When looking at the pictures of your 244's on the Audioholics review, it appears your spacing is built into the framing, however, I don't see any holes that would allow sound to come in from the sides? Are you saying the high end is traveling through the wood framing? Now when I look at the RealTraps design, it appears they have a slotted hole design around the perimeter of the frame, which appears to be aluminum?

Thanks, Randy
Our frame is built to the back so the sides are open for sound to come in. Even though the panel does have a natural spacer to it I still recommend spacing it off the wall to let sound come in from the back. It will also increase the low end absorption.

Glenn

A hollow one is definitely not as effective as a filled one. My concern is that if you're filling the entire cavity, the density of the fiberglass is less critical, and using a solid 703 superchunk style trap appears wasteful. A less dense product for starters is more "inviting" to moving air particles. It will reflect less sound. Energy conversion to heat through friction won't be as efficient as 703 or 705, but if you have enough fiberglass depth it will eventually happen deeper in the bowels of interstitial spaces. So if you place a 1 inch or 2 inch 703 FSK panel (with 45 degree miter cut sides) against a corner, floor to ceiling, and just stuff the cavity behind with fluffy R-38 insulation, you'd have an equally well performing bass trap. And it will cost a fraction of a solid 703 superchunk trap.
Tumara Baap

Itchy!

Btw, it only took 3 panels to make the basic superchunk, and 4 when I added a piece of FRK to the larger one. It does take more time to cut, but I am not sure how much you'll save versus the PIA factor of using the fluffy stuff. I thought you were supposed to pack the fluffy stuff when you used it for trapping, like the way it is in the package. The panels cost me $9 (round numbers), so $18 for two. Just curious... How much would the fluffy stuff cost to fill the cavity?

I am itchy just thinking about it! :p

I used some chair glides and thich felt to give my panels some space away from the wall. I found that I liked having the space away from the front wall for deeper absorbtion, but the side walls looked better with thinner panels... until my wife saw them...

http://gallery.avsforum.com/data/507/medium/More_HT_05_Medium_.JPG

Here are some more shots...

http://gallery.avsforum.com/data/507/medium/More_HT_00_Medium_.JPG

http://gallery.avsforum.com/data/507/medium/More_HT_12_Medium_.JPG

Our frame is built to the back so the sides are open for sound to come in. Even though the panel does have a natural spacer to it I still recommend spacing it off the wall to let sound come in from the back. It will also increase the low end absorption.
Hi Glenn, can you point me to some data on that spacing? Every SSC installation I've seen has them tight in the corner.

If you goto our website it has the 244 as A mount, Recommended wall mount and recommended corner mount. The Recommended wall mount is spaced off the wall. If you can not find it drop me a email and I can send it to you. AVS really does not want companies putting links to there websites.

Glenn

If you goto our website it has the 244 as A mount, Recommended wall mount and recommended corner mount. The Recommended wall mount is spaced off the wall. If you can not find it drop me a email and I can send it to you. AVS really does not want companies putting links to there websites.

Glenn
Oh, OK, I'm familiar with standing panels off the wall. I evidently misunderstood (or didn't read) you to be saying the "chunk" bass trap should be spaced out - no pun intended from the corner.

Can anyone tell me how Auralex Sheetblock sound barrier would be used? Would it be placed like the linacoustic or other such things to absorb, or deaden a wall? or is it for some other purpose? How would something like that over Homosote work?

I know these are insanely simpleminded questions, but I know NOTHING about acoustics and after reading here and other sites for two weeks I still Know NOTHING about acoustics. I am a 54 year old mother of five and this stuff is not going to come easy for me.

I have a room that was my bedroom that already has a "stage" area and the makings of a home theather it is down a downsloping hallway 30 ft from my main house on a concrete slab. I will be retrofiting it not redoing from scratch.

My stage is 140" wide and my speakers in front will all be behind an SMX screen of yet undertermined size. currently there is a 30" deep bookcase area along this entire wall and I would like to use that as the area to mount the various speakers behind the screen but I see I need to either put backing behind them or encase them more or something.

It will be a 7.1 speaker system with a B&W cm center speaker, front speakers are KEF 102's , rears are KEF Q3's and surrounds are KEF TDM 34 DS Sub is Velodyne 12" forget model number.

the room is about 170" wide by 18' long I say about because it has some closets and other small side areas off the main part of the room.
I am going to have three rows of Stadium style seating.

I am finding many of these sound treatment items very hard to find, I can get Auralex items online but not many of the other things.

Any suggestions? and please remember I am a lady at least try to be nice! LOL

I am building some acoustical frames and some are 1.5 inches deep.

I have 1" Linacoustic to use for this.

My question is how tight should I have the Linacoustic up against the GOM Fabric. I tried to just snug fit it in there but it still falls too deep and I have about 1/4" gap between the GOM and the Linacoustic.

Options

1. build out the depth to 1"

2. add 1/4" or 1/2" of batting (the linacoustic is attached to the wall already.) ....

thank you for you help..


One more thing...

Would using plastic door screen material over the frame hurt. You can get it in rolls at HD. It would keep everything in and the GOM tight on top.

I'm soundproofing my ceiling in my basement, R-19 in-between joists & I'm trying to figure out what's the best way to go for the buck.
Would people suggest:
A. RSIC-1 Sound Isolation Clip snapped into a 7/8" drywall furring channel attached to 1/2" drywall
or
B. IsoMax Resilient Sound Isolation Clip snapped into a 7/8" drywall furring channel attached to 1/2" drywall?

Both seem to run about the same amount of money, but if I go with a RC-1, the price goes down quite a bit. I'm on a budget, but I don't want to do to little & regret it later, but if most think the RC-1 would keep most of the lows downstairs, it'd save me $ in the long run, but if not, would you recommend RSIC-1 or IsoMax clips?
Thanks!

"Would using plastic door screen material over the frame hurt. You can get it in rolls at HD. It would keep everything in and the GOM tight on top. "

Speak into it and if you can not hear it reflecting back at you then you might just be ok. I have never tried it but I could see how it could work.

Glenn

"Would using plastic door screen material over the frame hurt. You can get it in rolls at HD. It would keep everything in and the GOM tight on top. "

Speak into it and if you can not hear it reflecting back at you then you might just be ok. I have never tried it but I could see how it could work.

Glenn
I think he means (simply) plastic "screen." So, yes, you can talk through it.

I think he means (simply) plastic "screen." So, yes, you can talk through it.


That is funny...yep it is a "Screen". Something like this..



http://metroscreenworks.ewdcheckout.com/images/PET%20SCREEN%202.BMP

I am in the process of finishing a 16 wide by 22 deep dedicated theater, and would like to add ~8 acoustic panels plus bass traps in 3 corners. The theater is located on the 3rd floor, with bedrooms below. The walls are 1/2 in sheetrock and the floor is 3/4 with carpet and no special padding. Ceiling height is 8 feet; walls are 6 feet with a 45 degree pitch from 6 feet to 8 feet.

Sound transmission to the floors below is surprising low, so my main objective is to reduce room reflections and control bass.

I can get Roxul RHT 80 mineral wool (2", 8 pcf) for 60 cents a sq ft, or the 703 OC 2" FRK for $1.07. The acoustic properties for the RHT 80 listed on Bob Gold's site are comparable, but I have seen concerns in various threads about 8 pcf being too dense. I have not seen a conclusive explanation on the difference. At approximately 150 sq ft, we are only talking $60, but would like to understand if there is enough of a difference. (The RHT supplier is closer, easier to get)

Thanks

I've always liked referencing Bob Gold's Coefficient chart http://www.bobgolds.com/AbsorptionCoefficients.htm , but I noticed he stopped the chart after Owens Corning 1280. While 1280 had an absorption coefficient (a.c.) of 1.11, which is bested by 703 (1.19), I couldn't help but notice this information available from Owens Corning (http://sti.fmpdata.net/ftp/datasheet/PDS-SSAMW.pdf), that type 1212 has a 12lb/ft density, where as 1280 has an 8lb/ft density. Looking at Bob's chart, one could assume that density is the big factor in why 4" thick 1280 has an a.c. of 1.11 @ 125 hz, while 4" thick 1240 only has 0.88 a.c. @ 125 hz.

My thinking is that if 1280's 100% greater density than 1240 amounts to an additional a.c. of .23, 1212's 50% greater density than 1280 could add at least another .11, pushing 1212 to an a.c. of 1.23 @ 125hz.

I know I'm coming late to this party, but if someone has information on 1212, I'd greatly appreciate learning about it. As Dennis Erskine can attest, fiberglass bass absorption is not part of the HAA curriculum.

> 1280 had an absorption coefficient (a.c.) of 1.11, which is bested by 703 (1.19) <

You need to take that with a large grain of salt. Data like this is not absolute for a variety of reasons, and it's just as likely for a material that measures less in the second or even first decimal place to be better than another that measures higher.

> fiberglass bass absorption is not part of the HAA curriculum. <

Are you saying HAA does not understand the importance of broadband bass trapping? :eek:

--Ethan

> fiberglass bass absorption is not part of the HAA curriculum. <

Are you saying HAA does not understand the importance of broadband bass trapping? :eek:

--Ethan
No, I'm not saying that. But in the three days of training, so much was packed in that bass trapping (and Helmholtz resonators) were only spoken about for about an hour. There wasn't the kind of time to go into building bass traps for clients, what materials to make them out of, etc.

No, I'm not saying that. But in the three days of training, so much was packed in that bass trapping (and Helmholtz resonators) were only spoken about for about an hour. There wasn't the kind of time to go into building bass traps for clients, what materials to make them out of, etc.
What was the bulk of the course focused on?

What was the bulk of the course focused on?
We focused on the length of sound waves and their interaction with walls, reflective surfaces, goals of good sound (focus, response, dynamics), speaker placement, when sound waves become omnidirectional, math equations, using acoustic test equipment and test tones - the list goes on and on. We discussed bass trapping, but not building one.

Now back to my original question - anyone use and/or test the Owens Corning 1212 material?

No, I'm not saying that. But in the three days of training, so much was packed in that bass trapping (and Helmholtz resonators) were only spoken about for about an hour. There wasn't the kind of time to go into building bass traps for clients, what materials to make them out of, etc.

Isn't that like learning how to build a car but not telling you how to put the wheels on? :eek: :D

Glenn