There is a plastic sheeting with an adhesive back...comes in rolls. It is used by contractors over carpet to prevent soiling the carpet during construction. This makes a good membrane. You can also use 3mil or 6mil plastic sheeting as well.

Thank you both for your replies. I was looking at the 'Resonant Membrane, Flat Panel Traps' section half way down the page of this link.

http://home.comcast.net/~thomasw-2/SubwooferSetupandEQpage9.html

The picture with reference to Ethan's website shows a plywood front and then discusses aborption to 1/8" = 150 Hz, 1/4" = 110 Hz, and 3/8" = 87 Hz based on the thickness of the plywood. Is this design outdated or just not as effective?

Also, I should probably know better than to provide a link from a comcast related site. ;)

You cannot make an effective reasonably wide-band membrane bass trap with this heavy a panel/membrane. Think in terms of paper thickness, not MDF thickness. :) I will often design with faced fiberglass, with the paper facing outward. This reflects highs and boosts lows a bit (though not uniformly).

Terry, I have a question about your response that I posted in my build thread "3FB's Foreclosure Home Theater". I'd be interested in your thoughts or anyone else's thoughts. Thanks.

Thank you both for your replies. I was looking at the 'Resonant Membrane, Flat Panel Traps' section half way down the page of this link.

http://home.comcast.net/~thomasw-2/SubwooferSetupandEQpage9.html

The picture with reference to Ethan's website shows a plywood front and then discusses aborption to 1/8" = 150 Hz, 1/4" = 110 Hz, and 3/8" = 87 Hz based on the thickness of the plywood. Is this design outdated or just not as effective?

Also, I should probably know better than to provide a link from a comcast related site. ;)
Yes, those numbers look quite plausible for the 3 1/2" depth which is specified. But remember that these are narrow-band absorbers, tuned to one specific frequency. That's why I qualified my reply with the words "reasonably wide-band." A narrow-band absorber will absorb little outside of its narrow tuned frequency. It can be effective for a single problematic room mode whose frequency you know, but not as a general-purpose device.

I just received my microsuede samples from ATS Acoustics and it is definately the nicest suede I've received so far. However, I was under the impression that it would be acoustically transparent, or semi-transparent. Using the ever-popular blow test, I failed miserably. Was I incorrect in thinking this was supposed to have a more open weave? Is it supposed to be used as a reflective surface or over an absorptive one?

I have samples from other companies that are definately more open, but they don't look as nice. Has anyone used this material before?

I just received my microsuede samples from ATS Acoustics and it is definately the nicest suede I've received so far. However, I was under the impression that it would be acoustically transparent, or semi-transparent. Using the ever-popular blow test, I failed miserably. Was I incorrect in thinking this was supposed to have a more open weave? Is it supposed to be used as a reflective surface or over an absorptive one?

I have samples from other companies that are definately more open, but they don't look as nice. Has anyone used this material before?
Microfiber suede is usually associated - at least in my mind - with SEATS.

I agree, as I have it on my own loveseat and sofa. However, I was in a demo theater recently that had it on the wall and it looked great. After seeing it for sale by many acoustic panel companies, I started collecting samples. The stuff that looks good seems too thick and the thinner stuff looks terrible. I just thought it might be a nice alternative to GOM.

I agree, as I have it on my own loveseat and sofa. However, I was in a demo theater recently that had it on the wall and it looked great. After seeing it for sale by many acoustic panel companies, I started collecting samples. The stuff that looks good seems too thick and the thinner stuff looks terrible. I just thought it might be a nice alternative to GOM.Even though it might have more HF absorption than GOM, you have to consider whether that is a good or a bad feature for your particular use. I wouldn't use it for a speaker grill...........................

Walt here, with a bass trap question. Assume a round tube, 12" diameter x four feet long, to be filled with rock wool. Does one "stuff the tube" with no open inside space, or does there need to be an void of "x" inches in order to be effective?
Walt

Neither - for good results you need a tube that's at least 18 inches in diameter or larger. The tube should be thin cardboard, stuffed fully with insulation. Or don't use a tube at all. It's the insulation that does all the absorbing!

--Ethan

Walt here, with a bass trap question. Assume a round tube, 12" diameter x four feet long, to be filled with rock wool. Does one "stuff the tube" with no open inside space, or does there need to be an void of "x" inches in order to be effective?
Walt

Walt - as per Toole's Toome, he recommends a depth of at least 12 inches so that could mean starting with a 24" diameter tube cut in half for a 180degree arc to provide the 12" radius. Just like other bass traps, an air space between the wall and the back of the tube helps lower the LF bass trap absorption performance, provided it's full of fibreglass etc. You can elect to hang the tube away from the wall to create the air space OR do what I suggested which is to use 1"*2" wood pieces to hold back the insulation from springing towards the wall if the tube is hung flush with the wall.

Obviously there are many other ways to get to a 12" depth meaning using larger diameter tubes to start with and smaller arc angles, but I already sent you some info on that . . . I don't mind sharing it with others if interested . . .

I am interested. I am mounting half columns at a diameter of 16-18" on the walls and am thinking of adding some cotton batting or insulation to the back of them. More info would be awesome.:D

Walt - as per Toole's Toome, he recommends a depth of at least 12 inches so that could mean starting with a 24" diameter tube cut in half for a 180degree arc to provide the 12" radius. Just like other bass traps, an air space between the wall and the back of the tube helps lower the LF bass trap absorption performance, provided it's full of fibreglass etc. You can elect to hang the tube away from the wall to create the air space OR do what I suggested which is to use 1"*2" wood pieces to hold back the insulation from springing towards the wall if the tube is hung flush with the wall.

Obviously there are many other ways to get to a 12" depth meaning using larger diameter tubes to start with and smaller arc angles, but I already sent you some info on that . . . I don't mind sharing it with others if interested . . .
kevin: thx for the reponse, but, that is not the answer to the question.
is a 12" tube stuffed with rockwool effective, or, does there need to be a void in the center? i recognize that the 'hemi' you sent info about has an opening for air. that would be a different application for me.
again, my thanks
walt

I am interested. I am mounting half columns at a diameter of 16-18" on the walls and am thinking of adding some cotton batting or insulation to the back of them. More info would be awesome.:D

Adammb - If you use say an 18" diameter column (tube?), then even with a 180degree arc your radius is only 9" (i.e. radius = half the diameter) which is too shallow a depth according to Dr Floyd Toole's research. With the tube only extending into the room by 9" at it's deepest point it's not likely to work as low into the bass region as you'd like . . . Can you get a larger tube to start with or live with the column intruding into the room a bit more?

If you can't then here's the data you'll need to make some decisions around your column/tube. For an 18" diameter tube, the following represents (i) the arc angle in degrees, (ii) the arc circumfrance in inches, (iii) the distance it sticks into the room in inches, (iv) the chord length across the wall from one edge of the arc to the other in inches.

90 / 14 / 2.6 / 12.7
120 / 18.8 / 4.5 / 15.6
150 / 23.6 / 6.7 / 17.4
180 / 28.3 / 9 / 18

I hope you don't mind the 30degree increments for the data. For smaller tubes like your's I'd suggest going with a 180degree arc for max benefit.

Hope this answers your question. Do you know how the make the rest of the hemicylindrical tube?

Adammb - If you use say an 18" diameter column (tube?), then even with a 180degree arc your radius is only 9" (i.e. radius = half the diameter) which is too shallow a depth according to Dr Floyd Toole's research. With the tube only extending into the room by 9" at it's deepest point it's not likely to work as low into the bass region as you'd like . . . Can you get a larger tube to start with or live with the column intruding into the room a bit more?

If you can't then here's the data you'll need to make some decisions around your column/tube. For an 18" diameter tube, the following represents (i) the arc angle in degrees, (ii) the arc circumfrance in inches, (iii) the distance it sticks into the room in inches, (iv) the chord length across the wall from one edge of the arc to the other in inches.

90 / 14 / 2.6 / 12.7
120 / 18.8 / 4.5 / 15.6
150 / 23.6 / 6.7 / 17.4
180 / 28.3 / 9 / 18

I hope you don't mind the 30degree increments for the data. For smaller tubes like your's I'd suggest going with a 180degree arc for max benefit.

Hope this answers your question. Do you know how the make the rest of the hemicylindrical tube?

Great Info. I put it into a spreadsheet for my sanity, but cannot upload .xls files. I pasted it in, but it was all messed up.

Tube Diameter = 18"

Arc Angle (Degrees)
Circumference of Arc (inches)
Distance from wall when flush-mounted (inches)
Total width of circumference (inches)

90 14 2.6 12.7
120 18.8 4.5 15.6
150 23.6 6.7 17.4
180 28.3 9 18

If you have the formulas, I could plug them in so that anyone can plug in their tube diameter and it would automatically calculate the data. If you are interested, please look to see if the labels make sense to you.

Mark

Great Info. I put it into a spreadsheet for my sanity, but cannot upload .xls files. I pasted it in, but it was all messed up.

Tube Diameter = 18"

Arc Angle (Degrees)
Circumference of Arc (inches)
Distance from wall when flush-mounted (inches)
Total width of circumference (inches)

90 14 2.6 12.7
120 18.8 4.5 15.6
150 23.6 6.7 17.4
180 28.3 9 18

If you have the formulas, I could plug them in so that anyone can plug in their tube diameter and it would automatically calculate the data. If you are interested, please look to see if the labels make sense to you.

Mark

*************
Mark - glad the info was helpful. I use a great math website called Wolfram and here is a link to the app that will do all the calculations for you:
http://demonstrations.wolfram.com/SagittaApothemAndChord/

You'll have to download the demo s/w and then you need only to specify what the tube radius is and the arc in degrees and the other variables are automatically calculated.

You'll note that the terms "Sagitta" and "Chord Length" are the math terms for what you called "Distance from wall when flush-mounted" and "Total width of circumference" respectively.

I started off with a 48" diameter (24" radius) and charted all the values from 90-180 degrees for planning purposes. I then settled on 130degree arc for my room's side walls (one hemicylindrical diffuser per side wall).

So your saying I would be better to do a larger diameter tube and not use a complete half. So in essence it would be about 10-12 out but have a radius larger than 10-12 inches. So starting with a 24" and using less than half of it and having it come out 12" but still being about a 20" width? Then stuffing it with cotton or insulation and leaving a gap between the wall and the insulation?

So your saying I would be better to do a larger diameter tube and not use a complete half. So in essence it would be about 10-12 out but have a radius larger than 10-12 inches. So starting with a 24" and using less than half of it and having it come out 12" but still being about a 20" width? Then stuffing it with cotton or insulation and leaving a gap between the wall and the insulation?

Sounds about right. Just to be clear, if you use a small radius hemicylindrical diffuser with a hard outer layer, it will diffuse the mid/hi frequencies and only effect the upper bass (providing it's stuffed with fibreglass etc). (The radius distance is what determines how low the absorption will work to.) So what's wrong with only affecting 2/3rds of the freq range you ask? It throws off the spectral balance of your speakers you fell in love with. A smaller radius tube will work IF you put some seperate bass trapping above or below it if the intrusion into the room isnt to your liking. . .

By the way, where are you placing these columns and is it for HT for 2-channel stereo music?

Here is my plan.

Two columns down the sides of the wall spaced evenly and two columns on the rear wall about 4-5 in from the sides. I also have some auralex megalenrds that I will use in the front corners.

I am also contemplating to have false soffits that come out about 16" and stuffing them with cotton batting and then placing paper backing in front of them so the highs do not get absorbed.

For more than bass I was going to have panels in between the pillars that were filled with 3" cotton batting but not the full size in between the pillars.

My room is 19x22x7'4". If you want to take a closer look at my build it is the sweetwood 11.1 thread.

I have also been trying to figure out how to place my seating depending on the bass wave zones. Could you direct me to a place to determine this?

How does that sound?

I stupidly started a new thread regarding improving RT60 times in my room but will continue on here in this thread. In summary my room is about 2500sqft which I covered with fabric panels a couple years ago. During that time period I experimented with a few acoustic treatments but felt the overall presentation coupled with the fabric was a too dead sounding room. Returning to the issue I measured the RT60 times and posted the graphs in the initial thread here http://www.avsforum.com/avs-vb/showthread.php?t=1222093&highlight=

The past couple days I removed the panels and purchased a case of 2" OFI-48 FSK insulation (Ottawa Fiber) which best approximated the frequency specific absorption values I felt I required. After a day of experimenting with placement of the acoustic insulation I settled on just two 2'x4' pieces placed horizontally touching the ceiling on the left and right front side walls adjacent to the screen. After initially loading up the room with the acoustic panels and measuring about between 2 and 2.5ms across the board and listening to the result it was clear, in an underwater way, the room and music were way too dead for my liking so I decided to try to target RT60 in the mid 3ms range which the results are below, along with an impulse response graph.

Just a note that with a room of this relatively small size the effective RT60 is far from a constant value and easily influenced by typical usage, reclining my 6 theater chairs has a fairly dramatic effect on the overall RT60 as does adding a few people to the arena. As such the multiple conditions the theater will be used should be accounted for and factored into the target RT60.

Though I loved the look of the theater with the fabric on the walls I'll now be leaving the walls bare except for the black velvet on the ceiling and front wall area.

Quite a difference in the measurements. How does it sound?

Jeff

Quite a difference in the measurements. How does it sound?

Jeff

Overall I like the balance better for both mc movies and 2-channel music, the upper frequencies have a far more natural ting to them now and any recorded high frequency room ambiance is more apparent as well. A great benefit is also the fleshing out of the rear channels, removing the wall fabric has really improved the sense of rear space and the entire presentation is more enveloping. I'll be picking away at a few areas over the next month or so but so far I'm pleased. My wife is pissed however.

Overall I like the balance better for both mc movies and 2-channel music, the upper frequencies have a far more natural ting to them now and any recorded room ambiance is more apparent as well. A great benefit is also the fleshing out of the rear channels, removing the wall fabric has really improved the sense of rear space and the entire presentation is more enveloping. I'll be picking away at a few areas over the next month or so but so far I'm pleased. My wife is pissed however.
Looks like the bottom got cleaned up a lot. My experience is that doing that removes a "veil" that masks the mids and highs, and produces the differences in balance and envelopment you noticed.

The wife thing, too, is not unusual. You know, don't you, that they just .. don't .. understand. ;)

Looks like the bottom got cleaned up a lot. My experience is that doing that removes a "veil" that masks the mids and highs, and produces the differences in balance and envelopment you noticed.

The wife thing, too, is not unusual. You know, don't you, that they just .. don't .. understand. ;)

Actually my wife is pretty cool with anything I do down here. Regarding the "veil", I watched Surveillance last night and for the first time for a long time was completely mesmerized with the sound, I also threw on Kung Fu Panda which I use for reference purposes and that, not too surprisingly, sounded outstanding as well. It would seem that with a more consistent RT60 individual sounds are more fleshed out and image with more body almost like you can sense a front and a back to it and overall a much better sense of space between them.

Actually my wife is pretty cool with anything I do down here. Regarding the "veil", I watched Surveillance last night and for the first time for a long time was completely mesmerized with the sound, I also threw on Kung Fu Panda which I use for reference purposes and that, not too surprisingly, sounded outstanding as well. It would seem that with a more consistent RT60 individual sounds are more fleshed out and image with more body almost like you can sense a front and a back to it and overall a much better sense of space between them.
I'm sure that overall consistent (ly good) reverb times help, but I vote for the cleaned up LF ringing as the main dif in your sound quality.

Jeff

I'm sure that overall consistent (ly good) reverb times help, but I vote for the cleaned up LF ringing as the main dif in your sound quality.

Jeff

Astute observation on the LF ringing. With the left over insulation I fashioned a quick and dirty 8" thick trap and placed it in the back left corner. Here's a the updated LF waterfall which does show an improvement.

Astute observation on the LF ringing. With the left over insulation I fashioned a quick and dirty 8" thick trap and placed it in the back left corner. Here's a the updated LF waterfall which does show an improvement.
Still too much ringing way down low. You need more bass traps and to reach that low, they'd need to be biguns. Along with the peaks (ringing), they would reduce the nulls you see in the LF response.

http://www.peparsplace.com/Pg_23.htm

Play some music - jazz seems to work best IMO - with a walking bass run. Listen for louder and softer - and missing - notes. When you hear all notes equally, you are done.

Jeff

walt here. i asked this question a while back and received no responses.. perhaps because there IS no answer. however, i'll try one more time.
we cover f/g absorbing units with gom, a known material.
what happens if we use either plastic or wire screening material in lieu of the gom?
i have triangle (superchunk) f/g stacks in the rear corners(floor to ceiling), covered w/gom. if i covered with screening, would there be a change in the mid/hi reflection? the lows would not be impacted, but the other freq's??
again, this may be uncharted territory, but somehow i doubt it.
thx
walt

Still too much ringing way down low. You need more bass traps and to reach that low, they'd need to be biguns.

http://www.peparsplace.com/Pg_23.htm

Jeff

I'm not too sure how to read the waterfall charts what areas do you see the ringing problem, below 30hz?

I'm not too sure how to read the waterfall charts what areas do you see the ringing problem, below 30hz?
Yes, and it is the most difficult to reduce. Lots of bass trap volume is needed to do it.

walt here. i asked this question a while back and received no responses.. perhaps because there IS no answer. however, i'll try one more time.
we cover f/g absorbing units with gom, a known material.
what happens if we use either plastic or wire screening material in lieu of the gom?
i have triangle (superchunk) f/g stacks in the rear corners(floor to ceiling), covered w/gom. if i covered with screening, would there be a change in the mid/hi reflection? the lows would not be impacted, but the other freq's??
again, this may be uncharted territory, but somehow i doubt it.
thx
walt
Chicken wire???

Yes, and it is the most difficult to reduce. Lots of bass trap volume is needed to do it.

The 40hz null I'm pretty much pretty stuck with but below that I'm not going to even attempt to attack that with insulation as as you say it will take a lot of cubic feet which, I'm convinced will have likely have more than deleterious effects above 40hz. I suppose I could make my riser into a Helmholtz resonator with a frequency centered around the 20hz but I rather enjoy the free chair and body vibrating anti-nodes down low.

Chicken wire???
no, screening such as for screen doors, or (here in florida) lanai's.(pool cages)
walt

On the waterfalls, what I see is a much more consistent decay time, not so much improvement of the really bad ringing at the very low end. I think pulling in the 500Hz might have been more significant (as shown on the RT60)...
BTW, with REW, at least in the current version, you can't really trust the waterfall plots unless you've got the frequency axis in LOG mode, you're in LIN mode...

The 40hz null I'm pretty much pretty stuck with but below that I'm not going to even attempt to attack that with insulation as as you say it will take a lot of cubic feet which, I'm convinced will have likely have more than deleterious effects above 40hz. I suppose I could make my riser into a Helmholtz resonator with a frequency centered around the 20hz but I rather enjoy the free chair and body vibrating anti-nodes down low.

Actually, IF you were to put in enough broadband absorption to tame <30, it would do wonders to improve a null at 40 as well. It would be absorbing the reflections causing the cancellation that looks like a null, leaving only the direct sound: voila! That eing said, it sure would be a lot of absorption to make it look nice on the graphs...

The 40hz null I'm pretty much pretty stuck with but below that I'm not going to even attempt to attack that with insulation as as you say it will take a lot of cubic feet which, I'm convinced will have likely have more than deleterious effects above 40hz. I suppose I could make my riser into a Helmholtz resonator with a frequency centered around the 20hz but I rather enjoy the free chair and body vibrating anti-nodes down low.
You seem to have a good grasp of the problem and the associated pluses and minuses of attacking it.

I hear ya on the 20Hz node!

Jeff

no, screening such as for screen doors, or (here in florida) lanai's.(pool cages)
walt
That would certainly pass bass frequencies.

Actually, IF you were to put in enough broadband absorption to tame <30, it would do wonders to improve a null at 40 as well. It would be absorbing the reflections causing the cancellation that looks like a null, leaving only the direct sound: voila! That eing said, it sure would be a lot of absorption to make it look nice on the graphs...
Yes, of course, but lots of volume needed to reach down there. Probably need the 24" x 24" x 37" version of the SSC trap. Or a very large resonator. Still, there's usually lots of content at 40Hz in LFE that's being sucked out so I'd go for it.

Greg - I might have missed it, but what type of fabric did you have up before you took is all down?

Actually, IF you were to put in enough broadband absorption to tame <30, it would do wonders to improve a null at 40 as well. It would be absorbing the reflections causing the cancellation that looks like a null, leaving only the direct sound: voila! That eing said, it sure would be a lot of absorption to make it look nice on the graphs...

A few years ago I attempted to tame the 31hz peak by purchasing a few bundles of the OFI-48. After weeks of experimentation the only remedy of any significance was to create a wall of absortion floor to ceiling about 8 feet out from the back wall (approx 1/4 wavelength) of the offending frequencies. This was prior to the two rows of seating I presently have which now makes implementation of the same solution a rather unpleasant movie-going experience for those in the back row.

A few years ago I attempted to tame the 31hz peak by purchasing a few bundles of the OFI-48. After weeks of experimentation the only remedy of any significance was to create a wall of absortion floor to ceiling about 8 feet out from the back wall (approx 1/4 wavelength) of the offending frequencies. This was prior to the two rows of seating I presently have which now makes implementation of the same solution a rather unpleasant movie-going experience for those in the back row.
so - - -is the point that we go to the pros for a mega-buck solution?
ASC makes what seems to be an industry recognized product (tube trap) that professes to control the lowest freq.'s. perhaps gik and ethan winers companies have products as well. there is a link earlier in this thread that connects to a diy ASC imitation - no idea if it is as effective as the real thing.
perhaps when kevinzoe logs back on he will have some insights.
walt

That would certainly pass bass frequencies.

yes, but, would it be more reflective than gom? my guess is that it would, but, how to test?
as stated in my earlier post, i would hope that someone in this ether world would have the answer.
however, my thanks to pepar!
and now to my man cave for some viewing.
walt

yes, but, would it be more reflective than gom? my guess is that it would, but, how to test?
as stated in my earlier post, i would hope that someone in this ether world would have the answer.
however, my thanks to pepar!
and now to my man cave for some viewing.
walt
One of the acousticians on the thread might have an answer. Otherwise I only know that while there are websites that give test results for commonly used materials, I don't think that door screen is one of them. Is there a reason why you can't/don't want to use what many others have used - GOM?

I am always at a loss as to why everyone always assumes that "pros" cost mega-bucks? Some pros can be had for $500 for giving advice to do exactly what you you are looking for, and considering how much went into a room cost and time wise...will that honestly break the bank to bring your room alive! The best answer I can give in that arena is ask a pro how much they cost, get references (do they know what they are doing), and then decide if your time and unanswered questions are worth the cost of the technician.

There are often easier solutions than slapping up tons of fiberglass to tame bass modes. A good place to start is to determine if a peak or null is actually due to a bass mode. Then proceed from there.

I am not familiar with OFI-48, but...if it is not unlike other fiberglass insulation, it works best as a frictional absorber. Understanding how the stuff we breathe is behaving in a theater room is of great benefit to determine how to treat your room.

To answer your question regarding screen or plastic...best answer I can give is give it a try! Not much spent if it turns out to be a failed experiment...and you're right....just about everything you can almost think of has been tried at one time or another. It's not often the materials alone...it's the combination of such materials that may or may not make the difference. Best wishes! :)

There are often easier solutions than slapping up tons of fiberglass to tame bass modes. A good place to start is to determine if a peak or null is actually due to a bass mode. Then proceed from there.
What else would cause a null?

Jeff

I am not familiar with OFI-48, but...if it is not unlike other fiberglass insulation, it works best as a frictional absorber. Understanding how the stuff we breathe is behaving in a theater room is of great benefit to determine how to treat your room.

The OFI-40/48 material is made by Ottawa Fiber and specs as the equivalent of OC 700 series. The product sheet for the 48 FSK board is below.

http://rds.yahoo.com/_ylt=A0geu.03Gm5LQjcBgbJXNyoA;_ylu=X3oDMTE0ZjcwaHVmBHNlYwNzc gRwb3MDMgRjb2xvA2FjMgR2dGlkA01BUDAxNV83OA--/SIG=12hpf8m3f/EXP=1265593271/**http%3a//www.ofigroup.com/products/can_pdfs/FSK48-factsheet.pdf

What else would cause a null?

Jeff


Technically you are correct. A null is the result of a mode. I should revise that and say if not a null, what else is causing a loss of SPL at a certain frequency...or a dip. Could be several things. First thing to do though is to see if it is a null at that listening position which can be verified just by calculating the modes for the room.

Hughman...thanks for the info.

so - - -is the point that we go to the pros for a mega-buck solution?
ASC makes what seems to be an industry recognized product (tube trap) that professes to control the lowest freq.'s. perhaps gik and ethan winers companies have products as well. there is a link earlier in this thread that connects to a diy ASC imitation - no idea if it is as effective as the real thing.
perhaps when kevinzoe logs back on he will have some insights.
walt

**************
With such a low freq peak, the resistive-type bass traps aren't likely to be the best solution. I think a better alternative would be to use a combination of multiple subwoofers and parametric eq. Then if you still need trapping a membrane/diaphragmatic or helmholtz type would be better suited.

**************
With such a low freq peak, the resistive-type bass traps aren't likely to be the best solution. I think a better alternative would be to use a combination of multiple subwoofers and parametric eq. Then if you still need trapping a membrane/diaphragmatic or helmholtz type would be better suited.
1. Speaker position.
2. Listener position.
3. Acoustical treatments.
4. Electronic correction.

Many/Most of us do not have the option of #2 as they are usually dictated by room size and layout, seats present, display size and location, etc. In other words ... other factors.

For #1, many times subs can be moved around, but the factors restricting #2 also many times limit #1.

More should be done with #3 but it sometimes runs afoul of aesthetics ... and even room space limitations. Nonetheless, acoustical treatments of room modes can make a HUGE improvement. Certainly moving a sub so as to not excite a particular room mode makes sense - and is free - but the mode is not eliminated .. and other modes are not addressed. Bass traps reduce the reflections that are the cause of room modes ... all of them. Install enough of the right traps and the room's LF response smooths out and sounds amazing. Unfortunately, most people are so unfamiliar with smooth, flat bass that they feel something is missing when they hear it. (But that's another subject entirely.)

Number four is the icing on the cake, but I would strongly recommend that something like the SVS AS-EQ1 (and multiple subs) be used to correct LF response. Simple equalizers don't come close to the improvements from this piece of gear. And it improves over all of the listening positions, not just one. And it works partly in the time domain so it can help with ringing. Electronic correction is not a substitute for acoustical treatments, but it will improve just about any room/system.

Just my $.02.

Jeff

***********
Hughman - As RT60 is typically associated with concert halls and generally large volume buildings, have you tried measuring a RT20 or RT30 should be a more realistic measurement for the home-based room size? It might be interesting to compare a RT20/30 measurement with your previous RT60 . . .

Just a thought . . .

I stupidly started a new thread regarding improving RT60 times in my room but will continue on here in this thread. In summary my room is about 2500sqft which I covered with fabric panels a couple years ago. During that time period I experimented with a few acoustic treatments but felt the overall presentation coupled with the fabric was a too dead sounding room. Returning to the issue I measured the RT60 times and posted the graphs in the initial thread here http://www.avsforum.com/avs-vb/showthread.php?t=1222093&highlight=

The past couple days I removed the panels and purchased a case of 2" OFI-48 FSK insulation (Ottawa Fiber) which best approximated the frequency specific absorption values I felt I required. After a day of experimenting with placement of the acoustic insulation I settled on just two 2'x4' pieces placed horizontally touching the ceiling on the left and right front side walls adjacent to the screen. After initially loading up the room with the acoustic panels and measuring about between 2 and 2.5ms across the board and listening to the result it was clear, in an underwater way, the room and music were way too dead for my liking so I decided to try to target RT60 in the mid 3ms range which the results are below, along with an impulse response graph.

Just a note that with a room of this relatively small size the effective RT60 is far from a constant value and easily influenced by typical usage, reclining my 6 theater chairs has a fairly dramatic effect on the overall RT60 as does adding a few people to the arena. As such the multiple conditions the theater will be used should be accounted for and factored into the target RT60.

Though I loved the look of the theater with the fabric on the walls I'll now be leaving the walls bare except for the black velvet on the ceiling and front wall area.

I would also consider the Audyssey SubEQ. The designers of the SVS EQ were of course Audyssey. Trust me when I tell you that Audyssey saved the best elements for their product. The prices between the two are very comparable.

***********
Hughman - As RT60 is typically associated with concert halls and generally large volume buildings, have you tried measuring a RT20 or RT30 should be a more realistic measurement for the home-based room size? It might be interesting to compare a RT20/30 measurement with your previous RT60 . . .

Just a thought . . .

No I haven't plotted RT20 or RT30 I just used the RT60 tab in REW, is this a new development on the leading edge of typical HT sized room acoustics? A quick search for RT20 on this entire site shows your post is the very first mention of it.

I would also consider the Audyssey SubEQ. The designers of the SVS EQ were of course Audyssey. Trust me when I tell you that Audyssey saved the best elements for their product. The prices between the two are very comparable.
I do trust you, but think you might be exaggerating a bit. ;)

Using the Audyssey Pro balanced mic would be nice - as I have one - but it's not a deal breaker. Ditto MultEQ Pro. The Pro kits themselves are expensive and that needs to be factored in to the "total cost of ownership" for those who don't already own one. At least there are no license costs to use Pro on the Audyssey Subwoofer Equalizer.

Most people do not need to setup two subs in two independent systems.

Beyond those differences, they are identical. :)

Jeff

I finally finished reading this thread from the very beginning. I must say, I was changing my mind (planned approach) several times, as there is lots of contradictions and different opinions :)

At this point, I decided to start with treating first reflection points (side walls first) and the back of the room (second row is near the back wall). I am still not sure if I want to put any panels behind my speakers (front wall), but most likely yes. I am still shopping around, but definitely I will use 4" for the back wall and probably 2" for the side walls. At this point my room is not treated at all, just the carpet on the floor.
Here is the output from REW, the blue line shows measurements without subwoofer turned on and the brown one shows mains with a sub. Should I be drawing any conclusion from these measurements? I see several peaks and nulls ;)....

Thanks,
Wojtek

Hi Jeff,

Mic sensitivity is quite a bit different between the two as well, and after talking with Audyssey repeatedly over this issue, there are significant differences worthy of the minute cost difference...and, IMHO, SubEQ just looks nicer...but I digress :). In addition, the setup for the SubEQ is so easy, I generally don't ask much at all to install it. Takes me roughly an hour just for the SubEQ if I don't do secondary verification or any other work. There are distinct similarities, but for an extra few bucks, I would lean toward the SubEQ myself for the additional features.. Just personal preference. Nothing more. :)

Hi Jeff,

Mic sensitivity is quite a bit different between the two as well, and after talking with Audyssey repeatedly over this issue, there are significant differences worthy of the minute cost difference...and, IMHO, SubEQ just looks nicer...but I digress :). In addition, the setup for the SubEQ is so easy, I generally don't ask much at all to install it. Takes me roughly an hour just for the SubEQ if I don't do secondary verification or any other work. There are distinct similarities, but for an extra few bucks, I would lean toward the SubEQ myself for the additional features.. Just personal preference. Nothing more. :)
You're probably right about the calibrated Pro mic being better to use for the subwoofer setup. When I overlayed a Pro calibration on my system, I thought I heard an improvement in the LF and Mains/SW integration. Some of that is undoubtedly due to the better (and individually calibrated) mic.

Jeff

One of the acousticians on the thread might have an answer. Otherwise I only know that while there are websites that give test results for commonly used materials, I don't think that door screen is one of them. Is there a reason why you can't/don't want to use what many others have used - GOM?

no, not really. it is a question of the intellectual type - i covered my treatments with gom, but, the superchunks covered in screen might have added to room reflections, (screen vs:gom) . i was hoping for additional insights, but, this is somewhat arcane, i suppose.
this is all new to me, and at some point, a trained pro will need to make a visit.
walt

I would also consider the Audyssey SubEQ. The designers of the SVS EQ were of course Audyssey. Trust me when I tell you that Audyssey saved the best elements for their product. The prices between the two are very comparable.

HI,

Is your recommendation of the SubEQ a general one or is there something in my graphs which, in your experience, highlights a specific area I would benefit (apart from the sub 30hz decay times)? The graphs depict the output from my front left speaker which has it's low fequency augmented by the Submerive for which I'm utilizing an outboard Mirage LFX-1 for low pass duties but, presently, I do not use any eq on the sub. Ideally I require a unit which will accept and apply a low pass slope from full range left and right input signals. I'd also prefer to send LFE to the same sub therefore at the end of the day three inputs would be required one with an indepedant crossover frequency and all three inputs preferably balanced.

no, not really. it is a question of the intellectual type - i covered my treatments with gom, but, the superchunks covered in screen might have added to room reflections, (screen vs:gom) . i was hoping for additional insights, but, this is somewhat arcane, i suppose.
this is all new to me, and at some point, a trained pro will need to make a visit.
walt

If you already feel that maybe a "pro" will in your future, why not just do it now and get it over with? Kind of like ripping the band-aid off quick. It won't hurt as much if you do it now and quickly rather than wait and do it slowly. :D Heck, you may even decide it was well worth it. If the person you decide to choose is worth their salt, you'll learn more about acoustics in a day than a year sifting through this forum. The problem with this or any other forum is that you have to know the exact question you're seeking to ask, which often leads to another question, etc. Then, you have to sift through a somewhat disorganized jungle in order to perhaps put together an answer for your question. Provided of course that the conclusion or snipets of information are correct to begin with.

Hughman,

Audyssey won't really allow you to customize LPF. It's entire purpose is to adjust everything automatically...relatively speaking. There is a rudimentary customizable filter interface in the software, but I never use it. Not high enough resolution nor enough range for me. In addition, if you want balanced inputs, you'll want to go with the balanced SoundEQ rather than the SubEQ. If you want a parametric EQ that can be customized to your heart's content, I would suggest looking into the QSC DSP's.

Regarding your RT60, I would focus on trying to get an actual time decay overall and not frequency based. I only use frequency based decays for large venues where certain frequencies are more important than others such as the speech range...it just depends on the application. For small rooms, it can be argued that RT60 really has no bearing. I do believe you had a waterfall plot, too. I don't remember what was there, but equalization will assist in ringing as will seating and sub placement. They are all factors. Best wishes! :)

Technically speaking, there is no RT in a small room.

Technically speaking, there is no RT in a small room.

Practically speaking, there is. :)

And even technically, RT exists in small rooms just as for large -- it just starts at a high frequency. Where a large concert hall may have a smooth, reverberant sound field starting at maybe 20-30 Hz, a small room's may start at 200-300 Hz. Everything scales linearly. And modern multiplex cinema theaters are small enough not to fit neatly into the large or small room category.

- Terry

Dueling Acousticians?

Dueling Acousticians?
Happens all the time in the real world. :)

Den frequency response plot curve utilizing radio shack SPL meter & tripod center listening area after sound treatment panels & corner superchunk.

166325

Sorry for the attachment, as not sure how to make the image show up in post.

Anyways, a look at the results & any comments are most welcome.

Room Set-up-

17' w x 11' d x 8' h
Front main towers full range
Sub xover @ 80 Hz
Early reflection panels: l/ r sides, back, l/ r front & 24" x 64" superchunk left rear corner
Floors wood w/ large rugs (basement underneath)
Walls wood paneling
Ceiling sheet rock w/ R30 insulated attic

vvvvv Thanks pepar, much appreciated ! vvvvv

Copy this image to your desktop and use the "attachments" button (looks like a paper clip).

http://www.peparsplace.com/storage/den.JPG

As much as 20dB between peaks and dips....hmmmm. I don't think the super chunks are a workin'. :) Have you calculated the modes for your room and is your sub in the corner? You may want to experiment with placement a little. Best wishes! :)

As much as 20dB between peaks and dips....hmmmm. I don't think the super chunks are a workin'. :) Have you calculated the modes for your room and is your sub in the corner? You may want to experiment with placement a little. Best wishes! :)
Haven't seen the "before" ....

Dueling Acousticians?

Not at all - they're both right. :eek:

If the second and subsequent reflections are 60+ dB down, then it's a reflection rather than reverb because it dissipated too quickly to register as reverb which is RT60 by definition. But an empty bedroom size space can have real reverb.

What did I win? :D

--Ethan

Not at all - they're both right. :eek:

If the second and subsequent reflections are 60+ dB down, then it's a reflection rather than reverb because it dissipated too quickly to register as reverb which is RT60 by definition. But an empty bedroom size space can have real reverb.

What did I win? :D

--Ethan


Apparently everyone wins, my room acoustics have improved measureably just by knowing this.

Doublemint gum? :D
I was thinking something for diplomacy. :)

On your waterfall, switch the freq axis to LOG mode.

(I posted this in its own thread a little while ago, but it was suggested i posted here to get a response.)

I read about the "super chunks" in which you cut a bunch of triangles out of the rigid boards and stack 'm floor to ceiling in a corner. All the DIY "super chunk" corner traps seem to do the triangle shape in the corner. If you have the room to do a full square instead of a triangle, is that a better way to go or is it not? Are there reasons for having the diagonal face instead of a square corner? I have the space to do the full squares in the front corners of my room. I'm thinking 12x12 squares for example, instead of 12x12x17 triangles.

I have several other questions, but they are related specifically to my situation. To avoid clogging up this master thread with a discussion specific to my situation, i'm starting a separate thread for that. If you would, please visit it (linky (http://www.avsforum.com/avs-vb/showthread.php?t=1225293)) and let me know your thoughts. Thanks!

What did I win?
Nothing ... you missed the homogeneous part.

nothing ... You missed the homogeneous part.
+1

On your waterfall, switch the freq axis to LOG mode.
Based on a reply a day or two ago to a graph, I'm guessing that these are not showing an acoustically healthy room? My room sounds to dead to my ears...

http://www.peparsplace.com/storage/rt60.JPG
http://www.peparsplace.com/storage/waterfall.JPG

Hey guys,

What about a rear wall where the rear wall is 18 feet behind the listener and 35 feet from the front wall/screen?

Hey guys,

What about a rear wall where the rear wall is 18 feet behind the listener and 35 feet from the front wall/screen?

That's not such a big deal from a modal or from a near-reflection standpoint, but decay times are going to be very long in a room that large. You trade one for the other.

Frank

Thanks,

It is a huge room. I know on this thread it may not be considered large but in all other respects it is quite large being that it is 40' wide by 36' long. However it is "T" shaped in that after 14' from the screen the width goes from 40' to 20' wide. The 138" screen and front speakers are mounted at the center of the T. The front row is what you might call "out in the open" in that the back of that row is 14', the second row is located 17-18' which is well inside the narrow portion of the T.

I have an 8' x 12' starceiling printed on 1" 703 (glued to MDF) on the ceiling. The rest is up for suggestions?

Im sure this has been mentioned before, but... APs are such a little known beneficial part of any HT but moderatly confusing. Should the topic not have its own sub-forum?

I have a bunch of questions and some of the info in this thread is extremely dated.

Does anyone visit an A/V forum that has more info on APs?

Thanks,
Rob

Nothing ... you missed the homogeneous part.

Actually, I mostly agree with you on this Dennis. To me, in order to be true reverb the added sound must swell over some amount of time, not just come quickly and decay.

--Ethan

What formula should I use to calc a target decay time for my room??

What formula should I use to calc a target decay time for my room??

I'm unsure of the specific forumula but a mixture of formaldehyde, ethanol, and methanol helps with decay time considerably. Very helpful I know.

What formula should I use to calc a target decay time for my room??

I don't think there really is one. First, it's frequency specific, so we have to start with that. There's so much debate on this in terms of what is "appropriate" and what isn't. It seems highly subjective to me.

Frank

I'm unsure of the specific forumula but a mixture of formaldehyde, ethanol, and methanol helps with decay time considerably. Very helpful I know.
Can tequila be substituted for the ethanol?

Can tequila be substituted for the ethanol?

Tokillya, Ohh yeah, bad reflections though, what about that slap echo..OUCH! Nice to see this thread is alive and well.

I don't think there really is one. First, it's frequency specific, so we have to start with that. There's so much debate on this in terms of what is "appropriate" and what isn't. It seems highly subjective to me.
Could you point me to a resource that would help me understand the issue?

Jeff

Could you point me to a resource that would help me understand the issue?

Jeff

I don't wish to impose but I read this last night and thought it was interesting. Perhaps the author is considered a quack within the acoustician society and the writings no more than BS but it's an interesting read anyway.

http://rds.yahoo.com/_ylt=A0geut5GAXJLSLkAQ.JXNyoA;_ylu=X3oDMTE0c2o3am9wBHNlYwNzc gRwb3MDMQRjb2xvA2FjMgR2dGlkA01BUDAxNV83OA--/SIG=1251ukrga/EXP=1265849030/**http%3a//www.gedlee.com/downloads/Chapter%25204.pdf

I don't wish to impose but I read this last night and thought it was interesting. Perhaps the author is considered a quack within the acoustician society and the writings no more than BS but it's an interesting read anyway.

http://rds.yahoo.com/_ylt=A0geut5GAXJLSLkAQ.JXNyoA;_ylu=X3oDMTE0c2o3am9wBHNlYwNzc gRwb3MDMQRjb2xvA2FjMgR2dGlkA01BUDAxNV83OA--/SIG=1251ukrga/EXP=1265849030/**http%3a//www.gedlee.com/downloads/Chapter%25204.pdf

I see you've paid the good doctor's website a visit. That's Dr. Earl Geddes who's Ph.D. was in small room acoustics and who is now selling his own line of speakers and doing consulting also.

I believe he's reputable although some of his ideas appear to contradict Dr. Floyd Toole's and Todd Welti's. For example, Geddes is a strong believer that 3 subs of different makes/brands and kinds (yes, mixing sealed with ported) randomly placed within the room will give just as good or better small room bass than Todd Welti's research and modeling using up to 5,000 subs within a room. Geddes stipulates that one sub must be in a corner while another must be elevated, so strickly speaking it's not random placement . . .

What aspects of his Chapter 4 from his book do you think are BS? Most of what he writes is pretty mainstream and accepted wisdom. . .

I have a question for you guys. My room is on 11' x 15' x 8'. I only have 3 wall - wall corners that I can do ssc traps. The front wall I can only manage 17" x 12" x 12" traps in each corner but in the 1 corner I have in the back I can do a 24" x 17" x 17". Would that be ok or should they all be the same size?

What formula should I use to calc a target decay time for my room??

Pepar - here's the calculation for rever beration time: RT = 0.049V/A
V = the total volume in cubic feet
A = the total absorption in the room in Sabins, calculated by adding all of the boundary areas multiplied by their respective absorption coefficients. (e.g. square footage of drapes * its absorption coefficient + square footage of carpeting * its absorption coefficient etc etc)

Typical target RT's appear to range from .2 -> .4 +- and is pretty much an individual taste/preference.

I see you've paid the good doctor's website a visit. That's Dr. Earl Geddes who's Ph.D. was in small room acoustics and who is now selling his own line of speakers and doing consulting also.

I believe he's reputable although some of his ideas appear to contradict Dr. Floyd Toole's and Todd Welti's. For example, Geddes is a strong believer that 3 subs of different makes/brands and kinds (yes, mixing sealed with ported) randomly placed within the room will give just as good or better small room bass than Todd Welti's research and modeling using up to 5,000 subs within a room. Geddes stipulates that one sub must be in a corner while another must be elevated, so strickly speaking it's not random placement . . .

What aspects of his Chapter 4 from his book do you think are BS? Most of what he writes is pretty mainstream and accepted wisdom. . .

I'm a layman but there was nothing in his writing I considered BS at all, I really enjoyed the article. His wall flex absorption thing might not be a practical solution but I generally agree that there's order and a musicality in chaos. I thought his writings were sensible and easy to understand but I like to leave an open for those who wish to make a counter argument, and there always is. I had no idea who the author was but my own personal listening experience gives some personal merit to his sub location theory.

No I haven't plotted RT20 or RT30 I just used the RT60 tab in REW, is this a new development on the leading edge of typical HT sized room acoustics? A quick search for RT20 on this entire site shows your post is the very first mention of it.

RT60 hogs all the limelight so it's no surprise you haven't heard of RT20 or RT30 for small rooms. It's a concept borrowed from large concert halls and scaled down for domestic sized rooms. Many knowledgable people believe that RT is unimportant or irrelevant including D'Antonio and Eger (1986), Geddes (2002), Jones (2003), Kuttroff (1998). Part of the reason being is that the numbers measured are so small compared to concert halls and the noise levels are usually higher in the home which limits how far the volume can fall before the noise floor limits it falling further . . . make sense?

Pepar - here's the calculation for rever beration time: RT = 0.049V/A
V = the total volume in cubic feet
A = the total absorption in the room in Sabins, calculated by adding all of the boundary areas multiplied by their respective absorption coefficients. (e.g. square footage of drapes * its absorption coefficient + square footage of carpeting * its absorption coefficient etc etc)

Typical target RT's appear to range from .2 -> .4 +- and is pretty much an individual taste/preference.Maybe I should be looking for a target curve; decay time vs frequency? I think I've already decided that the low 200ms range is too dead ... for me.

RT60 hogs all the limelight so it's no surprise you haven't heard of RT20 or RT30 for small rooms. It's a concept borrowed from large concert halls and scaled down for domestic sized rooms. Many knowledgable people believe that RT is unimportant or irrelevant including D'Antonio and Eger (1986), Geddes (2002), Jones (2003), Kuttroff (1998). Part of the reason being is that the numbers measured are so small compared to concert halls and the noise levels are usually higher in the home which limits how far the volume can fall before the noise floor limits it falling further . . . make sense?

If RT60 times are typcially used for concert halls and othe large venue llive type events then there's going to be a disparity between production values and reproduction values, reproduction for intent and purpose of this thread being in the home. Similar to voicing your speakers to always sound like a piano if you voice the RT of your room to mimic the live event large room RT60, even adjusted for room size, then wouldn't targetting that same RT target for reproduction purposes essentially color the sound??

I'm not too sure I'm convinced noise levels in the home are louder than concert halls, generally when I'm in a concert hall scenerio the breathing, talking, coughing, yapping, bickering etc. generated from a hundred or hundreds of the annoying idiot event goers creates a noiseating floor far higher than what I can achieve at home, where there's generally just one or two offenders.

If RT60 times are typcially used for concert halls and othe large venue llive type events then there's going to be a disparity between production values and reproduction values, reproduction for intent and purpose of this thread being in the home. Similar to voicing your speakers to always sound like a piano if you voice the RT of your room to mimic the live event large room RT60, even adjusted for room size, then wouldn't targetting that same RT target for reproduction purposes essentially color the sound??

I'm not too sure I'm convinced noise levels in the home are louder than concert halls, generally when I'm in a concert hall scenerio the breathing, talking, coughing, yapping, bickering etc. generated from a hundred or hundreds of the annoying idiot event goers creates a noiseating floor far higher than what I can achieve at home, where there's generally just one or two offenders.

Regarding your sentance: "if you voice the RT of your room to mimic the live event large room RT60, even adjusted for room size, then wouldn't targetting that same RT target for reproduction purposes essentially color the sound"

I highly doubt that you can make a domestic room have an RT of several seconds which often is the case in concert halls etc due to their size and construction, so if you try adding delay from your processor then of course you're going to colour the sound. (By the way, are you really a CDN as you spelled colour without the letter 'u'?!?) Did I misunderstand your question?

Regarding your sentance: "if you voice the RT of your room to mimic the live event large room RT60, even adjusted for room size, then wouldn't targetting that same RT target for reproduction purposes essentially color the sound"

I highly doubt that you can make a domestic room have an RT of several seconds which often is the case in concert halls etc due to their size and construction, so if you try adding delay from your processor then of course you're going to colour the sound. (By the way, are you really a CDN as you spelled colour without the letter 'u'?!?) Did I misunderstand your question?

Looking at it another way, record a live event in a large hall which has RT60times of X then playback the same recorded event in the same venue under the same conditions. Does the direct/reverberation/overall presentation sound similar to the original or does the original venue reverberation times now color the sound.

And you questioning whether I'm Canadian cuts me to the bone I'm, at these very moments, blowing (in my nicely heated cabbed tractor I might add) and flooding an approx 40,000 square foot hockey rink on lake in in my back yard. I hope you're not one of those Canadian posers. :)

Looking at it another way, record a live event in a large hall which has RT60times of X then playback the same recorded event in the same venue under the same conditions. Does the direct/reverberation/overall presentation sound similar to the original or does the original venue reverberation times now color the sound.

And you questioning whether I'm Canadian cuts me to the bone I'm, at these very moments, blowing (in my nicely heated cabbed tractor I might add) and flooding an approx 40,000 square foot hockey rink on the lake in my back yard. I hope you're not one of those Canadian posers.

Sorry to have cut you to the bone - hope you're a fast healer:) What do you mean by a "CDN Poser" by the way? I'm in Toronto GTA, where are you?

As for whether the original venue's reverb will colour the recorded reverb of your scenario, I would expect that it might becasue it's equal in length to the recorded amount made in the same venue. For domestic-type rooms I don't think there is an issue becasue the RT time is less than what's been recorded. As Toole writes, "it seems that the basic audible effects of early reflections in recordings are well preserved in the reflective sound fields of ordinary rooms. There is no requirement to absorb first reflections to allow recorded reflections to be heard."

Sorry to have cut you to the bone - hope you're a fast healer:) What do you mean by a "CDN Poser" by the way? I'm in Toronto GTA.

Yes I'm quite resilent, we'd be extinct othewise. Just what I thought.:D Quelle heure est-il, colour est-il, color est-il.

As for whether the original venue's reverb will colour the recorded reverb of your scenario, I would expect that it might becasue it's equal in length to the recorded amount made in the same venue. For domestic-type rooms I don't think there is an issue becasue the RT time is less than what's been recorded. As Toole writes, "it seems that the basic audible effects of early reflections in recordings are well preserved in the reflective sound fields of ordinary rooms. There is no requirement to absorb first reflections to allow recorded reflections to be heard."

This appears somewhat constistent with what Geddes is saying regarding keeping, above bass frequency, absorption in small rooms to a minimum. Does Toole provide an opinion on the preservation of later recorded reflections or reveberations. Think I'll buy Tooles book, from the few snippets I've seen on the web it looks to be quite good.

Actually, I mostly agree with you on this Dennis. To me, in order to be true reverb the added sound must swell over some amount of time, not just come quickly and decay.

--Ethan
Think mode density and overlap, Ethan.

- Terry

Think mode density and overlap, Ethan.

I understand, and clearly modal ringing is a type of reverb.

--Ethan

I have B&W CCM817 located in the ceiling. Do you think installing a back box would have any acoustic improvement?

I have B&W CCM817 located in the ceiling. Do you think installing a back box would have any acoustic improvement?
It will do something...an improvement? Roll the dice. The speaker's response was based upon some (unknown to us) open cavity behind it. You make the cavity significantly smaller, you significantly change the performance and FR of the speaker. If you want a high performance speaker (and for that kind of money, I think you would), get a speaker that's already in a backbox from the manufacturer.

I have a question for you guys. My room is on 11' x 15' x 8'. I only have 3 wall - wall corners that I can do ssc traps. The front wall I can only manage 17" x 12" x 12" traps in each corner but in the 1 corner I have in the back I can do a 24" x 17" x 17". Would that be ok or should they all be the same size?

It will do something...an improvement? Roll the dice. The speaker's response was based upon some (unknown to us) open cavity behind it. You make the cavity significantly smaller, you significantly change the performance and FR of the speaker. If you want a high performance speaker (and for that kind of money, I think you would), get a speaker that's already in a backbox from the manufacturer.

I was kind of thinking the same thing. I have been in the HT hobby for a while and one thing that I have learned is that you really don't know how it's going to sound until you try it. People give a lot of good advice; but, you really don't know how it's going to turn out until you try it in your room. Anyway, thanks for responding.

I have a question for you guys. My room is on 11' x 15' x 8'. I only have 3 wall - wall corners that I can do ssc traps. The front wall I can only manage 17" x 12" x 12" traps in each corner but in the 1 corner I have in the back I can do a 24" x 17" x 17". Would that be ok or should they all be the same size?
The more, the better and the bigger, the better. But they do not have to be the same size. Install what you can.

I have a question for you guys. My room is on 11' x 15' x 8'. I only have 3 wall - wall corners that I can do ssc traps. The front wall I can only manage 17" x 12" x 12" traps in each corner but in the 1 corner I have in the back I can do a 24" x 17" x 17". Would that be ok or should they all be the same size?

17x12x12 is just a hair small...the arbitrary minimum width is usually 18". That said, you have to treat the room as-is unless you want to change it. The fact that they're different in the back than in the front isn't ideal, but it's not a huge deal.

Frank

I'm considering building a QRD (slat) diffuser for my back wall, with a design frequency of around 2000 Hz, whose wells will be bottomed by FRK faced rigid insulation. Behind the diffuser will be about 4" thick of rigid insulation on the wall.

The idea is this: frequencies below whatever the FRK reflects (1-2khz) will be absorbed by the 4" insulation (to a low cutoff, of course), and above that will be diffused. I read somewhere that diffusing frequencies above 1-2khz might be most beneficial to creating the aura of spaciousness that diffusion can provide. By keeping the design frequency this high, the minimum listener distance to the diffuser is kept as low as possible.

What do you think? Preferably, I'd like to use something other than FRK, from an aesthetic point of view, such as thin wood, like Luan or even veneer. Would that work?

Thanks,
John

I'm considering building a QRD (slat) diffuser for my back wall, with a design frequency of around 2000 Hz, whose wells will be bottomed by FRK faced rigid insulation. Behind the diffuser will be about 4" thick of rigid insulation on the wall.

The idea is this: frequencies below whatever the FRK reflects (1-2khz) will be absorbed by the 4" insulation (to a low cutoff, of course), and above that will be diffused. I read somewhere that diffusing frequencies above 1-2khz might be most beneficial to creating the aura of spaciousness that diffusion can provide. By keeping the design frequency this high, the minimum listener distance to the diffuser is kept as low as possible.

What do you think? Preferably, I'd like to use something other than FRK, from an aesthetic point of view, such as thin wood, like Luan or even veneer. Would that work?



Thanks,
John

John - Lets back up a tad . . . It sounds like your main constrain is to "minimize the listener distance to the diffuser" . . . have I got that right? How far is the back wall from the listeners?

DIFFUSER TYPE OPTIONS: If this is the main constraint, then you may be better to build a Skyline diffuser rather than the QRD; as the QRD only diffuses horizontally, the Skyline diffuses horizontally AND vertically so with less horizontal energy coming at you, you can affort to sit closer to the Skyline than the QRD. Another option is to place absorption in the middle of the back wall and diffusion on either side of it, which may increase the distance between it and the listener(s) . . . Still another option is a hemi-cylindrical diffuser but like the QRD it only diffuses in one dimension - horizontally when oriented vertically. The hemi diffuser allows you to stuff the concave interior with fibreglass and the low freq absorption is a funtion of the radius depth (greater radius=lower freq absorption); just put some wooden veneer/laminate that comes with a pre-glued backing on the front convex part so as not to absorb the mid/high frequencies. (I just finished building two of these hemi-cylindrical diffusers and have also build several Sklyines, so PM me if you want pictures etc.)

DIFFUSER HIGH/LOW DESIGN FREQUENCIES: How high a frequency do you think your QRD will diffuse to?:) Most QRDs won't diffuse higher than 3KHz-4KHz which would give you a whopping 1 octave of diffusion from your planned 2KHz "design frequency" - hardly worth it in my mind. With Skylines, it's the block size (not length) that determines the upper freq range -- even with a 1" * 1" block size for a Skyline as used in George Massenburg's famous Studio C, it'll only work as high as about 6.75KHz. The highest note on a piano is about 4,186Hz to give this upper freq design some context.

For the low freq design, I'd suggest it go down to the Schroeder/transition frequency which for domestic rooms seems to be between 300-500Hz, which is only a range of about 9-10 semi-tones (not even an octave). The QRD well depth and Skyline cell depth determines the low freq diffusion effectiveness. I would think your 4" of absorption behind the diffuser (whichever kind you choose) is a good idea or put it below or above it in the floor or ceiling corners. You could build a 'box' to sit your diffuser on and fill the box with fibreglass to act as the bass trap so you'd be absorbing low freq's and diffusing mid/high freq's thereby maintaining the spaciousness you seek.

I would guess that you're thinking is that rigid insulation at the back of the QRD wells will 'reflect' mid/high frequencies which may work for the highs but less likely to work for the mid's so use instead Luan wood or wood laminate that is hard enough not to absorb them.

Hope this helps . . .

There is a how-to online from one of the frequent posters here about using plywood and making a resonator. Due to the complexities of a resonator, if I wanted to just make a trap in the corner but wanted it to look like a column, could it be covered with thin 3/8" MDF or will that reflect too much to make it work as a trap? I can use fabric and cover it but I'd rather paint it if possible.

MDF in front of a fiberglass-only absorber will prevent the absorber from working. So the answer is no, don't do that! :D

However, brown "box" cardboard works fine if it's not really thick, because bass passes through it easily.

--Ethan

I beleive that builders plastic also works - but you'd want to cover that with a fabric frame.

MDF in front of a fiberglass-only absorber will prevent the absorber from working. So the answer is no, don't do that! :D

However, brown "box" cardboard works fine if it's not really thick, because bass passes through it easily.

--Ethan

Ethan - clarification question if I may - at what general frequency range will the MDF prevent the fibreglass behind it from working as an absorber? Obviously, MDF will reflect high frequencies (with short wavelengths) but where is the line in terms of MDF thickness or low frequency for the a 3/8 or 1/2 inch MDF when bass will still pass through it into the fibreglass behind it?

Thanks Ethan,

I see photos of people doing it a lot but I suppose either they just think it will work (and are wrong) or they are making a resonator of some sort which is beyond my skill set at this time. However, I did order Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms today so after 500+ pages of that and sleeping at a Holiday Inn Express I may be closer.

So uhm... given this graph, where should i start?? :eek:

http://img94.imageshack.us/img94/5016/waterfallsubplusmainsno.jpg

I'm no expert, but from what I understand that looks aweful, something royal.

What are the dimensions of your room?

I assume zero treatments?

built 2 of these for my open living room so far! hope they work well. and baaahhhh to my floor, it is not level at certain places.

first time building these, oc703, 2x2" per frame. birch plywood - homedepot crap grade, birch that looked perfectly flat, but wasn't. ripped to size on a table saw and miter saw i have never used before.
burlap adhered to the sides of the oc703 with scotch 90 spray adhesive. No adhesive on the faces that are not covered with wood. friction fit in the frame. approximately $50 in materials for the both, maybe even less.
http://i150.photobucket.com/albums/s87/ufokillerz/ht/IMG_0489_resize-1.jpg

So uhm... given this graph, where should i start??

Over. ;)

I'd start with a focus on your low frequency issues and then work up the food chain from there. Have you posted pics of this space?

So uhm... given this graph, where should i start?? :eek:
Thanks for posting. I don't feel so bad now. :D

I would start with bass traps ... in the corners. If you are a DIY'er, check here (http://forum.studiotips.com/viewforum.php?f=8&sid=6e1d0cecf237956da126a389242490af).

built 2 of these for my open living room so far! hope they work well. and baaahhhh to my floor, it is not level at certain places.Nice clamps.

Nice clamps.

yea thats to fix a crack in the plywood, applied gorilla wood glue, and clamp for a day till dry, these babies are fresh from my factory in the other half of the living room.

Over. ;)

I'd start with a focus on your low frequency issues and then work up the food chain from there. Have you posted pics of this space?

I agree. Something doesn't look right though. How big is this space?

Frank

I'm no expert, but from what I understand that looks aweful, something royal. That's kinda what i was thinking too yeah :o

What are the dimensions of your room? 16'7" x 13'9", ceiling (drop tile) is about 91" in the back 2/3rds, then 94" in the front 1/3rd.

I assume zero treatments? Correct. That's why i came to this thread to see if treatments would help cure some of these problems :eek:

Over. ;) Where's the LOL smiley when you need it :) In my old house in Marietta (your neck of the woods, i really need to stop by sometime!) i had a 14'x30' dedicated room, which sounded pretty decent to me. Moved to this new place in Canton in Nov '08, and the basement was the only place i could practically set up a small "HT". The sound here has been less satisfying than at the old place (as should be obvious from the graph!). Been too busy with other things this past year (moved to a horse farm, so there's always something to do), but now i'm finally making some time to sit down and tackle this room to see what i can do with it.

I'd start with a focus on your low frequency issues and then work up the food chain from there. I had EQ'd my sub before to try to get a decent bass response in the main seat. I got it fairly flat with a nice roll-off. But i know that EQ should typically be the last thing to do. So reading here about bass traps got me thinking i should probably look into those :)

Have you posted pics of this space? In another thread in the Audio Setup forum, but i'll repost them here if that's alright:

http://img682.imageshack.us/img682/4010/tvroom.png

This room is in the basement, which is underground. It's a poured concrete foundation. Drywall all around. Front wall of the HT room has the concrete behind it. All other walls are studs + drywall.

The sub (15", 2'x2'x4') i built myself for the HT room in our previous home, which was 14'x30'. This new room is only 13'9"x16'7", so the sub is a big massive in here now. It seems i have this nasty null at 40Hz. I assume that's partially due to the placement of the sub in the center on the front wall.

The mains are sitting on top of the sub, and the TV (42" LCD) on top of the main center. I'm hoping to get back to a front projection setup in the next year or 2 (waiting for 3D projectors to become more mainstream) and have a ~6' wide acoustically transparent screen.

I can see putting some good size traps (super chunk style) in the front corners. The rear is the PITA. It has three doors (closet, bathroom, garage) which means i can't do anything significant on that wall. In the rear left corner i have barely any room due to the door to the garage swinging in. In the rear right corner i have that funky corner poking out. I've been playing with designs for a super chunk style bass trap there, and came up with this:

http://img229.imageshack.us/img229/1306/basstraprr.png

That's a LOT of material though! I don't have a big budget allocated for this; a couple hundred bucks is all i can spare at the moment on this. I'm fine with DIY-ing it, just trying to figure out where to start.

Thanks for posting. I don't feel so bad now. :D You're welcome :o

I would start with bass traps ... in the corners. If you are a DIY'er, check here (http://forum.studiotips.com/viewforum.php?f=8&sid=6e1d0cecf237956da126a389242490af). Thanks, i'll read up some more there as well. Already been reading a ton about bass traps and other acoustic treatments using rigid fiberglass panels, and i'm hoping to be able to do some of that. Just trying to figure out specifics for my situation now.

I agree. Something doesn't look right though. How big is this space? Pretty small - 13'9" x 16'7". It could certainly be that i'm doing something wrong with the measurements. I used REW (4.11), my laptop, and a Radioshack SPL meter. Hooked up to my AVR, and did all the calibration in REW (soundcard, mic/meter etc), and then measured. Is there anything in particular that looks off to you in that graph, or just the whole thing? Did i perhaps do something wrong generating the waterfall? I just clicked the "generate" button after the measurement...

at what general frequency range will the MDF prevent the fibreglass behind it from working as an absorber?

It depends entirely on the thickness. I do not have hard data, but I imagine it's out there if you Google it. Or maybe someone here can post a link. I can tell you that 3/8 inch thick MDF is much too thick, but 1/32th inch thick wood veneer is probably thin enough to pass most bass frequencies okay.

--Ethan

I do not have any measurements from "before" I installed my acoustical treatrments, but here are the measurements with no electronic correction and then with both the SVS AS-EQ1 and Audyssey MultEQ Pro applied. I will soon be adding more traps to try to clean it up under 100Hz and will post more measurements then.

http://www.peparsplace.com/storage/no_correction.JPG
http://www.peparsplace.com/storage/ASEQ1_MultEQ_Pro.JPG

pepar - thats really rather impressive.....I can see another sub and MultEQ in my future

You sure you dont want to rip out your treatments for the fun of it so we can see? :D

What program/gear do you do your measurements with?

pepar - thats really rather impressive.....I can see another sub and MultEQ in my future

You sure you dont want to rip out your treatments for the fun of it so we can see? :D

What program/gear do you do your measurements with?
Umm, no, I'm not that curious. Plus I *remember* how (bad) it sounded before the traps.

Room EQ Wizard, an M-Audio MobilePre sound "card", Audyssey Pro mic w/3rd party cal file and a 32-bit Win 7 HP laptop.

Once you've had two, you can never go back to one ... sub. ;) Actually, I have four subs - collocated pairs.

Pepar,

Are you using frictional absorption for the bass or something else, and how much? Those decay times look quite low, is there anything about the sound quality which you might refer to as stuffy or dry?

General question for anyone, can floor resonances of the overhead floor cause significant 10-30hz ringing (I've been thinking for a long time this might be my issue ) and if so can absorption be a practical solution other than redesigning the floor?

Pepar,

Are you using frictional absorption for the bass or something else, and how much?
Twenty-nine lineal feet of 17x17x24 superchunked OC703. Check my website linked in my sig.

Those decay times look quite low, is there anything about the sound quality which you might refer to as stuffy or dry?
Yes, a bit. And that's why I am going to remove some of the 2" Linacoustic on my front wall, reduce the size of the front left and right first reflection point absorbers (2" OC SelectSound Black), mount diffusors above and below the newly sized absorbers and install some diffusors in the rear of the room. Not sure I'll net much because I am installing about another twenty-four lineal feet of superchunk in the rear. I really want to knock down the ringing below 80Hz.

So i figured i'd run a waterfall of the soundcard... This is what i got:

http://img682.imageshack.us/img682/7936/waterfallsoundcard.jpg

I do not know what i was expecting, but this doesn't look right to me. What do you think? What's it supposed to look like? Since it's the loopback, shouldn't it basically drop off right away instead of decaying that slowly?

EDIT:

Well, i ran the same test on a desktop computer, and its soundcard gives me this waterfall:

http://img269.imageshack.us/img269/8297/waterfallrealteksoundca.jpg

I guess that's normal for soundcards then? Still puzzles me a bit; I would expect the decay to be immediate...?

I don't think that "stuff" below 50Hz on the purple graph should be there. Is that a laptop's integrated sound?

Here is a waterfall of REW's measurement of my USB sound "card" from the process of generating a CAL file. It is more of a professional device, so the nearly ruler flat response doesn't surprise me. What does surprise me is how very non-linear the two are that you measured. Perhaps a waterfall of a looped back sound card is not a valid measurement; mine has a similar falloff like yours, but then has some sort of ongoing broadband noise that ... goes off a cliff like a gate closed just short of 250ms.

http://www.peparsplace.com/storage/mobilepre_waterfall.JPG

I don't think that "stuff" below 50Hz on the purple graph should be there. Is that a laptop's integrated sound? Yup, it's the laptop's integrated sound. I guess i should not be surprised that it has those problems in the low end.

Here is a waterfall of REW's measurement of my USB sound "card" from the process of generating a CAL file. It is more of a professional device, so the nearly ruler flat response doesn't surprise me. What does surprise me is how very non-linear the two are that you measured. Perhaps a waterfall of a looped back sound card is not a valid measurement; mine has a similar falloff like yours, but then has some sort of ongoing broadband noise that ... goes off a cliff like a gate closed just short of 250ms. Interesting, thanks for posting that. Looks like it might be normal for the soundcard waterfall to have that "horizontal cylinder" look then. And i'm wondering as well if the loopback test is not a valid measurement to graph a waterfall.

The red graph i posted is for the on-board audio of a cheap desktop i had sitting around. It's a Microcenter special, the sound chip is a RealTek. I'm not terribly surprised that it's not ruler flat. The "saddle" type curve seems to be inverse to the FR graph, interestingly enough. I do not know if REW is using the calibration of the soundcard in that waterfall to overcompensate perhaps.

My normal desktop has an Audigy card, and that card's FR is ruler flat as well. The problem was when i hooked it up to my AVR to test, i got a mid-frequency "hum", which i was unable to eliminate, so i couldn't use it to do further measurements :(

My normal desktop has an Audigy card, and that card's FR is ruler flat as well. The problem was when i hooked it up to my AVR to test, i got a mid-frequency "hum", which i was unable to eliminate, so i couldn't use it to do further measurements :(
A laptop on battery power is the way to go. But the integrated sound on laptops is usually not duplex, i.e. cannot output on one channel while inputting (the test mic's signal) on the other channel. So nearly everybody uses a USB device.

Thanks for the info Pepar. Just for kicks I turned off the audio to produce a waterfall of the room/house itself. First graph is room with fridge running upstairs, next is with fridge turned off. As you can see the fridge being situation on the same floor span as the HT ceiling creates quite a spike at 20hz and it's harmonic at 40hz, both would appear to be excitation of floor resonanes at sub-harmonics of the fridge motor. I have no idea what's causing the 34 and 43hz spikes.

Thanks for the info Pepar. Just for kicks I turned off the audio to produce a waterfall of the room/house itself. First graph is room with fridge running upstairs, next is with fridge turned off. As you can see the fridge being situation on the same floor span as the HT ceiling creates quite a spike at 20hz and it's harmonic at 40hz. I have no idea what's causing the 34 and 43hz spikes.
In professional movie location sound recording, one of the first things they teach is "unplug the refrigerator."
:)

- Terry

In professional movie location sound recording, one of the first things they teach is "unplug the refrigerator."
:)

- Terry

That would be lesson #2, lesson #1 is alternative methods of keeping beer chilled.

That would be lesson #2, lesson #1 is alternative methods of keeping beer chilled.
Craft services. :)

That would be lesson #2, lesson #1 is alternative methods of keeping beer chilled.
Actually, alcohol on the set is generally a no-no. Otherwise you may never finish shooting the movie! Gotta hold out until the wrap party. :D

Actually, alcohol on the set is generally a no-no. Otherwise you may never finish shooting the movie! Gotta hold out until the wrap party. :D

And the shaky-cam was born.

And the shaky-cam was born.

Actually, the real "shaky cam" was developed by director Sam Raimi.

Enough with the OT already! I'm the worst offender!! :D

Thanks for the info Pepar. Just for kicks I turned off the audio to produce a waterfall of the room/house itself. First graph is room with fridge running upstairs, next is with fridge turned off. As you can see the fridge being situation on the same floor span as the HT ceiling creates quite a spike at 20hz and it's harmonic at 40hz, both would appear to be excitation of floor resonanes at sub-harmonics of the fridge motor. I have no idea what's causing the 34 and 43hz spikes.

Nice graphs and interesting audio insight from that darn fridge . .
Remember I mentioned a little while back about the "noise" level of the house in relation to RT20/30/60 discussion? You've got at least 65-70dB background noise! Would the other noise be from say the furnace?

Nice graphs and interesting audio insight from that darn fridge . .
Remember I mentioned a little while back about the "noise" level of the house in relation to RT20/30/60 discussion? You've got at least 65-70dB background noise! Would the other noise be from say the furnace?

Hopefully the fridge noise is temporary, It's been moved while some reno's are being done in the kitchen, if not some isolation devices maybe in order (the wife's going to love that one). I have no other mechanical systems operating in the home except another fridge in a room next to the theater which completely slipped my mind and I suspect is the culprit of the 34/43hz noise.
I've suspected for a long time floor resonances from the span may have been causing problems with decay times down low and evidenced by the excitation of the 20hz peak induced by the fridge I think I may have been correct. I originally designed the ceiling/floor to flex and dissipate energy at 20hz, I wonder went wrong :D.

Further to my recent room waterfall, here's the latest with both refrigerators off. Also, with the room at the most quiet I can make it (except for desktop running adjacent to HT to run program) here's a comparison frequency response of the room with and without the projector running.

For the theater designers, what ambient noise levels do you target for a theater with the projector running.

Hughman - About all you can do is build a hushbox or buy a quieter projector.

Is that LF rumbling from the projector??

So i figured i'd run a waterfall of the soundcard... This is what i got:?
Before we bother talking about decay times, we've got to get the FR looking right... it looks like you've got the "C-Weighted Mic" radio button in the MIC tab of the settings window, which should be unchecked for running a loopback measurement, or for that matter any measurement where you're not using a C-Weighted mic...

Hughman - About all you can do is build a hushbox or buy a quieter projector.

Is that LF rumbling from the projector??

I think I'll have to leave it as is or by a more quiet projector. I have a shelf system which enables me to raise or lower the PJ to adjust for bulb aging (high power screen). I'm presently running the PJ on high lamp mode.

I surmise at this point the Sub 20hz noise is likely an artifact of the rather large lake I live on and the ice which is in a constant state of expansion/contraction.

Before we bother talking about decay times, we've got to get the FR looking right... it looks like you've got the "C-Weighted Mic" radio button in the MIC tab of the settings window, which should be unchecked for running a loopback measurement I'm 99% certain i had it unchecked for the loopback test. But thanks for that thought, i will check it again tonight or tomorrow night when i get a chance.

A few points about reading REW graphs for everyone:
1: When posting a waterfall, make sure the frequency axis is in LOG mode. There is a known bug with the Freq axis in LIN mode that makes the plot unreliable.
2: Post an FR along with the waterfall with the same graph limits to make it easy to match up.
3: When posting your FR, before making the jpg, make sure to check the soundcard cal and mic cal buttons under the plot to display these traces on the plot. This allow people to see where in the very low or very high end your data becomes unreliable due to the effect of the cal files on your noise floor.
4: Don't sweat persistent noise very low, unless you absolutely have to and are absolutely sure your setup has a noise floor capable of these measurements.

Somewhat afraid to post here as I think youll have a field day with this but Id love to get your thoughts. I realize the room will never be acoustically perfect.

Ok---been lurking here for years. Now getting serious and actually close to finishing my theater. Heres the catch....its in an outbuilding/barn/playhouse behind our house. Its a neat building with a large playroom/gymnasium. The theater will be in the loft that overlooks the play area. The theater is 20 feet wide by 30 ft deep. The first 20 ft of the loft will be theater, with a bar gathering area in the back 10 ft. Jason from AVS did my prewire when I was very ignorant. Now nearly two years later and I know a lot more (but still learning) and Im doing most of the finish work myself.

Heres the dilemma: the loft is open to the gym below. Roughly 18 of the 30 ft of wall are open to below. Now I know the audiophiles are going to freak, but it is a cool thing to see. Hopefully these pics I post show up.

I dont care about limiting sound in the sense that its a separate building so I dont care about sound getting into the gym. We wont be playing hoops and watching movies simultaneously. I am very concerned when watching movies about echo bouncing back from the gym. So--Id like to be able to close off the opening during movie watching (I dont think it will matter much while watching sports as I likely wont be cranking the sound). Ive got some thoughts but would like to see what the forum thinks.

Thanks in advance....heres the pics to help explain:



http://i746.photobucket.com/albums/xx101/MUTTSx3/IMG_3228.jpg

http://i746.photobucket.com/albums/xx101/MUTTSx3/IMG_3230.jpg

http://i746.photobucket.com/albums/xx101/MUTTSx3/IMG_3229.jpg

Tony

Twenty-nine lineal feet of 17x17x24 superchunked OC703. Check my website linked in my sig.


Yes, a bit. And that's why I am going to remove some of the 2" Linacoustic on my front wall, reduce the size of the front left and right first reflection point absorbers (2" OC SelectSound Black), mount diffusors above and below the newly sized absorbers and install some diffusors in the rear of the room. Not sure I'll net much because I am installing about another twenty-four lineal feet of superchunk in the rear. I really want to knock down the ringing below 80Hz.

I'd just remove all first reflection point absorption so your room isn't as dead assuming your waterfall is accurate.

Hi, Looking to improve my Room Acoustics as they are probally needed.. All I have availble is a SPL Meter along with a Test Tones CD. Will I be able to test my room with that or do I need a Fancy Gizmo to do the readings??

Here is a Pic of my Room it is in the Basement with the Right and Rear wall being Cynderblocks with Drywall over... On the Front and Left Wall When I built it I put in 2" Insulation between the Studs to the Ceiling, the Styrofoam kind of Insulation..

Would Someone be able to tell me what to Add or do I need to make Measurments first??


http://img230.imageshack.us/img230/2163/htlayout.jpg
By the_nephilim (http://profile.imageshack.us/user/the_nephilim) at 2010-02-16



Also here is my Webpage with some Before and after shots. Also I havea 7' Drop ceiling and did NOT put any insulation inbetween the Joists above the ceiling Should I??


http://home.comcast.net/~glafsr/wsb/html/view.cgi-home.html-.html

http://s746.photobucket.com/albums/x...t=IMG_3228.jpg

Can't open the link...well, I can but it just takes me to the photobucket home page.

Frank

I'd just remove all first reflection point absorption so your room isn't as dead assuming your waterfall is accurate.
Thanks, Mike. The FRP absorbers are needed. There are other things I can do to increase reverb time if I want to.

Jeff

Can't open the link...well, I can but it just takes me to the photobucket home page.

Frank

Fixed....pics now in post. Blame the new guy!

Tony

Thanks, Mike. The FRP absorbers are needed. There are other things I can do to increase reverb time if I want to.

Jeff

You don't need the FRP treatment. They don't do anything beneficial, probably more harm than good being only 2" thick. They basically take your speaker's off-axis response and strip away the higher frequencies and send you back stuff between 200-500hz. I find treating the FRPs hurt dialogue in my experience. I would at least suggest taking the side and ceiling treatment down and seeing how it sounds. You can always put it back up.

You don't need the FRPs. They don't do anything, probably more harm than good being only 2" thick.
I had the benefit of using my theater without the absorbers for a while and then adding them one or, in the case of the front left and right, two at a time. I can assure you that they are doing a lot in the way of improving imaging of LCR. I understand your comment about them being only 2", but the bass traps handle what would be absorbed by increasing to 4".

I had the benefit of using my theater without the absorbers for a while and then adding them one or, in the case of the front left and right, two at a time. I can assure you that they are doing a lot in the way of improving imaging of LCR. I understand your comment about them being only 2", but the bass traps handle what would be absorbed by increasing to 4".

I'm talking about 200-500hz reflections coming from the FRPs. Bass traps in corners will not magically remove those.


There's a lot of information here if u have a little bit of time.

http://www.harman.com/EN-US/OurCompany/Technologyleadership/Documents/Scientific%20Publications/13686.pdf

I'm talking about 200-500hz reflections coming from the FRPs. Bass traps in corners will not magically remove those.
Ahhh, I see. Well, it is possible to up them to 4" because I am considering reducing them from 48x48 to 24x48 and mounting diffusors above and below them, and the diffusors will likely be 4" or so.

http://www.harman.com/EN-US/OurCompany/Technologyleadership/Documents/Scientific%20Publications/13686.pdf
Yeah, I've read that doc before. Dueling acousticians is what I see. Toole likes all lateral reflections, Geddes doesn't like the first(/early?) reflections, but likes the rest of them ... and they both can explain why.

Jeff

Toole doesn't mention personal preference but what the experiments tell him. I don't know if Geddes has some preference or he actually has data to say that first reflections are bad.

Edit: I actually have found some of his papers and am reading them over. I found this quote "Toole is a strong proponent of a large amount of VER (me-very early reflections but I don't know what they are) because of its increase of the spaciousness effect. He appears to discount the negative aspects of this on imaging however. (Dr. Toole, does not make many statements about "image", perhaps being concerned over its loose definition).

I think if you are going to tame the early reflections you should make the treatment at least 4" no matter who is correct on this matter.

Toole doesn't mention personal preference but what the experiments tell him. I don't know if Geddes has some preference or he actually has data to say that first reflections are bad.
OK, OK, if you're going to parse it that precisely, I guess I characterized it as personal preference for the purposes of saying it simply. They both use their data to support their positions. Geddes' data "says" first reflection smear the image and I agree based on my own experience in my theater.

Jeff

Can anyone clarify on whether or not you need to have A/T cloth on side wall treatments. I am wanting to have a 3-4" side wall treatments and want something that looks better and possible cheaper than GOM. I am going to use GOM for the front wall and speaker cloth for my false soffits but am wondering about the fabric to wrap around the side wall treatments.

The more I read the more that people say the opposite things. My guess is to use a fabric that is somewhat of a loose weeve but looks good and does not have a high reflective amount to it.

Any and all advice would be greatly appreciated as I want to order the GOM today and need to know if I need to order for the side walls.

Also, if I dont use GOM then I have a larger selection of colors.

I am working on building a pair of diffusors to place at the front wall behind my Magnepan 1.6's. The speakers are 19" wide by 65" high and I was going to make the diffusors 2'x4'. Is this a proper size or should they be wider/taller?

Also, how much distance should be between the speakers and diffusors? Is 3' to 4' enough? From what I have read, the distance is more critical between the listener and diffusor than it it is for the speaker and diffusor. Is this correct?

Thanks

Can anyone clarify on whether or not you need to have A/T cloth on side wall treatments. I am wanting to have a 3-4" side wall treatments and want something that looks better and possible cheaper than GOM. I am going to use GOM for the front wall and speaker cloth for my false soffits but am wondering about the fabric to wrap around the side wall treatments.

The more I read the more that people say the opposite things. My guess is to use a fabric that is somewhat of a loose weeve but looks good and does not have a high reflective amount to it.

You don't need to use GOM for wall treatments. If you want to make the best use of the absorptive material behind the fabric over the largest range of frequencies, make sure that you can blow through it relatively easily.

The rooms I design have calculated characteristics based on the absorption and diffusion of the materials in the room. If somebody is using a marginally acoustically transparent fabric, I need to know about it. But most people play it by ear, and don't hire an acoustician or do any math or modeling.

- Terry

You don't need to use GOM for wall treatments. If you want to make the best use of the absorptive material behind the fabric over the largest range of frequencies, make sure that you can blow through it relatively easily.

The rooms I design have calculated characteristics based on the absorption and diffusion of the materials in the room. If somebody is using a marginally acoustically transparent fabric, I need to know about it. But most people play it by ear, and don't hire an acoustician or do any math or modeling.
<rim shot> groan

<rim shot> groan

Hahaha....:D

Frank

You don't need to use GOM for wall treatments. If you want to make the best use of the absorptive material behind the fabric over the largest range of frequencies, make sure that you can blow through it relatively easily.

The rooms I design have calculated characteristics based on the absorption and diffusion of the materials in the room. If somebody is using a marginally acoustically transparent fabric, I need to know about it. But most people play it by ear, and don't hire an acoustician or do any math or modeling.

- Terry

I have read other posts saying this same thing about fabrics. Are there any exceptions to this rule?

I just received fabric swatches from a company that makes acoustic absorption panels. My wife picked one but it really doesn't allow air to pass easily. It is a microsuede fabric. Even though the company uses this fabric, is it still acceptable?

I have read other posts saying this same thing about fabrics. Are there any exceptions to this rule?

I just received fabric swatches from a company that makes acoustic absorption panels. My wife picked one but it really doesn't allow air to pass easily. It is a microsuede fabric. Even though the company uses this fabric, is it still acceptable?
I have measured only one "microsuede" fabric, and it reflected 4 dB at 1 kHz. That's more than half the sound energy unabsorbed! So you end up wasting a lot of potentially efficient panel area.

I know, companies sell these as acoustic panel fabrics. But they don't necessarily know anything about them.

- Terry

I have measured only one "microsuede" fabric, and it reflected 4 dB at 1 kHz. That's more than half the sound energy unabsorbed! So you end up wasting a lot of potentially efficient panel area.

I know, companies sell these as acoustic panel fabrics. But they don't necessarily know anything about them.
They point out how good they look and how they match the recliners. ;)

They point out how good they look and how they match the recliners. ;)

Exactly - They do look nice and match the sofa. :o Figures that was the one she picked over the other style they sell: Jute burlap. It was already hard enough selling her on the panels.

Are there any better acoustical fabrics out there? I'm going to send for some Guilford swatches to see what their quality is like.

Are there any better acoustical fabrics out there? I'm going to send for some Guilford swatches to see what their quality is like.
I don't know about "better quality." Guilford FR701 is top quality, and has been used in commercial applications for many years.

As for other fabrics, Jo-Ann has a couple of them that rate high enough in acoustic transparency to be used as speaker grill cloth: their speaker grill cloth (duh!), but also their burlap. I can make no representation as to quality or safety. One thing you buy with Guilford FR701 is peace of mind. It has fire ratings up the wazoo.

I am setting up what to use for bass traps in my false soffits and also my acoustical panels. I have been looking for acoustical cotton batting and find it quite expensive. Can I use insulation instead?

Has anyone done this before. I am a bit concerned having it exposed in my room because its itchy but you wont be able to see any of it as it will be behind fabric.

Can anyone chime in on the differences between insulation and cotton batting?

I am setting up what to use for bass traps in my false soffits and also my acoustical panels. I have been looking for acoustical cotton batting and find it quite expensive. Can I use insulation instead?

Has anyone done this before. I am a bit concerned having it exposed in my room because its itchy but you wont be able to see any of it as it will be behind fabric.

Can anyone chime in on the differences between insulation and cotton batting?

Insulation will work fine...preferably 4-6lbs mineral wool or Owens Corning 703. If you're covering it with fabric it'll be absolutely fine. There won't be any fiber migration to speak of.

Frank

I don't know about "better quality." Guilford FR701 is top quality, and has been used in commercial applications for many years.

As for other fabrics, Jo-Ann has a couple of them that rate high enough in acoustic transparency to be used as speaker grill cloth: their speaker grill cloth (duh!), but also their burlap. I can make no representation as to quality or safety. One thing you buy with Guilford FR701 is peace of mind. It has fire ratings up the wazoo.

I'm going to try JoAnn's this weekend. The bad thing about their speaker cloth is the limited color choices. My wife liked the microsuede because she thought the burlap would be a "dust collector." :rolleyes:

I can get a couple free swatches of the GOM. I will definitely check them out.
Thanks

Insulation will work fine...preferably 4-6lbs mineral wool or Owens Corning 703. If you're covering it with fabric it'll be absolutely fine. There won't be any fiber migration to speak of.

Frank

I was more referring to actual insulation thats rolled like you put into the wall cavity. I am more asking for the false soffits. I would assume filling this with regular insulation would have a similar effect that cotton batting would have in a false soffit and also a riser that would be used as a bass trap.I think I'm going to play it safe with the side treatments and use cotton batting or OC703 4" thick. Although the cotton batting I find is only either 3 or 5" thick.

Also, if I was to use paper backed insulation I wouldnt have to put a paper backing on the bottom to keep the highs from getting soaked up.

Any suggestions on this?

If you have a drop ceiling, do bass traps in the wall-ceiling corners work well? Do bass waves go right through a drop ceiling, or does a wall-ceiling corner even with drop ceiling still focus the bass and is thus a viable place to put a bass trap?

If you have a drop ceiling, do bass traps in the wall-ceiling corners work well? Do bass waves go right through a drop ceiling, or does a wall-ceiling corner even with drop ceiling still focus the bass and is thus a viable place to put a bass trap?

Yes, they still work. You're not wholly focused on tri-corner areas, so if you can't get all the way up to the hard ceiling then it's not the end of the world. Corner bass trapping still works well even with a drop ceiling.

Frank

Yes, they still work. You're not wholly focused on tri-corner areas, so if you can't get all the way up to the hard ceiling then it's not the end of the world. Corner bass trapping still works well even with a drop ceiling. Since i have access to the space above the drop ceiling, and the joists run parallel to the wall i'm thinking off, would it be better to put the material above the drop ceiling perhaps? (Assuming enough space above the drop ceiling to put a bass trap of the same size.) I know there are no absolute answers, i'm just trying to understand how bass interacts with a drop ceiling- whether it mostly goes through it, or mostly gets reflected, or if it's 50-50, or... Thanks!

Hey guys,

Just a quick question -

I visited Best Buy Magnolia Theater a couple times and noticed in one of the demo rooms, they have these big rectangular objects hanging on the wall. Its framed with wood, and has cloth in the middle. They are also shaped in a concave form, if you look at it from the side.

Can anyone explain to me what these do?

They seem to be at all the reflection points in the room. I was thinking about recreating these for my place, but I also was thinking about putting something on the inside of them such as "BMC" board from Ottawa Fibre Inc. (OFI). Or this other faced stuff called "FSK" to help with sound isolation, as to cut down sound from passing through walls. Im living in an apartment, so im looking into ways to help with acoustics, reflection areas, and sound isolation.

Thanks for everyones time.

Hi Guys,

I need some help as I continue on the path of treating my dedicated HT room. The image below illustrates my setup with 3 GIK 242s on each side wall.
Room is over 3000 cubit ft.

My room is slightly challenged due to half of the room being pergo (at ain stage) and asymetry from left and right front wall.

I've seen some immediate improvements in echo reflection with my current placements. I don't plan on building a dedicated screen wall, but what additional high priority treatments would you guys reccomend? I have considered putting additional panels behiind the left and right screen speakers. Would 242s or 244s be better here? My sub is located in back of room at the current time. I still get an extremely "live" sound from my main stage currently.

Any advice on next steps are appreciated.

http://www.gliffy.com/pubdoc/1903188/L.jpg

I've seen some immediate improvements in echo reflection with my current placements. I don't plan on building a dedicated screen wall, but what additional high priority treatments would you guys reccomend? I have considered putting additional panels behiind the left and right screen speakers. Would 242s or 244s be better here? My sub is located in back of room at the current time. I still get an extremely "live" sound from my main stage currently.

I'd do 244's there simply because you've got all 242's right now, so you could use some work down below 250Hz. It looks like you've got some space on the back wall, so a couple of 244's would be great there as well. Both of these additions will give you some low end control and knock down the roominess a bit as well.

Frank

I'd do 244's there simply because you've got all 242's right now, so you could use some work down below 250Hz. It looks like you've got some space on the back wall, so a couple of 244's would be great there as well. Both of these additions will give you some low end control and knock down the roominess a bit as well.

Frank

Thanks Wesel. Couple of other q's.

1) I have a curtain that currently covers 3 small windows in the back which helps a bit. I don't have any real wall space there other than at the floor level. Does lining the wall with diffusers help in this situation, or are they only for very specific applications?

2) What is the general rule of thumb for applying tri-corner traps? Do they help in all coners of a room, or only where there is a sub near? I considered one in the right corner.

Thanks Wesel. Couple of other q's.

1) I have a curtain that currently covers 3 small windows in the back which helps a bit. I don't have any real wall space there other than at the floor level. Does lining the wall with diffusers help in this situation, or are they only for very specific applications?

You could always do 244's on stands if you want...diffusers are effective from about 500hz on up, so I suppose it really depends on what kind of problems you're actually experiencing. If it's just that the room is too live, then absorption is really the way you need to go.

2) What is the general rule of thumb for applying tri-corner traps? Do they help in all coners of a room, or only where there is a sub near? I considered one in the right corner.

They help in all corners of the room, but it's important that they be applied as symmetrically as possible. In your case you have two unavailable corners diametrically opposed to one another. You could trap wall/ceiling corners...

Frank

Hey guys,

Just a quick question -

I visited Best Buy Magnolia Theater a couple times and noticed in one of the demo rooms, they have these big rectangular objects hanging on the wall. Its framed with wood, and has cloth in the middle. They are also shaped in a concave form, if you look at it from the side.

Can anyone explain to me what these do?

They seem to be at all the reflection points in the room. I was thinking about recreating these for my place, but I also was thinking about putting something on the inside of them such as "BMC" board from Ottawa Fibre Inc. (OFI). Or this other faced stuff called "FSK" to help with sound isolation, as to cut down sound from passing through walls. Im living in an apartment, so im looking into ways to help with acoustics, reflection areas, and sound isolation.

Thanks for everyones time.

bump for my question too please.

bump for my question too please.

http://www.realtraps.com/products.htm

Hi all,

I am VERY new to any kind of acoustic treatments, and am working my way through this thread. I have a small dedicated room in my basement, mostly home theater. It is a pretty small space, about 1400 cubic feet. Sealed space, front projector.

My biggest question/concern is my first reflection points. On my left side, I have glass french doors, and on my right side I have a window at the first reflection points for my main seating positions. I don't have a lot of options. I was thinking about putting up some heavy velvet drapes on each side, which I guess will help some with the highs. Another option would be to push the L/C/R speakers up against the front wall, which would move the first reflection off of the glass structures and at a wall point, which I could put up some panels.

Is it better to position the speakers as they are, 4' out into the room, treat the windows with drapes, and put panels and traps in other places throughout the room, or compromise the speaker location, putting them against the front wall to allow for a proper panel at the first reflection points?

Thanks!
Greg

Hi, Looking to improve my Room Acoustics as they are probally needed.. All I have availble is a SPL Meter along with a Test Tones CD. Will I be able to test my room with that or do I need a Fancy Gizmo to do the readings??

Here is a Pic of my Room it is in the Basement with the Right and Rear wall being Cynderblocks with Drywall over... On the Front and Left Wall When I built it I put in 2" Insulation between the Studs to the Ceiling, the Styrofoam kind of Insulation..

Would Someone be able to tell me what to Add or do I need to make Measurments first??


http://img230.imageshack.us/img230/2163/htlayout.jpg
By the_nephilim (http://profile.imageshack.us/user/the_nephilim) at 2010-02-16



Also here is my Webpage with some Before and after shots. Also I havea 7' Drop ceiling and did NOT put any insulation inbetween the Joists above the ceiling Should I??


http://home.comcast.net/~glafsr/wsb/html/view.cgi-home.html-.html

Any Hope or Help..I would really appreciate it ..;)

Hi, Looking to improve my Room Acoustics as they are probally needed.. All I have availble is a SPL Meter along with a Test Tones CD. Will I be able to test my room with that or do I need a Fancy Gizmo to do the readings??

Your questions aren't very specific, so here's some general advice on room measuring (and below that) room treatment:

All About SPL Meters (http://www.realtraps.com/art_spl.htm)

Room EQ Wizard, Windows and Linux and Mac OSX 10.4+, Freeware (http://www.hometheatershack.com/roomeq/)
ETF, Windows, $150 (http://www.etfacoustic.com)
FuzzMeasure, Mac, $150 (http://www.fuzzmeasure.com)
Using ETF (http://www.realtraps.com/art_etf.htm) explains how I use ETF, but the principles apply to all such programs.
Comparison of Ten Measuring Microphones (http://www.realtraps.com/art_microphones.htm)

Acoustic Basics (http://www.realtraps.com/art_basics.htm)
How to set up a room (http://www.realtraps.com/art_room-setup.htm)

RealTraps Articles (http://www.realtraps.com/articles.htm)
RealTraps Videos (http://www.realtraps.com/videos.htm)

--Ethan

I am planning to put corner loaded bass traps in the front corners of my listening room. They are expensive, but I am wondering about the relative benefit of treating the front corners from floor to ceiling. I could buy 4' high traps, or go the whole 8'. Will I notice the difference?

Will I notice the difference?

There will be almost assuredly be a measurable difference.

Will you notice it? There is only one way to find out. Certainly, many people with an ear for audio reproduction would notice it.

Without knowing the rest of the system and room, it's hard to judge -- even excepting for differences in individual perception and experience.

I am planning to put corner loaded bass traps in the front corners of my listening room. They are expensive, but I am wondering about the relative benefit of treating the front corners from floor to ceiling. I could buy 4' high traps, or go the whole 8'. Will I notice the difference?
Here's what I have ... and I'm adding more ....

http://peparsplace.com/assets/images/studiotips_superchunk_20.jpg

I moved into a new (to me) house and tried to recreate my living room layout as best I can in the below picture, prior to my PR-SC5507 arriving Wed. The room is an open 2 story room and I am hoping to tame this room a little and on a very tight budget (due mostly to the new pre-pro). If I can only afford to spend on either heavy curtains shown as blue lines over the windows with faux wood blinds at the top of the layout or a few acoustic panels in the areas marked with green lines, what would you do? I am also of course open to any giudance and suggestions.

http://picasaweb.google.com/hdkash/EDA5350#5443456759075424386
http://picasaweb.google.com/hdkash/EDA5350#5410424787087606578

Links to Picasa posted pictures

http://picasaweb.google.com/hdkash/EDA5350#5410424787087606578
http://picasaweb.google.com/hdkash/EDA5350#5443457776920064562

Thanks

Your questions aren't very specific, so here's some general advice on room measuring (and below that) room treatment:

All About SPL Meters (http://www.realtraps.com/art_spl.htm)

Room EQ Wizard, Windows and Linux and Mac OSX 10.4+, Freeware (http://www.hometheatershack.com/roomeq/)
ETF, Windows, $150 (http://www.etfacoustic.com)
FuzzMeasure, Mac, $150 (http://www.fuzzmeasure.com)
Using ETF (http://www.realtraps.com/art_etf.htm) explains how I use ETF, but the principles apply to all such programs.
Comparison of Ten Measuring Microphones (http://www.realtraps.com/art_microphones.htm)

Acoustic Basics (http://www.realtraps.com/art_basics.htm)
How to set up a room (http://www.realtraps.com/art_room-setup.htm)

RealTraps Articles (http://www.realtraps.com/articles.htm)
RealTraps Videos (http://www.realtraps.com/videos.htm)

--Ethan




Hi, Thnx for the links that should answer my Question.. Not to start and argument with you but I did ask a specific Question..

I had stated I have a SPL Meter and a Test Tone CD.. I then asked will I be able to test my room with the SPL Meter & Test CD I have or do I need a Fancy Frequencey measuring device???

So can I measure my Room with just a SPL Meter & Test Tone CD to find what kind of Acoustic treatment is needed for my Room??

Hi, Thnx for the links that should answer my Question.. Not to start and argument with you but I did ask a specific Question..

I had stated I have a SPL Meter and a Test Tone CD.. I then asked will I be able to test my room with the SPL Meter & Test CD I have or do I need a Fancy Frequencey measuring device???

So can I measure my Room with just a SPL Meter & Test Tone CD to find what kind of Acoustic treatment is needed for my Room??
Well, yes, that is what the Test Tone CD is for - measuring with a sound level meter. The first link Ethan posted explains the process. The other links he posted are for bonus points.

Some of us here are of the "teach them to fish" school of thinking. ;)

Jeff

Here's what I have ... and I'm adding more ....

http://peparsplace.com/assets/images/studiotips_superchunk_20.jpg


Pepar,

Do you plan on treating that maroon colored drywall at the back of your false wall with linacoustic or anything...is it needed?

By the way, nice superchunk bass traps! I bet they are really effective, yes?


...Glenn :)

Pepar,

Do you plan on treating that maroon colored drywall at the back of your false wall with linacoustic or anything...is it needed?

By the way, nice superchunk bass traps! I bet they are really effective, yes?

...Glenn :)
Glenn, this pic was taken during the addition of those SuperChunk traps. If you follow the home theater upgrade link in my sig, you will find the whole construction and upgrade process. Adding the traps made an incredible difference in my theater not just in the bottom end, but the entire range by cleaning up the ringing that had been masking the higher frequency content.

Yes, there is 2" of Johns-Manville Linacoustic RC on that wall during normal use.



Jeff

I moved into a new (to me) house and tried to recreate my living room layout as best I can in the below picture, prior to my PR-SC5507 arriving Wed. The room is an open 2 story room and I am hoping to tame this room a little and on a very tight budget (due mostly to the new pre-pro). If I can only afford to spend on either heavy curtains shown as blue lines over the windows with faux wood blinds at the top of the layout or a few acoustic panels in the areas marked with green lines, what would you do? I am also of course open to any giudance and suggestions.

http://picasaweb.google.com/hdkash/EDA5350#5443456759075424386
http://picasaweb.google.com/hdkash/EDA5350#5410424787087606578

Links to Picasa posted pictures

http://picasaweb.google.com/hdkash/EDA5350#5410424787087606578
http://picasaweb.google.com/hdkash/EDA5350#5443457776920064562

Thanks

Interesting. I'd be real tempted to put the TV where the loveseat is. That would give you more space on the left and right, and even space on the sides -- symmetry is key. It would also let you pull the seats a little further into the room.

Then some heavy (very heavy) curtains would help with the parallel walls in front/behind.

-----

If you want to stay with you current layout, being so close to one side wall is always going to a problem. Heavy curtains may help, but you have a severe lack of symmetry with the other side wall.

The idea of panels on the rear behind you, in your proposed setup, is very good.

will I be able to test my room with the SPL Meter & Test CD I have or do I need a Fancy Frequencey measuring device???

It's like saying I have a bicycle now, and asking if I need a car to go to the supermarket. Sorry, I was tired. :D The longer answer is an SPL meter and test tone CD can show you the raw response, but none of the time-based problems. It also depends on the test CD. Most have sine waves at third-octave intervals which is useless for assessing bass response. The RealTraps Test Tone CD (http://www.realtraps.com/test-cd.htm) at the RealTraps site is much better in that regard, but it still shows only the raw response. So if you really want to understand what's going on in your room, you'll need proper software like those I linked to.

--Ethan

I was wonder, at what dimensions do room modes not matter much? 40 feet? 100 feet?

I was wonder, at what dimensions do room modes not matter much? 40 feet? 100 feet?

Mike - by "not matter much" can I assume that you mean that the modes are inaudible, hence not a problem? Is so, then using 20Hz as the lowest freq that we can audibly hear (not feel), would mean a 28.25 foot dimension will have it's first axial mode at 20Hz calculated as 1130/(2*28.25).

Of course its 2nd and subsequent modes will be at 40, 60Hz etc which may be more (less) audible if constructive (destructive) interference causes a peak (null). All this is theoretical and may differ from our residential rooms due to boundary material used and their reflecting (e.g. cinder block) or absorbing (e.g. drywall) characteristics.

The larger the dimensions the lower the Schroeder/transitional frequency will become so build your music/HT 'man cave' as large as possible!

Thanks nathan_H, solid advice as I expected frm the folks here.
I tought about trying to rotate the layout but it bunched everything next to the fireplace and the room was already wired for speakers (where the Aplhas are about 12ft up th wall),so I am doing the best I can given what I have and I am leasing. If I could ony close of the room its in making a nice rectagular room above it.
I will get some heavy curtains put up a build a couple of panels to hang on the back wall

Mike - by "not matter much" can I assume that you mean that the modes are inaudible, hence not a problem? Is so, then using 20Hz as the lowest freq that we can audibly hear (not feel), would mean a 28.25 foot dimension will have it's first axial mode at 20Hz calculated as 1130/(2*28.25).

Of course its 2nd and subsequent modes will be at 40, 60Hz etc which may be more (less) audible if constructive (destructive) interference causes a peak (null). All this is theoretical and may differ from our residential rooms due to boundary material used and their reflecting (e.g. cinder block) or absorbing (e.g. drywall) characteristics.

The larger the dimensions the lower the Schroeder/transitional frequency will become so build your music/HT 'man cave' as large as possible!

Thanks!

...Kevin....I disagree. The room must be larger to provide the results you're suggesting and having a 20Hz null in the center of the room is not all that popular. 236" from the front wall ... you'd need some serious LCRs to handle that distance.

...Kevin....I disagree. The room must be larger to provide the results you're suggesting and having a 20Hz null in the center of the room is not all that popular. 236" from the front wall ... you'd need some serious LCRs to handle that distance.


Dennis - as one of the local pro's here, I will defer to your expertise, so could you kindly expand upon your point(s) above for all?
* Is my logic incorrect? Are you suggesting that 20Hz should not be the 1st mode but rather some higher multiple of it instead? E.g. if 20Hz is the 2nd mode then the dimension length should aim to have 10hz as its 1st mode.
* Is my math incorrect?
* 20Hz null in centre of room -> assuming someone sits in the middle of the room (which I would tend to doubt for music but perhaps HT), yes a null would be bad but wouldn't multiple subs ameliorate the problem? Are you suggesting moving the 20Hz null closer to the back wall so hence a longer dimension, similar to my point above by using 20Hz as the 2nd mode not the 1st mode?

thanks in advance,
kevin

Thanks nathan_H, solid advice as I expected frm the folks here.
I tought about trying to rotate the layout but it bunched everything next to the fireplace and the room was already wired for speakers (where the Aplhas are about 12ft up th wall),so I am doing the best I can given what I have and I am leasing. If I could ony close of the room its in making a nice rectagular room above it.
I will get some heavy curtains put up a build a couple of panels to hang on the back wall

I think your plan is reasonable. And having wiring already in place is nice.

About this comment: "bunched everything next to the fireplace", remember, you don't need to put the equipment rack and the sub on that wall next to the fireplace -- just the display and the L and R speakers. Even so, it may not be workable, but I thought I should mention it.

It's like saying I have a bicycle now, and asking if I need a car to go to the supermarket. Sorry, I was tired. :D The longer answer is an SPL meter and test tone CD can show you the raw response, but none of the time-based problems. It also depends on the test CD. Most have sine waves at third-octave intervals which is useless for assessing bass response. The RealTraps Test Tone CD (http://www.realtraps.com/test-cd.htm) at the RealTraps site is much better in that regard, but it still shows only the raw response. So if you really want to understand what's going on in your room, you'll need proper software like those I linked to.

--Ethan


OK THNX. That is what I thought.. will look over the links you sent me..

OK If I used the Rolls of Insulation for a Bass Trap what kind of Material can I encase it in for appearence ??

I am learning thnx fro those links,I am reading them all now..

OK If I used the Rolls of Insulation for a Bass Trap what kind of Material can I encase it in for appearance ??

Anything acoustically transparent...burlap works perfectly, or you can go with Guilford of Maine FR701 if you want something nicer. There are a million options.

Frank

So my room has several large windows and in conjunction with a 60" plasma and other items is relatively live. We live in the woods, and like natural light during the day. So my wife will probably not go for heavy curtains or drapes, best I could probably do is shades. I realize there is not much you can do absorption wise with shades, but any suggestions on a shade type or material that would somewhat ameliorate the reflectivity of the windows? One of the windows is at a first reflection point, so it is really problematic.

I don't know of anything that would add an absorptive element. Well, that's not true...I once saw 48" vertical blinds trimmed in pink fur in a girl's dorm room in college, but I doubt your wife would be down with that. :D 2" horizontal wood blinds can add a diffusive element, but that's not my favorite thing to do at reflection points.

Frank

I don't know of anything that would add an absorptive element. Well, that's not true...I once saw 48" vertical blinds trimmed in pink fur in a girl's dorm room in college, but I doubt your wife would be down with that. :D 2" horizontal wood blinds can add a diffusive element, but that's not my favorite thing to do at reflection points.

Frank

Thanks for your early morning reply, Frank. No I don't think pink fur will work for us! Sorry to hear you don't know of any satisfactory solutions for my problem :( Anybody else have any ideas? In searching the web this morning, RPG has this:

http://www.rpginc.com/residential/pdfs/ClearsorberBrochure2t.pdf

Has anyone tried it? Marketing hype or useful product?

You can look at AcoustiShades from Stewart Film (www.stewartfilm.com). You'll find them under Residential/Products/Special Applications. First reflections are not bad unless your speakers have horrible off axis response.

You can look at AcoustiShades from Stewart Film (www.stewartfilm.com). You'll find them under Residential/Products/Special Applications. First reflections are not bad unless your speakers have horrible off axis response.

My speakers are B&W 802D's. I thought after bass trapping, first reflections were the next most important things to address?

I'll bet this has been addressed in one way, shape, or form, but just in case it hasn't, I'd really like to hear what our local experts have to say about this:

http://www.audioholics.com/education/acoustics-principles/early-reflections-in-home-theaters-a-different-perspective

Ah...not certain what you're looking for here. Yes, fabric over fuzz applied to walls reflects a lot of the early reflections. Yes, early reflections can enhance sound quality and dialog intellibility, yes for hard reflections (close to a wall), diffusion is a good thing, and yes most people over absorb and yes many speaker manufacturer's don't give a twit about off axis response quality and yes, if the off axis response is bad, you don't want that "bad" sound reflected all over the room. And, why do you suppose you'll never get a polar response plot, or off axis response plot from B&W?

Ok...I opened the can of worms about off axis FR plots being "unavailable". Just try and get these things from manufacturers of consumer market gear (even worse, don't even think of asking boutique speaker manufacturers for this stuff). The absolute, only reason for not providing this information is because they know something they don't want you to know. Here are the excuses:

1. We don't measure that. (translation: we don't have a clue how our speakers perform but if you want real answers, talk to the marketing department).
2. We don't provide that information to consumers because they wouldn't understand it. (Translation: you and I are all stupid.)
3. None of customers would ever listen off axis. (Translation: They don't have a clue about in room acoustics OR all of their customers should be listening to their speakers in a freshly harvested wheat field.)
4. What are those? (real answer from a "high end" speaker designer selling really, really expensive two-channel audiophile speakers).
5. Our dealers wouldn't know what to do with them. (Translation: would you buy a speaker from this guy? Alternate translation: don't have 'em, never had 'em and our measurement equipment has been broken since 1970 and never fixed..besides, Mr. A's ears are better than any testing equipment.)

What about "THX" speakers. You may not like THX. You may not like THX speakers. You do know that an independent third party measured everything that can possibly be measured and it passed over their bar. (As far as I can determine, THX testing is on par with, or costs less than the same level of testing provided by other third party labs.)

Dennis,

Since you opened the (off-axis response) can of worms, what speakers manufacturers do you recommend? I ask because if this information is unobtainable, how are we supposed to choose speakers with decent or better off-axis response? Did I understand that you are saying THX certified speakers might be a decent option?

Thanks for any info you are willing to divulge.

Mark

6. If we gave you complete polar responses for our speakers, it would reveal them to be imperfect. I had one very high end (read "very expensive") speaker's engineer share some of his off-axis data with me. He was quickly overruled by management, and was forbidden to talk with me again.

Did I understand that you are saying THX certified speakers might be a decent option?
If you cannot measure the speakers yourself (accurately), then you know that a THX certified speaker has at least crossed their minimum acceptable (which is rather high) bar...which includes of axis response. This does not mean there are very good speakers which do not have THX testing, nor does it mean all THX speakers are appropriate for all rooms. What else can be said about THX testing? At least the manufacturer cared enough about their product's performance to get a third party opinion.

To Terry's experience, I measured a set of speakers and then called to ask whether I had a bad example or otherwise what was going on. The formal response came from their outside counsel suggesting my publication of that information would result in some very expensive legal fees. (I get a similar 'proforma' letter annually from a supplier (manufacturer) of a mass loaded vinyl product.)

JBL has off axis data, at least in their pro lines.

Also:

http://www.soundstageav.com/speakermeasurements.html

Virtually all Pro speakers have axis data available. (Actually, I don't know of any pro speakers which do not.)

Virtually all Pro speakers have axis data available. (Actually, I don't know of any pro speakers which do not.)
Would you say that speakers without this testing would not be taken seriously by professionals?

The pro space modeling programs are set up to use databases of speaker 3-d response data. The major competitive pro speaker maufacturers provide this data for these databases.

No real way to honestly consider them otherwise.

I guess the old standbys are available-
Looks
Price
"You know who" likes/uses them
and the ever popular "Trust your ears"

Has anyone heard or or used this product? It's use is stated on their site as:

Sound absorption in theaters, studios, and entertainment facilities.
For applications requiring a black, sound absorbing insulation.

The manufacturer is CertainTeed. I searched this forum and found nothing, but it looks like it may be a good solution for behind-screen-wall cavities.

http://www.certainteed.com/products/insulation/fiber-glass-insulation/batts---rolls/317352

Looks to be very similar to JM Linacoustic. If so should be great for front wall(s).
I assume it comes in 1" and 2" varieties.

Hopefully others will chime in to confirm

Has anyone heard or or used this product?

What specifically do you want to do with it? I agree with the previous poster that it would be great for the screen wall or even reflection points if the room is large enough.

Frank

frank: what would you be considering when you say large enough?
thx
walt

What specifically do you want to do with it? I agree with the previous poster that it would be great for the screen wall or even reflection points if the room is large enough.

Frank

I am considering using it behind my screen in a 3 x 15 area, covering up concrete block and providing sound absorption. I am guessing it is more economical than 2 x 4 panels or OC, very flexible and easy to work with. It is offered in 1, 1 1/2 and 2 inch versions.

I'm looking at some GIK 242s. I only need 2 of them. Not 3.

Anyone know why one must order 3 per box? Are they flexible on that?

Ask them, not us?

frank: what would you be considering when you say large enough?
thx
walt

*VERY GENERALLY SPEAKING*, 17'x20'x8 or larger.

Frank

*VERY GENERALLY SPEAKING*, 17'x20'x8 or larger.

Frank
would this material be effective behind non a/t screens?
walt

Ah...not certain what you're looking for here. Yes, fabric over fuzz applied to walls reflects a lot of the early reflections. Yes, early reflections can enhance sound quality and dialog intellibility, yes for hard reflections (close to a wall), diffusion is a good thing, and yes most people over absorb and yes many speaker manufacturer's don't give a twit about off axis response quality and yes, if the off axis response is bad, you don't want that "bad" sound reflected all over the room. And, why do you suppose you'll never get a polar response plot, or off axis response plot from B&W?

Thanks for the response, Dennis. What do you think about the discussion of RT60 times?

I'm looking at some GIK 242s. I only need 2 of them. Not 3.

Anyone know why one must order 3 per box? Are they flexible on that?



As a GIK customer I can tell you that 3 242s will fit within their chosen box size but you can buy just 1 or 2 if you wish . . .

Dr. Floyd Toole recommends a minimum absorption depth of 4" so perhaps their 244 or Monster trap may be a better way to go so that your frequency balance isn't thrown out of balance by only attenuating the high frequencies.

HEY GUYS!

Quick question about noise canceling. I just moved into an apartment that is on the second floor (and has a loft), and I was wondering how I can cancel out some noise coming from another apartment and also from the apartment below me.

Question #1: I have a set of Paradigm Studio 100s and im nervous about bothering the people below me. What steps can I take to help that out? I have carpet flooring, not wood - which I know helps in dampening...

Question #2: My bedroom wall happens to be lined up next to a kid's bedroom...a very young kid's bedroom - who sometimes throws a fit. What can I do to stop the noise from penetrating through this wall that doesn't involve tearing out the drywall and replacing the insulation with better stuff?


Thanks for your help in advance!

Anyone else tried to get off axis data out of their manufacturer this week?...I'd been wanting it for ages, but this recent discussion prompted me to ask....they're pretty much ignoring me now....

.....and I have what I regard to be pretty darn good speakers, its quite annoying, it'd make life much easier if I could allow for certain things (treatments) during construction....I wonder if they know the data or not or if its just really bad, which I suppose I dont want to know given how much coin I've sunk into the things

I read about a technique where you can use a mylar strip to determine where sound from your speakers is reflecting off the wall. You put a light source, such as a lamp without a shade, where the speakers normally sit. Then the place you can see the light on the mylar strip is where the sound reflects off the wall. This then would be where you would place the treatment. The problem I am having is that I cannot find the mylar material anywhere. I have checked the local craft stores and wal-marts. Does anyone know if regular metallic-type paper used for wrapping presents or as bows could be used for this? Or does it require mylar specifically for this to work?

I read about a technique where you can use a mylar strip to determine where sound from your speakers is reflecting off the wall. You put a light source, such as a lamp without a shade, where the speakers normally sit. Then the place you can see the light on the mylar strip is where the sound reflects off the wall. This then would be where you would place the treatment. The problem I am having is that I cannot find the mylar material anywhere. I have checked the local craft stores and wal-marts. Does anyone know if regular metallic-type paper used for wrapping presents or as bows could be used for this? Or does it require mylar specifically for this to work?

Don't over-complicate it. Just use a mirror! :)

I read about a technique where you can use a mylar strip to determine where sound from your speakers is reflecting off the wall. You put a light source, such as a lamp without a shade, where the speakers normally sit. Then the place you can see the light on the mylar strip is where the sound reflects off the wall. This then would be where you would place the treatment. The problem I am having is that I cannot find the mylar material anywhere. I have checked the local craft stores and wal-marts. Does anyone know if regular metallic-type paper used for wrapping presents or as bows could be used for this? Or does it require mylar specifically for this to work?


Johnny - you're making it too difficult for yourself - forget the mylar strip and get a hand held mirror instead, and an assistant. Sit yourself in your listening position chair and have your assistant slowly move the mirror across the wall starting next to the speaker and moving horizontally towards the back wall at tweeter height. You should see the speaker closest to the side wall first and a short distance away you'll see the speaker across the room. Each side wall has 2 1st reflection points.

Before you spend money foolishly, buy Dr Floyd Toole's latest book to educate yourself on acoustics and room treatments so you don't waste money putting the 'wrong' treatment up. Depending on if you're a HT or stereo listening person the teatment may vary . . .

I bougt some corner bass traps and am planning to straddle the front corners, just sitting on the floor. I have drapes, velvet-type material covering the front walls. Can I place the traps behind the drapes, or outside, or does it matter?

I bougt some corner bass traps and am planning to straddle the front corners, just sitting on the floor. I have drapes, velvet-type material covering the front walls. Can I place the traps behind the drapes, or outside, or does it matter?

Gravi - What kind of corner bass traps did you get as the kind of trap (i.e. helmholtz, diaphragmatic, resistive) will determine how to properly set them up for max effectiveness. . .

The bass frequencies won't "see" the velvet draps so putting the bass traps behind them is fine, depending on what kind they are. Which brand and model did you buy will help us know more.

You don't even need a mirror!
You can use a Lazar Level or Lazar podium pointer. It will reflect off most painted walls. Sit in the listening positions and aim it to reflect off the wall towards the speakers.

Johnny - you're making it too difficult for yourself - forget the mylar strip and get a hand held mirror instead, and an assistant. Sit yourself in your listening position chair and have your assistant slowly move the mirror across the wall starting next to the speaker and moving horizontally towards the back wall at tweeter height. You should see the speaker closest to the side wall first and a short distance away you'll see the speaker across the room. Each side wall has 2 1st reflection points.

Before you spend money foolishly, buy Dr Floyd Toole's latest book to educate yourself on acoustics and room treatments so you don't waste money putting the 'wrong' treatment up. Depending on if you're a HT or stereo listening person the teatment may vary . . .
thanks for the help.

Gravi - What kind of corner bass traps did you get as the kind of trap (i.e. helmholtz, diaphragmatic, resistive) will determine how to properly set them up for max effectiveness. . .

The bass frequencies won't "see" the velvet draps so putting the bass traps behind them is fine, depending on what kind they are. Which brand and model did you buy will help us know more.

They are fiberglass 4 inch thick traps. I bought the at www.acoustimac.com - good site, I liked them. They are basically rectangulat 2' by 2' but has tapered sides to fit against a wall corner. I can easily conceal them behind the draft. I see your point about bass frequencies but curious about higher frequencies and how they would behave.

Before you spend money foolishly, buy Dr Floyd Toole's latest book to educate yourself on acoustics and room treatments so you don't waste money putting the 'wrong' treatment up. Depending on if you're a HT or stereo listening person the teatment may vary . . .
Can you name three or four people other than Dr Toole who shares his position on first and early lateral reflections?

Well most of the people who think early reflections are bad are the people profiting off of it...

Also Toole is just going by his research, not personal opinion. But he doesn't say that attenuating first reflections is bad, he just says that you can if you want, but there are no real downsides to leaving them reflective, only upsides. I would suggest reading his book and deciding for yourself. I think you can find it on Google Books or on Harman's site (not his book but a research paper).

there are no real downsides to leaving them reflective, only upsides.

In the graph below, which frequency response would you prefer?

--Ethan

http://www.realtraps.com/rfz-response.gif

In the graph below, which frequency response would you prefer?

Well, if I listened to graphs, the answer is clear. ;)

However, I suspect that this test compared flat, unadorned, completely reflective side-walls with fairly-well treated, absorbent ones. This is certainly demonstrative but extreme, imho. Most cases fall in between these extremes. In addition, the use of wall-hangings and decorations can provide diffusion (rather than absorption) and ameliorate what you demonstrate.

Also, Toole's statements are based, not only on measurements, but on statistical samplings of listener opinion and, even then, he is not dismissive of treating the sidewalls. He discusses a trade-off in imaging specificity for soundstage width and immersion and this trade-off spans the continuum between what I assume are the two extremes you tested.

Another variable is the radiation characteristic of the speakers.

So, I do not think that this is a situation in which all the "right" is on either side.