bgarner:
Acoustically, assuming that you can breath through the fabric, it makes no difference at all.

The purpose of the fabric is to keep the insulation in place, to keep the fibers in place, to protect the trap from people touching or brushing against it, and for asthetics (i.e. it looks better).

If none of those are a concern with the back (such as a frame is against the wall), then you don't need covering on the back.

Thanks for the informaton. Off to get some materials and start building.

What's better? a cilinder bass trap or an absorption panel cut like a triangle and installed on a 2 wall/celining corner?

I was thinking of adding 2 triangles to the corners, using unicel panels covered with fiber glass and fabric, what do you guys think?

By the way, anyone knows if unicel is a good sound absorver?

Regards!

Why the limitation? Obviously, the cylinder has a LOT more surface area and will provide more absorbtion. However, if you're willing to give up the floorspace the cylinder takes up, why not consider using flat panels straddling the corner at 45 degrees for the top 4' or maybe even floor to ceiling?

Why the limitation? Obviously, the cylinder has a LOT more surface area and will provide more absorbtion. However, if you're willing to give up the floorspace the cylinder takes up, why not consider using flat panels straddling the corner at 45 degrees for the top 4' or maybe even floor to ceiling?In this config, what do you recommend to "cap" the end of the partial corner covering? Or leave it open?

Gray,

> do you recommend to "cap" the end of the partial corner covering? <

This has come up before. There's no benefit to placing a cap on a tube trap because there's nothing to seal. Rigid fiberglass is porous.

--Ethan

Gray,

> do you recommend to "cap" the end of the partial corner covering? <

This has come up before. There's no benefit to placing a cap on a tube trap because there's nothing to seal. Rigid fiberglass is porous.

--EthanSo you're saying this concept would also apply to a partially covered corner like bpape was describing? e.g. for a corner with a 2x4 panel stood in the corner, from ceiling down the wall 4', capping it (in other words, adding a base to it) it will have no significant effect?

And, when I said cap, I didn't necessarily mean to cap it with fiberglass. Maybe cap it with something with some more mass.

Thanks

No need to do anything to it unless you want to for looks purposes and/or to have something to staple the fabric to on the bottom.

Gray,

> for a corner with a 2x4 panel stood in the corner, from ceiling down the wall 4', capping it (in other words, adding a base to it) it will have no significant effect? <

It will have an effect - a negative effect! Especially if it's rigid and massive, because that blocks sound from getting to the rear of the panel and lowers the overall absorption.

--Ethan

Gray,

> for a corner with a 2x4 panel stood in the corner, from ceiling down the wall 4', capping it (in other words, adding a base to it) it will have no significant effect? <

It will have an effect - a negative effect! Especially if it's rigid and massive, because that blocks sound from getting to the rear of the panel and lowers the overall absorption.

--Ethan
I dont' think you and I are talking about the same thing. But to be sure...

Assume 8' tall room corner. 2' x4' fiberglass panels

Case 1: Stand 2 panels in the corner, so the corner is covered floor to ceiling with (2) panels oriented vertically. This "trap" has a top (ceiling) and a bottom (floor), adn a back (the 2 walls). Only way sound can get into the corner space behind the panel is through the panel.

Case 2: identical to #1 above, only remove the lower fiberglass panel. Now the "trap" has a top (ceiling), a back (the walls forming the corner), but it has no bottom. Sound can enter throught the panel, or through the open bottom.

Case 3: identical to #2 aboce only now you build a "floor". For this example this floow is constructed like a 2x4 floor with insualtion. This "floor" caps the bottom of the trap. The space below this "trap floor" is used for somethig else (equipment, storage, whatever). In case 3 sound can only enter through the panel, identical to case #1.

You are saying case 3# is bad becasue it "blocks sound from getting to the rear of the panel" ? Then by inference, a floor to ceiling trap would be bad, too, becasue it would also block sound from getting to the rear of the panel(?).

Or did you misunderstand what I was trying to describe? Thanks.

You'll be fine if you put a bottom on it. As I said, you need something to staple to anyway unless you're doing a free hanging frame. If you want the best of both worlds, cut a triangle for the bottom and then cut a hole in it to leave say 1-1/2 inch all around for attachment.

You'll be fine if you put a bottom on it. As I said, you need something to staple to anyway unless you're doing a free hanging frame. If you want the best of both worlds, cut a triangle for the bottom and then cut a hole in it to leave say 1-1/2 inch all around for attachment.Understood, sounds like a plan. Thanks.

Good question about the 3 scenarios

I was thinking of doing a triangle to cover the corner, but would it be better just to build a 2X4 panel and hang it on the corner, touching the ceiling? As in case 2?

I like the triangle idea because of the looks

Now, I know this has been explained a million times, but, if I do a panel as a bass trap, the paper side of the fiber glass would face the room and the pink stuff would face the corner right?, oposed to a high freq. panel where you place the pink stuff facing the room. Am I correct?

Gray,

> This "floor" caps the bottom of the trap <

I'm still not sure what you're describing. All I'm saying is if you block the triangle shaped opening at the bottom with a solid material, that will prevent sound from getting into the rear of the panel through that opening.

--Ethan

Newbie,

> the paper side of the fiber glass would face the room <

Yes, for bass trapping.

--Ethan

Ethan,

His point was that if you run an absorber floor to ceiling straddling the corner, you'll not get anything in behind it either. Very true.

Bryan,

> His point was that if you run an absorber floor to ceiling straddling the corner, you'll not get anything in behind it either. <

I'm not sure that's true. Low frequencies pass, or partially pass, through the panels. So anything that gets through the bottom half can now reflect off the corner and get up and behind the upper portion. If there were a solid triangle shaped block halfway up that would prevent this. I'm just thinking out loud, not arguing the case. But it seems plausible, anyway.

--Ethan

No. You'd just have 2 smaller cavities for it to get into. The whole idea was that you were saying that putting a bottom on it lost the ability for sound to get in via the bottom where it was open. In a floor to ceiling, it's the same thing. Anything that gets in has to come through the panel.


Sure, if you leave the bottom of a half corner trap open, there is more opportunity for sound to get in from the bottom. However, that does not make what is dealt with via that which comes in from the panel any less effective. You just don't get the 'bonus'.

Hi guys!

I finished my 2 triangles for bass traps

The are aprox 2 feet on each side

Now the problem is, how on earth do you hang those on the top corner? I have concrete walls and would probably have to drill.

Anybody has any idea on how to do it?

So these are equilateral triangles that just sit in the tri-corner? If so, and there's a wood frame around it, heavy duty velcro might do the trick - otherwise, a SMALL dab of construction adhesive would likely work - you'd just have to hold them in place somehow till it dries.

These assume you made the sides of the frame at the appropriate compound angle so each edge will sit flush with the wall/ceiling.

Can you hang them from the ceiling?

(MISTAKENLY POSTED IN MAIN FORUM, WHEN I MEANT TO PUT IN THIS THREAD.)

Looking for appropriate combination and placement of acoustical wall panels for sound absorption and diffusion.

Room specs are as follows:

- basement location
- 18w x 16d x 7.75h
- 2x4 stud walls with 5/8" sheetrock, painted
- drop ceiling with pretty good "acoustic tile"

http://www.patmedia.net/ray.purkis/SpeakerFinal.jpg

HT system specs:

- 50" Plasma, wall mounted (PIO 5050HD)
- 7.1 surround
- DefTech speakers, as indicated on diagram
- speakers wall mounted
- surround back speakers are bipolar

Aside from all the usual concerns, I'm particularly worried about:

- the angled corners on the back wall
- not "killing" the effect of the bi-polar speakers on the rear surrounds

Would love for any of the cogniscenti to provide a "stepped" recommendation? ("First you MUST do this, then you SHOULD do this, and then you COULD do this...etc")

While I'm pretty handy from a DIY standpoint, I'm really hoping to go with "ready to wear" fabric wrapped panels and the like.

Thanks in advance for your time and consideration!

This should probably be in the main forum or in the audio theory area.

Hi guys!

Yesterday I had a hard time hanging my triangle bass traps, I decided to use fishing line to hang them to the corners, but it was fisically imposible to put the triangles all the way up, so I left some space between the triangle and the ceiling.

Ethan once mentioned that if air can enter this type of bass trap, it would be a good thing, so in my case, I'm in the good zone right?

Check out the diagram...


2 more weeks to get my Samsung 60"!!!

... almost there... stay on target....they came .. from... behind!!!

Newbs,

> Check out the diagram... <

I think they'll work better if they're higher, to more completely cover the corner. If wire doesn't work, maybe you can use a few really thin nails?

--Ethan

fisically

Hmm.... (sorry, not usually a spelling nazi but.... )

Sorry about the word I invented!, feel free to correct me if I write something crazy like "fisically"

In other news , yesterday I finished hanging the treatment panels on the walls, and I figured a way to put the triangles exactly in the corners, using the same fishing line.

Attached are a couple of pictures of the left and right walls , as well as the treated corners.

The rooms looks small, but I think it's fine.

Feel free to comment on my panels, I haven't tested that configuration since I still don't get the equipment. You guys think it'll work?

Panels are 2X4, 2" deep
Triangles are 2X2X2, 2" deep

It should help some. It would be more effective if they were 4" thick and maybe had a little more surface area - but they look very nice - good job.

Thanks!

I will also add a nice rug that covers some area of the floor, but for the ceiling, back and front walls I'll do nothing

So, would you guys say, "ok, you're good to go" or more like "dude, you just covered the tip of the iceberg and you need to add more!!!!"

The wife acceptance factor is limiting the amount of panels, I was lucky to be allowed to have 4 and 2 triangles :p

Regards,

Try it and see. IMO, you're likely to need more bass absorbtion but what you have is better than nothing. At least with the panels you have, if placed correctly, you'll be way ahead of the game over most people in terms of controlling decay times, taming early reflections, and at least minimal broadband bass absorbtion.

How dangerous is it to place a spot light near a fiberglass panel? you guys know of any case of a panel bursting into flames because of overheating from direct light from a spot light? :eek: :confused:

I didn't know fiberglass was flammable ??

Is it straight fiberglass, cloth-covered, resin-impregnated? What kind of light? How far away?

it's covered in fabric and poly batting, with a wood frame

here's a picture

notice the spot light just ahead of the tiangle panel, that's the one that has me worried

If the cloth is fire rated, there should be NO concern. Even if so, you're far enough away from it that it shouldn't cause a problem IMO. Direct contact is another issue but you're inches away.

HTNewbie1974:
How dangerous is it to place a spot light near a fiberglass panel?
How about "if you can keep your hand between the heat source and what you're worried about for ten minutes, then it probably won't ignite or prematurely discolour. If you can't keep your hand there, then move it away or put drywall between them."

BTW, first glance at your left wall.JPG , I thought the text on the wall was "Parking Area". (After resizing the image, it turns out to be "Painting Area".)

I am about 1/3 of the way done reading - Master Handbook of Acoustics - 4th edition - Everest. I wish I would have bought this book long ago. It is the best $40 I have ever spent on my theater. If you are in any way interested in theater / music acoustics - get this book!

Yet another question about panel construction...

Has anyone tried to make a panel wider than 2'? I could spare a wider than 2' panel in the corners of my room, but don't want to make a tube trap as the fibreglass tubes are far more expensive ($24 per lineal foot, 20" dia, 2" th, ouch!). I could make them 2.5' or 3' wide, but am unsure if just gluing them together would work. I have only been able to find 2" 705 and 3" 703 locally. Not sure if this will solve the issue completely so want to overdo it the first time. I included a drawing of the room in case it helps.

Another question, which is more theoretical. If the FRK (faced) panels also work, then is the fibreglass actually slowing the air velocity or is the panel simply flexing? If I really care more about bass absorption than high freq reflection, do I want faced panels?

pierce,

> Has anyone tried to make a panel wider than 2'? <

I haven't done that so I can't say if it will be better or worse than 2 feet wide. The only reason I suggest it might be worse is at some point the material will be so far from the corner that it's not a "corner trap" anymore.

> If I really care more about bass absorption than high freq reflection, do I want faced panels? <

Yes. See my Density report, which also shows the difference between faced and unfaced rigid fiberglass:

www.ethanwiner.com/density/density.html

--Ethan

It will work fine to be wider - though I wouldn't get too ridiculous. If you need 2.5' or 3' wide - why not just turn the 2x4 panels on their side - cut to the appropriate width. Use the leftover on the inside to help tighten things up a bit.

There is no need to glue pieces together. For extra thickness, just frame them together or set them together and the framing/cloth will hold them in place. There is no need for them to be physically attached (or even touching totally) for them to function as the equivalent to 4".

Thanks bpape and Ethan! The density study was quite interesting and helpful. I think its interesting that the panels can be set in the corner and still work without rigid mounting. That is good though, it means less work!

I am in the process of acoustically treating my dedicated home theater. I'll be installing JM Insul-Shield on the walls and am looking for advice on locations for bass traps.

My room is 23 x 14. The ceiling slopes from the side wall to the ceiling starting at 70" up from the floor (see diagram below). The flat part of the ceiling is approximately 5' wide and 9' tall.

__
/ \
| |
-------

The "barn" shaped walls are at the two ends (long dimension) of the room, one of which has the screen and front speakers, and the opposite wall contains the entry door as well as equipment and storage cabinets. Links to pictures of each can be found in my signature (sorry no URL's allowed as this is my first post).

On the front (screen) wall, there is 70" of vertical corner available to install a corner base trap. On the back (equipment) wall the vertical corners are occupied by cabinetry. Above the cabinetry there is an open area along the sloped portion of the ceiling.

With this limited space, I was planning on installing base traps in the front vertical corners, as well as above the cabinets on the back wall.

Is there an alternate placement that would work better?

Thanks...

Michael

I am in the process of deciding how acoustically treat my dedicated home theater.

My room is 20' 7" x 17' 1" with 9' drywall ceiling. I have Jamo D7 THX Ultra II speakers (7) and a Martin Logan Descent sub. There will be a 7' riser the width of the room along the back wall. front speakers will be mounted at 5' and surrounds and rears will be mounted at 6'. If I will use the room for 80% home theater and 20% music, what acoustic treatments should I install?



Thanks,

Michael Bell

what acoustic treatments should I install?

A combination of absorption and some diffusion, basically, like always.

I recommend F Alton Everests master handbook of acoustics.

Michael,

> what acoustic treatments should I install? <

Bass traps in as many corners as you can manage, and mid/high frequency absorbers at the first reflection points. If you have hardwood floors you'll probably want a little more mid/high absorption on the ceiling. If you have large areas of bare wall, you'll need some absorption there too. That's the short answer. For the complete story see my Acoustics FAQ:

www.ethanwiner.com/acoustics.html

--Ethan

Great info, thanks for the help!

I am building a room 14'x9'x28' with the ceilings sloping to 6'5" because it is a bonus room above the garage. the rest of the house is on the first floor. Screen wall and left wall are to exterior. Right wall is to attic. floor to garage. back wall to pretheater room.
I am concerned about sound in the rest of the house. I do not intend on watching loud movies into the wee hours of the night but I just don't want the attic or garage to act like a speaker box. I used to live in a poorly constructed apt and the guys TV upstairs would just echo in my bedroom so I am fearful of this. my AV guy says I don't need special insulation techniques...just using cocoon blowin insulation around the room and regular drywall with 2x4 framing. Anyone have experience with this. I was thinking about greenglue or quietrock but would love to save the money.
He is also recommending Sonance inwall/inceilings and sunfire sub. Do the Sonance inwalls allow a lot of sound out the back of these and can I still blow insulation over them?
One more random question. The HVAC guy has started to put the 3 vents along the right side of the room at about 5 feet off the ground. I just realized there has to be a grill or something on the wall there which will be ugly. Any ideas on where else to put them?
ARthur
:confused: :confused:

I was hoping that someone could connect me to a good acoustic guy in Seattle. Any Ideas?

Thanks

Evan

How good is good?

i.e. what are you trying to, and budgetwise?

My theater is built, at least the room and sound system. I have an inwall Triad system. However, I'm experiencing a lot of reflected sound. The room has just aquired carpet. I have seats on order. But, playing audio sounds like I'm waiting for a concert and the sound is bouncing around the auditorium. Well, I've been reading about others making their own panels. Sounds interesting. But, I want the job done right. I see you're in Seattle, what's your experience? Would you like to see my echo chamber?

I'm just a DIYer, so if you want to go that route...

I've pmed you some other info though.

Hi everyone, I am just about finished painting my theatre room and am ready to do some acoustic treatment. I needed a few things cleared up though...

When finding the first reflection points using a mirror, am I supposed to do this for just the Front R/L speakers, or the center/rears as well? I read that only the point up to where your ears are should be covered as well, does this mean I shouldn't put any rigid fiberglass above ear level or on the ceiling?

I'm not totally sure why the entire front wall needs to be covered too. It seems like no sound would be bouncing off that area. But if it's recommended, I'll do it. However, what about the area with the screen? Should I put the fiberglass up all over the wall first, then put the screen up? Or put the fiberglass around the screen (making the screen appear as though it's impressed into the wall?)

I'm planning on using 2" thick stuff, and I want to space it out from the wall a bit. What would be the best material to mount between the fiberglass and drywall? Wood?

Thanks for any help. I'm almost done with the painting, so I hope to get started on this soon.

SuprSonik:
I'm not totally sure why the entire front wall needs to be covered too.'Needs to' depends on how good you want it.
Have a look for SBIR and 'speaker radiation pattern'.
You can still hear music and lyrics if you are beside, or even behind, a speaker. So sound bounces off the front wall, and superimposes with the sound that you hear, perhaps cancelling out some frequencies.

I recently found this good explanation of Speech Intelligibility
http://meyersound.com/support/papers/speech/index.htm

Hi everyone, I am just about finished painting my theatre room and am ready to do some acoustic treatment. I needed a few things cleared up though...

When finding the first reflection points using a mirror, am I supposed to do this for just the Front R/L speakers, or the center/rears as well?

No. Only the front speakers need to have their early reflections absorbed. This is to keep the front sound-stage tight and accurate. Reflection is good for the surround speakers.

I read that only the point up to where your ears are should be covered as well, does this mean I shouldn't put any rigid fiberglass above ear level or on the ceiling?
Not necessarily. It depends on how much absorption your room needs. As for the ceiling, sometimes there are early reflections which need to be absorbed there. This depends on the directivity pattern of your speakers, as well as how they are place.

I'm not totally sure why the entire front wall needs to be covered too. It seems like no sound would be bouncing off that area. But if it's recommended, I'll do it.

It may not be absolutely necessary. If you know beforehand that your front speakers do not significantly radiate at medium to high frequencies toward the screen wall (considering toe-in!), you don't need it. It is always a good safety measure, however. In commercial cinemas, where the speakers are located behind a perforated screen, front wall absorption is used largely to kill reflections from the screen back towards the front wall.

Absorption on the front wall also follows the live-end dead-end model (room is live in back, dead in front), which works well for home theater surround sound. The front wall is also generally a convenient, available area for absorption.

However, what about the area with the screen? Should I put the fiberglass up all over the wall first, then put the screen up? Or put the fiberglass around the screen (making the screen appear as though it's impressed into the wall?)

If you are using an ordinary non-perforated screen, you don't need fiberglass behind it.

I'm planning on using 2" thick stuff, and I want to space it out from the wall a bit. What would be the best material to mount between the fiberglass and drywall? Wood?

You could space it out with furring strips. Spacing the absorption from the wall enhances low frequency performance.

Regards,
Terry

Just for clarity, all 3 front speakers should have reflection points covered - not just L and R.

Also, I've found in some cases that even without a perforated screen, having some 3lb fiberglass behind the screen tends to help focus things from a center image standpoint. I don't worry about this too much unless the person is also going to be doing a lot of music listening - especially 2 channel. However, this is WAY less important than taking care of the reflection points elsewhere IMO.

bpape
However, this is WAY less important than taking care of the reflection points elsewhere IMO.
Yep.
It's a time and volume thing.
The volume/loudness/signal (speaker radition pattern) out the front of the speakers is louder out the front than the sides.
Reflections off the side walls (and floor and ceiling) arrive much closer in time to the dirrect sound than any reflection off the front wall.

"Spacing the absorption from the wall enhances low frequency performance."

Do you have any absorption coefficients for 1" OC 703 mounted with 1" spacing off the wall?

K,

> Do you have any absorption coefficients for 1" OC 703 mounted with 1" spacing off the wall? <

It will be very similar to 703 2 inches thick.

--Ethan

Thanks guys, I think I've got it now. If I have enough spare fiberglass left over, I'll put it behind the screen like bpape suggested. I've always preferred headphones for music, so this is mostly home theatre I'm talking about here.

The only place I've been able to find OC703 is this place (www.spi-co.com/servicecenterdirectory.mv), and I'll have to order in bulk of 96ft, and it will have to be shipped to me. I'd prefer to avoid this problem if possible. I know John Manville makes a similar material called Spin-Glas, but I haven't been able to find that locally either. Do you know of any other brands that make rigid fiberglass so I could check on those too?

CertainTeed makes a 3lb/cu ft equivalent as does Johns Manville

96sq ft is a pretty standard purchase for 1" - that's half a carton (12 pcs). For 2", it's a whole carton.

You can get less but by the time you pay the shipping, the cost per piece will kill you if you're only buying a couple of pieces. Shipping cost on something that size is purely by size - not weight. IOW, you'll pay the same amount to have 2 pcs of 1" shipped to you as you will 12 pcs.

I see...thanks. I have one more question; which is best for this type of use? "Plain", "Foil Scrim Kraft", or "All Service Jacket"? I decided on going with 1" because I don't want it to sound too dead. Here's the specs of Plain vs FSK vs ASJ according to Knauf's site:


---------------125hz 250 500 1000 2000 4000 NRC
Plain 1" (25mm) .08 .23 .62 .88 .96 .99 .65
FSK 1" (25 mm) .21 .63 .84 .93 .51 .22 .75
ASJ 1" (25 mm) .15 .71 .65 .82 .41 .16 .65

(Sorry, it's hard to get the frequencies to line up with the numbers.)

I'm not sure which frequencies I want the most absorption at for the best results?

Wouldn't the foil material reflect sound rather than absorbing it? Or am I confused? I was planning on wrapping it in some cloth material.

FSK and AJS seem to be better at low/mid frequencies, while plain is better at higher frequencies. Should I assume that plain is the best choice then?

Hi everyone. I live in Quebec, Canada:


Around here I'm having a hard time finding OC 703 or OC 705 to treat my home theater.


At the local Home Depot, they sell some Roxul Safe and Sound Mineral Wool which is 3 inches thick and 2.5 pcf. The absorption coefficients for this material looks a lot like the ones listed for OC703 (2 inches thick), according to bobgolds.com tables (The only significant difference I see is more absorption at 125Hz).

I've worked with this material in the past for wall insulation. To me it looks more like normal (not rigid) wool than rigid fiberglass.

Does anyone know if I can use those roxul "panels" instead of OC703 for every well described OC 703 usage? From an absorption point of view, they seem to be quite equivalent (am I right?). But if I use the Roxul Mineral Wool, lets say to treat first reflection points ,my whole front wall or to build corner bass traps, is there any special thing I must do (for example, should I compress it? Should I space the panels from the walls or leave them flat on the wall since Roxul seems to absorb more of the low freqs?)

To summarize, how can I get the OC703 effect while using the Roxul Panels?

Your help will be greatly appreciated...I've been reading this whole thread with a lot of interest!


Stephane Olivier

Having additional absorbtion at 125Hz is not generally a problem. Also, the difference between the 2 sets of specs is pretty insignificant - even at 125Hz.

I'd plot out what the room needs from a decay time perspective and plug in those values. I doubt you'll have any issues using it.

I'm on vacation this week and have been reading a lot of the acoustic threads. I can't remember where I read this, as it may have been a link from a link from a link. Anyway, for Bass Traps, I read that you could purchase Rolls of Fluffy insulation (didn't matter which type, i.e. R13, R19, R25), stack them three high with the plastic wrapping on, and cover them.

Will this work as an effective bass trap? If so, does it matter which thickness I purchase or if I buy them faced or unfaced?

that would work ok, the reason to leave it in the packaging is because it's compressed down to a lot denser, similar to the density of fiberboard that is often discussed here as the effective and economical route to treatments.

On the other hand, you could just buy batts of fiberboard and leave the batt in the corner if you wanted, too. Don't think the cost would be too different, and then if you did want to make some absorbing panels for reflection points etc to tame the RT60 time of the room, you could use some of those boards for that. Fluffy fiberglass rolls insulation won't be useful for that.

Thanks Chris. I'm definitely going to either use 1" or 2" OC703 Rigid Fiberglass for the First Reflection points. I've read quite a bit on here and it appears the rule of thumb is to use the 1" OC703 panels over the 2"?

I'm trying to decide now whether to use Rigid Fiberglass boards for the Bass Traps, or the rolls of fluffy insulation.

Thanks Chris. I'm definitely going to either use 1" or 2" OC703 Rigid Fiberglass for the First Reflection points. I've read quite a bit on here and it appears the rule of thumb is to use the 1" OC703 panels over the 2"?
If I might jump in, either 1" or 2" will work for early reflections. 2" gives you some addition absorption toward the bass because of the added depth. However early reflections are strictly higher frequency effects, so bass absorption doesn't matter.

Regards,
Terry

Thanks Terry. So, as long as I use some Bass Traps in my theater for the lows, I should be OK with 1" OC703 panels for my first reflections?

...that's where doing some models is helpful. Early reflections are a higher frequency issue; but, we also find most residential sized rooms will have a bump in decay times in the 250 to 500Hz range. So if that will be an issue, that can be part of an overall strategy to address both issues.

...that's where doing some models is helpful. Early reflections are a higher frequency issue; but, we also find most residential sized rooms will have a bump in decay times in the 250 to 500Hz range. So if that will be an issue, that can be part of an overall strategy to address both issues.
I agree, Dennis. And measurement can trump models. I recently measured a built but not treated room which had extremely good bass through mid-frequency reverberation times -- not so good high frequency characteristics.

Turns out that the room had an acoustical tile ceiling, which would explain the response I measured in this bare-walled, carpeted room. Now, I didn't have the specifics on the tiles, or how they had been installed. A model would have been a shot in the dark.

But the measurements told me what I need to know for treatment. This room is going to get 1/2" thick fiberglass absorption on the walls. Any thicker, and we run the risk of deadening the mid-range too much.

Regards,
Terry

Never purchased from them, but am going to buy some 703 material:

http://www.insulationworld.com/default.asp

I am a dedicated audiophile with a home theater I listen to music and movies in this room but if I had to go one way or the other I would lean to the music side for sound treatment. I had my room done by a contractor with no sound treatment accept thick velvet curtains on the front wall around the screen covering 95% of the front wall I have become so confused with what to do I have given up for now on doing anything for sound treatment and reading this board has done nothing but to confuse me even more is there a simple way to figure out what I can atleast start with for room treatment and a source to buy them ( I'm thinking sound treatment panels for mid to upper frequency) with out a lot of technical jargon can you guys give me some basic suggestions I do have pictures of the room if you would like me to e-mail them to you :D


Only recently after reading many many hours on this board and other material have I somewhat got an understanding of the terms and practices of proper treatment and still after thinking I got it I read Dr Dennis and Dr Terry's post and I feel dumb again, I call them doctors because if you ever had a doctor explain something in medical terms sometimes you can go away feeling am I going to die or did he say maybe :confused: I myself sometimes when talking to people about my profession or interest get carried away with terms that someone else in my field can understand but someone who does not might say is he on prozac. So to summarize HELP!! in terms I can understand and knowing it won't be perfect ;)

I am a dedicated audiophile with a home theater I listen to music and movies in this room but if I had to go one way or the other I would lean to the music side for sound treatment. I had my room done by a contractor with no sound treatment accept thick velvet curtains on the front wall around the screen covering 95% of the front wall I have become so confused with what to do I have given up for now on doing anything for sound treatment and reading this board has done nothing but to confuse me even more is there a simple way to figure out what I can atleast start with for room treatment and a source to buy them ( I'm thinking sound treatment panels for mid to upper frequency) with out a lot of technical jargon can you guys give me some basic suggestions I do have pictures of the room if you would like me to e-mail them to you :D

Hi kjohn,

Lacking acoustical measurements of the room (which I recommend because it is hard to do treatment without first having a diagnosis), I would start by putting 1"-2" thick acoustical panels at the 1st reflection points on the side walls. This is the equivalent of an acoustical vitamin pill for your room. :) Do a web search for "fiberglass acoustical panels."

Regards,
Terry

Terry thank you now I live in Canada is there someone here that you know of that can come out and give me a measurement. :D

Terry thank you now I live in Canada is there someone here that you know of that can come out and give me a measurement. :D
I recommend purchasing ETF, a product developed and sold by a fellow Canadian, Doug Plumb. This will perform a variety of acoustical measurements. A professional can then help you interpret these measurements, or you can simply post some graphs on this forum and see what responses you get. Our acoustical analysis software and procedures are now 100% compatible with ETF. So we can do our own detailed analysis, and even issue Alpha Certification, just from the ETF files.

Regards,
Terry

Hey folks,

Currently I'm in the planning stages of our next theater. I have decided that we will be going with a fixed 2.35:1 screen. The width will end up at 10 foot, which will force me to place all three front speakers behind the screen. (The room is actually 16 feet wide, but there is a concrete foundation angle where the right front would go, so to be equal the L/R fronts will be at the edges of the screen).

Due to the depth of the room, the speakers are essentially in the room (a storage room) that is behind the screen. I need to build 'back' into that room versus build out into the theater space.

Would you frame the front wall with three holes, the exact size of the speakers, and treat the remainder of the wall? If so, what is the ideal treatment in that scenario?

thanks.

From reading the different tables about panels density and absorption coefficients, I wonder what would be the effect of compressing the material to make it denser.

For example, if I use Roxul Safe'n Sound rockwool, which is three inches thick, and has a density of 2,5 pfc, and I compress it to get half the original thickness, my conclusion is the density should be doubled. Am I right? I would then get 5,0 pfc, very close to the OC705 density. Is my assumption right? My panel would be twice as dense, but half as thick. Would that change its absorption coefficients?

And what would then be the best way to absorb bass? the same amount of material uncompressed or compressed to half its original thickness?

Probably my questions are not very clear, but What I'm wondering about is the difference (or relation) between density and thickness. Can anyone answer my question(s).

The reason I'm asking this is that I want to make my sidewall panels as thin as possible...and the roxul wool I've got is quite easily compressible (lets say using a metal grid like I've seen once on this forum)...


Stephane Olivier

Yes. It would be twice as dense but half as thick. Would that change things? Yes it would. What would the result be? Impossible to say without testing it.

The material's ability to absorb bass frequency depends on a combination of thickness, density, and placement from a boundary or boundaries. They all work together. Can you get good bass absorbtion from 12" of 1lb/cu ft. material? Sure. Can you use 6" of 703 instead of 4" of 705? Sure - might even do better.

There is a point though where you just need a certain amount of thickness no matter what. I wouldn't try to get any kind of even relatively deep bass absorbtion with anything less than 3" thick - 4 to 6" is better no matter the material.

Density basically determines how much it will slow down larger waves. Thickness determines how much of a wave can be contained within the absorbant material. Distance (spacing) determines what part of the waves are in the absorbtion.

These are all velocity absorbers - not pressure absorbers. At a wall boundary, the velocity is zero - not a good place. As you move farther out, the velocity is higher - so the absorbers are more effective. Corner mounting is desirable for a couple of reasons:

- They are at the end of ALL of the frequencies and will grab a bit of everything.
- When you straddle a corner, you get almost a foot of airspace behind them (assuming 2' wide panels)
- You are exposing the material to both the length and the width of the space (assuming vertical wall/wall corners). For your 2' of material, you're actually covering 1.4' of the front wall and 1.4' of the side wall.

I will be using 703 oc 2" mount on the wall in a 2by 2 frame cover with fabric then using 1" trim on the outside to hold the fabric and the 703 in place also could this behave maybe a little like a diffusor and absorber since i'm using some wood on the outside of the panel.:rolleyes:

Framing the panels can provide some deflection - not really diffusion - unless they're spaced at controlled intervals in relation to their width and height. Then, the whole array could provide some diffusive properties.

Weight,

You may want to think about drilling holes in the wood so sound will get in the sides also.. Bryan will say that is only a bonus, but that is kind of like my girlfriend saying she saved us money because the shoes where on sale. :)

???

More like the other way around. Why buy them just because they're on sale? If you do the analysis based on the surface area of the panel, what you get from the sides IS extra - and maybe not desirable.

maybe not desirable?? Not so sure about that. Unless you think you could do to good of a job and knock down to much. For a bass trap you just can't have to much. ;)

That's a nice thing to say but you actually can have too much - though it's very tough. The issue is that you're also exposing more HF absorbtion to the room which may not be desirable. OTOH, it may be just fine.

Realistically, the amount of square footage you gain by poking holes is debatable in regard to the overall picture. In most cases, you'd probably be fine doing it if you want to spend the time. How much will you really get? Well let's see. If you poke a 2" dia hole every 6" (that's a LOT ) on both sides of an 8' tall frame, that would give you about 30 holes at approx 3.1 sq in each. That's about 94 sq inches. 144 sq inches in a sq ft so you're getting about an extra .6 sq foot of exposed area from 16 linear feet of edge 4" wide. The panel itself yields 16 sq ft (2' wide, 8' tall) so you're gaining an extra 3.8%

Guess you would have to build it to see if 6" is "a lot"... I think it is more like 3 inchs apart and 3 inch holes.. Now your talking more in the 10% range.. I see where you are going with that Bryan and most people just have a hard enough time building the frame without cutting there finger off!! ha ha ha

Yeah. Absolutely. If you really want to expose the sides, just get out your trusty router and route out the center 2" all the way down leaving some 'braces' every couple of feet. If you look at the design on Ethan's panels, that's providing some serious side exposure. Now with those, at least the numbers that are posted that you figure with include that side exposure so you can plan accordingly when doing your calculations.

BTW, if you cut 3" holes in a 4" panel side, you're getting pretty skinny on the outside (1/2"). And 3" holes on 3" centers will just exactly meet each other. I assume you meant 3" in between the edges of the holes. I was just throwing out some basic numbers to show what drilling 30 holes in the sides would do as far as surface area compared to the face itself.

Okay, after reading this entire thread (I think I'm now cross-eyed) you guys have convinced me I need to consider some bass trapping in my new room. Two questions:

1) My sub will be in one of the front corners (please save the "OMG - don't put that thing in the corner" argument as this is really my only option ;)). Will it be a good idea to build a corner trap above the sub - basically spanning the corner with fiberglass from the top of the sub to the ceiling?

2) My new room will have a cubby/alcove much like this one:
http://www.reedsplace.com/Theater/New%20Theater/bar.jpg

Would it be helpful to put a trap in that thing - or is the fact that it is not "connected" to the main boundary walls going to negate the effectiveness of a trap there? I was thinking that I could just build out the rear wall of the cubby with a couple of inches of fiberglass that is another couple of inches from the actual wall giving me a kind of panel trap across the back of the cubby hole area. Make sense?

I think putting a trap back in that area would be great. Though you are going to need more then just one..

Yes. That would be good. Also put one in the corner on the other side left to right at a minimum. You'll probably need more as Glenn alluded to but it's a start - then you'll be hooked.

Great - is the way I described building it correct?

kinda like this (view from top):

back wall -------------
air space x x
fiberglass -------------
| |
| |
| |

Also, do you think the corner trap over the sub is a good idea?

ebr,

I KNOW bpape will tell you he would like at least 12" of total depth for this trap. He'll also probably tell you to put in 4" to 8" thick material. I'm sure Bryan will ring in soon :D

I only say this because he's helping me with my room. I'm going with dual 2' deep x 2' wide monsters in rear of the room (which is about the exact same size as yours) behind a hidden wall.

Good luck on the build :) Oh, and great looking room!! I'm going to steal your light tray idea for mine -- hope you don't mind.

Steve

<I only say this because he's helping me with my room. I'm going with dual 2' deep x 2' wide monsters in rear of the room (which is about the exact same size as yours) behind a hidden wall.>

2 feet of rigid fiberglass???? Do you have some kind of 5hz problem we should know about... ha h aha

2 feet of rigid fiberglass???? Do you have some kind of 5hz problem we should know about... ha h aha
Actually, Bryan is talking about a 2' wide x 4" (might be 8") thick piece of a cotton material. Well put it floor to ceiling. Hell, it could be a small baby bed matress for all I know ;) We're still discussing what exactly he wants to put inside. All I know is it will go VERY low and just do wonders for the room.

Steve

Actually, 2' deep is only equivalent to the 1/4 wave of somewhere around 125Hz. Originally I had planned to do a REAL bass trap but we just didn't have the depth and also didn't have the luxury of doing just that since these are pretty much the only 2 bass absorbers we'll have in the room due to aesthetic concerns, no risers, etc. There will be cloth covered panels on all of the wall surfaces - except the back wall which is false (smaller panels) so sealed membrane absorbers are out. One rarely has an option like this in an existing space but when you do, it's nice to take advantage of it. The fill will likely be a mix of materials. I'm still doing the calculations.

In addition, once the room is mostly done and we take some measurements, we'll likely add a sealed membrane on the bottom 1/3 of the space between these 2 beasts tuned appropriately. The upper is still being decided. The whole back wall is false and about 2' deep to house the rear surrounds, the bass absorbers, and eventually a second HSU VTF3.

I wish there was some way we could get some bass control other places in the room but it's just not feasible with the design constraints. We'll make the most of what we have to work with.

I see...thanks. I have one more question; which is best for this type of use? "Plain", "Foil Scrim Kraft", or "All Service Jacket"? I decided on going with 1" because I don't want it to sound too dead. Here's the specs of Plain vs FSK vs ASJ according to Knauf's site:


---------------125hz 250 500 1000 2000 4000 NRC
Plain 1" (25mm) .08 .23 .62 .88 .96 .99 .65
FSK 1" (25 mm) .21 .63 .84 .93 .51 .22 .75
ASJ 1" (25 mm) .15 .71 .65 .82 .41 .16 .65

(Sorry, it's hard to get the frequencies to line up with the numbers.)

I'm not sure which frequencies I want the most absorption at for the best results?

Wouldn't the foil material reflect sound rather than absorbing it? Or am I confused? I was planning on wrapping it in some cloth material.

FSK and AJS seem to be better at low/mid frequencies, while plain is better at higher frequencies. Should I assume that plain is the best choice then?

I did not see a response to this reply. I am also curious about this.

Thanks.

Mark

I did not see a response to this reply. I am also curious about this.
Thanks.
Mark
Use one of the faced insulations if you do not want high frequency absorption. These get largely reflected off the facing. In treating early reflections, for example, which will be at medium to high frequencies, you would not use it.

Regards,
Terry

Exactly. The facing will reflect the mids and highs but bass the bass. Think about it logically - if you're worried about bass getting out of your room through drywall, this kraft paper has no shot at stopping it.

The FSK or FRK is fine - no need for FSJ - not even sure how that would work - never tried it. Also, what you need absorbed is part of the analysis that you do or hire someone to do for you that identifies all of the things in the room - floor, wall construction, windows, doors, furniture, people, etc. coupled with what you're using the room FOR (HT, 2 channel, recording studio, etc.) to determine how much absorbtion you need at each frequency range and where is the optimal place(s) to put it.

Since this appears to be the best place to ask: has anyone looked into Enermax rigid fiberglass (http://www.emcobp.com/en/02/p_02_01_01.aspx?p_prid=22). It has a foil facing and is said to be 14.5 lb/ft^3 and is made for sound applications.

Wondering if this would make a decent choice, covered in a porous material, for taming slap echo and the like (foil side against wall of course) and maybe used in combination with fluffy fibreglass/mineralwool to make bass traps.

For example, what about faux columns in the corners of the room made out of four pieces of rigid glass with a top and bottom, and filled with fibreglass/wool, and slid into the corner and covered with fabric to blend into the decor? It would then span the corners like is recommended, but would be more substantial than just 1 sheet put at an angle.

Probably already been raised somewhere, but I couldn't find it so I thought I'd ask.

Great source of info. by the way.

> Wondering if this would make a decent choice <

I looked only briefly, but I didn't see any absorption data. Usually, products sold for acoustics use have data that shows their performance at various frequencies. This is not to say that stuff is no good! Just that there's no way to know for sure.

> what about faux columns in the corners of the room made out of four pieces of rigid glass with a top and bottom, and filled with fibreglass/wool, and slid into the corner and covered with fabric to blend into the decor? <

Sure.

--Ethan

I may try this myself, but am hesitant to go through the trouble if it's likely not worth it (OC 703/705 aren't available around here as far as I can tell). I realise the absorption data aren't listed, but would it likely be decent for first reflections and/or high feq. absorption (and maybe a little mid-range if only 1 panel thickness is used)? I imagine that the materials are probably similar in many of these products, but would this density be too high for this sort of application, or is there such a dramatic difference that it could range from "fantastic" to "piece of ___" in the absence of said absorption data? I figure, even if it's not as good as the OC stuff, it may be easier for some people to find (Canadian HD stores).

Thanks.

I'd be very leary of using something with that high a density for early reflection point absorbtion. Even something like 8lb can cause high frequencies to just skip off instead of being absorbed.

Without numbers it's hard to say but it might very well do a decent job with the foil toward the room as a bass absorber.

I guess I should be looking for something else for this then. When I get around to tackling bass absorption maybe I'll pick up a sheet and see what happens.

Thanks for the feedback.

Since this appears to be the best place to ask: has anyone looked into Enermax rigid fiberglass (http://www.emcobp.com/en/02/p_02_01_01.aspx?p_prid=22). It has a foil facing and is said to be 14.5 lb/ft^3 and is made for sound applications.

The link specs said it was a wood product, not fiberglass. It was described as a being for noise isolation. It looks similar to Homosote, which has no value as a sound absorber. For a sound isolator, nothing beats sheetrock for the price!

Regards,
Terry

Oops, missed that. Just assumed it was fibreglass-based by the "look" of it at the Depot. Guess I'll hit the phone book and start calling around for the OC boards, it has to be here somewhere....

Out2inch,

Try SPI if you have one close to you.

Glenn

Ethan (or other experts)
I am currently selecting my ceiling tiles for my theatre and have selected a USG one, here is a link to it's specs: http://www.usg.com/products/ViewProductDetail.do?resource=/USG_Marketing_Content/usg.com/web_files/products/prod_details/USG_Ceilings_Premier_Hi-Lite_ClimaPlus_Acoustical_Ceiling_Panels.htm

It has a .75 NRC, does this mean it has a better accoustic rating then using drywall? Any benefit of the perfed (.75) over the non-perfed (.60) tiles?

Thanks for any and all info.

Ethan (or other experts)
I am currently selecting my ceiling tiles for my theatre and have selected a USG one, here is a link to it's specs: http://www.usg.com/products/ViewProductDetail.do?resource=/USG_Marketing_Content/usg.com/web_files/products/prod_details/USG_Ceilings_Premier_Hi-Lite_ClimaPlus_Acoustical_Ceiling_Panels.htm

It has a .75 NRC, does this mean it has a better accoustic rating then using drywall? Any benefit of the perfed (.75) over the non-perfed (.60) tiles?

Thanks for any and all info.
0.75 is good for a 5/8" acoustic ceiling tile. A 1" tile will yield greater absorption. But this number doesn't tell you much, since it does not break down the absorption by frequency. It also assumes an E-400 mounting - a 400 mm (16 inch) space above the tiles.

It is both better and worse than drywall. Much better at absorbing sound within the theater, and much worse at keeping sound in or out of the theater.

Regards,
Terry

0.75 is good for a 5/8" acoustic ceiling tile. A 1" tile will yield greater absorption. But this number doesn't tell you much, since it does not break down the absorption by frequency. It also assumes an E-400 mounting - a 400 mm (16 inch) space above the tiles.

It is both better and worse than drywall. Much better at absorbing sound within the theater, and much worse at keeping sound in or out of the theater.

Regards,
Terry


So, does this mean that I will need less acoustic treatments on my walls? Keeping sound within the room is not a goal of mine, so that is OK to me. Sound quality is more important. Also, I am planning to mount these tiles with the CeilingMAX system (for headroom constraints) so that 16" clearance above them will not exist, wish it could though.

Also, planning on R-25 insulation above the tiles, does it do anything for sound performance in addition to the USG tiles?

Thanks

I got mine from a roofing wholesaler that sold Owens Corning roofing materials. If you can get it thrown on the next truck from the factory, shipping won't be that expensive.

The insulation above will provide some extra control in the lower frequencies and is definitely recommended. The drop ceiling will provide some absorbtion in-room in the mids and highs but not much in the bottom end. You'll still need to control the bass but watch how much other HF absorbtion you have in the room so you don't overdo it in the highs.

With absorption above, you still cannot ignore the walls. At a minimum, they will need treatment at early reflection points between front speakers and seating area. This can be either absorption or diffusion. Also, be careful that opposite, parallel wall surfaces are not bare. Again, absorption or diffusion is required.

All absorption on the walls is not a good idea in light of the ceiling absorption, and mostly diffusion should probably be used. There should be sufficient vertical diffusion so that the sound hitting the walls will scatter towards the ceiling. Otherwise, the reverberation may be uneven and long, with a slower decay horizontally (between wall surfaces) than vertically (between ceiling and floor).

Regards,
Terry

Story time... sorry, I'm excited and ready to get to work!

After an exhaustive search all over the Dallas area with no luck, I stopped by a large HVAC place 2 buildings down from my office and asked about duct board. I made a list thanks to Bob Gold's site that included (9) Popular Rigid Fiberglas boards from: J/M, OC, Certainteed and Knauf.

They didn't have any of them but they had OC 475 EnDuraGold in 4'X10'X1"

I came back to my office and tried to look it up and Bob's list didn't include it... so I did a search and in page 14 of this thread there was mention made of it and the poster said that the Absorption Properties were not good. I continued to searched the OC site and found the specs on the product.

Product------------- thickness 125hz 250hz 500hz 1000hz 2000hz 4000hz NRC
Average of 9 Products--1" (25mm) 0.08 - 0.26 - 0.64 - 0.89 - 0.97 - 0.99 - 0.69
Type 475 EnDuraGold---1" (25mm) 0.08 - 0.19 - 0.69 - 0.94 - 0.99 - 0.98 - 0.7


SCORE!! That is perfect! The properties are dead on.

I was going to buy it from the HVAC place at $45 a sheet, but instead the parts guy did me a favor and called in an order for me at another place on the other side of me office and I got it for about $30 a sheet. All that looking and it was right under my nose...

Ricos,

I live in Dallas also and found a few other places that sell fiberglass that may work for you too. Check out these two threads:

This place sells Mineral Wool
http://www.avsforum.com/avs-vb/showthread.php?p=5847246&highlight=dallas#post5847246

Check out this post and the one a few down from this one for Insulshield (and the like)
http://www.avsforum.com/avs-vb/showthread.php?p=6017867&&#post6017867

Let me know how it goers. I'm going to need to purchase some around the end of the year.

Steve

Not sure I want to re-flame this debate, but I am interested in the experiences of those who have used the "first reflection point" method of acoustical treatment for theater rooms with multiple rows of seating.

I used this tool --> http://www.avsforum.com/avs-vb/showthread.php?t=604400 (thanks Easley) to model just some of the first reflection points for my setup and pretty much found that I would need to cover most of the side walls (at ear level) with absorption (this is what I've always done as my first room was designed by DE).

I got reflection points ranging from 45 to over 110 inches out and this tool is calculating precise points. In reality, the speaker doesn't emit sound from a precise point - it is from a cone ranging from a few inches to several inches across. In addition it doesn't radiate in a straight line - it radiates in a sphere - producing a larger and larger area of "affected" sound waves the further away from the speaker you get.

Accounting for this broader band of sound as well as the range for all the seats, it seems like trying to target absorption at exact reflection points for such a setup of multiple speakers and seating would be futile and just end up with basically the same setup I've always had - absorption all along the side wall at ear level.

For those of you who have treated your rooms with this "first reflection" method - have you found the same thing, or did you target just a couple of "sweet spots" for your treatments?

Terry, at one of my midpoint areas(along my long wall) is a door, is there a way to treat a door to "diffuse" the sound?

Thanks for all your help.

Terry, at one of my midpoint areas(along my long wall) is a door, is there a way to treat a door to "diffuse" the sound?

Thanks for all your help.
Sure. Just build some diffusers onto the door. Here is a rather fancy one made of hardwood that I designed for a client:

http://www.tmlaboratories.com/door_web1.gif

Those are RPG Skylines on either side of the door. They might just as well have been fastened to the door, except for the aesthetics of the Skylines, which didn't go with the room. So we buried 'em behind some nice Guilford fabric.

Regards,
Terry

ebr,

Yes. You can end up with a lot of points - specifically one for each seat for each of the LCR speakers. I personally don't generally absorb reflections deliberately from the surrounds. I prefer to leave the surround field more lively. This does not mean that there is no absorbtion in the rear half and rear wall - just more judicious and more broadband. Some will disagree with that. Works for me.

Thanks Brian. I was only modelling LCR as I knew we didn't want to mess too much with the reverberant field for the surrounds. I guess I was just a little surprised to find that the two supposedly different methods of treatment - really weren't *that* different. But, that's a good thing, I guess :).

I'm with Brian. I only deal with LCR early reflections. Surround sound reflections are not an issue for home theaters, as they do not affect the front sound stage.

- Terry

Hey guys. I was wondering what you folks thought about acoustic panels (for absorption) being made out of a solid panel (mdf or ply) with a layer thick carpet padding, covered with some fabric. I am going for a nice clean look and I want to save money. Is that too much to ask?? :)

What do you think about that idea?

Hey guys. I was wondering what you folks thought about acoustic panels (for absorption) being made out of a solid panel (mdf or ply) with a layer thick carpet padding, covered with some fabric. I am going for a nice clean look and I want to save money. Is that too much to ask?? :)

Yes. ;)

Go with 1-inch or more Johns Manville Linacoustic or other roll-type fiberglass. It is not that expensive, and is much more effective than thick carpet padding.

- Terry

Using carpet padding as a acoustic panel is not the right thing to do... If you want to save money that is fine, but use mineral wool or oc 703. Treating your room with products that do not have any testing at all is really flirting with disaster. Companies like ours and others spend big money to test our products in a lab. This is so people know what they are using.
Ask yourself a question, would you buy a speaker with no testing or build a speaker without some kind of proven method behind it? Your room acoustics are more important then any other gear you have to achieve good sound. :)



Hey guys. I was wondering what you folks thought about acoustic panels (for absorption) being made out of a solid panel (mdf or ply) with a layer thick carpet padding, covered with some fabric. I am going for a nice clean look and I want to save money. Is that too much to ask?? :)

What do you think about that idea?

... flirting with disaster.

LOL! That was the name of my race boat.

Woodmonkey - man from one "non-expert" to another. Call a couple HVAC installers and ask them what kind of 1" fiberglas duct board they use. Chances are it will be Owens Corning or Certainteed. Then ask who their supplier is.

This stuff is EXTREMELY easy to cut to size and cover. A little spray glue and some staples and you are done. Put some finishing nails in the wall at a slight upward angle and push the pieces into place. The end.

I'm sure I'll get blasted for a non-technical approach and that the acoustic coefficients of the spray glue will discombobulate the space-time continuity or something like that... but it is very effective.

LOL! That was the name of my race boat.

Woodmonkey - man from one "non-expert" to another. Call a couple HVAC installers and ask them what kind of 1" fiberglas duct board they use. Chances are it will be Owens Corning or Certainteed. Then ask who their supplier is.

This stuff is EXTREMELY easy to cut to size and cover. A little spray glue and some staples and you are done. Put some finishing nails in the wall at a slight upward angle and push the pieces into place. The end.

I'm sure I'll get blasted for a non-technical approach and that the acoustic coefficients of the spray glue will discombobulate the space-time continuity or something like that... but it is very effective.
Yes, the spray glue will in fact discombobulate the space-time continuum, but a little bit works quite nicely. :)

- Terry

^^^ That wasn't as bad as I thought... ;)

"LOL! That was the name of my race boat."

Sailboat??? What kind?? I have spent many of days racing sailboats. boy I miss those days.

"I'm sure I'll get blasted for a non-technical approach and that the acoustic coefficients of the spray glue will discombobulate the space-time continuity or something like that... but it is very effective. "

Not at all.. It is a matter of looks, time and if you want to know what is going into the room..

myfipie... I raced offshore powerboats on the APBA Pro-Series circuit. I have a 34' Eliminator V-bottom with twin 500 HP Mercs in Factory 2 class, she ran 96.5 MPH on radar. I love going fast on the water (Top speed 165 MPH in a 46' Skater cat with twin 1400 hp Sterlings).

Thanks for not lighting me up on my lay-person's description. I find that there are many times when the incredible knowledge on this forum can overpower the novice. If I was given a more direct approach, it would have taken me MUCH less time to track down the stuff I needed. BobGold's co-efficient charts are key!

I did a search for Auralex sound panels but received no hits. My HT is 18x26 9' ceilings with speakers behind screen, 2 long side walls and back wall is a patio door with 2 side windows which are covered with heavy curtains. I'm planning on ordering Sonoflat panels from Auralex, local dealer, but I'm wondering if anyone has any experience with placement and installation? Behind my screen is a 2' x 12'
cavity for my 2 fronts, center, and sub, should I place panels behind the screen, behind the speakers? Where would you put them on the side walls. Side walls from floor to ceiling are 7'6" then a 18" soffit = 9', floor is carpet, wall with screen covered with black fabric. Can anyone help me sort this out? I definitely need bass traps.

I did a search for Auralex sound panels but received no hits. My HT is 18x26 9' ceilings with speakers behind screen, 2 long side walls and back wall is a patio door with 2 side windows which are covered with heavy curtains. I'm planning on ordering Sonoflat panels from Auralex, local dealer, but I'm wondering if anyone has any experience with placement and installation? Behind my screen is a 2' x 12'
cavity for my 2 fronts, center, and sub, should I place panels behind the screen, behind the speakers? Where would you put them on the side walls. Side walls from floor to ceiling are 7'6" then a 18" soffit = 9', floor is carpet, wall with screen covered with black fabric. Can anyone help me sort this out? I definitely need bass traps.

Try this dedicated Auralex forum (http://www.avtalk.co.uk/forum/index.php?t=thread&frm_id=11&rid=77&SQ=1132776564).

I use Aurlaex in my cinema and it's the best upgrade I've ever done.

Norm,

> should I place panels behind the screen, behind the speakers? Where would you put them on the side walls ... Can anyone help me sort this out? I definitely need bass traps. <

Yep, all rooms need bass traps. There's a lot of advice about bass traps and panel placement in my Acoustics FAQ:

www.ethanwiner.com/acoustics.html

--Ethan

myfipie... I raced offshore powerboats on the APBA Pro-Series circuit. I have a 34' Eliminator V-bottom with twin 500 HP Mercs in Factory 2 class, she ran 96.5 MPH on radar. I love going fast on the water (Top speed 165 MPH in a 46' Skater cat with twin 1400 hp Sterlings).

Thanks for not lighting me up on my lay-person's description. I find that there are many times when the incredible knowledge on this forum can overpower the novice. If I was given a more direct approach, it would have taken me MUCH less time to track down the stuff I needed. BobGold's co-efficient charts are key!

Well 6 knotts is really fast to me!!! ha h aha

I got to tell you that sometimes we get so lost in the science that people get plan turned off to acoustics, throw up there hands and say for get it, in fear of doing it wrong.. Really the only thing you can do wrong is do nothing at all. :D
We all owe a lot to Bob!!

Glenn

I have a question for you HT gurus. Forgive my newbie-ness. :)
Why do so many folks use GoM fabric on their walls? I can understand its use when its hiding speakers, but what purpose does it serve on the wall? An accoustically transparent material seems like it would do nothing for sound. Hopefully someone can set me straight. Thanks.


Marc

because usually there is absorbing material behind it, or diffusors or other acoustical devices and speakers and whatnot. It's mainly for aesthetics, and to be transparent to any of the aforementioned devices that would be behind it. ;)

Exactly. The idea is not no have to worry about the look of what's behind. Whether it's a full covered wall of batting/duct liner or scattered treatments so you don't have to worry about aesthetics of patterns and spacing - the cloth does the trick.

In the same vein, I need advice on two things;

1. What other fabrics besides GOM can I use? Names would be nice.

2. I can't find OC 703 anywhere. Mind you I have only checked HD and Rona?
Where should I look?

Thanks
John

My understanding is that OC is going to get harder and harder to find... If you want to build yourself you may want to contact Bryan about getting some.. BTW Bryan I got the notice that OC is going up 9%..

Glenn

John- I see you're in Canada as well (I'm in winnipeg). I phoned a few places too- and actually had luck with a local building supply store this week. They had no issues ordering in 703. The only catch was that I had to buy a minimum of 12 2x4 sheets of it. Kind of pricey though- they wanted cdn$18 per sheet. So my advice is to phone local places. If they carry OC product, they should be able to get it in.

fiberglass board like OC 703/705 is more industrial/commercial insulation you usually wont find it at HD or similar. Look in the yellow pages for insulation supply places, hvac supply etc and call and ask for rigid fiberglass board such as OC 703, they'll know what you're talking about shouldn't take you long. If you're on the boonies obviously you'll probably need to find places near civilization, but shouldn't be hard to find, there are other brands than OC its all the same stuff and bout the same price so they'll know what you mean. BTW it's usually used for big HVAC ducting and such, but any competent commercial supply guy will know exactly what you're talking about.

Can anyone direct me to someone in San Diego who sells any of the accepted 1" absorption materials listed on this thread? I'm coming up with absolutely nothing so far. Thanks.

Hi-

I finally got through this thread and am well on my way to reading Ethan's FAQ. It is still not clear to me what might happen to bi-polar speakers if you treat the front wall. I am okay the thought of removing the first reflection from the speakers I have, but I'd like to hear from people that have heard them. Has anyone done this?

I finally got through this thread and am well on my way to reading Ethan's FAQ.

Congratulations... :)

HH

Congratulations... :)

HH

At least I have pics of MY HT online... ;) :P
:D

I have a few more...

- What does putting in a broadband bass absorber do for total output? I understand it will tame my peaks (and reduce smearing). Will my max SPL drop a few db? Will it just flatten the response but allow the SPL to flow? (Let's assume I EQ'd my peaks out with regards to max SPL... make sense?)

- It's pretty easy to understand how absorbtion will reduce a peak. How does it effect a null? For converstation, assume both a dip and a deep drop.

- What are some good ways to treat a null with bass traps? Would you only trap a portion of the room (i.e. one wall with the room dimension causing the null)?

- I am considering broadband bass traps in certain corners of my room. Only one corner allows for floor to ceiling (soffit) treatment using the 2' hypotenuse 703 method I have read about. How effective would it be do only do from the floor to half way up? I might go from 2' to 1' to smaller (so I can make it all the way up). Any comments on that?

- My current surrounds are bi-polar and would be located close to any corner bass trap I might construct. Is it advisable to use a semi-reflective surface on a portion of the trap so I can keep the surround non-locatable?

PS... pics of my HT in the link in my sig...

Thanks!

I have a few more...

- What does putting in a broadband bass absorber do for total output? I understand it will tame my peaks (and reduce smearing). Will my max SPL drop a few db?

Hi,

Over at Siegfried Linkwitz's web site (http://www.linkwitzlab.com/rooms.htm) there's a discussion of how to calculate Amplifier power needed to sustain a Reference Level if you know the type of speaker, the volume of your room, the Reverberation Time of your room, the efficiency of your speakers and the reference level desired.

As mentioned above the amount of amplifier power needed to sustain a particular sound pressure level depends on a number of factors, including the overall Reverberation Time of the room. So depending on how much the broadband bass absorber decreases Reverberation Time there could be a measurable effect on power requirements, and therefore maximum SPL level.

For example, when I used Mr. Linkwitz's method to calculate the per channel requirements of my home theater it came out to about 152 watts to sustain a 100 dB sound pressure level from one of my main speakers based on my room's Reverberation Time of 230 ms. If my room had a Reverberation Time at twice that duration (460 ms) the required power would only be about 76 watts to maintain a 100 dB sound pressure level.

However, while my power requirements might be reduced if I removed half of my absorption, the increase in Reverberation Time would adversely impact the sound quality for multi-channel listening, which depending on whose formula you use, should ideally be roughly 230 ms for my room size.

Larry

After reading this thread, it is obvious to me that no matter what I would do to treat a room, it would be wrong.

Is there not a good book or two out there with full intructions or specifications on how to build a quality (not nerd-prefect) HT of varying sizes? Maybe THX Specs or the like.

Honestly, the amount of varying opinions and minute details in this thread seems very piecemeal to me.

Hi,



As mentioned above the amount of amplifier power needed to sustain a particular sound pressure level depends on a number of factors, including the overall Reverberation Time of the room. So depending on how much the broadband bass absorber decreases Reverberation Time there could be a measurable effect on power requirements, and therefore maximum SPL level.

For example, when I used Mr. Linkwitz's method to calculate the per channel requirements of my home theater it came out to about 152 watts to sustain a 100 dB sound pressure level from one of my main speakers based on my room's Reverberation Time of 230 ms.

Larry

Wouldn't it just have been a hell of a lot easier to use a dB meter and turn it up until you reached 100dB's? Save your pencil lead maybe?

Larry-

EDIT

Thanks for the link... I am too tired for math in the morning, but it looks like a reduction in ring time equates to a reduction in power requirement. Did I miss a section on the SPL being absorbed by traps?

Now I wonder if the reduction in ring time offsets the absorbed sound? ...check my math (if you like)... like I said, I am generally too tired to think in the morning. ;)

...no more math before coffee

Larry-

Thanks for the link... I am too tired for math in the morning, but it looks like a reduction in ring time equates to a reduction in power requirement.
No. 'Fraid its the other way around. A reduction in reverberation time results in an increase in power requirement. That's because increased reverberation provides more sound energy storage in the room. An amplifier doesn't need to put out as much power to excite the room to a particular sound level. The downside, however, is a reduction in clarity of transient sound.

Regards,
Terry

Tweaks,

> Did I miss a section on the SPL being absorbed by traps? <

Terry is of course correct - adding absorption to a room reduces the overall level if for no other reason than it reduces the energy from reflections. But...

At bass frequencies adding absorption generally increases the level because deep nulls, which are very common throughout a room, are raised.

--Ethan

No. 'Fraid its the other way around. A reduction in reverberation time results in an increase in power requirement. That's because increased reverberation provides more sound energy storage in the room. An amplifier doesn't need to put out as much power to excite the room to a particular sound level. The downside, however, is a reduction in clarity of transient sound.

Regards,
Terry

No more math before coffee!
;)

That was more intutive anyway.

Tweaks,

> Did I miss a section on the SPL being absorbed by traps? <

Terry is of course correct - adding absorption to a room reduces the overall level if for no other reason than it reduces the energy from reflections. But...

At bass frequencies adding absorption generally increases the level because deep nulls, which are very common throughout a room, are raised.

--Ethan

So that explains it... trapping reduces peaks (and overall output) but increases nulls by absorbing the cancellations. (...again... too tired to think in the morning).

Is there any simple math or rules I might use? My concern is I am going to improve my room so much that I'll need (... REALLY need) another sub. My Ultra is doing pretty well right now...

Tweak,

> My concern is I am going to improve my room so much that I'll need (... REALLY need) another sub. <

I'd say that's unlikely. If anything, adding a lot of bass traps will give you more output. And the sub will also not have to work as hard thereby lowering distortion. My living room HT is pretty large at 25 by 16 with an 11 foot peak ceiling. I have an original 11-inch cube Carver Sunfire subwoofer and 38 traps. I get a huge amount of very deep bass in this room, even from that tiny sub.

--Ethan

Tweaks,

> Did I miss a section on the SPL being absorbed by traps? <

Terry is of course correct - adding absorption to a room reduces the overall level if for no other reason than it reduces the energy from reflections. But...

At bass frequencies adding absorption generally increases the level because deep nulls, which are very common throughout a room, are raised.

--Ethan
Okay, let's go to the videotape, and see if this matches our recent experiment! :)

Here are the mean dB sound levels for the average of all seven positions, as taken directly from the spreadsheet:

79.1 dB - empty room
78.8 dB - 2 Mondo traps
78.7 dB - 4 Mondo traps
77.8 dB - 17 Mondo traps

Looks to me like the bass sound level decreased with increased absorption. However this effect was not huge -- only 1.3 dB going from empty room to 17 Mondo traps. It is hardly worth worrying about.

Regards,
Terry

Tweakophyte:

What does putting in a broadband bass absorber do for total output? I understand it will tame my peaks (and reduce smearing). Will my max SPL drop a few db? Will it just flatten the response but allow the SPL to flow? (Let's assume I EQ'd my peaks out with regards to max SPL... make sense?)

Absorbtion reduces the height of modal peaks, and reduces the depth of modal nulls.

Absorbtion also reduces the sound pressure level of a steady noise, according to the formula:
reduction in SPL = 10 log (a2 / a1)
where a1 is the absorbtion in sabins of the before room, and
a2 is the absorbtion in sabins of the room after additional treatment.

As you add absorbtion you will turn your volume knob up to achieve the same SPL.
You can keep adding absorbtion until your speakers start distorting, or melt and fail completely.

- What are some good ways to treat a null with bass traps? Would you only trap a portion of the room (i.e. one wall with the room dimension causing the null)? Have one.

Absorbers damp a mode. They treat both peaks and nulls of that mode.


- I am considering broadband bass traps in certain corners of my room. Only one corner allows for floor to ceiling (soffit) treatment using the 2' hypotenuse 703 method I have read about. How effective would it be do only do from the floor to half way up? It would be a little more than half as many sabins.

Wouldn't it just have been a hell of a lot easier to use a dB meter and turn it up until you reached 100dB's? Save your pencil lead maybe?

Hi Dallas,

Either I'm missing the humor in your posting, or you are missing the point. Since I didn't see any of those cute smilely faces ;) ;) ;) etc., in your posting indicating your response was tongue-in-cheek, I'll assume that you're serious.

Tweakophyte asked whether adding a broadband bass trap would effect his maximum SPL, not how far should he twirl his dial to reach a given SPL dB. My calculation was intended to demonstrate that there could be a significant difference in power required to reach a given SPL if the total absorption of a room were to change significantly.

I appreciate your concern, but with today's computers not a lot of expensive pencil lead was harmed in the making of these calculations. :p

Seriously, I had recently gone through the exercise to calculate the how much amplifier power I would need to sustain reference levels in my home theater when playing some of the more energetic action movies. It was virtually no additional effort to substitute another value for Reverberation Time. On the other hand, ripping out half of my insulation to empirically demonstrate the differences, now that would have been an effort. :eek:

Larry

Bpape gave me this info from another area:
If you're looking at answers about the bipolar surrounds then the answer is that yes - it will absorb some of the mids and highs depending on if they're angled or not will determine how much to a certain extent.

To negate this (on the rear wall anyway and for surrounds), the bass absorbers in the corners could (maybe should depending on the room analysis and what it needs in terms of HT absorbtion - don't want to overdo the highs) be covered with a scrim of some sort. I have the FRK (just the facing) that you can attach via spray adhesive - or you can use kraft paper. This will reflect the highs and make the mid frequency absorbtion less efficient. Think of an absorbtion 'curve' that starts out at about 1.2 or so at 125Hz and gradually goes down after 250Hz to around .3 at 4kHz.

On the front wall, that's a bit trickier. Bipolar speakers in front present some challenges and issues. If it's just a rear tweeter, I'd scrim face just behind the tweeter - maybe 1 sq ft and leave the rest of the front wall soft to deal with surround reflections from the front. Whether or not you can scrim face the bass corner absorbers depends on how close your speakers are to the corners. Normally, I'd say leave the middle soft and scrim the top and bottoms. But, with the rear tweeter, you might not be able to do that - might have to scrim the whole thing - or just the middle foot or 2 for the rear tweeter.

Some people just treat bipoles in a room like a normal speaker and absorb the rear wave. While this gets rid of the anomolies generated by a bipolar design, it also can tend to skew the frequency response as those were voiced with that tweeter in the equation.

The cotton is a great product. It's class A fire retardant, non-shedding, non-itching, totally natural, etc. No gloves or long sleeves required to work with it. Cutting it is a bit of a trick but if you take your time and use a VERY sharp razor knife at a shallow angle and with multiple light strokes it's not too bad. This is for the thicker stuff. For the thinner 3lb and 6lb material, you can acutally use a good sharp pair of scissors (big ones) or can also use the knife as described above. I have people who cut it into triangles to stack up solid all the time.

Some material cost/handling questions... With kids, I am concerned with contamination.

How many of you have worked with Cotton absorbers compared to the semi-rigid fiberglass (703)? How does the performance compare for say, a Mondo Trap? How is the cost?

Also, I have access to some excess (maybe 30-40ft) of Linacoustic. How is that to work with compared to the 703?

I am thinking about making some front-wall absorbers behind the mains, some mondo and semi-mondo (2' and 1' sides) traps in the back corners (and maybe front), and some treatment above the screen-wall. (see the pics in my gallery or my sig.)

Any comments?

PS Ethan, Terry... I bumped your eq vs treatments thread...
nudge, nudge

...and thanks to all of you for you comments...

Answers! And Questions?!?!

Hello people of the acoustic treament thread, I would like to give you some info on my experiecnes. I decided that using 703 wasnt gonna work for me becuase I didnt want to wrap all that stuff in fabric. So I went in the search for Black Acoustic Sound Board. I have found it. Available by Knauf, at a place is round rock TX called, General Insulation (they have a website). I found this loaction out by contacting Knauf directly from thier site, and I got an email back in a very short time.

I called this place, and they do not have it in thier Round Rock store, only in Dallas, but can get it to me, it sells in 4'X10'X1" sheets. It is 1 dollar per square foot, and only sells in 100 square foot sets. So I have to buy 200 or 300 square feet. That is the info, now here is the questions...

I wanted to use it on my front wall completly and my celing. The celing to make the celing black, and the front wall for front wall absorption, along with bass traps, I figured that I would do all of celing and wall, and corners, and that was 288 square feet. I was not sure how much this stuff was when I mad this decision. It will cost me $356.40 total for delivery and tax. I am not sure if I wanted to spend this much (was thinking $200). So I was thinking about cutting back to 200 square feet, which will allow the whole celing (to make it black) and some of the front wall and bass traps. The area is 16X12X8 rectangle, with the screen on the 12 foot wide wall. What would you do? Thanks for the replies.

Bpape gave me this info from another area:

The cotton is a great product. It's class A fire retardant, non-shedding, non-itching, totally natural, etc. No gloves or long sleeves required to work with it. Cutting it is a bit of a trick but if you take your time and use a VERY sharp razor knife at a shallow angle and with multiple light strokes it's not too bad. This is for the thicker stuff. For the thinner 3lb and 6lb material, you can actually use a good sharp pair of scissors (big ones) or can also use the knife as described above. I have people who cut it into triangles to stack up solid all the time.

I did exactly what Bpape suggested (Thank-U Bpape) "cut it into triangles to stack up solid" I did this in all four corners (BAC stacked floor to ceiling covered with GOM)

I don't have fancy gear to test everything for showing graphs, just the Excel & Rat Shack type of things...

But my ears tell me that my room is a lot better with BAC in corners and 103 panels on the walls and it looks OK to the WAF part.

HH

Terry,

> let's go to the videotape, and see if this matches our recent experiment! :) <

Ha ha.

Seriously, I'd say that's more a function of trying to use "mean" to tell what's going on audibly. Perhaps I should have phrased it the way I usually do: Adding bass traps generally increases the perceived level of bass in a room. Whether you have to turn up the volume knob an extra dB or whatever to get the same volume measured on an SPL meter is less of an issue to me. Even at the same volume setting I'd say that the nulls coming up will more than counter the peaks going down. Audibly, of course! :D

--Ethan

I am a bit confused....I read on manufacturer sites that sound absorbing cloth and other insulation types can be installed behind the drywall between the studs....I am assuming that you would only do that in the case that you want to stop noise from passing through....A set-up like that would not actually help within the room at all right? I mean the drywall would be reflecting the sounds back and forth correct? I am may be way off, but from what I've read I was under the impression that the absorbing material must be directly exposed to the sound....

In any case, I am about at budget's end but I need to do some accoustic treatments for the walls/ceiling (absorbtion). I do not want to use fiberglass because I worry about my childrens exposure to material that will be "exposed" behind GOM. Can someone give me a reasonably priced alternative that is not in any way toxic? Also, please post where they may be ordered from... Reminder: I am seriously low on funds after renovating the entire basement and all the new equipment, so I am looking for effective but inexpensive treatments (I don't mind if it requires a lot of labor.)

Thanks,
Rudedoggy

I did exactly what Bpape suggested (Thank-U Bpape) "cut it into triangles to stack up solid" I did this in all four corners (BAC stacked floor to ceiling covered with GOM)

I don't have fancy gear to test everything for showing graphs, just the Excel & Rat Shack type of things...

But my ears tell me that my room is a lot better with BAC in corners and 103 panels on the walls and it looks OK to the WAF part.

HH

Did you worry about the color of the BAC? Did you make any panels with this for you front wall? It looke like the cotton has a little more acoustic absorbtion than the 703 down low, and is pretty close to the Linacoustic I grabbed from bob's site.

Product thickness mounting density 125hz 250hz 500hz 1000hz 2000hz 4000hz NRC
703, plain 2" (51mm) on wall 3.0 pcf (48 kg/m3) 0.17 0.86 1.14 1.07 1.02 0.98 1.00
Echo Eliminator (Cotton) 2" 3pcf A 0.35 0.94 1.32 1.22 1.06 1.03 1.15
Permacote® Linacoustic® R-300 2" (51mm) 3.0 pcf (48 kg/m3) 0.26 0.73 1.10 1.10 1.04 1.03 1.00

Harley, did you check out the price of other options? Why cotton?

Does anyone have pics of this stuff?

Thanks,

Harley, did you check out the price of other options? Why cotton?

Does anyone have pics of this stuff?

Thanks,
bpape (Bryan) has a few pics of the cotton on his website. Here are a few -- left is the 2", right is 4" material:

http://sensiblesoundsolutions.com/images/BAC_1.gif http://sensiblesoundsolutions.com/images/basbus_1.jpg

Steve

Did you worry about the color of the BAC? Did you make any panels with this for you front wall?

Harley, did you check out the price of other options? Why cotton?

No worry GOM covered it up.

Corner panels are BAC covered with GOM.

Yes on price options....BAC at the time seemed the way to go and it was so easy.

I took a few Pics of the room but I don't know how to get them to display?

PM me with your email and I'll send them to you if you want to see what a amateur can do to mess up good intentions

HH

Here is a thought...What do you anticipate the problems would be if I did NOT drywall the inside of the theatre room, and instead. filled the space between the studs with accoustic cloth insulation, walled it with duct liner, and used gom attached to 1 X 2" firring strips which I will attach to the door stud. Then stretch the fabric to the inside of a stud roughly 50 inches horizontally and the take a second piece of gommed firring strip and attach it likewise to the same stud and continue on down the wall.... (I probably didn't explain it right) It should appear boxed that way (I can use molding over top and bottom) but there would be no drywall used (two side are concrete with 2 X 4 's used as furring strips to give a little width for the duct liner - duct liner only on the concrete sides - maybe double sheeted). I could then 2 layer the drywall on the outside of the theatre walls for sound deadening... Would this be a dysfunctional setup? I am concerned about how the wall sound would play out and if there are any drawbacks for not using the drywall on the interior of the walls... Any comments/concerns would be appreciated...

It would seem to me that the 4" of cloth between the studs and the duct liner covering it would be a pretty absorbent combo, but then again I know very little about anything audio...


Thanks,
Rudedoggy

I'm no expert, but I'm guessing much too absorbent.

Also, I'm not sure that construction would pass code.

Is drywall required under code in a basement? The accoustic cotton I am talking about is actually used to replace R13 and R19 fiberglass and in and of itself would meet code...I don't know about the replacing of drywall will duct liner as a violation of code. Both have some fire resistance ( I am pretty sure that was listed under the liner..)...maybe someone can answer that? Also, how much is too absorbent? Anyone else have any suggestions on my earlier post?

Thanks,
Rudedoggy

Looks like I'll be constructing some floor to ceiling corner bass absorbers the next couple weeks and have a few questions.

I can not source Owens corning 703 or 705 locally so will be using Ottawa Fibre OFI-48 3lb 2x4 foot 2" thick material doubled up, maybe tripled, the acoustic properties of the FRP faced material look excellent

First question.....when doubling up faced material should only the first outside layer be faced or is there any bass advantage to using faced material for both layers? I'm not too concerned about mid to high frequency absorption at this point.

Secondly, should doubled layers be glued together or would a slight space between them absorb bass better.

Third, I was planning on making enough absorbers for four corners of the primary HT area but due to the room(s) configuration might it be better if one or two were situated elsewhere. I don't have any analyzing programs at this point except for the usual meter and test cd's so am looking for general/probable positioning advice for the room(s).

Attached is the room layout which is a basement, doubled up 1/2 inch drywall over 3" styrofoam board over concretre /fiberglass insulated 5/8 drywall ceiling. Flooring is (soon to be again) carpet over pad. The viewing area is about 19' long and 12' wide at the front and back, obviously wider in central area. Entire speaker/screen area and back wall lined with black velvet.

I'm am not using subwoofers and my general bass response shows a belled hump from 80 to 200 hz will lulls on either side and an 10db gain between 25 and 30hz. While the FR doesn't really look that bad the bass definitely is a little indistinct and needs improvement.

Thank-you

When using faced product, you should remove the facing from everything except the face that is toward the room. The other pieces should be unfaced.

You don't need to glue multiple layers together. If you want to add air space, that can only help by getting the front one further into the room.

Looking at your sketch, I'd do the front corners and the wall/ceiling corners in the front and rear of the theater area. It's such an odd shaped room that you'll still need some more but that will be a start.

Some of your FR issues are likely due to SBIR from the mains being close to boundaries andnot absorbed. You might also want some bass absorbtion beside the speakers to help smooth things out. If you got a sub, you could tune the bass response without having to move the mains.

Also, the seating appears IIRC to be pretty close to the back wall. I'd move it out - that will help smooth things also.

When using faced product, you should remove the facing from everything except the face that is toward the room. The other pieces should be unfaced.

You don't need to glue multiple layers together. If you want to add air space, that can only help by getting the front one further into the room.


Ok great, this will reduce the cost and simplify the construction.


Some of your FR issues are likely due to SBIR from the mains being close to boundaries andnot absorbed. You might also want some bass absorbtion beside the speakers to help smooth things out. If you got a sub, you could tune the bass response without having to move the mains.

My room is still packed away due to a water leak but IIRC the speakers average about 10" from the side walls and the rear of the 18" deep speakers are about 35" from the rear wall. I just downloaded Ethan Winers Boundary Frequency/Distance calculator and this would indicate the side wall distance shouldn't really come into play at the frequencies I'm having problems with but the rear wall distance very well could be contributing to the problem. Regardles, my side walls are covered with velvet attached to a frame which I can easily fit some absorption panels behind to experiment.

Also, the seating appears IIRC to be pretty close to the back wall. I'd move it out - that will help smooth things also.

The seating puts the listeners head in the 40-44" range from the rear wall. Moving out definitely helps the bass response but then puts me too close to the video screen plus it encroaches on the path to the door beside the bar. I can only hope the traps will help somewhat.

Thank-you for spending time answering my questions.

Great answers as usual, Bryan!

Regards,
Terry

Still want to get some expert accoustical advice on the following:

Here is a thought...What do you anticipate the problems would be if I did NOT drywall the inside of the theatre room, and instead. filled the space between the studs with accoustic cloth insulation, walled it with duct liner, and used gom attached to 1 X 2" firring strips which I will attach to the door stud. Then stretch the fabric to the inside of a stud roughly 50 inches horizontally and the take a second piece of gommed firring strip and attach it likewise to the same stud and continue on down the wall.... (I probably didn't explain it right) It should appear boxed that way (I can use molding over top and bottom) but there would be no drywall used (two side are concrete with 2 X 4 's used as furring strips to give a little width for the duct liner - duct liner only on the concrete sides - maybe double sheeted). I could then 2 layer the drywall on the outside of the theatre walls for sound deadening...

Would this be a dysfunctional setup?

I am concerned about how the wall sound would play out and if there are any drawbacks for not using the drywall on the interior of the walls... Any comments/concerns would be appreciated...

It would seem to me that the 4" of cloth between the studs and the duct liner covering it would be a pretty absorbent combo, but then again I know very little about anything audio...


Thanks,
Rudedoggy

Still want to get some expert accoustical advice on the following:

Here is a thought...What do you anticipate the problems would be if I did NOT drywall the inside of the theatre room, and instead. filled the space between the studs with accoustic cloth insulation, walled it with duct liner, and used gom attached to 1 X 2" firring strips which I will attach to the door stud. Then stretch the fabric to the inside of a stud roughly 50 inches horizontally and the take a second piece of gommed firring strip and attach it likewise to the same stud and continue on down the wall.... (I probably didn't explain it right) It should appear boxed that way (I can use molding over top and bottom) but there would be no drywall used (two side are concrete with 2 X 4 's used as furring strips to give a little width for the duct liner - duct liner only on the concrete sides - maybe double sheeted). I could then 2 layer the drywall on the outside of the theatre walls for sound deadening...

Would this be a dysfunctional setup?

I am concerned about how the wall sound would play out and if there are any drawbacks for not using the drywall on the interior of the walls... Any comments/concerns would be appreciated...


Hi Rudedoggy,

It would be dysfunctional for sound isolation. Sound would travel easily to adjacent rooms, and vice-versa. I don't know about your local building code requirements, but this could be a show-stopper.

For sound quality otherwise, it might be good. I say might because one would have to calculate the absorption of what you propose, and see if it is well balanced for all frequencies. You might have to use some drywall or better, diffusive treatment to reduce absorption. You might also have to use different thicknesses and densities of absorber than just duct liner.

Regards,
Terry

Anyone ever hear of a product called sound board by Weyerhauser. I saw some at Home Depot when I was looking for a solution for some accoustic paneling. It is a very fibrous soft wood product 1/2" thick and they are 4'X8' sheets and they are only $8 each. I was going to double them up for 1" and than wrap with a nice cloth and than hang on walls about 1' off the walls. They also had some JM 2" thick foam stuff also in 4'X8' sheets for about $20 each. I was also thinking I could manufacture some bass traps out of those by cutting into 12" squares and stacking them or 12" strips and attaching them all together to make a sort of 12" sq pillar 8' high. Would this work as a bass trap as well.

Anyone ever hear of a product called sound board by Weyerhauser. I saw some at Home Depot when I was looking for a solution for some accoustic paneling. It is a very fibrous soft wood product 1/2" thick and they are 4'X8' sheets and they are only $8 each. I was going to double them up for 1" and than wrap with a nice cloth and than hang on walls about 1' off the walls. They also had some JM 2" thick foam stuff also in 4'X8' sheets for about $20 each. I was also thinking I could manufacture some bass traps out of those by cutting into 12" squares and stacking them or 12" strips and attaching them all together to make a sort of 12" sq pillar 8' high. Would this work as a bass trap as well.
Forget about them both. :)

What you need is fibrous, open material with moderate air flow resistance (fiberglass, mineral fiber, cotton, polyester). Neither of these materials will work.

Regards,
Terry

I'm not sure if this question goes in this forum or in the construction forum . . .

My speakers are built into my screen wall, to be flush with the screen. They sit about 4 inches above the stage area. The stage area is poured concrete and extends about 24-30 inches in front of the speakers. My concern is about early reflections from the stage. My questions are:

(1) should this be a concern?

(2) if it should be a concern, what should I cover the stage with? Carpet? GOM over linacoustic / sound board? Other? Rarely will anyone stand on the stage, but I'm sure it will happen from time to time.

Thanks

I'd cover in carpet generally. Whether it's a reflection point or not depends on where your seats are.

I am sorry if this has been answered before, There is soo much in here now it is hard to read it all, im trying.

I just called SPI, and they said they carry 703! (Victory) in single sheets of "non-faced" that I can buy at 1.30 a sqare foot. Or Faced in bundles of 192 square feet at .73 a sqare foot. Could someone please exaplain the difference between faced and non-faced? And what should I do if I get the non-faced?

Terry,

I have a 19.5 X 11.5 ft room 7.5 tall. Two basement walls. 6.1 sound system. I am thinking about taking the carpet up the first 3 or so feet of the wall and doing a chair rail and some framed "boxes" with GOM covering holding cotton duct liner (.60NRC I believe) along all back and side walls. Will this be sufficient you think? I have no understanding of the underlying science of all this - which I might add you all have me in awe of.

Thanks,
Rudedoggy

I need to sound proof my dorm room a little so that I don't get complaints from the people living upstairs and downstairs anymore. They've mostly been about the bass coming through. What are some cheap solutions I can get for this? I was thinking placing a dynmat mat under the sub and acoustic panels like these http://www.envisiononline.net/acousticpanel.html on the ceiling. Would this do the job or do I need some sort of sound proofing material?

I already have carpet on the floor, but the sub isn't on carpet. The floor is made of cermaic tiles and the ceiling looks like some stone or something.

I really don't know about this stuff and I don't need anything fancy.

DarkSyde - 1.30 for 1" 703 unfaced is pretty steep but they'll sell it to you a piece at a time. Conversely, 1" FACED 703 for .73 sq foot is pretty reasonable. If you can use all of the material, you can easily peel the facing off.

For reflection points you want unfaced. The faced has a kraft paper and foil scrim on one side. This can be very useful when place on top of thicker material for bass absorbtion without overdeadening the highs.

Doggy, that will be VERY overly dead IMO. I wouldn't do the carpet up the wall thing.


Sorry Borky. Hate to break it to you but you're not going to soundproof a dorm room no matter what. Even if you could, cheap and soundproofing don't go together. It's all in how the structure is built which you can't control. Nothing you do inside the room (other than may be a LITTLE but by putting the sub on something like an Auralex SubDude) is going to do much of anything in the way of soundproofing - sorry.

Oh, and thanks Terry.

What would putting a few acoustic panels like maybe this kit http://www.sweetwater.com/store/detail/RoomDST36B/ do? Wouldn't they "absorb" some of the sound?

Bork,

That is a kit that is used to control the acoustics in the room.. It has nothing to do with soundproofing at all.. Soundproofing is totally differant thing, as Bryan is trying to point out to you..

Glenn

Terry,

I have a 19.5 X 11.5 ft room 7.5 tall. Two basement walls. 6.1 sound system. I am thinking about taking the carpet up the first 3 or so feet of the wall and doing a chair rail and some framed "boxes" with GOM covering holding cotton duct liner (.60NRC I believe) along all back and side walls. Will this be sufficient you think? I have no understanding of the underlying science of all this - which I might add you all have me in awe of.

Thanks,
Rudedoggy

Is it really bad to do partial carpeting on the walls? I could have sworn I read someone saying to do it....Also, this is going to be used almost entirely for movies/home theatre, so shouldn't I want it to be "dead" as possible? It is all very confusing. Please help a newbie out with some advice guys...

Does anyone know if carpet padding has any absorbtion (NRC). I don't know what to look for for absorbant materials but it would seem to be a low cost alternative if ti does have any NRC value... Is there any common materials you can think of that have a respectable NRC other than fiberglass? Certain cloth types, batting you get form a fabric store etc etc etc

thanks,
Rudedoggy

bpape, yea, I know 1.30 is kinda high, but I figured that is the price I pay for not buying a whole bundle. I think 2 sheets to play with is worth the price hike.

Simpler question for the non-faced vs faced. What should I do for corner bass traps? Faced or non- and if faced, facing which way?

This is what I am gonna start with and go from there, see how I like it and then think about buying a bundle or 2. Thanks.

Well I am getting ready to put my acoustic pannels together, I have mineral wool, speaker grill cloth, trying to figure out what I want to attach the stuff too. Maybe some lighter wood, foam board, who knows. I hope to put them together tomorrow. I hope everything works as planned.

Dog,

> Is it really bad to do partial carpeting on the walls? I could have sworn I read someone saying to do it <

Just because you read it somewhere doesn't make it true! The Internet is a great democracy, and anyone can say anything. Unfortunately, that's what they usually do. :D

Seriously, the real issue is how well a given material absorbs and, just as important, over what frequency range. Carpet absorbs only the highest frequencies, so the risk is that you'll end up with a room that's too dead sounding yet too boomy at the same time.

--Ethan

Ok thanks, carpet should be out...Now, lets say instead I do ceiling to midway to floor with boxes (covered with GOM) with batting in them and use some silence FR fabric at the bottom instead of carpet.... Would that be a better solution?

Also, I was still wondering if anyone know if carpet padding has any absorbtion (NRC). I don't know what to look for for absorbant materials but it would seem to be a low cost alternative if ti does have any NRC value... Is there any common materials you can think of that have a respectable NRC other than fiberglass? Certain cloth types, batting you get form a fabric store etc etc etc.


thanks,
Rudedoggy

P.S. If anyone is interested in splitting a bolt of black silence fabric contact me. It is like $3 less per yard that way.... I plan on ordering some in the next week or so.

I guess I'll put a subdude under the sub and see what that does. I was considering a dynmat too, has anyone ever tried one of those with a subwoofer?

bpape, yea, I know 1.30 is kinda high, but I figured that is the price I pay for not buying a whole bundle. I think 2 sheets to play with is worth the price hike.

Simpler question for the non-faced vs faced. What should I do for corner bass traps? Faced or non- and if faced, facing which way?

This is what I am gonna start with and go from there, see how I like it and then think about buying a bundle or 2. Thanks.

You would want to keep the facing to the front of the panel, NOT THE BACK. :D
Keep it on if you want to not absorb high end, but also keeping the facing on will act as a membrain which will absorb more low end.. For only having 2 I would go with them faced and see if that helps..

Glenn

Doggy,
If you want some acoustical value, use acoustical materials - sorry. Don't mess with carpet pad, boxes, etc. Get some rigid fiberglass, acoustical cotton, or mineral wool that is specifically tested for use as acoustical materials. You'll spend more time and hassle trying to save a few cents, not really save much, and end up with something that doesn't work NEARLY as well.


Dark,
If you're going to make a judgement as to what it can do for you in the bottom end, you're going to need more than 2 pcs - especially as it's only 1" material if my calcs are correct. To do much of anything in the bass, you'll want 4". A box isn't a bad investment.

Hey guys. Do any of you use those accoustic foam panels (the wedge type) as sound absorbers in your rooms? Compared to the prices of standard accoustic panels, these things are a steal! Is there a drawback to using this material?

Some of these room kits are really reasonable.

marc

If you are going to use foam then you want to use 3" or more and from Auralex.. Companies like Foam by mail sell junk.. But even with 3" foam from Auralex you are going to still have to put bass trapping to absorb low end. Foam will not absorb that and if you just put foam in without bass traps then your high end will be tamed but the low end will be bouncing all around in your room. Making the bass unclear and muddy... Low end is the area you really want to focus on first...

Glenn

bpape,

I already went the route of trying to locate rigid fiber and linacoustic in my area and it was a no-go. It seems that for the most part hardware/building supplies wish to deal only with contractors or in larger orders. I spent weeks trying to find the formaldehyde free rigid fiberglass with no success. Besides that, markup on anything listed as 'acoustic' seems to be fairly ridiculous for the most part. No blame for that, its just high in demand - especially any type of installation right now... Add shipping on to it and your talking some serious money for the most part...As for the acoustic cotton, it seems like a reasonable alternative, but of all the companies supposed to carry it, only yours has even replied to my requests for a quote.

Thats why I was wondering if anyone has tested the NRC of some of the more readily available/household type items that you can pick up at say Walmart/Lowes (like the carpet padding I mentioned)?

I realize this will probably yield second rate alternatives and not necessarily a 'made for acoustic' material - which may not be an option for the audio purists in the house, but would be a convenient for those of us on a tight budget with little time to scour the nation for JM black acoustic board sources...

I have even been considering wrapping some of the contractor ceiling tiles listed as acoustic ($23 for box of 10 - 24" X 48"X 5/8" - .55 NRC tiles at Lowes) in GOM...

Before I take that route though, I wanted to challenge the more curious/industrious experts here to provide some other pedestrian and readily found options that might be comparable to some of the professional stuff. I would bet some of you audio geeks ( I say that with affection) have already tested the NRC's of stuff like Walmart pillow stuffing and stuff for NRC values - so now is the time to sing out.

Thanks,
Doggy

>I have even been considering wrapping some of the contractor ceiling tiles listed as acoustic ($23 for box of 10 - 24" X 48"X 5/8" - .55 NRC tiles at Lowes) in GOM... <

That can work but you are going to have to pull the facing off each layer then stack them together make a 4" panel.. With that not sure what you would get, because you have just changed the panel..

>Before I take that route though, I wanted to challenge the more curious/industrious experts here to provide some other pedestrian and readily found options that might be comparable to some of the professional stuff. I would bet some of you audio geeks ( I say that with affection) have already tested the NRC's of stuff like Walmart pillow stuffing and stuff for NRC values - so now is the time to sing out.<

Get some fluffy fiberglass in a bag and stack it up in corners for floor to ceiling.. You can put a fauls wall in front of it..

Glenn

rudedoggy:

Where are you in the world?
Did you try internet dealers?

Home Depot around here sells acoustic ceiling tiles that are made out of yellow fiberglass. Just take the plastic wrapper off the box and leave them 4" thick. I don't know how expensive that is. In Ontario Canada, Roxul Safe N Sound is also available at home depot.

There's a variety of things that can be done with fluffy fiberglass pink. Including compressing your own absorber out of it, or just using it as fill for deep (2' +) bass traps.

Walmart pillow stuffing is Polyester Batting. Probably OK. Don't know about the cost / ft^3 though.

Hey guys. Do any of you use those accoustic foam panels (the wedge type) as sound absorbers in your rooms? Compared to the prices of standard accoustic panels, these things are a steal! Is there a drawback to using this material?

I assume you mean aside from their ugliness. My wife would not tolerate any of these in any color.

Kal

Actually guys, I was hoping someone could point out some more novel materials rather than the fiberglass route.

The challenge is to find common materials (ie packing styrofoam, pillow stuffing, ball of tape - I don't know...) and come up with a "true find" in terms of absorbtion - with NRC numbers. The material needs to be common, non-toxic, inexpensive, and have a decent NRC. Making something out of a combo of such materials would be good too.

I just thought it might be cool to get the acoustical geniuses out there to stretch those minds a bit and think out of the box.With the obvious talent assembled throughout this thread, I'm betting some really interesting ideas might come to light...


I am in Southern Illinois by the way... Also, why would I have to remove the facing off the ceiling tiles? I assume the NRC of .55 is as installed (in a ceiling) which would have the facing intact and towards the room. So what would be the difference draped in GOM and facing out from the wall?

Thanks guys,
Doggy

Actually, I think that NRC rating for the ceiling tiles assumes a 16" airspace above (behind) them...

Stuck flat on a wall, I don't think they do that much.

Actually guys, I was hoping someone could point out some more novel materials rather than the fiberglass route.

The challenge is to find common materials (ie packing styrofoam, pillow stuffing, ball of tape - I don't know...) and come up with a "true find" in terms of absorbtion - with NRC numbers. The material needs to be common, non-toxic, inexpensive, and have a decent NRC. Making something out of a combo of such materials would be good too.

Doggy,

Acousticians have tried just about everything over the years. What works ideally well are thick, fibrous materials that permit air to penetrate. This rules out closed-cell foam and pretty much anything heavy and board-like.

The good news is that there are lots of materials that qualify: fiberglass, mineral wool, acoustical cotton, and dense polyester batting. Open-cell foam also works, though not as efficiently so you have to use a thicker layer of it.

I don't think that there are any secret materials to be found at Home Depot or Lowes. Their stuff is pretty ordinary, since it is sold for common, high-volume applications. :(

Regards,
Terry

Terry - I thought I had heard you mention that a 'dead' room was better for HT(98%). However, another member told me I should avoid carpeting the lower half of my wall because it would make the room too dead...Can you clear this up for me? Do I want it roadkill dead or just critically injured...If dead is better, shoudln't the carpet be ok then?

P.S. I also was thining of putting some traps in the back two corners. and a off/on mix of batting/duct liner in boxed squares above the chairrail....

Thanks,
doggy

rudedoggy:

There's a few insulation contractors in Illinois listed here
http://www.bobgolds.com/InsulationContractors.htm

avoid carpeting the lower half of my wall

http://www.bobgolds.com/AbsorptionCoefficients.htm
lists
1" linacoustic 0.04 0.26 0.69 1.00 1.07 1.02

I chose that because several Dennis Erskine theatres seem to have 1" linacoustic on the lower half of 3 walls (left, right, rear).

That's read, for 1" linacoustic:
near 125hz has an absorbtion coefficient of 0.04
near 250hz has an absorbtion coefficient of 0.26
near 500hz has an absorbtion coefficient of 0.69
near 1000hz has an absorbtion coefficient of 1.00
near 2000hz has an absorbtion coefficient of 1.07
near 4000hz has an absorbtion coefficient of 1.02

1.00 is sort of 100% absorbtion. 0.00 is sort of 0% absorbtion. (it's not a percentage, it's the results of a test, so you can get values like 1.50 without much problem, but anything around 1.00 is about as good as it gets)

A broadband absorber, to me, is one that has 1.00 absorbtion from 125hz through 4000hz.

Carpet.

2291 Floors, 10 mm soft carpet on concrete Ref. Dalenbäck, Datensatz der CATT-Software, November 2000. Data-Category in CATT: CARPET_SOFT, C: Floors, D: 10
0.09 0.08 0.21 0.26 0.27 0.37

506 6mm pile carpet bonded to closed-cell foam underlay (Ref. 18)
0.03 0.09 0.25 0.31 0.33 0.44

2006 Carpet heavy, on concrete Ref. Harris:Handbook of Acoustical Measurements and Noise Control, McGraw Hill 1991
0.02 0.06 0.14 0.37 0.60 0.65

Two things you'll notice about carpet:
a) it's much less absorbant than linacoustic,
b) it's very unpredictable absorbtion depending on what kind of carpet you use

Multiplying absorbtion coefficients, by square footage, gives absorbtion in Sabins.

Everything in the room -- couches, people, cats, walls, whatever --
a) absorbs some sound (how much is frequency dependant as well as material)
b) reflects some sound (how much is frequency dependant as well as material)
c) transmits (through) some sound (how much is frequency dependant as well as material)

The goal is for each frequency to have the sum of the Sabins in the room, be about equal. That is the Sabins at 4000hz, be about the same as the Sabins at 63hz.
Another goal is to have the right number of Sabins (to many and the room is too dead, too few and the room may be echoey).

Wierd sounding rooms are ones with lots of HF absorbtion, but little or no MF or LF absorbtion, or have the absorbtion in the wrong places giving reflection problems that affect speach inteleigibility and imaging.

Doggy. I believe what was said was that you shouldn't carpet the bottom of the walls and put batting on the top as the room would be too dead AND UNBALANCED. It would IMO have too much HF absorbtion and not enough in the mids/bass.

As for the materials, unfortunately, finding a non-fiberglass material that is cheap is almost impossible. To get enough high density batting is going to cost you. Acoustical cotton can be reasonable in some cases. Mineral wool has some of the same chemicals you're trying to avoid as fiberglass, foam is either more expensive or not worth much depending on the quality of the foam.

Has anyone even used Autex Quietstuf or rigid duct liner? Is it even available in the U.S? If so where?

Thanks,
Doggy

Is it possible to design a wall so that it would absorb lows mids and highes simular to the way they did on the DIY show..... except only drywall every other stud pocket and fill the other pocket with say oc 703 and covering with GOM leaving a 6-8 inch pocket of dead space behind the 703 panels. (sorry if I am showing my ignorance on this subject. but I am trying to understand the best construction methods BEFORE is cover my walls in drywall)
Not sure if this would work or not. If not what would. I have approx 6" behind the studs before you get to the styro foam covered concrete walls on 3 sides and 8" to the drywalled forth wall. (basically a room in a room.)

You can certainly design treatments into the wall structure. If you're going to leave the drywall off of A VERY FEW stud cavities, then the back side of those cavities will need to be drywalled or you'll lose your isolation.

Also, bass absorbtion is best done at the end of the boundaries. The wall is certainly at the end of one boundary and a little of it is at the then of a second. Corners are at the end of both and the tri-corners are at the end of all 3. Those are the most efficient places to provide bass control.

So it sounds like the best solution is going to be fiberglass batt insulation in all stud caveties covered by drywall and I see there are pre packeged room treatments that would have tri-corner base traps in the upper corners of all 4 corners and gom covered pannels for the first and second reflective points for the side walls all for less than 400.00 (this seem like a great deal to me). My next problem is I have a beam 6x8 that spand the width of my room at about 9 1/2 feet fron the front wall. will I need to treat the corners on the front and back side of the beam. ( it is covered in drywall ) or can I get by withe the four room corners ant the front 2 heam corners.

A question on front wall treatment. I am usin all inwall speakers. so how do i treat my front wall if the speakers are in wall. the front wall is 12 x 7 the screen is 100in. and the left and right speakers are just outboard of the screen. the center channel is below due to low celing height. Need some help please.

For the front wall, treat around the speakers to leave them exposed. It can actually work quite well with them in-wall and all of the wall treated.

Don't worry about the corners around the beam. Deal with the 4 room corners if you can - and don't forget that you have 4 other corners you can also use - the ones that run horizontally at the wall/ceiling intersections.

Has anyone ever purchased this kit: http://www.sweetwater.com/store/detail/RoomDST36B/ ? It seems like an inexpensive way to lightly treat my HT/music listening room at home and make things sounds better. Also, what's the difference between panels that are flat and those that have wedges? I really don't know anything about this acoustic treatment stuff, but I would like to get some general understanding.

Borky:

I think of absorbers as tools to meet a goal.
I have no opinion on the suitability of anything mentioned in this post for your room.

Your 'sweetwater' link is actually this product:
Auralex Roominator 36 (contains 18 Charcoal Gray DST-112 panels and 18 DST-114 panels). http://www.auralex.com/sound_control_D36/sound_control_D36.asp

Absorbtion coefficients for those two are:
DST-112: 0.12 0.27 0.54 0.71 0.83 0.99
DST-114: 0.16 0.26 0.57 0.75 0.90 1.00

They are 1'x1' panels, so that's 36 ft^2 of surface area, for $139, or $3.86 / ft ^2.

vs

1" linacoustic: 0.08 0.31 0.64 0.84 0.97 1.03
2" 703: 0.17 0.86 1.14 1.07 1.02 0.98
4" 703: 0.84 1.24 1.24 1.08 1.00 0.97

2" 703 is about $0.75 / ft ^2, but probably needs covering cloth and time to build and mount.

4" 703 is about $16 per 2'x4'x4" panel, and you can buy a wrap kit for $30 (TeaBagz), so that's $46 / 8 ft^2, or $5.75 / ft ^2 -- but you get 7 times the absorbtion at 125hz with that (0.84 / 0.12 = 7), and you can make corner traps out of them for bass absorbers. GoM as covering may be cheaper per ft^2 than TeaBagz, but I haven't checked prices on GoM lately. GoM is more work and a better look.

Do you have any links for the above mentioned acoustic panels?
Also I understand Teabagz is just something to put the material inside, sort of a liner? Why do I need that, can't I just use the panels on the walls?

Borky:
Do you have any links for the above mentioned acoustic panels?
Linacoustic is manufactured by Johns Mansville and is acoustical HVAC duct liner, but works well on walls.
703 is a rigid fiberglass product made by Owens Corning.
Neither is really an 'acoustical panel' in the sense of a finished product, but rather a building material, thus happens to be relatively inexpensive, yet works well.
For a decent list of typical alternatives (other than and including linacoustic and 703) please see
http://www.bobgolds.com/AbsorptionCoefficients.htm

Also I understand Teabagz is just something to put the material inside, sort of a liner? Why do I need that, can't I just use the panels on the walls? In the case of the auralex foam product you found, you can just glue them to the walls and you're done. Same with auralex MegaLENRD's. Being able to just place them and you're done, has a lot of appeal to a lot of people.

In the case of 703, if you bump into it you may get fiberglass into the air, and if you hang it over your head you're almost certain to get more dust on everything in the room than you're accustomed to -- unless you cover it. It's relatiely easy to rip off a bite sized chunk, so I wouldn't want babies crawling near it for a variety of reasons.
In the case of linacoustic, as duct liner, it is treated so that even a stiff wind won't blow fiberglass into the air, but the black twoards-the-room side isn't pretty, so most people cover it with something that's pretty.

Borky,

> Why do I need that, can't I just use the panels on the walls? <

This always boils down to a compromise between several competing goals:

1) How much you're willing to spend

2) How much work you're willing to do

3) How nice you want it all to look

4) How good you're hoping the result will be (acoustically)

A lot of folks here are die-hard DIY'ers who love their workshops and prefer to save money rather than buy a commercial product. Others can't be bothered with sawdust and fiberglass powder, or they value their time at more than $6 per hour and would rather buy one thing and be done with it. Neither approach is wrong.

--Ethan

I have an odd SBIR question that I hope you acoustic gurus can shed some light on.

The front of my room will have a "notch" in it due to the foundation walls that make up the front part. Like this:

-----------------------------
| |
| |
--------- |
| |
| |
The notch will never be visible because it will be hidden behind the proscenium wall. However, this means I cannot put the speakers where I normally would - out wide behind the proscenium wall.

In another thread, it was pointed out that putting my L/R speakers behind my screen (as I planned) would create a very narrow angle to the listening position and be detrimental to the imaging of the front sound field.

So, my question is, if I were to put a speaker here (where the 'S' is):


-----------------------------
| |
| |
--------- S |
| |
| |

Would I have SBIR issues (the face of the speaker would be in front of the side wall, but the speaker body would be right up against it). Or, other issues due to having one side of the speaker right up against a boundary and not the other?

I wouldn't be opposed to buying the fiberglass insulation like the 703, but problem is, I called a few stores in my area that the main OC site claims are dealers and they carrying nothing like that.

Also, does anyone know the absorbtion coefficients for these panels: http://www.envisiononline.net/acousticpanel.html ?
I don't see them anywhere on the site.

Borky:

There's a couple of stores in New Jersey listed at
http://www.bobgolds.com/InsulationContractors.htm

I think that:
a) http://www.gikacoustics.com/
b) Auralex TrueTraps (http://www.auralex.com/acoustic_foam_trutrap/acoustic_foam_trutrap.asp) (test data (http://www.auralex.com/testdata/test/mastertable.pdf))
c) and of course ethan's http://www.realtraps.com
sell ready made acoustic panel absorbers, and perhaps more importantly list absorbtion coefficients for them.

Hi Guys. I have a question about treating my side walls with OC703 1" panels at the First Reflection points.

I am very clear that I need to use Unfaced fiberglass. However, the ONLY place in my area where I can purchase 703 (found on the spi website) does not carry Unfaced boards. They can order them for me, but I have a feeling it will be more expensive. What will be the effect of using Foil or Paper covered (I don't know which acronym goes with which one FSK, etc.) fiberglass panels, with the paper or Foil facing the drywall? I plan on just covering these with Muslin or GOM and gluing to the back of the panel.

If someone could let me know, I'd greatly appreciate it. I'm going to have the company give me a price quote on the Unfaced (and faced depending on what is said here).

Any thoughts on my delimma?

Hi Guys. I have a question about treating my side walls with OC703 1" panels at the First Reflection points.

I am very clear that I need to use Unfaced fiberglass. However, the ONLY place in my area where I can purchase 703 (found on the spi website) does not carry Unfaced boards. They can order them for me, but I have a feeling it will be more expensive. What will be the effect of using Foil or Paper covered (I don't know which acronym goes with which one FSK, etc.) fiberglass panels, with the paper or Foil facing the drywall?
No difference at all. :)

If the faced insulation was the other way 'round, there would be a big difference. You would no longer have as efficient a wide-band absorber, but one better at absorbing low frequencies.

Regards,
Terry

No difference at all. :)

If the faced insulation was the other way 'round, there would be a big difference. You would no longer have as efficient a wide-band absorber, but one better at absorbing low frequencies.

Regards,
Terry

Thanks Terry, that's great to hear. Let me ask you this. I really like nice shapes and overlayed effects from makers, such as kinetic, etc. However, I want my panels to be DIY. I was thinking of this, and you tell me if this would be a big No No!

Use a piece of MDF either painted or covered with fabric at the First Reflection Points. On top of the MDF, I would have a 1" rigid board (OC703) covered in fabric. That would give me a nice 3D look to my panels without Over Absorbing by using (2) 1" panels to create the depth. Would using MDF as a back layer be OK as I'd think that would be similar to the panel attached to drywall?

Thanks Terry, that's great to hear. Let me ask you this. I really like nice shapes and overlayed effects from makers, such as kinetic, etc. However, I want my panels to be DIY. I was thinking of this, and you tell me if this would be a big No No!

Use a piece of MDF either painted or covered with fabric at the First Reflection Points. On top of the MDF, I would have a 1" rigid board (OC703) covered in fabric. That would give me a nice 3D look to my panels without Over Absorbing by using (2) 1" panels to create the depth. Would using MDF as a back layer be OK as I'd think that would be similar to the panel attached to drywall?
An MDF back should be no problem when covered with rigid fiberglass. Just make sure that it is fastened to the wall firmly and doesn't rattle.

You mean "either painted or covered with fabric" at the exposed sides, right? Otherwise, I don't understand.

- Terry

You got it. In simplistic design, the MDF will be a larger rectangle and the Fiberglass panel will be a smaller rectangle attached to the MDF. It will just give my panels a layered effect to look nicer (IMO)

tonybradley
What will be the effect of using Foil or Paper covered (I don't know which acronym goes with which one FSK, etc.) fiberglass panels, with the paper or Foil facing the drywall?Acoustically, it'll be just fine.
Structurally it might be easier to support, or even glue, the facing to the wall.
If you covered your entire wall in them, then you'd have humidity/mold issues, but just a first reflection point, or even half the wall, shouldn't be a problem IMO.

For 1" first (and early) reflection points, go ahead and buy whatever's cheapest, such as faced 703.

I presume you're covering them in something eventually.

Tony,

> What will be the effect of using Foil or Paper covered <

FRK is not good for for first reflection control, but the solution is very simple: Turn the panels around so the bare fiberglass faces the room. You could peel off the FRK facing, but there's no real need to if you simply reverse the panel.

--Ethan

Bob and Ethan,

Thanks. I knew I'd want the 'unfaced' portion towards the room. I just wasn't sure if there would be some wild effect with the foil or paper against the drywall.

I am using OC 703 on side walls up to ear level. On floor I have concrete and rear area is on a 12 inch riser. When I carpet should I use padding under or glue carpet down directly to cement and riser?

I would use padding because it makes the carpet more comfortable and last longer. I don't think it's going to have too much of an impact on deepening the absorption of the carpet, it won't absord much bass because it's so thin, so I don't think I would say that acoustics is something I'd consider when deciding about carpet padding. But I'd certainly use very thick padding(as thick as you can get) on cement because it makes the space more comfortable over cement without subflooring. You might not need as thick padding on the riser if you wanted to save some cash.

In a recent thread I asked about faux fur covered fiberglass for acoustical panels (safari theme type room). Here is a related, but different question:

One of my subwoofers will be in a cabinet / enclosure that is built into the wall, so that the front of the sub will be flush with the wall (and all space around the sub packed with insulation so that the enclosure does not result in boominess).

The sub enclosure is located directly opposite where one of my acoustical panels will go. I would like for the room to appear symetrical in regards to the treatments on the walls. Accordingly, instead of a cabinet front with speaker grill cloth covering the sub woofer enclosure, I'm thinking of covering the sub enclosure's opening with the same type of faux fur fabric that will cover the acoustical panel on the other side of the room. However, I don't want to do something that distorts the sound from the sub.

The faux fur fabric can be blown through. There is about the same resistance in doing so as blowing through 2 layers of GOM. The "fur" is about 1/3" - 1/2" long.

My thought is that since the sub (Klipsch thx ultra 2 sub) will only be playing from around 15hz up to somewhere between 80hz and 150hz (depending on where it is set on installation, calibration, etc.), the faux fur fabric would not have any discernable effect on these frequencies, right???? Can anyone confirm that I'm ok doing this?

Thanks much.

I'm confused over how to treat my rear wall and would like to hear some acoustical treatment expertise. My room is 15'9" wide and 19' long. (The rear wall and the front / screen wall are the 15'9" walls). I have 2 rows of seats. My rear row of seats is about 6" - 12" from the rear wall. I have a 7.2 setup with side surrounds and 2 rear surronds.

My question is whether, with the rear seats so close to the rear wall, should I treat the wall with absorbtion or diffusion or some combination of both?

Thanks.

Westshorestudios,

I myself would go with abortion on the back wall. Diffusion, IMO, really is good in a large room and with the back sets so close the the back I can't see how diffusion is going to work for you.

Glenn

Westshorestudios,

I myself would go with abortion on the back wall.
Glenn

I think that is illegal in most states.

Happy New Year!

Oh God Eric, way to much partying last night!!!!!!! Sorry about that. "Absorption" :)

Hello,
I am new here I know I am about to ask a question that has already been asked (can't seem to find it)

Insul-Shield, I called the manufacturer and they told that they did not make that product anymore. I called to see where I could buy it in my location (Columbus, OH).
So, what are folks using in its place?

Thanks

Any number of things are comparable. From JM - the Linacoustic RC coated black is what I used and is very similar to the old InsulShield.

Hello,
I am new here I know I am about to ask a question that has already been asked (can't seem to find it)

Insul-Shield, I called the manufacturer and they told that they did not make that product anymore. I called to see where I could buy it in my location (Columbus, OH).
So, what are folks using in its place?

Thanks

Owens Corner 703 unfaced 1" is popular. I bought an bonded acoustical cotton equivalent. I'm not using the cotton on a wall and it's a little more money.

Speaking of JM...

Is the Johns Manville Spin-glass board basically the same thing as the OC 703? I am looking at the 2" thick 815 (3pcf) because I can find it locally and in-stock.

The specs look different here:
http://www.bobgolds.com/AbsorptionCoefficients.htm
FR ....125hz 250hz 500hz 1000hz 2000hz 4000hz NRC
815...0.27 0.91 1.11 1.09 1.09 1.09 1.05
703...0.17 0.86 1.14 1.07 1.02 0.98 1.00

...another quick one... I think...

If I mount the rigid fiber board (like 703 or the JM 815) on a thin piece of wood for support, then space it away from the wall, will I still get the benefit of absorbing lower freqencies? Also, if I take one of these panels and put it in a corner, will it work to absorb deeper bass?

This way is easier and cheaper than making a frame, but I am not sure if I need the back of the fiber board to be open.

Hello,
I am new here I know I am about to ask a question that has already been asked (can't seem to find it)

Insul-Shield, I called the manufacturer and they told that they did not make that product anymore. I called to see where I could buy it in my location (Columbus, OH).
So, what are folks using in its place?

Thanks

FYI, I recently (about 6 weeks ago) purchased InsulShield IS300 unfaced 2x4 1" thick panels special ordered from Menards.

Mark

703 and 815 are very similar.

If you mount either on a board then there is no benefit to spacing it off the wall. If you need to mount it to something, just leave the perimeter of the board so most of the fiberglass is not backed. Then you'll benefit from the spacing.

When I am treating my front, is it generally effective to just have the 2" (OC703 or JM815) basically flush with the wall, or should I go for some spacing.

My thought is for the front wall and first reflection points, I can take the easy route and use the plywood. When I get to the corners I will either double up (and make a 4") or build a frame and create some space.

Not that this gets repeated a lot, but if I am going for bass trapping in the corners using a panel, it is better to double up to make a 4" panel, or space a 2" panel 2" away from the wall? In that case if I have foil scrim, I assume it faces the wall for general absorbtion and faces the room for "bass only"? How about for the front corners versus the rear?

They should also call this the acoustical treatment validation thread ;)

Thanks again,

Is 86 cents per foot an ok price for OC 703?

Westshorestudios:
For 2" thick 703 material, I've seen prices over the past two years between $0.50 and $1.50US per square foot.
My rule of thumb that for 2" thick material, once you've found stuff for less than $1 per square foot, stop looking -- it's not worth the effort any more.
So, 86 cents is an ok price per square foot of OC 703 2".

Tweakophyte:
If I mount the rigid fiber board (like 703 or the JM 815) on a thin piece of wood for support, then space it away from the wall, will I still get the benefit of absorbing lower freqencies?
It depends on lots of things. I'd try to stick with one of the known and tested designs -- otherwise you're just hoping and who knows what you'll end up with.

If you have
- porous absorbtion, then wood, then a 2" air gap, then your wall (gypsum/drywall)
worst case you'll get a resonance that will reduce your soundproofing.

Generally speaking, wood is a reflector.
If you have wood in a sealed enclosure, it can be a membrane trap.
FRK (basically paper or foil) on the outside of fiberglass certainly reflects, but is light enough that it lets some sound through.

Ignoring what you might get for absorbtion -- why would you cover the entire back with plywood and then space it from the wall? Are you trying to hold up the fiberglass?
I'm trying to figure out how and why you're mounting the fiberglass to this piece of floating plywood. Why not just have the four corners. And if you're gluing the 703 to the wood, could you fill the wood with holes (i.e. 80% holes, 20% wood). Why not just six spacers (2"x4x"4") and use impailing clips on them to hold up the fiberglass. (BTW, I've never heard of anyone glueing fiberglass to wood. Usually they are some kind of nailed/clipped, or held by gravity, or a frame, or spring ties. Mine were friction fit into an exoskeliton frame)

Hi Bob-

Thanks for the response. The reason for the plywood backing is to give the fiberglass additional structural support, to give me something I can staple fabric to, to make it easier to hang, and to save a few bucks and time compared to making a frame (the 1/4" board is about $3.50 and is already 2'x4'). I would take the fibreglass panel and wrap it with fabric to attach it to the plywood. I was thinking I would use these types of panels for general absorbtion, hung directly on the wall.

I would use another approach for bass trapping in the corners. I am thinking of 2" or 4" of fibreglass in a frame, possibly spaced away from the wall. For example, I could use a 1"x3" frame with 2" of fiberglass and, hung flush on the wall have 1" of spacing for the fiberglass, itself. I could also use the foil scrim (availble to me from the same supplier) facing the room, away from the room, or in the middle of two, 2" pieces of fiberglass in a 4" frame.

I have not played with any type of rigid fiberglass, so I am not familiar with how it would stand on its own with. Do you need a frame (either for support or to attach it to a wall)? How easy does it dent? Can you attach fabric directly to it? I have young kids and a wild, yellow lab, keeping them whole is a concern, as is having exposed nails (for mounting on a wall).

I've seen some simple frames made from 1"x2" and L-brackets... the problem is I have no electric cutting tools. Any other money saving shortcuts here?

One more clarification. I won't be able to just cover the whole front wall, so I was planning on hanging a few panels for absorbtion on the front wall and first reflection points. I was also planning on bass traps (i.e. thicker than 2" or spaced away from the wall) in the rear corners, and maybe the front corners. Is that okay?

Thanks again,

Bump... any comments on my post above?

Thanks,

Tweakophyte:

I'm a DIY guy with carpentry/plumbing/electrical/welding skills -- so I tend to think in those terms.

I have not played with any type of rigid fiberglass, so I am not familiar with how it would stand on its own with. Do you need a frame (either for support or to attach it to a wall)? How easy does it dent? Can you attach fabric directly to it?
Without a frame you can wrap it up like a christmas present in fabric. If it's against the wall you can lean gently against it and it won't dent (much), but if you push your finger into it you'll make a hole quite easily. If it's across a corner then leaning against it, or hitting it with a vacume cleaner will sooner or later snap it in two.

I've seen some simple frames made from 1"x2" and L-brackets... the problem is I have no electric cutting tools.That might be your best course. Home Depot can cut the wood for you, and you can screw them together. I'm thinking 1/2"x4"x4' and 1/2"x4"x2'1" boards as an outer edge frame, without L brackets. That would create a frame that's got a 2'x4' inside surface. Wrap 2" of 703 (or whatever) in polyester batting (optional), and put that in the front of this frame (friction fit), then wrap the whole frame in any fireresistant fabric you can blow through. The rigid rockwool will keep the frame square, the wood of the frame will keep it stiff, and the fabric may help to pull it together. There is no 'back' to this style. A vaccume cleaner would bounce off the wood. And if anyone falls on it, the 703 will simply push back further into the frame without breaking. It would look something like (but not exactly like) this http://www.bobgolds.com/Absorber/OLD/IMG_0152.jpg

Any variation you come up with based on skills and parts availability is likely fine.

Tweakophyte:

I'm a DIY guy with carpentry/plumbing/electrical/welding skills -- so I tend to think in those terms.


Without a frame you can wrap it up like a christmas present in fabric. If it's against the wall you can lean gently against it and it won't dent (much), but if you push your finger into it you'll make a hole quite easily. If it's across a corner then leaning against it, or hitting it with a vacume cleaner will sooner or later snap it in two.

That might be your best course. Home Depot can cut the wood for you, and you can screw them together. I'm thinking 1/2"x4"x4' and 1/2"x4"x2'1" boards as an outer edge frame, without L brackets. That would create a frame that's got a 2'x4' inside surface. Wrap 2" of 703 (or whatever) in polyester batting (optional), and put that in the front of this frame (friction fit), then wrap the whole frame in any fireresistant fabric you can blow through. The rigid rockwool will keep the frame square, the wood of the frame will keep it stiff, and the fabric may help to pull it together. There is no 'back' to this style. A vaccume cleaner would bounce off the wood. And if anyone falls on it, the 703 will simply push back further into the frame without breaking. It would look something like (but not exactly like) this http://www.bobgolds.com/Absorber/OLD/IMG_0152.jpg

Any variation you come up with based on skills and parts availability is likely fine.

Bob, after looking at the coefficient chart, I noticed that R-11 Unfaced (On Wall) 3.5" has better absorption numbers than the 1" OC703. I want to make sure I'm reading this correctly. Could I make a frame and use R-11 with pollyester batting overtop of it, wrapped in fabric and get the same/better results than 1" 703? Only thing is, the panels would be about 4" thick instead of around 1". If I were to compress some of the fluffy fiberglass, would that negate it's properties at 3.5" thick?