Acoustic Treatment Ideas..

[martino]

I'm sure this topic has been discussed to the max already...sorry for asking....I would like feedback from folks who have had success in making their own room treatments. I'm most interested in absorbsion and corner bass managment.
I have some ideas in my head but I thought ask the folks who have already done it.

Thanks

Martino

[---k---]

This is what mine look like:

[ThomasW]

Here are a couple of links to checkout

http://home.comcast.net/~audio-worx/page2DIYpanels.html

http://home.comcast.net/~thomasw_2/SubwooferSetupandEQpage9.html

[martino]

Looks good Ryan..I assume you are happy with them.
Also
Thomas; thanks for the links..very helpful.

Martin

[---k---]

Yeah, I like mine. The improvement from the first corner trap was very noticable. The second one, not so much because it really isn't in a corner, but it was subtle. The front three panels also gave very subtle improvement.

The links Thomas gave you are good. I like the stuff over at audioholics for beginers. There is tons of stuff all over the place at AVS.

Did you have specific questions? You said you had some idea, what were you thinking?

[kgveteran]

I built a pair of Jon Risches tube traps.They are 48" tall and 18" in diameter.I'm very impressed with the results.The pair cost 175.00 total.

I also have a design for DIY diffusers that work fantastic also.Just for numbers , a 48"x48" panel cost about 30.00. My back wall was a big problem.It would reflect almost 80% of the front sound stage.Now there is no beaming and the side surrounds create a nice null as intended.They suite me fine but i've read some idea's about mounting them in a frame and covering with acoustic fabric to make them look better.They are made of styrofoam and can be painted (spray gun ) with latex house paint.

Panels are the easiest.Owens-corning 703 board seems to be the king for DIY.I used 2" thick panels 24"x48".

[dyazdani]

See this thread as well, I have some pics of my DIY absorbers.

DIY Panels

[RobP]

Hey KG, do you have any pics of your traps and diffusers?

[martino]

Thanks to all..KG I also would like to see any pics..The idea of a cylindrical bass trap appeals to me most.
This Owens Corning 703 board....is this rigid board insulation or what? and do I get it at Home Depot?
Please tell me about your bass traps

Thanks

Martino

[ThomasW]

There are pics and links to several cylindrical traps (including the Risch recipe) in the second link I posted

[martino]

I feel I have some bare walls that need help..I'm happy overall with my sound, but my left Channel B-W 803S is only 6in from the side wall and 2 ft from the back wall..I think it needs a trap behind it.
also my rear wall is pretty bare..not sure if I need absorbsion or diffusion there...since it's a bit of expieirmentation I want to keep the cost as low as poss.

Thanks
Martino

[martino]

There are pics and links to several cylindrical traps (including the Risch recipe) in the second link I posted

Thanks Thomas! I really like the half circle tube traps the Doug Ploss makes..seems simple..I'll get after it ASAP.

Hey Thomas..whats your opinion on a rear wall..I'm running a 5.1 surround system with B-W 602's as rears..I also have my sub in the rear of the room (it seems to preform best there) my ceiling slopes from 8ft to 12 ft with 4X12 beams on it..natural diffusion? so I don't think I get a lot of frequency bounce as in a square room..also because my "front" wall is only 50% there as it opens to my entry / dining room. The room is also carpeted with a couch and chairs...so whats your educated guess on the rear wall..diffusion or absorbsion?

[ThomasW]

Diffusion vs absorption depends on the distance the listener is from the rear wall and whether or the primary source is 2 channel or multi-channel.

If your choice is multi-channel, then go with absorption.

[---k---]

If you see the yellow stuff in that first picture I posted, that is OC703, a rigid fibreglass insulation that can not be purcased from Home Depot, but at specialty supply houses. For my two corner traps, I used 4" of OC703 with regular R30 behind the OC703 to give the bass trap more extension. The traps are roughly 2'wide x 4' high x 16" deep across a coner. To make them, I just used two peices of 1/2" MDF cut in a triangles and then some 2x2 for the vertical support. No braces. And then wrapped with fabric. The wall are 2'x3.5'x3" thick of OC703. I constructed a simple 1x4 frame so that the 703 would be snug and then just wrapped in fabric. There are a lot more photos in those directories if you want to look.

If you want to experiment (and I suggest you do), get a box of OC703 for ~$75, which will have 6-2"thick 2'x4' peices in it. Then, you can place the peices around the room and see the effect for yourself. Call around to your local HVAC supply stores to find it. OC703 is very common, but there are lots of other product which are very similar in form and function.

Bob Golds also has a great website with tons of good info:

https://www.bobgolds.com

His absorption coeffiecient page will show you all the other products that are similar to the OC703 and acceptable to use.

[kgveteran]

Here are some pics of the panels and traps and City scape diffusers. Sorry about the grainy pics but thats my camcorder/digital camera combo.I think you guys get the idea.

The diffuser depth is variable from .5" to 7". No lenth of depth is the same. I'll upload the directions if anyone is interested.Hope someone trys them.

I was using panel absorbers in the back of the room and found it too dead.I like a mix of aborbtion and diffusion.And coupled with the bass traps it works out well.

[martino]

Thanks Ryan; those Bob Gold things are huge!..Industrial strength. Looks like ther are lots of choices..how did you fix on OC703??

Martin

[martino]

Here are some pics of the panels and traps and City scape diffusers. Sorry about the grainy pics but thats my camcorder/digital camera combo.I think you guys get the idea.

The diffuser depth is variable from .5" to 7". No lenth of depth is the same. I'll upload the directions if anyone is interested.Hope someone trys them.

I was using panel absorbers in the back of the room and found it too dead.I like a mix of aborbtion and diffusion.And coupled with the bass traps it works out well.

Please upload directions on making..I don't think the wife would sign off on the cityscapes..but the other two look good.

Thanks

Martin

[basementjack]

Guys, great post, I always love reading about this kind of stuff.

[---k---]

Thanks Ryan; those Bob Gold things are huge!..Industrial strength. Looks like ther are lots of choices..how did you fix on OC703??

Martin

I'm not sure I understand the question.

[ThomasW]

He referring to KG's skyline diffusers as posted to Bob Gold's webpage.

People thinking about copying that particular design should note that extruded polystyrene foam is quite flammable and only meets building code when covered with a fire-resistant material.

Most of the time skyline diffusers are made from solid material such as wood which means that they're quite heavy.

[BobEllis]

Thanks for the warning Thomas - I was all set to give the skyline diffusor in foam a try until you mentioned flammability.

Since I need to make my "decorations" of less flammable materials, I guess I should wrap my brain around the diffusor chapter in F. Alton Everest's "Master Handbook of Acoustics." Rather than just throw random blocks up, I might as well throw some math at the problem to make the most of my efforts and dollars. Has anyone made diffusor gratings as described in Chapter 14 and would be willing to share the design?

[kgveteran]

I guess it's back to the drawing board on the skylines.

Is there a material that can be sprayed on the foam to comply with code?

[ThomasW]

Here's a link to a calculator

http://www.mhsoft.nl/DiffusorCalculator.html

I think 2"x2" fir/pine would be the good choice. Foam even the fire treated stuff has uneven acoustic characteristics

Is there a material that can be sprayed on the foam to comply with code?

Not that I'm aware of. All the insulating foams burn, that's why they're located behind the drywall

[kgveteran]

Please upload directions on making..I don't think the wife would sign off on the cityscapes..but the other two look good.

Thanks

Martin

here is the page I used to make the tubetraps.http://www.geocities.com/jonrisch/basstrap.htm

The panels are made of OC703.I cut 2"x4" sheets of very thin plywood.Using liquid nail, glued the plywood to the back of the OC703. Then I purchased some acoustic fabric from a local fabric store.Make sure the fabric is an open weave.Also make sure it is thin, I've seen some panels made out of thicker fabric and they look "homemade".Simply wrap the fabric like a present on the corners (ask the wife, they know about wrapping gifts) and stamp the fabric tight on the back with a staple gun. Now you can drill 1/4" holes through the plywood on the back( careful not to drill all the way through) and hang them like a picture frame.I used the 2" stuff.

Edit, I've emailed Dow with a question concerning their product and fire safety.I'm hoping something can be done.This is a great project, the material is light,easy to work with and affordable.As to the acoustic properties of this project, it falls into a catagory that I call the 80% rule.I'm positive they diffuse sound.I'm positive they are not 100% perfect, but they work up to my 80% perfect rule.

[martino]

I'm not sure I understand the question.

Sorry; thinking of 5 things at once.
Wondering how you decieded to use OC703 insulation when ther are many different ones ie: 701,702 etc..The owens corning site says 707 is an accustic insulation...how come nobody works with this?
Do you recommend Kraft faced, alluminum faced or nude?

Cheers

Martino

[martino]

here is the page I used to make the tubetraps.http://www.geocities.com/jonrisch/basstrap.htm

The panels are made of OC703.I cut 2"x4" sheets of very thin plywood.Using liquid nail, glued the plywood to the back of the OC703. Then I purchased some acoustic fabric from a local fabric store.Make sure the fabric is an open weave.Also make sure it is thin, I've seen some panels made out of thicker fabric and they look "homemade".Simply wrap the fabric like a present on the corners (ask the wife, they know about wrapping gifts) and stamp the fabric tight on the back with a staple gun. Now you can drill 1/4" holes through the plywood on the back( careful not to drill all the way through) and hang them like a picture frame.I used the 2" stuff.

Edit, I've emailed Dow with a question concerning their product and fire safety.I'm hoping something can be done.This is a great project, the material is light,easy to work with and affordable.As to the acoustic properties of this project, it falls into a catagory that I call the 80% rule.I'm positive they diffuse sound.I'm positive they are not 100% perfect, but they work up to my 80% perfect rule.

Thanks kg..is the 703 foil backed? And why does everyone use 703..whynot 702, 701 ??

Martino

[kgveteran]

Very sad to say the skylines are going.Dow recomended another product, but I'm sure I'll come up with something better than 500lbs of wood on my walls.

Back to the drawing board!

[Dennis H]

What's the problem with wood other than the weight? Build the panels small enough, say 2'x2', and you'll have no problem lifting each one and fastening it in place.

[kgveteran]

The only other choice is to use the panels I have as molds.I was on a site yesterday and there are some great products.Most lighter than plaster and of course fire retardent.

Wood is a very viable option.I'll replace them one at a time.I'm also looking into Thermax.Its fiberglass based, but looks kinda messy to cut.

[BobEllis]

Here's a link to a calculator

http://www.mhsoft.nl/DiffusorCalculator.html

<snip>

I used that calculator and was surprised at how much wood it ends up being. For a 800-3440 Hz diffusor (2"/5 cm columns) it needs 48'/15.8 meters of column material to make a 2'x2' panel. think 3 2x4 studs - not terribly heavy, but a fairly significant weight in a small area.

You want diffusion down to 500 Hz? You're up to 5 studs and a foot deep panel. 250 Hz? 10 studs over 2' deep.

This much I've picked up from Everest - put varying depth notches in the ends of the 2x2's and you'll increase the upper frequency limit. (RPG Diffusor Systems does this to three levels in their diffusor panels)

KG - your molding idea is sounding awful good. Keep us posted on your progress.

[kgveteran]

This is going to turn into a monster.I ran some numbers using 2x4's.I would make the panels 12" x 24".That size would allow me to replace all the panels I now have ( in multiples as Dennis H has suggested ). Each panel would have varying depth of .5-7".I would do this:

If I took a 7" section with square ends, that 7" section could be cut on a diagonal anywhere along it's lenth to make two pieces.Each piece adding in lenth to 7".besides the 7" sections, I could make one 12" x24" panel with three 8' lenths.Keep in mind my 80% rule, I'm not looking for perfection, because it does not exist. I have to call my local lumber yard to see what a 8' 2x4 weighs.That is going to be an interesting conversation!

[ThomasW]

I have to call my local lumber yard to see what a 8' 2x4 weighs.

They won't be able to answer that. If you go to HD or Lowes and play in the pile you'll find some are double the weight of others. The weight depends on how tight the grain is, the amount of moisture and 'pitch' in any given piece.

[dyazdani]

Thanks kg..is the 703 foil backed? And why does everyone use 703..whynot 702, 701 ??

Martino

I did not use 703 - I found a different model of rigid fiberglass that had similar acoustical specifications. Mine had foil on one side.

[---k---]

I used 703 because it was the most common, what a lot of other people used, and was easy to get. There are a lot of other products that will work similar, but I just went the easy route.

Foil-Face or Paper Faced, or Plain is a good question and depends on what you are trying to acheive. If you need absorption at all freqencies, you want plain (or the foil, with the foil at the wall face), because the foil will refect the high freqencies and not let them be absorbed. Same with the paper, but to a lesser degree. If you are only trying to absorb the low freqencies, the foil face is perfect.

The Master Acoustical Treatment thread over at AVSforum.com in the Dedicated Home Theater Builder forum covers most of this. It is a very very long read with lots of info. Another very good starting point.

[kgveteran]

They won't be able to answer that. If you go to HD or Lowes and play in the pile you'll find some are double the weight of others. The weight depends on how tight the grain is, the amount of moisture and 'pitch' in any given piece.

. :

[Kingdaddy]

Contrary to what others are saying here and elsewhere, I've found that in my room I need a huge amount of coverage to make a difference, every ceiling wall junction and corner needs to be covered to make a real improvement. I have 6 2x4' OC 705 panels in a small room and still need more. I’m very confused by those who report great success with one or two traps that barely cover any surface area, from what I’ve learned about acoustic treatments that is very unlikely. Of course a small room is terrible for bass and the smaller the room the more densely spaced the modes are and therefore much harder to correct without near complete coverage, so maybe my results are skewed by my terrible 14’x14’ room.

[kgveteran]

KD, I use (16) 2'x4'x2" 703 panels for absorbtion.the whole back of my room, which is 1/3 of the room as a whole is diffusers.I need two more big tube traps like in the front of the room.

You are right.It takes alot to do a multi-channel room right.Remember KD, what sounds right to you.Add treatment until you like the way it sounds.

[Kingdaddy]

KD, I use (16) 2'x4'x2" 703 panels for absorbtion.the whole back of my room, which is 1/3 of the room as a whole is diffusers.I need two more big tube traps like in the front of the room.

You are right.It takes alot to do a multi-channel room right.Remember KD, what sounds right to you.Add treatment until you like the way it sounds.

Yea, thats more like what I would expect for real improvement, a few corner traps wont cover enough area to any good IMO. I’m not sure you could ever have too much form my initial experiences with my room.

BTW, how big is your room, I can barely fit any more traps, I need to make several small ones to do the job right and OC 705 is very expensive.

[---k---]

KingDaddy,
I posted that exact same thought over at AVS a while ago. After having read/built/tested, I would agree with you to some extent. I commonly hear that you need to add ~30% absorption to be audiable. 30% is a LOT. I also commonly hear that treating the two first reflection points and the front to corners will do a lot. I think both are correct.

If your first reflection points aren't treated, a very low amount of treatment will make a big differance in the imaging, but won't do much to smooth the FR or reduce the RT60.

If you have very little bass trapping in your room (few big sofas, ect) treating the corners will make a big differance, because you are coming from nothing. But, once you get these done, I think it will take a large amount of absorption to further improve the room.

I have added 15%-20% absorption to my room. ETF doesn't really show big improvements, but they are visiable, and I can hear improvements in the rooms clarity. My wife also says she can hear some improvements. So....

[ThomasW]

I need to make several small ones to do the job right and OC 705 is very expensive.

Then use the wood frame filled with fiberglass batt designs that started all this....those are inexpensive to build

[kgveteran]

KD,
My room is 13.5 x 15.5 x 9 . I use four on the ceiling, the rest are on the side walls and the front wall.

Whats great is how the front of the room absorbs sound, so your voice is very defined.The back of the room where the diffusers are, the voice has more life to it with no real reflections.Acoustic treatments are very underated.