Is OC better than BAC for corner traps?

HH

Is OC better than BAC for corner traps?
It's the density that matters, not the manufacturer.

It's the density that matters, not the manufacturer.
True for fiberglass. But for different materials, like BAC (bonded acoustic cotton), you really have to compare flow resistivity.:) Some porous materials are essentially equivalent in flow resistivity for a given density, and this just happens to be true for fiberglass and acoustic cotton. But this is not the case with rockwool, for example.

Regards,
Terry

True for fiberglass. But for different materials, like BAC (bonded acoustic cotton), you really have to compare flow resistivity.:) Some porous materials are essentially equivalent in flow resistivity for a given density, and this just happens to be true for fiberglass and acoustic cotton.

Should I shop the price not the product between OC & BAC?

HH

Should I shop the price not the product between OC & BAC?

HH
Yes, but don't restrict yourself to Owens Corning. The other fiberglass manufacturers of the world:

CertainTeed
Johns Manville
Knauf

Regards,
Terry

Thanks Terry.

HH

Window plug.

I can’t go into too much detail because it might violate forum rules.

I just got a quote for a pretty nice window plug from an acoustical company for my front window. Its a 5' x 5' window. They will include a custom 2" of sound paneling on the side facing the HT. They want $1100 for it. Seems a bit high. I’ve been acquiring 2' x 4' x 4" paneling from an AVS selling for $70ish bucks each. But I could really use that thing and its made pretty nice. The window is smack in the middle of my front reflection point so having the panel on t would really help out sound. Right now I lean a panel up against the window. Below is the best pic I got right now. The plug would also help out a lot on some minor lighting streaks that get through the curtains (at the folds) during the day onto the screen.

Any good opinions out there?

http://www.silverti.com/ht/ht1_hh_files/image002.jpg

Window plug.

I can’t go into too much detail because it might violate forum rules.

I just got a quote for a pretty nice window plug from an acoustical company for my front window. Its a 5' x 5' window. They will include a custom 2" of sound paneling on the side facing the HT. They want $1100 for it. Seems a bit high. I’ve been acquiring 2' x 4' x 4" paneling from an AVS selling for $70ish bucks each. But I could really use that thing and its made pretty nice. The window is smack in the middle of my front reflection point so having the panel on t would really help out sound. Right now I lean a panel up against the window. Below is the best pic I got right now. The plug would also help out a lot on some minor lighting streaks that get through the curtains (at the folds) during the day onto the screen.

Any good opinions out there?
You could build one yourself. Is that what you're asking?

You could build one yourself. Is that what you're asking?

No, I dont have the skills, tools or drive to build one myself. Im better at building servers.

No, I dont have the skills, tools or drive to build one myself. Im better at building servers.

Stack some servers up in the window..vertically. :D

No, I dont have the skills, tools or drive to build one myself. Im better at building servers.Then you better build enough of them to clear $1100. :)

Im having problems sourcing linacoustic RC, fibre glass insulation.

My HVAC guys are wondering if other fibre glass insulation products will work. Is it just a measurement of thickness and R rating? They have other products that are 4x8 sheets, 1" thick and have a R rating of 4 or close to it. They have CertainTeed products and its not rolls but boards so its even easier to install (I think).

Im having problems sourcing linacoustic RC, fibre glass insulation.

My HVAC guys are wondering if other fibre glass insulation products will work. Is it just a measurement of thickness and R rating? They have other products that are 4x8 sheets, 1" thick and have a R rating of 4 or close to it. They have CertainTeed products and its not rolls but boards so its even easier to install (I think).
http://www.spi-co.com/

Thanks for the link but I still would like to know if different products do the same thing as linacoustic. I have connections with builders so I can get things near cost and no shipping costs, its cheaper for me if I can get some locally.

lol, I could re-read the first page and findout that Certainteed Certpro Acoustaboard Black is the same as linacoustic for sound :D

Thanks for the link but I still would like to know if different products do the same thing as linacoustic.
Density (not R value) and thickness determine acoustic performance for fiberglass duct liner. Linacoustic has a density of about 2.25 pcf, but I think compares well to 3 pcf fiberglass because of its inner fiber-sealing layer. All 3 pcf insulation is generically termed "type 300", and is essentially equivalent, regardless of manufacturer.

Regards,
Terry

Density (not R value) and thickness determine acoustic performance for fiberglass duct liner. Linacoustic has a density of about 2.25 pcf, but I think compares well to 3 pcf fiberglass because of its inner fiber-sealing layer. All 3 pcf insulation is generically termed "type 300", and is essentially equivalent, regardless of manufacturer.



Thanks! Is it okay to go with 1" 3 pcf? The certaPro Acoustaboard Black has two densities 2.25 and 3.00, Im just confused on which one I should order tomorrow.

penngray:

You can compare a lot of things, here: http://www.bobgolds.com/AbsorptionCoefficients.htm
find "CertainTeed" on that page.

If you find absorption coefficients for a product that isn't on that page, just let me know.

Whew! I can't believe I ate the whole thing...101 pages, 3017 post, 3 days.

I have specific questions for the pro's on there so I will start a threat with a Visio drawing of my space and the "plan".

Thanks for all the great info everyone!

mike

Thanks! Is it okay to go with 1" 3 pcf? The certaPro Acoustaboard Black has two densities 2.25 and 3.00, Im just confused on which one I should order tomorrow.
The difference is pretty minimal. While absorption coefficients are reported to 2 decimal places, the margin of error for the standard reverberation room method used limits the accuracy to something only slightly better than 1 decimal place. In theory, the 3 pcf should absorb a bit more at 250 to 500 Hz than the 2.25 pcf of the same area. In practice, I'm not sure at all that you could tell the difference. Check out the prices between the two, and go with the cheapest.

Regards,
Terry

You can compare a lot of things, here: http://www.bobgolds.com/AbsorptionCoefficients.htm
find "CertainTeed" on that page.

If you find absorption coefficients for a product that isn't on that page, just let me know.


Thanks for the link!!!

btw, My brother and best friend live just of Bronte Rd. in Oakville. Its a great city!!

I need some experts to chime in. Would 2 layers of ~0.60-0.75" 1.5pcf fiberglass insulation work o.k. for acoustic panels? I am not sure of the manufacturer. I know it is not ideal to the 3-6pcf, but looking at the numbers for OC701 on Bob's site they do not look horrible. I have the ability to buy some old office cubicle walls very cheap and was wondering if I could use the insulation for acoustic panels. I was also thinking about using the wood from the panels for the frames. The wood alone is worth the price. The fabric covering them, which is a light tan, will not work for me so I would most likely sell it making them even cheaper. Is anyone interested? Does anyone have any thoughts/comments. I am looking for feedback to either help me make the decision to buy them or to just walk away if it would be too much work and not worth my time. Thanks in advance.

Continuing my saga of replacing the panels that the lady of the house didn't like the look of with something more acceptable.... The GIK panels (model 242) arrived and she likes them! Hey, that's great. Gonna order a second set, soon.



Thanks for the pics, though they may have served only to dissuade me from ordering those from GIK. They're a little too amateurishly "lumpy" in the corners, due to material folding at the ends. Granted, they appear to make them about as well as you'll ever see for this type of construction style. I've seen enough cheesy DIY examples of this type of 2' x 4' treatment and GIK DOES put most of those to shame, but perhaps still not quite taut or crisp-looking enough for my tastes. Then again, theirs are a bit cheaper in price than some of the other ones I am thinking of, so everything is a trade off, I suppose.

I wonder if their tri-traps are a little "tighter" looking? I think the material folded ends are hidden below the end caps, so those might provide a tidier look that I am more disposed to liking.

Someone has suggest that I will be okay if I run the acoustic on 100% of my walls and if I do that I should add some bass traps to the ceiling (by the screen) and on the back wall (probably corners too).

I have read here that its not good to run acoustic sound absorption stuff on 100% of the wall so which is it?

My HT build thread.....http://www.avsforum.com/avs-vb/showthread.php?t=1000239

Thanks for the pics, though they may have served only to dissuade me from ordering those from GIK. They're a little too amateurishly "lumpy" in the corners, due to material folding at the ends.

I too thought those corners were pretty lumpy. I built several 2x4 panels covered in GOM, and I got the corners looking much better. Basically along the two short ends I have a single "triangle" fold that is glued down.

It's not rocket science, but if I had paid for pre-made panels and gotten lumpy corners like that I would have returned them.

Someone has suggest that I will be okay if I run the acoustic on 100% of my walls and if I do that I should add some bass traps to the ceiling (by the screen) and on the back wall (probably corners too).

I have read here that its not good to run acoustic sound absorption stuff on 100% of the wall so which is it?
The latter. Rooms become too deadened long before their walls are 100% covered.

I too thought those corners were pretty lumpy. I built several 2x4 panels covered in GOM, and I got the corners looking much better. Basically along the two short ends I have a single "triangle" fold that is glued down.

It's not rocket science, but if I had paid for pre-made panels and gotten lumpy corners like that I would have returned them.
Some commercially available panels are made from fiberglass batts with edges/corners which have been chemically hardened. Those are "cleaner" looking, but are m-o-r-e expensive. This design is not practical for DIY. The only design remaining that will produce a more, um . . finished look with taut covering is one with a frame and a back.

Some commercially available panels are made from fiberglass batts with edges/corners which have been chemically hardened. Those are "cleaner" looking, but are m-o-r-e expensive.
Yes. And even for these, it is best to stick to the denser, most rigid fiberglass -- OC 705 or other 6 pcf material.

Regards,
Terry

Some commercially available panels are made from fiberglass batts with edges/corners which have been chemically hardened. Those are "cleaner" looking, but are m-o-r-e expensive. This design is not practical for DIY. The only design remaining that will produce a more, um . . finished look with taut covering is one with a frame and a back.

I will say that using the fiberglass resin from home depot on the edges did work pretty well. Using tan colored GOM, you can see the edges aren't perfectly square because the resin didn't apply perfectly. On the black GOM covered panels it looks really awesome.

I'm a perfectionist, but I do think the resin route works well for a DIY method. If it didn't cure so darn fast then the edges could be even more square. I mixed it in 8oz batches and working time was maybe 5-7 minutes, tops. 8oz covered about three sides of a 2x4' panel.

Odor is HORRIBLE so get a good VAC mask or you might pass out or suffer brain damage. :D

Update: By accident I found some much slower curing epoxy that someone might want to use instead of the home depot stuff. http://www.tapplastics.com/shop/product.php?pid=27& The "Slow" version has a 30-minute pot life which would make it vastly easier to apply it in a more controlled and careful manner.

Here are some black GIK 244 Bass traps. 2'x 4' Acoustic 4" Panel (5.5" total thickness). I picked them up at my neighbors and borrowed his wheel barrow. I have not been feeling well and I missed delivery, but they have arrived. The other day I hooked up my speakers to both sets of in-wall wire and ran some wire from the plates (I am spray painting with satin black Krylon) to my speakers using only my separates as amplification. I didn't explain what I had done...but I had a comment that the pitch had changed, and that the bass seemed to be coming from the back of the room more. I had explained afterwards that these were on the way. Hope they like them.

http://farm4.static.flickr.com/3254/2298369619_57365ba70e_o.jpg

I too thought those corners were pretty lumpy. I built several 2x4 panels covered in GOM, and I got the corners looking much better. Basically along the two short ends I have a single "triangle" fold that is glued down.

It's not rocket science, but if I had paid for pre-made panels and gotten lumpy corners like that I would have returned them.

Well, I didn't take them apart to see but I *think* though they have a nice wood frame in the back -- that helps with rigidity and hanging, and adds an air space between the panel and the wall -- the edges and corners of the front are fiberglass. I guess that might mean they don't stay as square as they should be.

Or did I get some damaged goods? The shipping may have messed with them a bit. I guess I should ask the GIK guys. They've been helpful throughout the process. Looking at SteveMo (http://www.avsforum.com/avs-vb/member.php?u=41862)'s pictures, the top/bottom edges don't look totally square, either....

I will say that using the fiberglass resin from home depot on the edges did work pretty well. Using tan colored GOM, you can see the edges aren't perfectly square because the resin didn't apply perfectly. On the black GOM covered panels it looks really awesome.

I'm a perfectionist, but I do think the resin route works well for a DIY method. If it didn't cure so darn fast then the edges could be even more square. I mixed it in 8oz batches and working time was maybe 5-7 minutes, tops. 8oz covered about three sides of a 2x4' panel.

Odor is HORRIBLE so get a good VAC mask or you might pass out or suffer brain damage. :D

Update: By accident I found some much slower curing epoxy that someone might want to use instead of the home depot stuff. http://www.tapplastics.com/shop/product.php?pid=27& The "Slow" version has a 30-minute pot life which would make it vastly easier to apply it in a more controlled and careful manner.
If I was going this route, I'd experiment with some kind of a form to hold the edges while the resin hardened. As crisp as the commercial ones are, I'd bet they're using some kind of mold.

If I was going this route, I'd experiment with some kind of a form to hold the edges while the resin hardened. As crisp as the commercial ones are, I'd bet they're using some kind of mold.

I"m sure they do use some type of mold. The but the resin is so tacky, that I would think any type of form would have to be teflon coated. But given the longer working time, I think it would be possible to get pretty good coverage and then sand the edges once it has hardened. Too bad I didn't find this stuff until I was completed with all my panels. :(

I"m sure they do use some type of mold. The but the resin is so tacky, that I would think any type of form would have to be teflon coated.(
I'm thinking a "wax paper" lined mold.

I'm thinking a "wax paper" lined mold.

We use a "teflon" tape at work all the time for curing epoxy samples. It works very well.

We use a "teflon" tape at work all the time for curing epoxy samples. It works very well.
Is that like tape used by plumbers on threaded pipes? Wider, maybe?

Is that like tape used by plumbers on threaded pipes? Wider, maybe?

No, it has adhesive on one side and is a clear brown in color. I honestly have no idea where you could even find it, but it is very useful.

Well, I didn't take them apart to see but I *think* though they have a nice wood frame in the back -- that helps with rigidity and hanging, and adds an air space between the panel and the wall -- the edges and corners of the front are fiberglass. I guess that might mean they don't stay as square as they should be.

Or did I get some damaged goods? The shipping may have messed with them a bit. I guess I should ask the GIK guys. They've been helpful throughout the process. Looking at SteveMo (http://www.avsforum.com/avs-vb/member.php?u=41862)'s pictures, the top/bottom edges don't look totally square, either....

Here are some new photos, with the panels mounted (well, the ones behind the couch aren't really mounted in their final spot, since they'll move to the side walls, and I'll place a couple of 244s behind the couch where you see these). I'm thinking they look pretty good :)

http://i208.photobucket.com/albums/bb269/nathan_h_photos/IMG_6916.jpg
http://i208.photobucket.com/albums/bb269/nathan_h_photos/IMG_6917.jpg
http://i208.photobucket.com/albums/bb269/nathan_h_photos/IMG_6918.jpg

I want to make corner wall bass traps and I have OC 703 1" on order. Can I double the 1" up to make 2" in the corners does this help with Bass sound absorption? Or should I just order OC 705?

My understanding: 703 is fine, but you should use 4" straddling the corners.

so correct me if Im wrong....

1" OC 703 100% of the front wall.

1" OC 703 around the bottom of the side and rear walls, 4' high?

4" OC 703 in the corners

and maybe a couple 2x4 1" panels on the celing close to the front wall? My ceiling is drywall and will be painted. I will fabric the side walls. My floor will be carpet.


Also, my room is just a frame so I can maybe add more framing at 45 degree angles with 2x4s to each corner and then it would be easier to apply OC 703 to the corners??

No, it has adhesive on one side and is a clear brown in color. I honestly have no idea where you could even find it, but it is very useful.

FWIW McMaster-Carr seems to have a variety of such tapes (http://www.mcmaster.com/nav/enter.asp?pagenum=3353).

I would like to cover my OC 703 (just purchased 12 2x4x1 sheets from ebay for $130 shipped) with Dazian Blackout satin coth (100% Polyester )

would this cause any problems?

http://www.dazian.com/cgi-bin/page.pl?action=show_style&style_id=456&group_id=119&cat_id=45

I know Dazian makes acoustically transparent fabrics, but I don't think this is one of them.

And, generally speaking, are man-made fibers more likely to reflect highs rather then pass them through to be absorbed by the panels?

so correct me if Im wrong....

1" OC 703 100% of the front wall.

1" OC 703 around the bottom of the side and rear walls, 4' high?

4" OC 703 in the corners

and maybe a couple 2x4 1" panels on the celing close to the front wall? My ceiling is drywall and will be painted. I will fabric the side walls. My floor will be carpet.


Also, my room is just a frame so I can maybe add more framing at 45 degree angles with 2x4s to each corner and then it would be easier to apply OC 703 to the corners??

I think people would agree that building "super chuncks" for bass traps in the corner is somewhat more effective than just placing full sheets diagonally across and leaving a free space cavity behind them. "Super chunk" is basically a stack of triangle shaped OC70x stacked up so that it's a solid corner. It's more work to get installed, but gives you more material for increased sound deadening.

full sheets diagonally across and leaving a free space cavity behind them. "Super chunk" is basically a stack of triangle shaped OC70x stacked up so that it's a solid corner. It's more work to get installed, but gives you more material for increased sound deadening.

So if I build triangle frames and fill them with OC703, I should get a decent bass traps. That is what Im thinking of doing. I will cut my OC703 to fill the triangle corner frames.

I know Dazian makes acoustically transparent fabrics, but I don't think this is one of them.

And, generally speaking, are man-made fibers more likely to reflect highs rather then pass them through to be absorbed by the panels?


I was hoping it wouldnt effect the absorption too much. The GOM stuff so far hasnt passed the wifes approval.

I was hoping it wouldnt effect the absorption too much. The GOM stuff so far hasnt passed the wifes approval.

What's wrong with GOM? I got their black and tan colors, and I'm very pleased with them. You can order samples and get a better feeling of the color. I got 8-9 samples and found two that were perfect.

So if I build triangle frames and fill them with OC703, I should get a decent bass traps. That is what Im thinking of doing. I will cut my OC703 to fill the triangle corner frames.
You will not only get the best traps that a small amount of money can buy, you will get very close to the best traps that nearly any amount of money can buy.

http://www.atsacoustics.com/item--Roxul-Rockboard-60-Case-of-6--RB60.html

Is what I used for my bass traps, those sheets are 2" thick by 2'x4'. They measure very well compared to OC705 and are a good bit cheaper. And they stand up straight when leaned against a wall, unlike OC703. I use the Rockboard 60 in my studio as well. $60-$65 shipped for a box, +walmart fabric, +adhesive spray...hmmm, yummy. I did two 4" traps for the front corners on the floor going upwards and two 2" traps going from them towards my center speaker. Then I had some acoustic foam left over from a studio I worked in, and shoved them behind the 4" traps, probably doesn't help much, but if it gives a little more absorption all the better.

http://i30.photobucket.com/albums/c349/TimRP/DSCF0159.jpg

What's wrong with GOM? I got their black and tan colors, and I'm very pleased with them. You can order samples and get a better feeling of the color. I got 8-9 samples and found two that were perfect.

I have no problems with it, its the WAF thing and she wants some input if Im "stealing" the bonus room and making it a HT ;)

are there different textures of GOM?

I have no problems with it, its the WAF thing and she wants some input if Im "stealing" the bonus room and making it a HT ;)

are there different textures of GOM?
There are, but you should limit your choices to the acoustically transparent fabrics.

http://www.silentsource.com/acousticore-colorchart1.html

There are, but you should limit your choices to the acoustically transparent fabrics.


Man, there is so much reading and so many different opinions on this stuff.

I read that 100% polyester products allow substantially all the sound directed against the panel to pass into the glass fiber layers, the Dazian Blackout satin is 100% polyester


I also read that its not really acoustically transparent material we need for sound absorption but its material that does not reflect sound, as long as the material doesnt reflect much sound we are good.

I guess it comes down to how much reflection really happens because logically if the material is not acoustically transparent then it does reflect sound (atleast a little bit).

My freaking head hurts...Atleast I think I got a good deal for OC703 and I just ordered Roxul Rockboard 60 for the bass traps. Things are coming together, I just wish I could figure out the fabric.

btw, Thanks for the link :D Im going to order a sample of the Anchorage Style 2016 ONYX color

Man, there is so much reading and so many different opinions on this stuff.

I read that 100% polyester products allow substantially all the sound directed against the panel to pass into the glass fiber layers, the Dazian Blackout satin is 100% polyester


I also read that its not really acoustically transparent material we need for sound absorption but its material that does not reflect sound, as long as the material doesnt reflect much sound we are good.

I guess it comes down to how much reflection really happens because logically if the material is not acoustically transparent then it does reflect sound (atleast a little bit).

My freaking head hurts...Atleast I think I got a good deal for OC703 and I just ordered Roxul Rockboard 60 for the bass traps. Things are coming together, I just wish I could figure out the fabric.
Yes, the problem is not that it doesn't pass frequencies, but that it might reflect them.

I did this up pretty fast in MS paint. What do you guys think? The panels would be typical 4' x 2' x 4" acoustic panels with black GOM. When the screens down they would be hidden behind it. I'm thinking about placing 1 foot tube traps in the corners next.

http://i184.photobucket.com/albums/x25/tleavit/Panels.jpg

Don't forget you side, back, ceiling reflection points. With the screen down, you'll need some other absorption in the room.

Don't forget you side, back, ceiling reflection points. With the screen down, you'll need some other absorption in the room.

Ya, I already have 2 at the primary front reflection points (you can barely see one on the left, they aren’t mounted yet, one is leaning on top of my sub). I’m slowly adding the panels as I can afford them. 2 went in the sides, Ill get 3 to 5 on the front next. Then I'll throw some up on the rear and then a few more on the sides and figure out what to do on the ceiling. I'll throw some tube base traps in the corners and call it as good as it can get in the room after that I recon.

pepar, again thanks for the link. I sent an email to silent source for some samples and they are sending them too me now. Great customer service!!!

I bought a package of 2" Rockwool and just made four 3" thick 2x4 frames. I will cover them with the GOM fabric. Questions is: Should I put a single sheet inside each frame or squeeze two sheets in each frame? Or should I go out and buy a 3" Rockwool package instead?

Build 4" frames! Seriously, why did you do 3"...

Build 4" frames! Seriously, why did you do 3"...
I had that same comment in the reply window two times and decided against posting it. :)

Adding another inch to the depth might be possible. I might also load two sheets in and try to cover it with GOM so that the "proud" rockwool got rounded over into nice edges.

I did some more hard core measuring down there and came up with a new pattern. What do you guys think? Between the 2? Both give me space in the corner to put up tube bass traps. In the second picture, I threw in some sides that will go in also. To boot, when the screen is down, they will be hidden.



http://i184.photobucket.com/albums/x25/tleavit/Panels.jpg


Or

(that panels actually slip behind the TV perfectly due to its mount)

http://i184.photobucket.com/albums/x25/tleavit/DSC03973.jpg

From my understaning, for the most part, the more coverage up front, the better. However, once again, won't most of this be rendered ineffective with the screen down?

From my understaning, for the most part, the more coverage up front, the better.In theory yes, in practice it's a change so somethings will sound better and some things not as good.

I did my entire front wall in 4" with a 4" air gap (8" total), and that's the way its been for a year and a half now.
Before I did that I remember listening to the closing credits of We Were Soldiers and just being in acoustic awe. It was a perfect moment. I had everyone I knew come by and listen, and they all heard and understood and commented on its accoustic wonderfulness. I played it over and over again while I was alone. Ummmm. Gooood.
Then I wrecked the room support that was absolutely perfectly tuned for those 2 minutes of that one DVD out of my 2500 DVDs. :)

Any ideas for a 4'wx6'l window? I don't want to cover it with framing and drywall, but don't mind putting something over it. I was thinking of an acoustic treatment and mirror another opposite it on the other wall. Any other ideas?

I was hoping someone might have an idea for my situation or is a fiberglass panel the best option? The carpet went in Saturday and now I am changing my focus onto the window and room treatments.

I was hoping someone might have an idea for my situation or is a fiberglass panel the best option? The carpet went in Saturday and now I am changing my focus onto the window and room treatments.

Since you will see the panels from both sides (right?) you might look at the bass trap bags at Ready Acoustics. You would have to trim one bag down, but should give a professional finished appearance on both sides. I can't remember if you have to buy a whole set, or could just get two bags.

You could also cover it in GOM, paying attention to hide the seams where you won't see them from the front or back.

The panels would be lightweight, so holding them in place would not be hard.

I had that same comment in the reply window two times and decided against posting it. :)

Adding another inch to the depth might be possible. I might also load two sheets in and try to cover it with GOM so that the "proud" rockwool got rounded over into nice edges.

When I went to Home Depot, 2" looked really flimsy and 4" did not look esthetically good which would have caused a problem with the wife. I thought i could somehow push the 2" Rockwool towards the front part and keep it staple. I quickly found out after building the frames that it wasn't going be possible to keep the Rockwool in the front part as I wanted. I'll try to squeeze two of them and cover them with GOM and see what happens. Worst case I can mill them at 2".

Dear all, I have a question about fiberglass. The shop that I can find selling OC703 has them on a roll, instead of a 2' x 4' board. It feels very fluffy, like a very light blanket. It is labelling 48kg/m3. Is it the same as a rigid board type? Or they are two different things? Thanks all.

Is it the same as a rigid board type? Or they are two different things? Thanks all.

Im not the expert on this but if its not compressed into a rigid board it wont have enough density for acoustics. I would say very light and fluffy is not good.

Ebay has some 2x4 OC703 recently for a good price, check it out

or

Local HVAC supplier will have something CertainTeed [ToughGard Duct Board] it has decent acoustical performance #s.

I have learned that anything with "acoustical" in the name is extremely marked up these days.
anything with "acoust

Dear all, I have a question about fiberglass. The shop that I can find selling OC703 has them on a roll, instead of a 2' x 4' board. It feels very fluffy, like a very light blanket. It is labelling 48kg/m3. Is it the same as a rigid board type? Or they are two different things? Thanks all.
703 on a roll? Check again to see that it's 703. I'd be surprised because, I believe, the density prevents it from being rolled.

703 on a roll? Check again to see that it's 703. I'd be surprised because, I believe, the density prevents it from being rolled.

Ya I can't see 703 being on a roll. I ordered a couple of bales of it, and there's no way you could roll-up 703 without causing serious damage to it. I would not describe 703 as a light fluffy blanket. It has density, does not easily bend and I'd certainly describe it as semi-rigid.

Sounds like the stuff you saw is the typical house insulation used in attics or wall cavities that is light and fluffy like a blanket and cannot support its own weight.

OC703 is rigid enough that you can support a 2'x4' sheet on the very ends and it won't deform.

Thanks for all your help. I am not living in US. That's why I am having a hard time finding the OC703. It is strange that the roll has the density 48kg/m3 labelled on the bag, but it feels very light with a large bundle. I will see if other shop sells the board type. Again, thanks all.

Thanks for all your help. I am not living in US. That's why I am having a hard time finding the OC703. It is strange that the roll has the density 48kg/m3 labelled on the bag, but it feels very light with a large bundle. I will see if other shop sells the board type. Again, thanks all.

You can use it, you just need to compress it into a 2x4 DIY box and use chicken wire or something. I saw some pics somewhere about someone creating DIY base traps that way with regular "fluffy" insulation.

luckybeanbean:

Don't be obsessed with 703. Almost anything on this page will do: http://www.bobgolds.com/AbsorptionCoefficients.htm . Several will work better than 703.

luckybeanbean:

Don't be obsessed with 703. Almost anything on this page will do: http://www.bobgolds.com/AbsorptionCoefficients.htm . Several will work better than 703.

Thanks BasementBob, I finally found a shop selling 703. But the shop owner tells me it is not recommended to use in home environment, because it is carcinogenic. True?

Thanks BasementBob, I finally found a shop selling 703. But the shop owner tells me it is not recommended to use in home environment, because it is carcinogenic. True?

False, you put the same stuff in your walls, just the stuff in the walls is not compressed. It can be a irritation to your skin and lungs if you touch/rub/wave it around, so that the lose particles become airborne and then touch your skin/inhaled by your lungs. Needless to say the stuff won't kill ya, just use nitrate gloves those gloves that nothing can penetrate, don't rub your face in it, wear a mask if you must, and don't wave it around like a flag. Once covered with fabric, even see thru GOM, you are more then covered, or its covered, or the covering, ah...you get the gist.

BTW, when I installed my insulation (in wall) for the basement I didn't do any of that protective stuff, but then it was covered in plastic with little vents, so I really never came in contact with the stuff. But on the other hand (well both hands) I did use gloves for my rockboard 60 bass traps installs.

Once covered with fabric, even see thru GOM, you are more then covered, or its covered, or the covering, ah...you get the gist.


um....the fibers will still break free and flow into the air in the room...how mcuh I dont know but I was thinking about this last night when I was testing putting GOM over the OC703 or Rockboard stuff ( I have both).

There is nothing really stopping the small mciro fibers from getting out. All I can say is Filter the rooms properly :D

Thanks BasementBob, I finally found a shop selling 703. But the shop owner tells me it is not recommended to use in home environment, because it is carcinogenic. True?

What doesn't cause cancer these days? :D Just cover it with GOM, and as others have said, wear protective gear when you are cutting it and installing. I even left the back of the my clouds and wall/ceiling pieces uncovered on the back. I have bigger fish to fry than worrying about a random fiberglass fiber working lose and making its way into my lungs.

But while I was cutting it I looked like a space alien...gloves taped to long sleeve shirt, breathing mask, tape around my collar, shoes, etc. Darn hot too..and I ended up throwing away the shirt I worked in because it was covered in little fibers.

I finally found a shop selling 703. But the shop owner tells me it is not recommended to use in home environment, because it is carcinogenic. True?
False.

Read this thread Recording.org: Exposing the Myths of Fiberglass (http://www.recording.org/ftopict-21013.html). Believe everything Rod Gervais says. Rod is a multi-disciplined engineer. His background in construction is wide ranging, from national museums to recording and movie studios and huge soundproof hotels. They guy literally will not use a product in a way that has not been scientifically proven in a way he and his peers approve of, and as a result his projects work as designed the first time every time. It's why we believe him. He's got a reputation par excellance as long as I've known him.

After you put up a rigid panel, or before you cover it in GoM, vacume it to remove all the little loose fibers. Reduces dust.


That said, you can always go green.
i.e. leave man made fibers and go to Cotton or Sheep Wool as an absorber material:
http://www.acousticotton.com/
http://www.bondedlogic.com/
http://www.acousticalsurfaces.com/echo_eliminator/echo_acou_test.htm
http://www.secondnatureuk.com/

Now for the part where I don't know what I'm talking about:
Watch what they use to fireproof cotton though. Yes, Boric Acid is a weak acid that is used to treat ear infections, cold sores, and vaginal yeast infections and hospitals used to use it an eye wash for children. Mix Boric Acid too dense and suddenly it's rat poison. I don't know.

thanks everyone. I will go ahead with the fiberglass. Here is the framework of my absorber and panel traps. I will link some more photos when I finished treating my place. Thanks again

thanks everyone. I will go ahead with the fiberglass. Here is the framework of my absorber and panel traps. I will link some more photos when I finished treating my place. Thanks again
Nice start!

I'm planning on building the traps w/ OC 703 triangles from floor to ceiling in the front behind the false wall. However, I'm not sure what to do in the back. If you take a look @ my HT design (image here (http://i273.photobucket.com/albums/jj229/SPDSpappy/HTRoomLayout2.jpg)), you'll see that the left rear corner of the room is where my equipment closet is. I can probably fit the same triangle built trap on the right side rear (will depend on how the seats actually end up fitting), but not sure if I should put in the 3 corner traps (2 front, 1 rear), or just stick w/ the 2 in the front and do something different in the back. Your thoughts?

I'm planning on building the traps w/ OC 703 triangles from floor to ceiling in the front behind the false wall. However, I'm not sure what to do in the back. If you take a look @ my HT design (image here (http://i273.photobucket.com/albums/jj229/SPDSpappy/HTRoomLayout2.jpg)), you'll see that the left rear corner of the room is where my equipment closet is. I can probably fit the same triangle built trap on the right side rear (will depend on how the seats actually end up fitting), but not sure if I should put in the 3 corner traps (2 front, 1 rear), or just stick w/ the 2 in the front and do something different in the back. Your thoughts?
I am a step or two ahead of you. Search this thread for my posts w/pics re the traps behind my false wall. They made a dramatic improvement and had me thinking that I did not need to add traps in the rear. I will be taking some FR and decay measurements soon, but I *think* that I do need more traps.

anyone used R-max sheathing?....http://www.nottatwater.com/specialty/Rmatte%20Plus%203.pdf

R-matte plus 3 is a rigid foam plastic thermal insulation board composed of polyiscyanurate foam bonded to a durable white-matte non glare
aluminum facer and a reflective reinforced aluminum facer.

I was in lowes on the weekend and I saw these 4x8 sheets and I thought they would be great for the upper half of the walls instead of some sort of poly batten.


Anyone have an opinon on this?

thanks everyone. I will go ahead with the fiberglass. Here is the framework of my absorber and panel traps. I will link some more photos when I finished treating my place. Thanks again

Very cool looking.

But what are you going to do about that A/C unit? That thing has got to be so loud that the benefits of acoustic treatment are almost lost?

As I near the first summer with my dedicated room, which so far doesn't have A/C, I am struggling with a similar issue.

anyone used R-max sheathing?....http://www.nottatwater.com/specialty/Rmatte%20Plus%203.pdf

R-matte plus 3 is a rigid foam plastic thermal insulation board composed of polyiscyanurate foam bonded to a durable white-matte non glare
aluminum facer and a reflective reinforced aluminum facer.

I was in lowes on the weekend and I saw these 4x8 sheets and I thought they would be great for the upper half of the walls instead of some sort of poly batten.


Anyone have an opinon on this?
I do. :)

Poly batting adds sound absorption at mid to upper frequencies -- though not nearly as efficiently as dense fiberglass. It is a porous absorber. Rigid foam is not, so these two materials are not equivalent.

The facts about poly batting have been long misrepresented on this forum. I was quite dumbfounded when I first came here and learned of the story going around. I can only surmise that the CEDIA acoustical powers that be (I won't mention names :)) were just following a rote formula, and didn't know all the "whys" of it.

"Diffusion" was the original claim for upper wall polyester batting. I debunked that, since a homogenous absorber does not add diffusion by any known physical means. Now the story is something like "making the upper space even beneath the upper GOM." The only problem with that explanation is that you don't need anything at all behind stretch-mounted fabric. It is fully supported at its edges. And besides, as I said (and which can easily be shown in testing) polyester batting is not acoustically inert.

So unless, through acoustical modeling or testing, you know that you need some absorption in these physical areas, then I say save your money and don't use anything.

Regards,
Terry

Thanks Terry,

its hard to figure out what is right and wrong and since this is DIY project I really want to learn how to figure it all out on my own.

I have OC703 on the bottom half of the walls and the full front wall, with Rockwool 60 for bass traps in the corners. Why? well after reading probably 20-30 different HT threads it just seems they all do the same thing and the results are awesome to them.

This leaves the bottom 1" thicker then the top so to keep the wall at the same depth Im just looking to put something on the upper wall. It always helps to have soemthing on the upper walls so that my fabric will look good (using furring strips, etc).
So what should I use if I still want something behind it?

So what should I use if I still want something behind it?
Air is good. :)

If there is an issue with seeing through the fabric, a second, neutral-colored fabric used as a scrim will solve this.

Regards,
Terry

Air is good.

If there is an issue with seeing through the fabric, a second, neutral-colored fabric used as a scrim will solve this

Where can I buy this "Air" thing you talk about it ;)

I will see how the fabric looks without at the top without anything behind accept drywall. I will also use 1/4" inch thick furring strips.

I have chair rail between my top section and my bottom accoustically treated section so it might be okay.

Where can I buy this "Air" thing you talk about it ;)

I will see how the fabric looks without at the top without anything behind accept drywall. I will also use 1/4" inch thick furring strips.

I have chair rail between my top section and my bottom acoustically treated section so it might be okay.

Both the black and "straw" GOM provide highly opaque coverage. Both provided me 100% (and I do mean 100%) hiding of the yellow OC703 behind the fabric. So I doubt you would need two layers.

Very cool looking.

But what are you going to do about that A/C unit? That thing has got to be so loud that the benefits of acoustic treatment are almost lost?

As I near the first summer with my dedicated room, which so far doesn't have A/C, I am struggling with a similar issue.

Oh, that ac unit will be gone and the window will be block. thanks for the reminder.:)

:) Begs the question of how you'll control the room temp after it's gone...

anyway to acoustically treat a window without removing it?

I think my window is at a reflection point in the room.

anyway to acoustically treat a window without removing it?

I think my window is at a reflection point in the room.

I had a similar dilemma in my HT. I ended up rotating my HT 90 degrees so the TV was in front of the window. If you don't want to look out the window, I don't see why covering it with an acoustical panel(s) wouldn't do the trick.

anyway to acoustically treat a window without removing it? I think my window is at a reflection point in the room.

Put a panel there on a stand. Or hang a panel from the ceiling. Or get a really heavy curtain and close it when listening.

--Ethan

I recall someone recommending not to have back-panels on my ceiling tiles after I ordered them. I have tried removing those and it causes a slight null at around 160Hz, it smooths out my response from 100Hz to 60Hz and it increases the response from 10Hz to about 25Hz. This is after removing almost a complete row of them from the sides of my room.

Should I continue to remove these?

Above my tiles there isn't much. There is a layer of pink stuff I put across the ceiling joist I put up in a few hours. Above that is steel and concrete. Two steel beams run across the room horizontally and there is gaps between those. I need insulation for the back of my room and I was considering taking all the insulation out of my ceiling and placing those in my back wall area that is not filled with insulation. Then I could fill the ceiling with something else somehow. I was thinking maybe some Roxul but I am not sure how to place it. Any advise?

http://farm3.static.flickr.com/2420/2327022133_a33811322e_o.jpg

http://farm3.static.flickr.com/2227/2327837234_2d622b7e13_o.jpg

I will go ahead and continue removing the back-panels and do some testing without them. My ceiling runners will not support the size weight of them anyway and they keep becoming loose so it is at least worth a try.

Dear all, I was going to make a panel bass trap with a 4" depth with 1/8 plywood. Planned to put 2" oc703 inside with 2" air space, but my worker has accidental stuffed 4" inside the box and sealed it. Although it can still vibrate, but minimally. It will be very painful if I need to remove all of them and do it again:( How would it affect the performance? thanks

Did you really want a tuned panel absorber to begin with? The one you describe has a center frequency of about 170 Hz, with a bandwidth of only about 40 Hz. That's pretty limited absorption, unless you know you need to treat these specific frequencies.

Not much changes with the full 4" of porous interior absorber (frequency goes down a bit). I think that plywood is stiff enough not to be effected by the contact. Not so with a limp panel, like mass loaded vinyl.

Regards,
Terry

Put a panel there on a stand. Or hang a panel from the ceiling. Or get a really heavy curtain and close it when listening.

how about build a nice 2" panel that fits into the window, I can remove it when I need too. The Dedicated HT room isnt so dedicated according to the wife :D

or I was thinking about buying sound "sound absorptions sheets" I found on ebay that I can make curtains out of....

NRC Rating: .70
Size/Weight: Approx. 80’’x 44’’; Weight: 4.5-6 lbs; Thickness: .25"-.5" (per sheet)
Coverage Area: Approx. 195 square feet
Color: White
Made from natural acoustic cotton/wool technology
Simple to install. Hung on walls, ceilings or over windows in minutes with Megaclips
Lightweight & Durable
Environmentally friendly - No Fiberglass!!

Did you really want a tuned panel absorber to begin with? The one you describe has a center frequency of about 170 Hz, with a bandwidth of only about 40 Hz. That's pretty limited absorption, unless you know you need to treat these specific frequencies.

Not much changes with the full 4" of porous interior absorber (frequency goes down a bit). I think that plywood is stiff enough not to be effected by the contact. Not so with a limp panel, like mass loaded vinyl.

Regards,
Terry

Thanks Terry, glad to know that the panel absorber still works. The panel is actually 1/4" instead of 1/8", my mistake. My room is 12' x 18' x 8.6', so I would like more 90-100hz absorption.

Another question from the noobie section.

How wide and thick do corner bass traps have to be. Im still considering DIYing them by creating a tri-angle frame for each corner that fits 100% of the corner. I was think of having it 12"x12"x12". is that too much or not enough for bass traps. I would fill the bottom 4 feet with Rockwool 60 and the top with just poly batten.


I can only put them in 3 corners too because one corner is a door.

Another question from the noobie section.

How wide and thick do corner bass traps have to be. Im still considering DIYing them by creating a tri-angle frame for each corner that fits 100% of the corner. I was think of having it 12"x12"x12". is that too much or not enough for bass traps. I would fill the bottom 4 feet with Rockwool 60 and the top with just poly batten.


I can only put them in 3 corners too because one corner is a door.
Why not go all the way to the top with the Rockwool? Tricorners are extra-good.

As for the size, you mean 12"x12", with the diagonal of course being greater than 12" right? (~17" according to that Pythagoras guy :))

This is a good size for the 60 kg/m^3 rockwool. If you doubled the size, this would only improve absorption below about 60 Hz, according to my back-of-the-envelope guestimate.

Regards,
Terry

Another question from the noobie section.

How wide and thick do corner bass traps have to be. Im still considering DIYing them by creating a tri-angle frame for each corner that fits 100% of the corner. I was think of having it 12"x12"x12". is that too much or not enough for bass traps. I would fill the bottom 4 feet with Rockwool 60 and the top with just poly batten.


I can only put them in 3 corners too because one corner is a door.

I cut the 2x4 sheets of OC703 into eight triangles. This resulted in lengths along the walls of about 18" if memory serves me right. The hypotenuse is about 24". I agree with the other guy, why not go full height with the Rockwool?

ok, so i started reading this thread about an hour ago, i got to page 4 or so of 104. is there a guide or manual, free or for sale that gives general directions or is this too room specific. i have already begun my home theater and don't want to screw it up (too badly). anyone have any idea what denis E's lowest design package goes for? i already have my room dimentions, chairs picked projector picked etc. i think i'll do ok for the most part, but the room acoustics are going to give me headaches...i'ld rather build the room than read till my eyes bleed. My preference would be not to use furring strips. i can handle installing panels both as an asthetic and acoustic treatment once the room is built. any thoughts on a consolodated resource. perhaps i'll pm this to denis...

ok, so i started reading this thread about an hour ago, i got to page 4 or so of 104. is there a guide or manual, free or for sale that gives general directions or is this too room specific. i have already begun my home theater and don't want to screw it up (too badly). anyone have any idea what denis E's lowest design package goes for? i already have my room dimentions, chairs picked projector picked etc. i think i'll do ok for the most part, but the room acoustics are going to give me headaches...i'ld rather build the room than read till my eyes bleed. My preference would be not to use furring strips. i can handle installing panels both as an asthetic and acoustic treatment once the room is built. any thoughts on a consolodated resource. perhaps i'll pm this to denis...

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

anyway to acoustically treat a window without removing it?

I think my window is at a reflection point in the room.
You can make a fabric-covered "plug" for it out of rigid fiberglass which fits tightly into the window recess. This will also block the light from the window.

Make two of them, and hang the other one on the opposite side wall for perfect symmetry!

Regards,
Terry

Terry Montlick:
I concur with your signature.

Terry Montlick:
I concur with your signature.

Wow..had no idea..that's terrible the site had to be taken down!

I recall someone recommending not to have back-panels on my ceiling tiles after I ordered them. I have tried removing those and it causes a slight null at around 160Hz, it smooths out my response from 100Hz to 60Hz and it increases the response from 10Hz to about 25Hz. This is after removing almost a complete row of them from the sides of my room.


It seems to me that it is a problem with my back wall...

Indeed. That is an outrage. Is the subject forum accepting donations for their defense fund?

I vote we take all this to another thread. I'll leave it to someone else to start it. I know this main thread is already plenty long, and we don't want to turn off anyone on the fence about acoustic treatment.

Why not go all the way to the top with the Rockwool? Tricorners are extra-good.

Pure cost question.

I have to buy more Rockwool, I was wondering if there is a "diminished returns" effect after I have so much already, more likely I dont have enough yet and there is probably a "diminished returns" effect or "Deading" of the room if I go too far.


bw, yes it wasnt 12x12x12 I had a typo, its 12x12x17 sorry about that.

Pure cost question.

I have to buy more Rockwool, I was wondering if there is a "diminished returns" effect after I have so much already, more likely I dont have enough yet and there is probably a "diminished returns" effect or "Deading" of the room if I go too far.


bw, yes it wasnt 12x12x12 I had a typo, its 12x12x17 sorry about that.

Since the greatest benefit for any acoustical treatment is always at the beginning, you could put a "diminishing returns" point anywhere! But to absorb bass in the above-subwoofer range (>80 Hz), all the corners are useful. And it is hard to "overdeaden" a room with just corner treatment. The lower down below around 80 Hz, the more aggressive and extensive the treatment has to be, simply because it becomes less effective.

Regards,
Terry

Need some direction on ideas for front wall treatment.. I know there is tons of stuff mentioned in this thread and have kinda skimmed but want to ask outright with the hopes of a simple answer or a link to what I need to know..
Front wall is about 13' 1/2" drywall and 8' (drop ceiling).. I was hoping to get some kind of curtain or fabric to hang on the front wall from a local JoAnn Fabrics or similar.. can anyone provide a name of a material i should look for at a store like this just to cover the front wall in hopes to help with the acoustics..

Need some direction on ideas for front wall treatment.. I know there is tons of stuff mentioned in this thread and have kinda skimmed but want to ask outright with the hopes of a simple answer or a link to what I need to know..
Front wall is about 13' 1/2" drywall and 8' (drop ceiling).. I was hoping to get some kind of curtain or fabric to hang on the front wall from a local JoAnn Fabrics or similar.. can anyone provide a name of a material i should look for at a store like this just to cover the front wall in hopes to help with the acoustics..
No fabric at JoAnns will really help with acoustics. It is too thin to do much of anything. Such fabric can, however, be used to hide acoustic treatments, such as fiberglass.

Regards,
Terry

I'm planning for the acoustic treatments in my HT room. I will be doing what seems to be the recommended approach: front wall and first 2' of side walls fully covered in OC/Linacoustic and then lower half of side walls treated. I have some questions regarding these materials however.

I will not be making standalone panels. I will be furring out the depth of the product I choose and covering with GOM. So I'll be doing the absorbing 'wall' approach.

Is there a reason to prefer the rigid boards over the rolled product? It seems like the rolls of Linacoustic are significantly cheaper per square foot, but with slightly lower NRCs.

Which leads me to my next question. Is there a reason to prefer the OC703 over the Linacoustic R300? The reason I ask is that most people refer to the OC703 when building panels. Is this simply because they come in 2'x4' sheets rather than 4'x8' R300? I have a lot of surface to cover, so the larger boards are appealing. I just don't see the R300 mentioned as much.

When I look at the NRCs for both rigid products, they appear mostly identical. And the Linacoustic is black with a surface treatment that may make it easier to handle (?). I also think that the 1.5" thick Linacoustic would be friendlier for the furring I'd be doing.

Now for costs. I have an idea what the OC703 and RC products go for, but what have people paid for the R300?

Any input would be helpful.

Thanks!

The acoustical differences between these fiberglasses is so small as to be insignificant for the majority of cases. The rolls of Linacoustic have somewhat lower density, and the facing makes them a bit easier to manage and perhaps not quite as irritating to the skin.

Go with whatever you can get a good price on and install the easiest.

Regards,
Terry

Is there a reason to prefer the OC703 over the Linacoustic R300?


I think its all about price. Anything with "acoustic" in it for some reason is 3x the price, marketing at its best kind of like "Monster" ;) My local supply company found it shocking that the R300 was extremely over priced compared to TG EI800 or TG EI475, which are similar duct boards.

OC703 isnt even the best price stuff..Rockboard60 is thicker and cheaper.

question about using rigid styrofoam.

I have 12 sheets of 2x4 OC703 that Im going to be placing around my walls below ear level in my HT room. Most is going to be front wall and side walls but I will have some on the back wall too.

I will have gaps in my wall and I dont want to frame around the 2x4 sheets, instead I want to fill the gaps. I know poly batting will work but what about rigid styrofoam 1" thick. I see 4'x8' sheets at HD all the time for $10 or so can I use this as a "filler" between the OC703?

question about using rigid styrofoam.

I have 12 sheets of 2x4 OC703 that Im going to be placing around my walls below ear level in my HT room. Most is going to be front wall and side walls but I will have some on the back wall too.

I will have gaps in my wall and I dont want to frame around the 2x4 sheets, instead I want to fill the gaps. I know poly batting will work but what about rigid styrofoam 1" thick. I see 4'x8' sheets at HD all the time for $10 or so can I use this as a "filler" between the OC703?

Rigid styrofoam isn't an acoustic absorber. It will fill space -- that's about it.

Poly batting is a reasonable effective absorber, depending on density. Dense (semi-rigid to rigid) fiberglass is an extremely effective absorber.

Regards,
Terry

The acoustical differences between these fiberglasses is so small as to be insignificant for the majority of cases. The rolls of Linacoustic have somewhat lower density, and the facing makes them a bit easier to manage and perhaps not quite as irritating to the skin.

Go with whatever you can get a good price on and install the easiest.

Regards,
Terry

I think its all about price. Anything with "acoustic" in it for some reason is 3x the price, marketing at its best kind of like "Monster" ;) My local supply company found it shocking that the R300 was extremely over priced compared to TG EI800 or TG EI475, which are similar duct boards.

OC703 isnt even the best price stuff..Rockboard60 is thicker and cheaper.


Thanks to you both for the replies. This is pretty much what I figured.

What company makes 'TG EI800 or TG EI475'. I Googled it and found Knauf Elcipse Duct Board. Is this correct?

No fabric at JoAnns will really help with acoustics. It is too thin to do much of anything. Such fabric can, however, be used to hide acoustic treatments, such as fiberglass.

Regards,
Terry

What about using very thick blackout-style (ie, reflective at high frequencies) pleated curtains for diffusion? Not really useful, either? (I'm guessing not.)

Studiotips is back on line.

What about using very thick blackout-style (ie, reflective at high frequencies) pleated curtains for diffusion? Not really useful, either? (I'm guessing not.)
Depends on the material. Thick velour (18-32 ounce, the kind used for heavy stage curtains) has decent absorption, especially when draped loosely with lots of folds to 1/2 width. But in general, thin fabrics will not absorb, but simply allow sound to pass through and bounce right back out. :(

Regards,
Terry

Rigid styrofoam isn't an acoustic absorber. It will fill space -- that's about it.

Poly batting is a reasonable effective absorber, depending on density. Dense (semi-rigid to rigid) fiberglass is an extremely effective absorber.

Regards,
Terry


As always thanks Terry!!

I wasnt really worried about acoustic absorption. I just wanted a "filler" so that my bottom half of the wall is an uniform 1" all the way around. I do believe I have enough 1" OC703 and I can just fill the spaces left over with the 1" styrofoam.

What company makes 'TG EI800 or TG EI475'. I Googled it and found Knauf Elcipse Duct Board. Is this correct?

From my printed out quote I think its CertainTeed ToughGard Duct Board.

I do believe its this

http://www.certainteed.com/NR/rdonlyres/146430D1-21FF-4C44-9DBB-033FEEDBECEB/0/3034006ToughGardDuctBoardSpecSht.pdf

The 2" EI800 stuff is what we want....NRC of .95

2x48x120" 160@1.19 (4 sheets) around $190, which i think its great because that is about 20 24x48 sheets. 20 OC703 sheets are over $200.

From my printed out quote I think its CertainTeed ToughGard Duct Board.

I do believe its this

http://www.certainteed.com/NR/rdonlyres/146430D1-21FF-4C44-9DBB-033FEEDBECEB/0/3034006ToughGardDuctBoardSpecSht.pdf

The 2" EI800 stuff is what we want....NRC of .95

2x48x120" 160@1.19 (4 sheets) around $190, which i think its great because that is about 20 24x48 sheets. 20 OC703 sheets are over $200.


I will certainly try to find a Certainteed dealer locally. I found one for this product with the same name.

http://www.knaufusa.com/products/building_insulation/commercial_building_insulation/knauf_air_duct_board-agm.aspx

I'm finding most of these manufacturers have quite similar products the more I look into it...

Then I found this:

http://www.knaufusa.com/products/building_insulation/commercial_building_insulation/knauf_black_acoustical_board.aspx

Again looks like splitting hairs at NRCs with 2" thick 3pcf boards whether Certainteeed, OC, JM, or now Knauff. I think the challenge is finding a local distributor who even knows what we're talking about when you call and want 'duct liner' and is willing to order it. Especially problematic with the large form factor boards (which I'd prefer) and thicknesses OTHER than 1" or 2" (I'd like 1.5").

I called McCormick Insulation out in Maryland (I'm in MI) based on a post here somewhere for Linacoustic RC. The guy actually knew exactly what I was talking about and offered some alternatives. I'm hoping to hear back from him tomorrow.

I called McCormick Insulation out in Maryland (I'm in MI) based on a post here somewhere for Linacoustic RC. The guy actually knew exactly what I was talking about and offered some alternatives. I'm hoping to hear back from him tomorrow.
They have locations all over the U.S.

http://www.spi-co.com/

I've only had luck finding JM (John Manville) IS 300 and IS 600 locally. It also comes in 4'x8' sheets which actually works out better for me since it's mainly to treat the front and rear (if needed) walls.

The specs are:

IS 300 2" (51mm) 3pcf (48kg/m3) 0.24 1.00 1.11 1.08 1.06 1.05 1.05
IS 600 2" (51mm) 6pcf (96kg/m3) 0.38 0.93 1.10 1.07 1.07 1.07 1.05

I've searched the forum with the built in search tool and google but neither can find references to the IS 600. Is the IS 600 a match to the 705 FRK or just 705? Is the IS 600 ideal for bass traps?

My thought is putting is 300 on the entire front wall and then making triangle/chunk bass traps with the is 600 in the front corners.

A minor twist is in my HT I'll have about 40 linear feet of the 70' perimeter covered in a thick theater like fabric which will remove mostly highs, maybe too much... This is why I wonder if the front wall should be the IS 600 so I don't remove too much high?

All surfaces, even the ceiling, in the room are cement, no framing, studs, or sheetrock behind the curtains, columns or AT screen.

Anyone use Johns Manville 475 Duct Board (rigid)? A company my dad works with can get some for a good price. It comes in 4'x10' sheets, 1 in thick. I did find it on jm.com and it has what appears to be good acoustic properties, but then again, I am not an expert in reading it. It has a foil backing, but it could be pulled off it it's a bad thing to have.

Anyone have any experience or opinions on such a product. Is it all the same? Should the foil be pulled off?

Well, I found a PDF on JM's site and it appears to have acoustic properties of everything else:

Thickness Frequency (Hz)
Type (inches) (mm) 125 250 500 1000 2000 4000 NRC
475 1 25 .07 .25 .63 .90 .97 1.00 .70

So it looks fine and just another variation of the same.

It has a foil backing, but it could be pulled off it it's a bad thing to have.


I have read that the foil would reflect the sound, you need to probably pull it off. Of course a true expert here will confirm that at some point.

I also read that if the foil is against the drywall it's no different than the drywall itself reflecting the sound. Plus it would be reflected after being absorbed by the panel, so the amount reflect would be greatly reduced, if not absorbed again going back through the panel. But, I am no expert either :)

I also read that if the foil is against the drywall it's no different than the drywall itself reflecting the sound.

yes, if its against the wall I believe you are okay....doh! I didnt think of that. Its late :D

I've only had luck finding JM (John Manville) IS 300 and IS 600 locally. It also comes in 4'x8' sheets which actually works out better for me since it's mainly to treat the front and rear (if needed) walls.

The specs are:

IS 300 2" (51mm) 3pcf (48kg/m3) 0.24 1.00 1.11 1.08 1.06 1.05 1.05
IS 600 2" (51mm) 6pcf (96kg/m3) 0.38 0.93 1.10 1.07 1.07 1.07 1.05

I've searched the forum with the built in search tool and google but neither can find references to the IS 600. Is the IS 600 a match to the 705 FRK or just 705? Is the IS 600 ideal for bass traps?

My thought is putting is 300 on the entire front wall and then making triangle/chunk bass traps with the is 600 in the front corners.

A minor twist is in my HT I'll have about 40 linear feet of the 70' perimeter covered in a thick theater like fabric which will remove mostly highs, maybe too much... This is why I wonder if the front wall should be the IS 600 so I don't remove too much high?

All surfaces, even the ceiling, in the room are cement, no framing, studs, or sheetrock behind the curtains, columns or AT screen.

Rockboard 60 might be better for down low bass trapping.

http://www.atsacoustics.com/item--Roxul-Rockboard-60-Case-of-6--RB60.html

http://www.roxul.com/graphics/RX-NA/Canada/Product%20Literature/Tech%20Data/RockBoard60-8-7-07.pdf

EDIT: I was looking wrong (wasn't comparing the same thicknesses), the 600 stuff looks great. But what does it cost?

I've done a search, but this thread is pretty long, so I apologize in advance if my answer is in here somewhere.

Anyway, I want to treat the corners of my theater, but I'm limited in trap size by aesthetics. I want to put two vertical corner traps on the screen wall. A pleasing size would be ~10"x10"x14" (triangle) by ~5' tall.

On the rear wall (wall/ceiling junction) it would be ~11"x11"x16" by ~ 15' wide.

http://www.c-not-k.com/OddsEnds/MtHebron/HomeImprovement/Cadd/Thumbs/HomeTheater-Plan.gif (http://www.c-not-k.com/OddsEnds/MtHebron/HomeImprovement/Cadd/Full/HomeTheater-Plan.gif)

My question is how effective will traps of this size be? Is something this size better than nothing?

IIRC, a traps lowest effective frequency is based on the biggest quarter-wavelength that will fit (ignoring the effect of the absorption material. I was going to use OC 703.) This would be easy to calculate this for a rectangular trap. How would you calculate that for a triangular one?

Thanks

...
IIRC, a traps lowest effective frequency is based on the biggest quarter-wavelength that will fit (ignoring the effect of the absorption material. I was going to use OC 703.) This would be easy to calculate this for a rectangular trap. How would you calculate that for a triangular one?

For a really big flat absorber, a quarter wavelength is the depth at which you typically get close to maximum absorption. But you get some piece of lower frequencies, since absorption in not an all-or-nothing proposition.

And there is a more important thing in acoustics called the "edge effect." This happens when waves are roughly comparable in size to the absorber. The waves bend in toward the surface, so that the effective absorption area is larger. This is a wave diffraction phenomenon, and I don't have a good "cartoon physics" way of portraying it! :)

But the end result is good. You get additional low frequency absorption which is related to the width of your corner absorber, not just its depth. I don't know of anything like an accurate formula for it, though.

Regards,
Terry

Rockboard 60 might be better for down low bass trapping.

EDIT: I was looking wrong (wasn't comparing the same thicknesses), the 600 stuff looks great. But what does it cost?

It's $.13 more a sqft than 300. The 300 price though seemed a little high.

I've done a search, but this thread is pretty long, so I apologize in advance if my answer is in here somewhere.

Anyway, I want to treat the corners of my theater, but I'm limited in trap size by aesthetics. I want to put two vertical corner traps on the screen wall. A pleasing size would be ~10"x10"x14" (triangle) by ~5' tall.

On the rear wall (wall/ceiling junction) it would be ~11"x11"x16" by ~ 15' wide.

http://www.c-not-k.com/OddsEnds/MtHebron/HomeImprovement/Cadd/Thumbs/HomeTheater-Plan.gif (http://www.c-not-k.com/OddsEnds/MtHebron/HomeImprovement/Cadd/Full/HomeTheater-Plan.gif)

My question is how effective will traps of this size be? Is something this size better than nothing?

IIRC, a traps lowest effective frequency is based on the biggest quarter-wavelength that will fit (ignoring the effect of the absorption material. I was going to use OC 703.) This would be easy to calculate this for a rectangular trap. How would you calculate that for a triangular one?

Thanks

It's not that the 1/4 wave is as low as it will absorb anything, it's that it's where it's most effective. Smaller absorbers will still reach down into lower frequencies, just not with a large coefficient per unit area.

Absorbers the size you're specifying will still do some good down into the subwoofer range and are certainly better than nothing.

Bryan

Anyone have any knowledge or links on the acoustical numbers of carpet pad?

I have lots left over still and I was actually thinking of using it on the top half of the walls if it doesnt have much absorption. I have decided that I do want something under my fabric on the top half of the walls still (atleast today I have decided that....flip/flop....flip/flop)

After extensively searching, questioning and reading... I have found a local HVAC dealer that sells OC703 but for $111.00 a case (72 sqft) I am debating on going with a product called Fibrex (http://www.fibrexinsulations.com/products/industrial_board.html)
which is a hell of a lot cheaper and since I didn't take into account acousitcs when builing my theater (dumb mistake) I don't want to go over board on expensive techniques that might not be much better than the corner trap I am building using this Fibrex.. Does anyone know anything about it and would say for the difference in price which is at $40.00/case (64 sqft) it would be good to use.

That's just a brand of mineral wool. It will work fine - though it's nasty to work with compared to 703. Use the 1240 for reflection duties and 1280 for bass absorbers unless you're doing chunk style solid ones, then the 1240 will be fine.

Bryan

That's just a brand of mineral wool. It will work fine - though it's nasty to work with compared to 703. Use the 1240 for reflection duties and 1280 for bass absorbers unless you're doing chunk style solid ones, then the 1240 will be fine.

Bryan

I'm planning on the corner chunk type trap... but if i try to get this in triangle cuts and wrap with GOM or Speaker cloth what could i use to keep the front of the trap flat and some what decent looking.. I have read that someone used an FRK(?) panel in the front of the trap for a flat surface... where do I find a FRK panel? or what else could be used that would not affect the purpose of the trap itself?

OK I just got some reasonably priced 2' x 4' x 6" rigid fiberglass bass traps and placed them in all 4 corners of my HT. The problem I have is that they are directly in line with the backside of my Def Tech bipole towers and are definitely absorbing the highs. My question is can I put something on the face of the trap to reflect the highs or would I be better off opening them up and putting some FRK on the inside of the face? I guess I really don't want to mess with the fiberglass if I don't have to.

My question is can I put something on the face of the trap to reflect the highs or would I be better off opening them up and putting some FRK on the inside of the face? I guess I really don't want to mess with the fiberglass if I don't have to.
You can use ordinary, inexpensive Kraft paper over the fiberglass, then cover it back up with fabric. Be sure to comply with all local building codes, as the Kraft paper (as well as FRK - Foil Reinforced Kraft paper) is not flame retardant or noncombustible.

Regards,
Terry

Anybody with information on where I can purchase OC703 in the Dallas / Plano, TX area.

Thanks

Anybody with information on where I can purchase OC703 in the Dallas / Plano, TX area.

Thanks
http://www.spi-co.com/servicecenterdirectory.cfm

Hey,

WAF is too low on my plans to have 48" Linacoustic from floor to chair rail, so I'm wondering if I could reverse it and have plain wall from floor up to 34-36" and then take the Linacoustic up to the ceiling? This is a multi-use family/media room, so she's got some aesthetic sensitivities I need to work with...

Would that work for broadband bass absorption, but not "kill" the room with too much absorption? Here's a pic of my friend's room--he's the carpenter I'm having do my room. 106237 In my case, I would have the Linacoustic inside taller upper boxes, while just having paint or wainscotting (sp) below.

My ceiling is not treated, nor with WAF can it be.

I have carpet on the floor, but one back corner is an 8' wide diagonal wall with fireplace and tile surround (i.e. live acoustically). 106236

I also have a window on my far right side and several doors in the room (one double french glass door, and two 36" door to storage areas).106234. Otherwise the whole room would be treated from 36" off the floor to my 8' ceiling (- my crown moulding height).

My room is 15'W x 27'D.

Here's another shot to get a feel for the room--I'm going to build a stage front with columns to house my Dali Mentor 6s and build-in my Mentor Vokal center for behind my screen.

I also plan to cover the front wall with 2" of Linacoustic behind my SmX Cineweave 120" diag screen.

So, will my inverted boxes (filled with 1" Linacoustic) be workable?

Thanks for the help!
Phil

Someone may have a better set of answers for you but here is my impression:

WAF is too low on my plans to have 48" Linacoustic from floor to chair rail, so I'm wondering if I could reverse it and have plain wall from floor up to 34-36" and then take the Linacoustic up to the ceiling?

Short answer is "No." Long answer is that the Linacoustic is for higher frequency absorption, and you want that at likely first reflection points (like your original plan to have it UNDER the chair rail). You COULD get by with not putting it everywhere, but just at the key first reflection points, found via the mirror method:

http://www.avsforum.com/avs-vb/showthread.php?t=868585


Would that [putting it above ear height throughout the room] work for broadband bass absorption, but not "kill" the room with too much absorption?

From what I have experienced, not so much. One or two inch thick linacoustic on the walls doesn't do much for bass trapping. You'll do better with something thicker, filling a corner.

---

There are some nice looking ways to do acoustic treatment. Lots of great photos in this thread and many construction threads.

Some do, some don't. The idea is to cover a certain percentage of the wall with more absorbtion. If you go higher on shorter walls, you are actually increasing the percentage of the wall that is covered.

I don't know any general rule of thumb about this. Dennis could probably provide a more experienced answer for this type of implementation.

While plowing through this amazing thread, I'm wondering if a "general rule" surfaced that will help me with my WAF problem!

I can either go up to 38" (including top trim--either chair or ledge molding) with Linacoustic, or above that height to the ceiling. Either way, I can only get away with a wall that has cloth for 1/3 or 2/3 with the other being painted or other hard-surfaced.

Any help much appreciated!
Phil

If

[QUOTE=nathan_h;13517022]Someone may have a better set of answers for you but here is my impression:



Short answer is "No." Long answer is that the Linacoustic is for higher frequency absorption, and you want that at likely first reflection points (like your original plan to have it UNDER the chair rail). You COULD get by with not putting it everywhere, but just at the key first reflection points, found via the mirror method:

http://www.avsforum.com/avs-vb/showthread.php?t=868585



From what I have experienced, not so much. One or two inch thick linacoustic on the walls doesn't do much for bass trapping. You'll do better with something thicker, filling a corner.[QUOTE=nathan_h;13517022]

Thanks for the insight Nathan.

So, keeping my original idea of having 1" linacoustic all the way around the room up to 38" would still work?

However, what exactly is it doing for me? What frequencies is it helping me with?

Thanks,
Phil

allredp, Im not an expert but Im applying OC703 around most of my room like you.


I have 24 2x4 sheets of OC703 that I will place about 40" high around my room, side and back walls. In the corners Im building thicker bass traps (triangle corner traps) with Rockwool 60. My front wall will have be covered top to bottom with OC703..

I dont have reflection coverage on my cieling yet either :( still figuring that one out.


I still dont have enough OC703 and Im Still sourcing out cheaper alternatives. I think I have some certaboard duct liner (1 /12 " 4x10 sheets) 4 sheets for around $200 locally. Thats $1.19 per sq ft.

ebay has 4 cases of 12 OC703 1" stuff for around 125 shipped...thats about $1.30 per sq ft.


The OC703 will absorb the higher frequences 250 and up.....so you need thick corner stuff to absorb your bass frequences.

So, keeping my original idea of having 1" linacoustic all the way around the room up to 38" would still work?

However, what exactly is it doing for me? What frequencies is it helping me with?

Thanks,
Phil

Yep, putting the treatment at ear level (especially at the angle of incidence that the mirror method indicates) is the right thing to do.

Frequencies:

http://www.bobgolds.com/AbsorptionCoefficients.htm

Hi all, quick qestion regarding a panel build. I searched this thread with no luck. In some builds, I've see that people have painted wooden frames to keep any light coloured wood from showing through the material used to cover the panel. (black speaker cloth for me)
What about the insulation? The 703 I have is yellow. Will I need to use two layers of speaker cloth?

Thanks for any advice.

Jay

Hi all, quick qestion regarding a panel build. I searched this thread with no luck. In some builds, I've see that people have painted wooden frames to keep any light coloured wood from showing through the material used to cover the panel. (black speaker cloth for me)
What about the insulation? The 703 I have is yellow. Will I need to use two layers of speaker cloth?

Thanks for any advice.

Jay

I used GOM cloth to cover my OC703 and one layer provides 100% coverage. Not sure about regular speaker cloth..

I used GOM cloth to cover my OC703 and one layer provides 100% coverage. Not sure about regular speaker cloth..

Thanks, I have a feeling that GOM is a bit "thicker" than speaker cloth. Oh well, time will tell!

Thanks,
Jay

I haven't been in this thread for a LONG time, but just happened back in.

1" linocoustic up to 38" is fine so long as your ears are less than that when listening.

The linocoustic is NOT designed for bass trapping and it will do very little of that. It's for mid and high frequency reflection and the associated flutter echo and other delay induced acoustical problems that come along with that. Accordingly you want it at any reflection point from the speakers to your ears.

There are several calculations that show that linocoustic from floor to ceiling generally will create a room that is too dead.

In my room I've got it up whatever the roll height was - 4 feet I think. And batting above that. All covered up with fabric. Typical Dennis Erskine type design from 3-4 years back. Then I've got a large amount of bass trapping behind my perforated screen.

Has your wife seen the fabric? Personally I think the fabric covered wall is much more attractive than paint, but to each his own. My room is black and dark grey all around including ceiling - totally designed for optimal viewing. Wife loves it, but it's only for movies, we don't use it for anything else. She was a skeptic, until she watched a movie and was amazed how everything but the movie screen just melted away.

cheers.

Has your wife seen the fabric? Personally I think the fabric covered wall is much more attractive than paint, but to each his own. .

Depending upon the fabric, of course, a fabric covered wall can look quite attractive and classy. This is based upon a dealer showroom example I've seen using a GOM Anchorage fabric with has a subtle texture to it. Looked elegant, with the added benefit of disguising all the wall treatments hidden behind it.

In other words, I agree.

1" linocoustic up to 38" is fine so long as your ears are less than that when listening.

The linocoustic is NOT designed for bass trapping and it will do very little of that. It's for mid and high frequency reflection and the associated flutter echo and other delay induced acoustical problems that come along with that. Accordingly you want it at any reflection point from the speakers to your ears.

There are several calculations that show that linocoustic from floor to ceiling generally will create a room that is too dead.

...Then I've got a large amount of bass trapping behind my perforated screen..

Awesome help!

So, I'll keep with the WAF plan and make my 1" linacoustic-filled "boxes" around the whole room up to 38" high.

I'll also try to figure out some side and rear wall treatments that will help with first reflection points.

I'm also going to "kill" my front wall with 2" linacoustic behind my AT screen (SmX CineWeave) and on/in my columns on either side of the screen that house my Dali Mentor 6's.

Bryan Pape of GIK also suggested that I do a chunked triangular floor/wall bass trap all along my back wall behind my sofa/sectional.

Cool--thanks for all the help!

I'm within days of starting the build-out...

This is based upon a dealer showroom example I've seen using a GOM Anchorage fabric with has a subtle texture to it. Looked elegant, with the added benefit of disguising all the wall treatments hidden behind it.


I really like the Onyx anchorage fabric!! Its very WAF too! Buts its $17/yd, YIKES!!!!

Im going to Jo-Anns this weekend (if I can find a 50% coupon somewhere).

If treating a room, what treatments does one attack first?

I.e., once measurements are taken, I would assume bass traps are added first as they could influence the RT60 numbers at higher frequencies. Then re-measure and address first reflection points. Then re-measure and correct RT60 for high frequencies. Am I correct?

db

If treating a room, what treatments does one attack first?

I.e., once measurements are taken, I would assume bass traps are added first as they could influence the RT60 numbers at higher frequencies. Then re-measure and address first reflection points. Then re-measure and correct RT60 for high frequencies. Am I correct?

db
I think most of us do the general treatments, i.e. thin, first and add traps later. Whether or not that's "by the book" will need to be addressed by the pros on this thread. I will add that the amount of mid- and high-frequency absorption added by corner bass traps is usually relatively minimal.

A 'protocol' question:

If I am to take various measurements and post for comment as I go through the process, should it be to this thread or my construction thread (Mayflower) or to yet another thread (e.g., Mayflower Acoustics)?

db

My opinion, this thread is plenty long, so a few more posts won't hurt. I say, try to keep it to the meat and potatoes, but post it here.

I'm is the design processes of my home theater and have started to look at how I'm going to handle the acoustics. The room is 13'4" by 20' by 9' with a tray ceiling. I'm planing on doing bass traps in the front 2 corners useing 703 or whatever and either 703 or linacoustic on the front wall except behind the screen. I'll do something for the first reflection points as well. My question comes to the rear of the theater. Other then a bar top and pilars where my speakers will be housed, it will be open to my large pool table, bar, card table room. How is this normaly handled, or is it. I'm kind of hopeing that the treatments I mentioned would be enough to allow my room to sound pretty good. I know having an open rear wall is not ideal but it's what I would perfer, as I have alot of people over for fights and big games.

Thanks

Brian

First, I want to apologize for not reading this thread from beginning to end, or even reading the last 10 pages. After posting this, I'll try to read as much as possible, but was just hoping to throw a couple of quick questions out there, regarding first reflection points.


1. When we are talking about first relection points, are we pretty much talking about the tweeter? What I mean is, if we are using a laser pointer or flashlight with a mirror, and bouncing that off a wall to the speaker, do we want the laser pointer light, or center of the flashlight beam to hit the tweeter, and thus that would be the "eye of the storm" so to speak in terms of the first reflection for that particular speaker?

2. If say, my "eye of the storm" for my left main is around 36 inches up at a particular spot on the wall. How much area around that precise point is also reflecting the sound? What I'm getting at with this question, is what kind of circumference around the "eye of the storm" is reflecting sound? Like 2 feet in every direction, 3 feet in every direction, etc, etc...

3. Continuing from question 2, if my linacoustic is 47 inches up, and the first relection point is 36 or so inches, do I need to be at all concerned with reflections above the 47 inches of linacoustic? Because I could treat just that small portion of the wall (above the furring strip at the 49 inch mark) alot higher, even all the way to the ceiling, but I don't know if that's necessary, or actually overkill. I know that you don't want to cover all your walls from floor to ceiling in linacoustic, cause it will totally deaden the room, but at the spot of first relection, do you actually want to go floor to ceiling in that particular spot? At alot of specialty home theater stores, they typically have oc703 panels wrapped in GOM, and they have them a foot or so off the ground, and they extend well past ear level.

4. Does linacoustic help any at all towards traping bass? What I mean by this, is that in my front corners, I have oc703 superchunks, but I was thinking on the side walls, close to where the superchunks are, I might as well go floor to ceiling with the linacoustic (just close to the corners), just to help out a little bit more with traping bass, but I guess if linacoustic doesn't help whatsoever in that regard it would be a total waste?

5. Regarding the side surrounds, should linacoustic be behind the side surrounds? How large a circumference behind the side surrounds?

Again, I'm sure that all these questions I'm asking right now have been answered somewhere in this thread, maybe even within the last 10 pages or so, and I'm going to begin reading the thread, but I'm going to be putting up the fabric this weekend, and I want to make sure I make any last minute adjustments before the fabric goes up. If any of these questions can be answered, that would be great, if not, hopefully I'll have enough time to read through the thread and find the answers before the fabric goes up above the chair rail.

Depending upon the fabric, of course, a fabric covered wall can look quite attractive and classy. This is based upon a dealer showroom example I've seen using a GOM Anchorage fabric with has a subtle texture to it. Looked elegant, with the added benefit of disguising all the wall treatments hidden behind it.

In other words, I agree.

Yeah, my wife has seen the fabric and is still adamant about not having a "pillowed-room" look.

BTW, the Anchorage is not AT, right? But, that's ok because the upper part is not meant to be "dead" anyway, right?

Thanks for the suggestions and all the help.

One more question: what's the deal with soffits?

I see them in most professional rooms and so many of the DIY rooms here! I can't tell if very many have bass-trapping in them, but they are everywhere.

Is that something I should be looking at for my room acoustically, or is it mostly for aesthetics and lighting options, etc.?

Thanks!

the rear of the theater ... will be open to my large pool table, bar, card table room.

An opening that gives a lot of space behind you is a Good Thing. The most damaging reflections at bass frequencies come from the wall behind you. So the farther back that wall is, the better.

--Ethan

First, I want to apologize for not reading this thread from beginning to end

No need to apologize. This thread is way too long, is full of conflicting and often wrong information, and has long overstayed its welcome IMO. :D

1. When we are talking about first relection points, are we pretty much talking about the tweeter?

Yes, early / first reflections are mainly a mid and high frequency issue. But it's not a single reflection point as much as an area. 47 inches high is probably okay. Much more here:

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

and here:

http://www.realtraps.com/art_room-setup.htm

--Ethan

BTW, the Anchorage is not AT, right? But, that's ok because the upper part is not meant to be "dead" anyway, right?

Thanks for the suggestions and all the help.


allredp, what do you mean?

AT is acoustically transparent which is only meaningful if you are covering speakers with it. When just covering walls any material that is not reflective works very well. The goal is to simply allow sound to be absorbed by the panels.

btw, its funny your wife didnt want a pillow room :D Mine said the same thing but when I showed her pics and showed her the material I will be using she was amazed. Although Im still having sticker shock with the anchorage GOM stuff....$17/yd???? Give me a break!!!

Its hard to hide 4x2 sheets of OC703 without something ;) and placing fabric panels around the room looks even worse unless you do panels everywhere and that is very time consuming.

allredp, what do you mean?

AT is acoustically transparent which is only meaningful if you are covering speakers with it. When just covering walls any material that is not reflective works very well. The goal is to simply allow sound to be absorbed by the panels.

btw, its funny your wife didnt want a pillow room :D Mine said the same thing but when I showed her pics and showed her the material I will be using she was amazed. Although Im still having sticker shock with the anchorage GOM stuff....$17/yd???? Give me a break!!!

Its hard to hide 4x2 sheets of OC703 without something ;) and placing fabric panels around the room looks even worse unless you do panels everywhere and that is very time consuming.

Hey Penngray,

Yes, I didn't mean behind the room, but just around the other three walls. I'm planning on packing 2" of Linacoustic behind my AT screen (as well as my center speaker--the Dali Mentor Vokal).

You know I tried to show her some pics, and it did help me with a few items, but she still isn't going for anything but paint and pictures above my dinky 38" height! You're so right about the individual panels bit...

I did get her to concede that I should have a couple columns in the back to balance out the room. I can fill them with mineral wool, floor to ceiling, though they won't be in the corners.

BTW, what will two columns 16"W x 6"D x 7.8'H (floor to ceiling) filled with chunks of mineral wool do for bass-trapping? They would be divided off-center on my back wall which is only 2-3' back from my listening position.

Appreciate the help!

An opening that gives a lot of space behind you is a Good Thing. The most damaging reflections at bass frequencies come from the wall behind you. So the farther back that wall is, the better.

--Ethan

Hey Ethan,

What if your sub is placed right against the back wall?

Does that change where you want treatments?

I'll have 1" linacoustic all along the back wall where I'll have my sub firing sideways.

What do you think?

Thanks,
Phil

You know I tried to show her some pics, and it did help me with a few items, but she still isn't going for anything but paint and pictures above my dinky 38" height! You're so right about the individual panels bit...

I did get her to concede that I should have a couple columns in the back to balance out the room. I can fill them with mineral wool, floor to ceiling, though they won't be in the corners.


In the end my wife is okay with the HT build (if I ever finish it) but she did ask last night where the toy closet is going (we have a 16 month old!!)....yikes!!! :D

Columns might work really well for you!! They will be great for bass absorption!!

In the end my wife is okay with the HT build (if I ever finish it) but she did ask last night where the toy closet is going (we have a 16 month old!!)....yikes!!! :D

Columns might work really well for you!! They will be great for bass absorption!!

Funny! I remember well... Mine are all teenagers now, so it's about scheduling time between all the x-box and sleepovers, etc.

Anyone else have insight to my column/bass-trap idea?

One more question: what's the deal with soffits?

I see them in most professional rooms and so many of the DIY rooms here! I can't tell if very many have bass-trapping in them, but they are everywhere.

Is that something I should be looking at for my room acoustically, or is it mostly for aesthetics and lighting options, etc.?

Thanks!

first about the Anchorage fabric; as mentioned a little while ago, yes, they are fine for allowing absorption to take place. In fact, I've seen this fabric given as an option on at least 2 or 3 acoustic treatment websites, as an "upgrade" to the standard GOM 701 series of fabrics.

re: soffits. I think they are used because they are one graceful way of secretly adding some extra trapping; thicker bass type trapping, mostly.

re: soffits. I think they are used because they are one graceful way of secretly adding some extra trapping; thicker bass type trapping, mostly.


Also, they hide any ugly pipes, ducts, wires or whatever needs to be hidden.

Yes, early / first reflections are mainly a mid and high frequency issue. But it's not a single reflection point as much as an area. 47 inches high is probably okay. Much more here:

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

and here:

http://www.realtraps.com/art_room-setup.htm

--Ethan

Ethan, since neither of your links addresses it, I take it that you are not a proponent of treating the front wall?

I thought the Anchorage was AT (I sure hope so, since I was planning on using it in my false wall in front of speakers...)?

I'm using soffit's to put my can lights in so I'm not opening up huge holes in my DD ceiling.

What if your sub is placed right against the back wall? Does that change where you want treatments?

You mean front wall, yes? My sub is in the front left corner, and it's great there. I have bass traps in all corners, and for that corners the trap is above the sub.

--Ethan

Ethan, since neither of your links addresses it, I take it that you are not a proponent of treating the front wall?

The front wall is as good a place as any for general absorption to reduce ambience. But unless the room is really tiny it won't be much of a reflection place. I do in fact have an article about this:

http://www.realtraps.com/art_front-wall.htm

--Ethan

The front wall is as good a place as any for general absorption to reduce ambience. But unless the room is really tiny it won't be much of a reflection place. I do in fact have an article about this:

http://www.realtraps.com/art_front-wall.htm

--Ethan

ah, thanks.. I'll go and have me a look. :)

I thought the Anchorage was AT (I sure hope so, since I was planning on using it in my false wall in front of speakers...)?



I think two people just confirmed that it was, one being me. So yes, don't fret about it, the Anchorage is AT.

The front wall is as good a place as any for general absorption to reduce ambience. But unless the room is really tiny it won't be much of a reflection place. I do in fact have an article about this:



ok, so by "ambience", you mean what, exactly? Just want to be sure I am understanding you correctly.

From your article, you don't seem high on the concept of front wall treatments*, UNLESS, you have speakers that just so happen to radiate enough mid to high frequencies off to the sides and rear to make it worthwhile, which most speakers apparently do not. Or, unless you have a multi-channel system with rear speakers pointing towards the front wall, in a room that is rather small. Have I accurately portrayed your philosophy on this matter?

I also take it that you would even go so far as to say that placing 4"+ wall panels on the front wall is not all that necessary either, particularly if you are able to sufficiently treat the corners of the front wall/ceiling with 4"+ corner panels or larger diameter tube traps, etc. Or to put it another way, would you advice placing 4"-6" wall panels on the front wall ONLY in situations where you are unable to adequately bass trap in the corners?


*to be clear, I'm not including 4"+ corner bass trapping within that description of "front wall treatment"

Regarding first reflection points, I did the mirror trick thing with a flashlight, and marked the points of first reflection with a tiny patch of blue painters tape. Here is a pic of it:

http://i58.photobucket.com/albums/g257/Anthony1fromDP/Picture1124.jpg

If you look closely at this picture, from left to right, you'll see three little strips of blue tape on the linacoustic. This wall, is to the right of the screen. The first blue strip, corresponds with the tweeter of my right Energy C8 tower speaker. The second blue strip, corresponds with the tweeter of my Energy AC300 center. The third blue strip, corresponds with the tweeter of the left Energy C8 tower speaker (on the opposite side of the room)

The center channel is really low because I need to build a proper stand for it, and it's on a temporary stand. However, I have to locate it below the screen, and it will only be about 10 inches higher, if that.

Anywho, the blue stips of painters tape towards the top, the reflections coming from the Energy C8 towers, are at about 38 inches or so off the ground, and the linacoustic goes up to 47 inches. Above the linacoustic is a 2 inch furring strip, and I could put additional linacoustic above the furring strip. Since the reflection of sound hits a general area of the wall, I was trying to figure out what might be the circumference of the reflection, to determine if part of the reflection is hitting above the furring strip, to the area that currently doesn't have any linacoustic on it.

I've heard that putting linacoustic above ear-level isn't necessary, but I've also heard that some people go floor to ceiling at the first reflection points. I'm going to be putting my fabric up very soon, and I'm trying to decide if I need to put any linacoustic above the furring strip at the 49 inch mark of the wall. (linacoustic is from floor to 47 inches up, and then the 2 inch furring strip).

I have a riser for the second row of seating, and the riser is approximately 13 inches off the ground, so i'm going to put an extra 13 inches of linacoustic above the furring strip parrallel to the riser, but was wondering if I should put any linacoustic above the furring strip anywhere else.

Regarding first reflection points, I did the mirror trick thing with a flashlight, and marked the points of first reflection with a tiny patch of blue painters tape. Here is a pic of it:

If you look closely at this picture, from left to right, you'll see three little strips of blue tape on the linacoustic. This wall, is to the right of the screen. The first blue strip, corresponds with the tweeter of my right Energy C8 tower speaker. The second blue strip, corresponds with the tweeter of my Energy AC300 center. The third blue strip, corresponds with the tweeter of the left Energy C8 tower speaker (on the opposite side of the room)

The center channel is really low because I need to build a proper stand for it, and it's on a temporary stand. However, I have to locate it below the screen, and it will only be about 10 inches higher, if that.

Anywho, the blue stips of painters tape towards the top, the reflections coming from the Energy C8 towers, are at about 38 inches or so off the ground, and the linacoustic goes up to 47 inches. Above the linacoustic is a 2 inch furring strip, and I could put additional linacoustic above the furring strip. Since the reflection of sound hits a general area of the wall, I was trying to figure out what might be the circumference of the reflection, to determine if part of the reflection is hitting above the furring strip, to the area that currently doesn't have any linacoustic on it.

I've heard that putting linacoustic above ear-level isn't necessary, but I've also heard that some people go floor to ceiling at the first reflection points. I'm going to be putting my fabric up very soon, and I'm trying to decide if I need to put any linacoustic above the furring strip at the 49 inch mark of the wall. (linacoustic is from floor to 47 inches up, and then the 2 inch furring strip).

The wavelengths from a tweeter are pretty small, and I assume the tweeter on this speaker is located several inches above the lower frequency drivers. Because of the small wavelengths, there is very little spread at the first reflection points. So you should be fine with just fiberglass as it is now.

I have a riser for the second row of seating, and the riser is approximately 13 inches off the ground, so i'm going to put an extra 13 inches of linacoustic above the furring strip parrallel to the riser, but was wondering if I should put any linacoustic above the furring strip anywhere else.
You should be okay here as well, as the reflection geometry should be much the same.

Regards,
Terry

For those only treating the 1st reflection points, don't forget to do the "mirror/blue-tape-trick" for each seat.

I think two people just confirmed that it was, one being me. So yes, don't fret about it, the Anchorage is AT.

Sorry, the last one I saw I thought said that it was not AT...

You mean front wall, yes? My sub is in the front left corner, and it's great there. I have bass traps in all corners, and for that corners the trap is above the sub.

--Ethan
Hey Ethan,

Actually I did mean "back" wall, as in the back of my room.

I currently have my sub in the front R corner (where it takes advantage of the corner boundary boost); however, I'm seriously considering moving it to the back of my room. I was told by another "pro" that for the best acoustics I really don't want my sub in a corner.

Frankly I'd love to move the sub to the rear for aesthetic reasons also--it is oversized for my space in the front R corner (due to a closet door :() and, it would look better (as in not be seen) in the back.

I've attached a couple pics to show what I mean in my room (15'D x 27'W x 7.8"H). Here's the spot in the back of my seating where I'm considering putting my SVS Ultra (with arrow to potential placement) 106662 and here's a pic of the front build-out plan where I'm going to be treating the behind the screen area with 2" of linacoustic 106663. Notice too, that I'm running 1" linacoustic all the way around the room (shown by the goofy looking "boxes" I've drawn on the pic). I also plan to have some chunked trapping for my one corner in the room, and I'm also going to stuff two rear columns on my back wall full of mineral wool...

So, what are the advantages and disadvantages of a sub in the back of the room, behind, but close to the seating?

Help is much, much appreciated!

Thanks,
Phil

Subj: Acoustic Treatments (Cross post from Mayflower construction thread)

I took the time to sketch the as-built floorplan and estimated the longitudinal room modes for the different parallel surfaces. I have included them on the floorplan.

My question is whether the irregular parallel surfaces (e.g., the room length has a 22' section at longest, but only 18.5' for the outer 3.5' on each side.) weakens the dominant modes and helps me out or just introduces more strong modes.

From the floorplan, the lenght, width and height are substantially broken up by various room features.

If I do install bass traps (I'll have measurements by next week - carpet goes in tomorrow), any suggestions where? I'm thinking superchunks in the rear corners (under the soffits) and maybe on the stage in the corners against the front wall.

Any other predictions from the group at large?

db

http://idisk.mac.com/dbbarron1-Public/Theater/predicted modes.jpg

ok, so by "ambience", you mean what, exactly?

Ambience is like reverb, but the term is more appropriate to domestic size rooms that don't have true reverb as you'll find in an auditorium or gymnasium. So ambience is really more a collection of individual reflections that decay quickly over time. But those reflections still make a muddy mess of the sound in much the same way reverb does in a gymnasium. It's just that the decay times are shorter. And ambience doesn't swell initially over time the way true reverb does.

Have I accurately portrayed your philosophy on this matter?

Yes.

I also take it that you would even go so far as to say that placing 4"+ wall panels on the front wall is not all that necessary either, particularly if you are able to sufficiently treat the corners of the front wall/ceiling

Thick absorbers on the walls are still useful because they give that much more bass trapping in the room. The main point of my Front Wall article addresses the inadequacy of 1-inch thick material which is very common in DIY home theaters. Even two inches is not thick enough to help at bass frequencies. In my mind (uh oh) the ideal room will have 12-inch thick fiberglass on all walls and the ceiling, but with portions covered by cardboard or thin plastic etc (or reflective diffusors) to avoid being totally dead.

--Ethan

I was told by another "pro" that for the best acoustics I really don't want my sub in a corner.

Here's my take on that:

http://www.realtraps.com/art_sub-placement.htm

what are the advantages and disadvantages of a sub in the back of the room, behind, but close to the seating?

I can theorize a few pros and cons, but I've never actually tried that so it would not be an informed opinion. My gut feeling is it's better to have the sub closer to the mains in the front of the room. As explained in the article linked above, the only way to know for sure is to measure the LF response at high resolution.

--Ethan

Regarding subs, what's the way to go if you're using two of them? For some reason, I was under the impression to have them located in completely opposite corners. I have one sub in my front left corner, and one sub in my back right corner. Basically, in completely opposite corners. Not sure why I thought that this was the way to do it.

Regarding subs, what's the way to go if you're using two of them? For some reason, I was under the impression to have them located in completely opposite corners. I have one sub in my front left corner, and one sub in my back right corner. Basically, in completely opposite corners. Not sure why I thought that this was the way to do it.
Don't know why you thought this either. :)

Multiple sub placement is a complex subject. For a place to start, there is Floyde Toole's white paper:

http://www.harmanaudio.com/all_about_audio/loudspeakers_rooms.pdf

He has a basic discussion of room modes and how two subs can help.

There is no generally agreed upon procedure, though. Rooms are different, no simple sub configuration can solve all problems. Side sub placement can increase envelopment, but does necessarily improve room modes. More than one sub removes the option of the "crawl" technique, by which you exchange places with your sub and find a good spot easier. Dennis E. advocates a dual sub placement method developed by Gerry Lemay, which kinda sorta works. Etc., etc. :(

Regards,
Terry

I went for the four sub design (two on front wall and two on back at 1/2, 2/3 position on each).

Will have testing next week.

ok, so i have actually tried to read some of this thread. i understand that a dead front wall is a good thing and more than 2" of fiberglass is recommended. i am insulating my walls with cellulose behind a material called insulmesh. i will have about 6" of it behind all my walls. would it make sense to NOT cover this insulation on the front wall? i will have a false wall covered with black speaker grill fabric. is this a good idea?

this insulation procedure is called dense packing by regal industries (google for more info). so is cellulose any good or should i do that wall in fiberglass?

ok, so i have actually tried to read some of this thread. i understand that a dead front wall is a good thing and more than 2" of fiberglass is recommended.

By one person, anyway. :)

i am insulating my walls with cellulose behind a material called insulmesh. i will have about 6" of it behind all my walls. would it make sense to NOT cover this insulation on the front wall?
You mean not using inner sheetrock? That would be a gross code violation, not to mention a bad idea in general. You would loss any possible sound isolation. :(

Regards,
Terry

By one person, anyway. :)


You mean not using inner sheetrock? That would be a gross code violation, not to mention a bad idea in general. You would loss any possible sound isolation. :(

Regards,
Terry

its a basement theater, so there's poured concrete walls on 3 sides, the front wall being one of them.

its a basement theater, so there's poured concrete walls on 3 sides, the front wall being one of them.
Once you finish the space, it is now "habitable," and other code regulations kick in. Of course, you don't have to have it inspected. But there could be a problem later, in selling the house to a buyer skeptical of what you have done.

But potentially more important is the sound isolation problem. The concrete walls conduct sound to the upper part of your house, and stud walls with sound isolation construction are necessary to deal with this.

Regards,
Terry

the stud wall above is for the garage. i'm not worried about sound travel as this end of the house is not used for much. i am doing some sound abatement, however, more cellulose.

code and sound isolation aside, how would this cellulose behave compared to fiberglass?

thanks

code and sound isolation aside, how would this cellulose behave compared to fiberglass?

thanks
While not the equal of fiberglass, a few inches of thickness would probably provide very good, wide-frequency sound absorption. Exact performance depends on density of packing and specific material, etc.

Regards,
Terry

Below are my first room measurements. (room is complete except for treatments - see Mayflower Construction thread); fyi, tried to measure STC of the room - first very rough measurement is about 40db for mid frequencies and 30+db for low frequencies. Room is double 5/8+GG w/steel studs and fully insulated. Oh well.

Subjectively, there are lot of higher frequency reflections within the stage alcove containing the LCR speakers. I can walk into that space and hear the increased ambiance.

Also, when music is playing, the whole room, and particularly the alcove inside corners sound very heavy - lots of bass buildup in the inside corners of the alcove. I don't 'hear' any bass buildup in any other room corners.


Floor Plan

http://idisk.mac.com/dbbarron1-Public/Theater/predicted modes.jpg

Speaker Freqency Response at 1/2m (1/3 oct smooth).
http://idisk.mac.com/dbbarron1-Public/Theater/fresponse1m.jpg

Speaker Freq Response at listening position (1/3 oct smooth)
http://idisk.mac.com/dbbarron1-Public/Theater/fresponselp.jpg

RT60 at listening position
http://idisk.mac.com/dbbarron1-Public/Theater/rt60lp.jpg

For initial treatments prior to re-evaluation, it would seem like I need to treat the entire alcove for high and low frequency as a start. Perhaps thinker treatments across the entire alcove walls or just 1" on walls and super chunks in alcove corners?

Comments appreciated.

db

Depending upon the fabric, of course, a fabric covered wall can look quite attractive and classy. This is based upon a dealer showroom example I've seen using a GOM Anchorage fabric with has a subtle texture to it. Looked elegant, with the added benefit of disguising all the wall treatments hidden behind it.

In other words, I agree.

Quoting myself, because I AM that important :p, I need to make one small correction. There is no real texture to the Anchorage fabric.. it turns out what I thought was Anchorage, was actually a GOM fabric group called "Shagreen" instead. Just in case anybody was keeping track. ;)

........Thick absorbers on the walls are still useful because they give that much more bass trapping in the room. The main point of my Front Wall article addresses the inadequacy of 1-inch thick material which is very common in DIY home theaters. Even two inches is not thick enough to help at bass frequencies. In my mind (uh oh) the ideal room will have 12-inch thick fiberglass on all walls and the ceiling, but with portions covered by cardboard or thin plastic etc (or reflective diffusors) to avoid being totally dead.

--Ethan

Ok, thank you for the clarifications (and confirmations). :)

Regarding subs, what's the way to go if you're using two of them? For some reason, I was under the impression to have them located in completely opposite corners. I have one sub in my front left corner, and one sub in my back right corner. Basically, in completely opposite corners. Not sure why I thought that this was the way to do it.

Not sure if this is the thread for sub location discussion but I guess it does relate a little to acoustics ;)

I have two subs and I will be placing them side by side to double the output. I have read that if you place them on opposite ends or complete apart you could have phase issues, etc and the output doesnt double if they are separate by so many feet.

........Thick absorbers on the walls are still useful because they give that much more bass trapping in the room. The main point of my Front Wall article addresses the inadequacy of 1-inch thick material which is very common in DIY home theaters. Even two inches is not thick enough to help at bass frequencies. In my mind (uh oh) the ideal room will have 12-inch thick fiberglass on all walls and the ceiling, but with portions covered by cardboard or thin plastic etc (or reflective diffusors) to avoid being totally dead.


Very interesting because Im doing that "inadequate" 1" on my walls ;)

but also.....

Im building 3 corner traps too. Triangle traps, 6 feet high, 12"x12"x17", filled with Rockwool60. I can not do 4 corners because I have a door in the way but the door is going to have 4" worth of 2x4 rockwool 60 too, one more thick bass trap!

I believe these bass traps will handle my bass neede, I HOPE! :confused: Its a 13x24 room.

Further to my prior post, I have measured some higher resolution spectra placing the mic in the front left alcove corner. (I measured in every corner and in this one all the modes are by far the most pronounced).

Again for reference, the floor Plan

http://idisk.mac.com/dbbarron1-Public/Theater/predicted modes.jpg

Here is the front left corner (in alcove) spectra
http://idisk.mac.com/dbbarron1-Public/Theater/duffel.jpg

The dark blue is the native measurement; the light green is with a large duffel stuffed with blankets and towels in the right front alcove corner.

Taking the modes from left to right:
25 Hz - This mode appears to correspond to room dimensions of the theater plus playroom outside it as demarked by concrete walls. It is small at the LP, and some room lift at this freq is not entirely undesirable - Other treatments may mitigate this mode some - otherwise leave alone.

52 - This mode appears to correspond to the room length. As the back wall should remain unabsorbitive, This can be treated by (1) super chunks in the rear corners or (2) super chunks in the front alcove corners or (3) heavy aborbtion on the screen wall.

78, 169 - I believe these dips correspond to modes relating to the floor to ceiling distances. The floor is carpeted with heavy pad (only absorbtion in room right now). What can I do about this? Strangely enough, the dips are worse with the duffel in place.

120 - Corresponds exactly to the wide of the alcove containing the stage and LCRs. Clearly the duffel bag help this greatly. I believe super chunks in the alcove corners or heavy treatment of the alcove side walls and front wall will help this.

In view of all the above, I plan to pickup some 2'x4'x4" mineral board this week (local mechanical insulation contractor) and experiment some more. I know there is mixed opinion on 4" front wall treatment, but in my case, I think treating the whole alcove (sides of alcove and front wall of alcove) with 4" may solve everything at once with the danger of it being too absorbitive of higher frequencies. Any comments on this point.

Treating the front wall should also bring my overall RT60 down into the 0.34 range. In that regard, some minor 1" treatments of the first reflection points may be all I need after this front wall/alcove work.

Comments appreciated.

db

Id just like to say that previously I thought HT was about good equipment equalling awesome sound.I then assumed audyssey was the way to go.But I was wrong, I recentley had a manual calibration (HAA is what we call over here using sencore units) and the difference was clearly night and day.Im just awaiting the room treatment,hopefully next week which I've been told it's even going to improve it more.But you guys on this particular thread are definetley on the ball when it comes to HT, there are many people out there that still believe audyssey(eq) is the way to go.I don't even use it anymore.
Sorry to take off topic, just very excited!

Not sure if this is the thread for sub location discussion but I guess it does relate a little to acoustics ;)

I have two subs and I will be placing them side by side to double the output. I have read that if you place them on opposite ends or complete apart you could have phase issues, etc and the output doesnt double if they are separate by so many feet.
I presently have dual subs placed within one RADIUS (of the driver) so they couple. They are behind my false wall 1/3 the room width from the side wall. Audyssey and SVS are close to releasing a device that will optimize two non-co-located subs for both level, phase, EQ and time domain EQ. When they do that, I will set up an identical pair in the rear.

I recently bought some Revel Performa speakers and I found them to be a little to bright for my taste. I think I like warm sounding speaker and I love My Mirage speakers a lot. so I want to treat the room to get the best out of them. I am about to purchase some bass traps (also called broadband traps??) to treat my L-shaped room. I am going to place some traps on the front wall behind my Omnipolar speakers (Mirage OM-9 and OM-C2) and hang some bass traps on the rear wall ( I have OM-R2 x 4 surrounds here). Is this going to cause too much adsorption and defeat the Omnipolar characteristics of a speaker? I googled but nothing came up. I wonder if Ethan, Glenn, Bryan or Mirage owners chime in here. Thanks for your help.

BTW, the front and back wall are the only two places I can put any kind of treatment. Unfortunately I 'm married!! :D

I recently bought some Revel Performa speakers and I found them to be a little to bright for my taste. I think I like warm sounding speaker and I love My Mirage speakers a lot. so I want to treat the room to get the best out of them. I am about to purchase some bass traps (also called broadband traps??) to treat my L-shaped room. I am going to place some traps on the front wall behind my Omnipolar speakers (Mirage OM-9 and OM-C2) and hang some bass traps on the rear wall ( I have OM-R2 x 4 surrounds here). Is this going to cause too much adsorption and defeat the Omnipolar characteristics of a speaker? I googled but nothing came up. I wonder if Ethan, Glenn, Bryan or Mirage owners chime in here. Thanks for your help.

Ill be using fonics, they also have a very nice cosmetic look to them.

Ill be using fonics, they also have a very nice cosmetic look to them.

Sorry, I am new to this but what are fonics?

Sorry, I am new to this but what are fonics?

googled, appear to be an australian company for panels

http://www.fonic.com/

Ill be using fonics, they also have a very nice cosmetic look to them.

Thanks for your reply but that is just a product recommendation and does not answer my question.

I recently bought some Revel Performa speakers and I found them to be a little to bright for my taste. I think I like warm sounding speaker and I love My Mirage speakers a lot. so I want to treat the room to get the best out of them. I am about to purchase some bass traps (also called broadband traps??) to treat my L-shaped room. I am going to place some traps on the front wall behind my Omnipolar speakers (Mirage OM-9 and OM-C2) and hang some bass traps on the rear wall ( I have OM-R2 x 4 surrounds here). Is this going to cause too much adsorption and defeat the Omnipolar characteristics of a speaker? I googled but nothing came up. I wonder if Ethan, Glenn, Bryan or Mirage owners chime in here. Thanks for your help.

BTW, the front and back wall are the only two places I can put any kind of treatment. Unfortunately I 'm married!! :D
Broadband absorbers are just that - broad in the range of frequencies absorbed. I've never heard them called "traps." Bass traps of the foam or fiberglass variety (or a few more similar materials) do absorb broadly, but due to the usually small surface area, they do not provide significant absorption at mid and higher frequencies for the purposes of reducing reverb time. And they are placed in corners. Broadband absorbers are typically hung on walls, first at first reflection points and then other locations as needed.

Honestly, in my opinion, the treatment necessary for a good sounding home theater flies in the face of what omnipolar speakers are all about. Many of us have an entirely dead room front, so - poof - there goes the reflections from the front wall. Again, just my opinion . . . :)

(see prior posts for room description and initial testing)

I hooked up my four subs tonight - located at the 1/3 and 2/3 position on the front and rear wall.

I compared this to the output of my center channel speaker below.

http://idisk.mac.com/dbbarron1-Public/Theater/foursubsvnone.jpg

The top response are the four subs, the bottom response is the center channel. All measured at the listening position. No averaging.

The subs are crossed over to the center channel at 80Hz.

Note the substantial decrease in room mode effect below 100Hz. Did not think it would be so pronounced. This is WITHOUT any room treatment. With the four subs, the 25 Hz mode is gone; the 78Hz dip is substantially mitigated and the remainder of the response is all together nicer. Room treatments should fix this up even more and address the 100hz+ issues (which are easier to deal with using absorbtion than the lower frequencies).

Please also note that the center speaker rolls off below 50Hz; the subs is designed with the 20Hz boost seen - I intent to EQ this to taste.

db

I started my own thread about this, but so far have no replies in that thread, so I might as well post it in this thread too. Basically, I'm trying to get some opinions on using linacoustic above 4 feet from the floor. I know, normally it isn't recommended to use any linacoustic above ear level, but was wondering if there is certain situations when it makes sense to use it above the 4 foot mark.


Here are my questions:

1. Put 2 feet (width) of linacoustic from floor to ceiling on the side walls right next to the corner?

2. Put 13 inches of linacoustic above the chair rail, parrallel to the riser (or actually where people sitting on the riser would get their first relections). The 13" extra of linacoustic would make sure it was above their ear level. Yes or No?

3. Put linacoustic in the area behind the side surround speakers?

4. Put linacoustic above 4 feet at the points of first reflection to account for the radius of the reflection, part of which is above the 4 foot level?




I'm trying to get any opinions or feelings on these questions, because yesterday and the day before I installed my fabric on the lower sections of the side walls. (to the chair rail). Today and tomorrow, I'm supposed to do the top portion. But before I start stapling the fabric up, I need to put any linacoustic above the chair rail, where it makes sense. Once I get my fabric stapled up, there's no going back.

I recently bought some Revel Performa speakers and I found them to be a little to bright for my taste. I think I like warm sounding speaker and I love My Mirage speakers a lot. so I want to treat the room to get the best out of them. I am about to purchase some bass traps (also called broadband traps??) to treat my L-shaped room. I am going to place some traps on the front wall behind my Omnipolar speakers (Mirage OM-9 and OM-C2) and hang some bass traps on the rear wall ( I have OM-R2 x 4 surrounds here). Is this going to cause too much adsorption and defeat the Omnipolar characteristics of a speaker? I googled but nothing came up. I wonder if Ethan, Glenn, Bryan or Mirage owners chime in here. Thanks for your help.

BTW, the front and back wall are the only two places I can put any kind of treatment. Unfortunately I 'm married!! :D

Someone with experience with Omnipolar speakers and acoustic treatment please chime in!

Oh, I should probably mention that my side surrounds are direct radiating. So, I'm not trying to bounce sound off the side walls on purpose.

I started my own thread about this, but so far have no replies in that thread, so I might as well post it in this thread too. Basically, I'm trying to get some opinions on using linacoustic above 4 feet from the floor. I know, normally it isn't recommended to use any linacoustic above ear level, but was wondering if there is certain situations when it makes sense to use it above the 4 foot mark.
It is sooo easy to over-deaden a small room. I can't think of any situation where I would apply absorption above ear level, at least not the entire area.

Omni's in a home theater environment are just not optimal. As has been said, to properly treat a hometheater, the front wall needs to be pretty dead to keep the surround channel reflections from mixing with and smearing the front soundstage. This is the same reason that rear tweeters and speakers like Maggies and ML's don't work the best for home theater duty.

Most of the Revel's are pretty neutral in the frequency response realm. Sounds to me like you want something that's more rolled off rather than neutral. If that's the case, then it sounds like the choice is a speaker that's more laid back but still a direct radiator.

Bryan

^^^Thanks, Bryan.

It is sooo easy to over-deaden a small room. I can't think of any situation where I would apply absorption above ear level, at least not the entire area.

My room is 19.9' wide x 26' long x 8'3" high. Would this be considered a small room? What about the whole poly batting thing? Some people have said that putting poly batting above your linacoustic is a waste of time and money, from a performance aspect, but if you want to do it, to maintain a consistent 1 inch thickness, along with the linacoustic, for aesthetic purposes, then go ahead.

I was going to get the poly batting until I heard that.

What about the whole poly batting thing? Some people have said that putting poly batting above your linacoustic is a waste of time and money, from a performance aspect, but if you want to do it, to maintain a consistent 1 inch thickness, along with the linacoustic, for aesthetic purposes, then go ahead.

I was going to get the poly batting until I heard that.


I was told that too and I do believe it doesnt have much acoustical absorption value (not enough to matter, just high freq stuff) but Im doing fabric on all my walls so when I put a 1" furring strip up and staple the fabric to it, I will want something about 1" thick so that I dont have fabric slack, fabric sagging and so on. Plus, my corner basstraps are going to be 100% of the corner so to get a nice flow of color, etc Im using fabric on all walls.

Using fabric on upper walls seems to be very popular and it looks better then solid color painted walls from a HT perspective but that is obviously subjective.

Just having painted walls on the upper portion should be 100% okay.


I wonder what absorption value egg crate foam has???? I have picked up some for my two Sub DIY projects but Im now thinking that it might be okay to use on the upper walls. Its denser and seems to create less of a "pillow" effect. Does it absorb too much sound...maybe I should put reflect substrate on top of it? as usual, Im confused!!!!!

but Im doing fabric on all my walls so when I put a 1" furring strip up and staple the fabric to it, I will want something about 1" thick so that I dont have fabric slack, fabric sagging and so on.


You know, after just stapling a bunch of fabric yesterday and the day before, I'm not too sure if there really would be any slack or sagging. The staples are what holds the fabric in place. The key, is to be pulling on the fabric enough to keep it super tight, but not enough to mess it up, and then while it's like that, staple it to the furring strips. Once that is done, I don't think whether or not you have anything underneath the fabric is going to matter at all in terms of sagging and slack.

Now, having said that.... If you have kids, you might want to have something under the fabric, so if they touch the walls, it's like they are touching something with substance, and they don't poke at it, and make a hole in it or something. Since I have a 5 year old and 7 year old, I might should worry about that a bit. Right now, it would be hard for them to do much of any damage to the fabric above my chair rail, and below the chair rail is all linacoustic, so hopefully they won't be able to puncture that, but eventually as they grow taller, they could touch the top part, and if there isn't anything behind the fabric, it could be easier to puncture the fabric accidentally.

My room is 19.9' wide x 26' long x 8'3" high. Would this be considered a small room? What about the whole poly batting thing? Some people have said that putting poly batting above your linacoustic is a waste of time and money, from a performance aspect, but if you want to do it, to maintain a consistent 1 inch thickness, along with the linacoustic, for aesthetic purposes, then go ahead.

I was going to get the poly batting until I heard that.
Almost any room in a residential setting is going to be "small." Movie theaters and concert venues are "large." Personally, I would determine what was needed to "sound good" and then try to make it "look good." When the lights are off, it all comes down to the picture and the sound.

Alex solomon:

re omni-polars

http://www.bobgolds.com/SpeakerTests/20060810/home.htm

You know, after just stapling a bunch of fabric yesterday and the day before, I'm not too sure if there really would be any slack or sagging. The staples are what holds the fabric in place. The key, is to be pulling on the fabric enough to keep it super tight, but not enough to mess it up, and then while it's like that, staple it to the furring strips. Once that is done, I don't think whether or not you have anything underneath the fabric is going to matter at all in terms of sagging and slack.

Exactly. I bought batting having read these forums and started putting it up on my walls when I realized that it wasn't doing anything - nothing acoustical and nothing structural. It doesn't even have the firmness of linacoustic, so I don't think it will do much to help with kids hands on the wall either. So I stopped putting it up and never looked back.

Unfortunately, I lost me Jo-ann's receipt and they aren't nearly as forgiving as Lowes/HD. So if anyone still wants to put up abtting andlives in central Ohio...

Exactly. I bought batting having read these forums and started putting it up on my walls when I realized that it wasn't doing anything - nothing acoustical and nothing structural.
Well, the batting is providing modest amounts of absorption, particularly at high frequencies. Whether or not you need this absorption is another matter. Many people use batting sucessfully. I prefer to acoustically measure a room, model what it actually needs, and prescribe specific acoustical treatments accordingly.

Regards,
Terry

Now, having said that.... If you have kids, you might want to have something under the fabric, so if they touch the walls, it's like they are touching something with substance, and they don't poke at it, and make a hole in it or something.

That is my worry even with adults. Someone will place their hand on the wall and it will feel weird, wont it?

Over time too I believe it will sag, no matter how much we think we stretch the fabric when installing I believe it may stretch further over long periods of time if push on. The "padding" may help with this, then again it may not.

Decisions, decisions, decisions.....:(

Well, the batting is providing modest amounts of absorption, particularly at high frequencies. Whether or not you need this absorption is another matter. Many people use batting sucessfully. I prefer to acoustically measure a room, model what it actually needs, and prescribe specific acoustical treatments accordingly.

Regards,
Terry
Gosh, what a novel concept - use science. :)

I prefer to acoustically measure a room, model what it actually needs, and prescribe specific acoustical treatments accordingly.

Regards,
Terry



Gosh, what a novel concept - use science.



Measuring means that the room has to have funiture, carpet and so on before any fabric is up so are you saying the acoustical treatments are the last thing installed.

and what DIY measuring tools are available, outside of flash lights and mirror tricks?

Measuring and modelling is more of a profession install and costs thousands of $$$, I think many DIYers are not going to spend that and are looking to get "best guess" solutions.

In anything there is a diminished returns theory that can be applied. If we place enough 1" around the bottom half of our rooms, full 1" on the screen, speakers front wall and thick bass traps in corners are we not creating a pretty good acoustical room that is probably 90% effective??

That 90% improvement for most of us is far more then we can ever dream to start with. The last 10% are for those who still want to listen too Vinyl ;)

Measuring means that the room has to have funiture, carpet and so on before any fabric is up so are you saying the acoustical treatments are the last thing installed.

and what DIY measuring tools are available, outside of flash lights and mirror tricks?

Measuring and modelling is more of a profession install and costs thousands of $$$, I think many DIYers are not going to spend that and are looking to get "best guess" solutions.

In anything there is a diminished returns theory that can be applied. If we place enough 1" around the bottom half of our rooms, full 1" on the screen, speakers front wall and thick bass traps in corners are we not creating a pretty good acoustical room that is probably 90% effective??
If you do that, you will be creating a dead room. I'm a DIY'er myself. I have a completely dead front and I put carpet on the walls below ear level; I wish I hadn't. I recommend that DIY'ers go s-l-o-w in adding treatments beyond first reflection points and bass traps.

If you do that, you will be creating a dead room. I'm a DIY'er myself. I have a completely dead front and I put carpet on the walls below ear level; I wish I hadn't. I recommend that DIY'ers go s-l-o-w in adding treatments beyond first reflection points and bass traps.

wow, really :(

Learn as we go but Im happy (for this reason) to be addicted to the forum and slow at getting the room done!!

Okay, now back to the details because Im confused once again! you room is too dead, with just a dead front (is that 1" or 2") and carpet on the lower walls (38" and below) ??

I thought leaving the top half of the walls reflective made sure the room wasnt dead? and I figured I would just place 2x4 OC 703 1" every 2 feet around the bottom, catching the refection points.

Sounds like no matter what Im doing I am better off finishing the funiture, carpet and so on before doing the acoustical stuff

but now there is "schedule" conflict. Baseboard goes in before carpet usually (no?) but I can not put the baseboard on until the OC703 and fabric is up....grrrrrrr!!!

Here was my quick DIY best guess from all the reading and all the happy HT owner posts...I was happy until today :(


First relection points cover.....use Mirror, flash light to find them....check!!
Add OC703 1" to the whole front wall.....check!!
Add OC703 1" along the wall behind the row of seating (I have one row and its 2 feet from the back wall)...check!!
three corners will have 12"x12"x17" 6 foot tall rectangle bass traps...check!! Last corner has a door so I will add 4" of OC703 to the door itself....check!!
What ever gaps I have on the lower sections I was going to fill with poly batting or eggcrate foam. I wanted a uniform 1" area so I can place fabric over it all.

I think one must (within your resources) first set some design goals, then in a planned iterative process, measure, treat, measure, treat, measure, treat, measure.

I took baseline measurements and then decided I would first treat room modes (bass absorbtion), remeasure and then address the screen wall, then remeasure and then address first reflection points. If my RT60 is falling too fast, I would go lighter (but adequate) on treatment at the next iterative point.

As an example, corner treatments with 4" roxul appears to have sufficiently addressed bass modes, but has already lowered my RT60 from .42 to .35. This is prior to the screen wall treatment. If after the screen wall treatment, I am in the .2-.3 range of RT60, I will not treat the whole lower side walls, but use strips of absorbtion at 1st reflection points to insure the room does not get 'too dead'.

Also - what is 'too dead' - it would be nice to have some objective criteria. For my purposes, 'too dead' is an RT60 below 0.20.

db

Also - what is 'too dead' - it would be nice to have some objective criteria.

Very true, I have spent a long time reading HT threads to get ideas and so on and one thing I have noticed is that MOST do have OC703 1" or similar all over the bottom half of the walls and from the results posted people love their theaters so if most are doing it and are happy, Im hoping I will be happy too.

pepar's comments was the first time I read someone saying they did too much, maybe I have missed the rest though. Pepar has a great point about doing too much so I want to make sure I dont have it all wrong.


I think one must (within your resources) first set some design goals, then in a planned iterative process, measure, treat, measure, treat, measure, treat, measure.


That will be just too teadious for me, I simply wont go over it more then once. I was hoping that there is a "blueprint" too it and there are several articles to that effect that have helped me tremendously.

I can always do it and if it sucks too much I will remove the fabric, place tin foil or something similar over parts of the walls to change it.

Measuring means that the room has to have funiture, carpet and so on before any fabric is up so are you saying the acoustical treatments are the last thing installed.

Not really. We routinely measure rooms with just drywall. Acoustical modeling allows us to place any furniture the client likes in them, and then specify treatment.


Measuring and modelling is more of a profession install and costs thousands of $$$, I think many DIYers are not going to spend that and are looking to get "best guess" solutions.

Not from us it certainly doesn't! If you want "the works" -- sound isolation, HVAC, 3D rendering, then yes. But many people go with as much analysis as they think they need or can afford.

In anything there is a diminished returns theory that can be applied. If we place enough 1" around the bottom half of our rooms, full 1" on the screen, speakers front wall and thick bass traps in corners are we not creating a pretty good acoustical room that is probably 90% effective??

Maybe yes, maybe no. Certainly, if you want a completely DIY project, you "takes your chances" in not having a professional involved in the pretty technical field of acoustics. Of course, this can be part of a trial-and-error learning process which many people enjoy.

Regards,
Terry

If you do that, you will be creating a dead room.

Interesting. I had gotten the impression that for Home Theater (*not* for music) a pretty dead room was pretty desirable. Do you find that the room being dead is a problem with accurate sound reproduction during movies, or that it makes the room feel uncomfortable while not watching? Or is this a music listening room for you as well?

In my case (working with bpape), I'll have dead front/rear walls (2" 703), and essentially 1" 703 up to 5' on left and right walls (full height behind the screen to 3' in front of the screen). That sounds pretty close to the room described by penngray (front covered, half-height on side walls). I'll actually have a bit more than he has (and some big bass traps in all corners).

I'm not too worried about over doing it, however. All of my treatments (except for the bass traps) will be in framed panels on the walls, with the panels going floor to ceiling. I'll be able to adjust the treatment amount later if needed after measuring. I plan to go wild with the PC/sound-card/mike measurements, although I've got no idea if I'll be able to do any useful analysis...

Paul:

It appears you are spending lots of time and resource on the project. Suggest you go over to hometheatershack.com and get a copy of REW (room eq wizard) and read the forums. For the cost of a calibrated mic and mic preamp (about $100 total), you can have quite an effective measuring system.

There are simply too many variables to consider to conclude how any particular room will behave without measuring it.

db

Okay, now back to the details because Im confused once again! you room is too dead, with just a dead front (is that 1" or 2") and carpet on the lower walls (38" and below) ??

I thought leaving the top half of the walls reflective made sure the room wasnt dead? and I figured I would just place 2x4 OC 703 1" every 2 feet around the bottom, catching the refection points.
It's a small room. Did I mention that it's too easy to over deaden a small room? ;)

The thick rug/foam backing covering the floor between the first row and the screen is being removed. And since I lowered my LCR to very close to ear level, I will be trimming my front L&R first reflection point absorbers - 2" OC SelectSound Black covered with GOM - from 48x48 to 24x48 and am seriously considering installing diffusion (Skyline LP looks interesting) above the new absorber to cover the underlying carpet. I do not have a completely dead room, but I feel as though I need put a little air into it. Also, I'd like to increase the sense of envelopment from my side surrounds - dipoles.

Following my own recommendation to go slow, I will yank the rug and trim the front/side absorbers before adding any diffusors.

Interesting. I had gotten the impression that for Home Theater (*not* for music) a pretty dead room was pretty desirable. Do you find that the room being dead is a problem with accurate sound reproduction during movies, or that it makes the room feel uncomfortable while not watching? Or is this a music listening room for you as well?

In my case (working with bpape), I'll have dead front/rear walls (2" 703), and essentially 1" 703 up to 5' on left and right walls (full height behind the screen to 3' in front of the screen). That sounds pretty close to the room described by penngray (front covered, half-height on side walls). I'll actually have a bit more than he has (and some big bass traps in all corners).

I'm not too worried about over doing it, however. All of my treatments (except for the bass traps) will be in framed panels on the walls, with the panels going floor to ceiling. I'll be able to adjust the treatment amount later if needed after measuring. I plan to go wild with the PC/sound-card/mike measurements, although I've got no idea if I'll be able to do any useful analysis...
Well, I certainly will defer to bgape's experience, but is your entire back wall treated?

I have an extremely accurate front stage and excellent mains/surrounds integration. I would say that it is due in equal parts to my acoustical treatments, the M&K S-150 THX-based speaker system and Audyssey built into my OP 885. Having said that, I'll reiterate that I want to increase the sense of envelopment from my surrounds.

There are some new studies from some well known acousticians - Toole, IIRC - who are heading in the direction of recommending completely eliminating absorbers on the sides. I'm not ready to do that, but it is interesting reading.

It's a small room. Did I mention that it's too easy to over deaden a small room? ;)
...
I do not have a completely dead room, but I feel as though I need put a little air into it. Also, I'd like to increase the sense of envelopment from my side surrounds - dipoles.


Makes sense. I can see two issues:
- just walking around the room, if it sounds like one of those anechoic chambers, it might be a bit wierd.
- surround 'atmosphere'.

I hadn't been too worried about the former, but the latter makes sense. In an ideal world you'd have a totally dead room and some kind of speaker array on all sides. 256:12 sound tracks, with a fully enveloping set of speakers.

In the real world, especially with dipole side speakers not pointing at the listeners, if you have a totally dead room you'd hear very little from the sides at all. I hadn't thought about it that way...

Paul:

It appears you are spending lots of time and resource on the project. Suggest you go over to hometheatershack.com and get a copy of REW (room eq wizard) and read the forums. For the cost of a calibrated mic and mic preamp (about $100 total), you can have quite an effective measuring system.

db

I've been over there. At one point I downloaded the ETF demo and played with it (using my RS analog sound meter as a mic). I'll look into REQ. Analysis is on the list to do once the room is carpeted and the equipment in (or at least the room dust free).

Well, I certainly will defer to bpape's experience, but is your entire back wall treated?


My room is 16' wide, with a 10' high ceiling. Soffit and light shelf take up two feet, so the side/back walls are 8' high.

The middle 11' of the back wall, 8' high, will be treated with 2" 703. The angled entrance area near the door won't be, and there is a closet door on the rear right that won't be. See my sig for a link to pictures that may help understand.

One problem I can see with not treating the back wall: It is a first reflection point! My rear seat ears are only 3-4' from the back wall. Back wall reflections will likely be even closer in time than side wall reflections for the back row.

We'll see how it goes.

Makes sense. I can see two issues:
- just walking around the room, if it sounds like one of those anechoic chambers, it might be a bit wierd.
- surround 'atmosphere'.

I hadn't been too worried about the former, but the latter makes sense. In an ideal world you'd have a totally dead room and some kind of speaker array on all sides. 256:12 sound tracks, with a fully enveloping set of speakers.

In the real world, especially with dipole side speakers not pointing at the listeners, if you have a totally dead room you'd hear very little from the sides at all. I hadn't thought about it that way...
The LEDE (live end-dead end) stuff is a holdover from 2-channel reproduction. No clear and unanimous path has been arrived at for multi-channel. I've got the dead end part down quite nicely, especially with the addition of the superchunk bass traps. As for the rest of the room, with the exception of the rear wall first reflection point absorber, I feel that what I have done is not quite right for 7.1.

Just my $.02.

http://www.peparsplace.com/upgrades2008 082_s.jpg

One problem I can see with not treating the back wall: It is a first reflection point! My rear seat ears are only 3-4' from the back wall. Back wall reflections will likely be even closer in time than side wall reflections for the back row.

We'll see how it goes.
Try treating only the exact first reflection point.

Try treating only the exact first reflection point.

I could do that. It would be pretty much the full width, but would only need to be between 3-6' off the ground. For now I'll stick with the plan and see how it feels.

The easy thing would be to make the rear row have high back chairs. Problem solved. :)

I just realized something: I left out critical information (and am not accurately representing Bryan's plan).

The rear wall is completely covered with 2" 703 *with FSK* (aka the paper insulation cover). It will therefore act as some absorption in the middle, but not low (too thin) or high (paper). The sides and front are the same as mentioned above.

This will help: [edit: this is Bryan Pape's plan]

http://i194.photobucket.com/albums/z196/pgmeyer/avspics/bpape_plan.jpg

Paul--I'm not a technician, so I fear this will sound stupid! I'm firing away, anyway... :o

On your diagram, what are the yellow boxes on the very bottom that look like they are another set of L/C/R with what appear to be the reflections coming off them?

Is that just the 1st reflection pattern?

Also, how do the bass absorbers work placed directly in your double-door way?

Thanks for any insight!

Best to you,
Phil

I didn't mention it, but that is bpape's plan for my room, I can't take credit for it.
The 'virtual' speakers are just reflections of the front speakers through the left wall to make it easy to draw the first reflection points. If you draw speakers on the other side of the wall the same distance from the wall as the main speakers, and then draw a straight line from them to each head, the intersection with the left wall is the reflection point. Easier than trying to measure all the angles.

As for the bass trap over the door, it's shown as two, but I'm actually doing it as one:

http://i194.photobucket.com/albums/z196/pgmeyer/avspics/DSC_9749.jpg

The attic over the left wall/door is actually about 6-8 feet above the ceiling, so I have room to walk around up there. I cut back and rearranged some ceiling drywall supports up there and carved out a 2.5'x4'x2'deep bass trap in the ceiling over the door. It'll be covered with some kind of cloth panel (tbd).

Pmeyer...In your analysis, it says bass absorbers 17x17x24 from bulk Cotton.

What is bulk cotton? it can be used instead of rockwool or oc703??

It's normal house insulation created from recycled blue-jeans. Here's a link for a picture (this isn't the brand I got, I just googled for cotton insulation r-13)

cotton insulation (http://www.soundaway.com/R13_16_UltraTouch_acoustic_insulation_p/22001.htm)

Mine is similar to that, but thicker (about 5") and 24" wide.

The only reason Bryan marked my bass traps that way is that I've got three rolls of it lying in the garage and had a local source. It's a lot easier to work with than fiberglass. I picked up three rolls at one point. Unfortunately, my source (Eco-wise in Austin) temporarily doesn't carry it any more.

I'll probably still do my front bass-traps out of 703. My back right bass trap is big enough and deep enough that I'll probably use the cotton. Especially since I can compress it vertically and get it a bit denser in the frame back there.

I don't know what I'll do over the door. 2x4 sheets of 703 will fit up there nicely and will be easier to hold up than the floppy bulk cotton would be. If I do cotton, I'd need to build some kind of grating to keep it from coming down, and compressing it would be difficult.

Hmm, for fabric covered walls, that acoustic cotton looks nice. No harsh fibers, similar price to 703, and good coefficients. Other than it's lack of rigidity, are there any cons I'm missing?