Well, I have been following this and other threads for a long time and have been reluctant to take the plunge because it seemed complicated to get it right and the cost was too much especially looking at off the shelf products. I liked the look of the studio foams like Sonex and Aurelex but the cost to treat my room was approximately $800. I saw several comments on here that the cheap foam does not work, B.S. I bought foam from the foam factory on e-bay and installed 8 bass traps in (2) 8 ft columns in the front of the theater and 54 1 foot sq. 3" wedges at all of the FRP's and the results were dramatic. The sound improved so much that my 7 year old and my wife both described the sound improvement much the way I heard it. I am extremely happy and all for $140 delivered to my door. Thanks for all of the info I guess all I am trying to say is it is not as complicated as it may seem.

Rich

Hey guys,
I have a couple of questions regarding DIY Acoustic Panels. I'm trying to do this the economical way DIY BABY! The retail products are just too expensive and from what I've seen the DIY stuff is just as effective but at a fraction of the cost. Here are my questions.

1) Is there a good substitue to OC703. Can I just use any old fiberglass insulation of R13 rating? Or does it have to be OC703? Cant find this in any local hardware store :-(

2) My plan was to build a tiered type of panel. Build a rectangular wooden frame stuff it with fiberglass insullation, peg board on one side wrap it in poly matting then cover it with speaker covering. Second would be to build a smaller panel same way and just change the color to mix up the contrast for astethic reasons to match the decor of the room. The question is if I tier the acoustic panels two levels will this affect the reflective properties and efecttiveness of the panel?

3) can people post some pics of thier panels. I'm looking for some ideas and I've already seen a couple of really good ones.

I have an 18x20x8 foot room with 2 15" 1000w subs sealed enclosure and 7.1 surround 650w reciever. PSB Silver's all around.

GsHTPC:

You can use anything with similar absorption coefficients, and get similar results.
This page lists a few alternatives
http://www.bobgolds.com/AbsorptionCoefficients.htm

Your local hardware store won't sell rigid insulation. But you can get them from many insulation distributors in your area. Check your yellow pages.
http://www.bobgolds.com/InsulationContractors.htm

can people post some pics of thier panels. I'm looking for some ideas and I've already seen a couple of really good ones.
There's lots of them around. Once upon a time I collected a few links and put them at
http://www.bobgolds.com/AbsorptionCoefficients.htm
starting about 80% of the way down look for "Jon Risch's Absorbers" through "Vshine's Wall Absorbers"

Well, I have been following this and other threads for a long time and have been reluctant to take the plunge because it seemed complicated to get it right and the cost was too much especially looking at off the shelf products. I liked the look of the studio foams like Sonex and Aurelex but the cost to treat my room was approximately $800. I saw several comments on here that the cheap foam does not work, B.S. I bought foam from the foam factory on e-bay and installed 8 bass traps in (2) 8 ft columns in the front of the theater and 54 1 foot sq. 3" wedges at all of the FRP's and the results were dramatic. The sound improved so much that my 7 year old and my wife both described the sound improvement much the way I heard it. I am extremely happy and all for $140 delivered to my door. Thanks for all of the info I guess all I am trying to say is it is not as complicated as it may seem.

Rich

Imagine the improvement if you'd used something that was actually effective below 100Hz or so. Yes - it will help some - but nothing like thicker mineral wool, 703, etc. down in the deep bass.

In any case, you've at least addressed part of the room acoustics which is more than many people do.

Bryan

Imagine the improvement if you'd used something that was actually effective below 100Hz or so. Yes - it will help some - but nothing like thicker mineral wool, 703, etc. down in the deep bass.

In any case, you've at least addressed part of the room acoustics which is more than many people do.

Bryan

Their corner traps look pretty good down to 125hz (which is the lowest they publish data for). Doesn't look as effective as treatments made of fiberglass but I'm guessing it sounds about as good as auralex foam products. The thing that would worry me is their "life expectancy" of 5-10 years. I've had some auralex panels for more than 5 years, and they are about the same as the day I bought them. And I'm guessing my real traps panels will still be solid, even after I have departed from this life!

But for someone not DIY inclined, on a tight budget, this cheapo foam (which is fire-rated, according to the web site) could be a way to save a few bucks and "get religion" with regard to acoustic treatments. Is it the best solution? Heck no. Would it be worth paying a bit more and getting a fiberglass-based solution? I think so. But I'd guess in almost any room, it would make a positive difference compared to a "no-treatments" option.

Dear all, I am going to construct a home theatre within a month. I just found out that the only thing I can get in my area is 1" 705 FRK. If I am planning to make a 2" one, do I need to peel off the paper facing before combining them? Thanks

Dear all, I am going to construct a home theatre within a month. I just found out that the only thing I can get in my area is 1" 705 FRK. If I am planning to make a 2" one, do I need to peel off the paper facing before combining them? Thanks
Peel? I didn't know it was peel-able.

Where are you located?

Peel? I didn't know it was peel-able.

Where are you located?

I am located in Hong Kong. So, in that case, I am stuck with 1". If I leave the facing on, and when I stack it, the air can't go through, so 1" +1" FRK can't = 2" FRK, right?:confused:

I am located in Hong Kong. So, in that case, I am stuck with 1". If I leave the facing on, and when I stack it, the air can't go through, so 1" +1" FRK can't = 2" FRK, right?:confused:
That would be my guess, but hopefully Bob, Bryan or someone will chime in.

For places you need only 1", just turn it around. If you need 2", peel off the FRK from one of the pieces, put the foil toward the wall from the other piece and use a bit of spray adhesive to bond them together.

If you want the FSK exposed in some places, you still should peel off one of the pieces and bond together. The other issue with the FSK with the foil out is that it is visible for light reflection through porous cloth. If you can get just the FSK separately, you should attach it with the paper side out so you minimize light reflection issues.

Bryan

ducts. how can i treat the existing duct work to reduce sound escaping to other rooms and reduce vibrations and sound when the HVAC is running.

it is not an option to replace the runs in the HT with flex duct. is their anything simple that you all can recommend? what should i wrap the duct work with?

i did a quick search, but came up with zero.

much thanks. later.

Quick question for you guys - haven't seen it addressed yet in this thread:

I have a 15 cu. ft. vented, A/V equipment cabinet that, due to house layout limitations, must be exhausted into the listening room. I'm using quiet DC fans from Active Thermal Mgmt, but still want to acoustically insulate the inside of the exhaust duct (reduce fan & air speed noise). I'm concerned about using any fiberglass-based product since the deadening material will be in the air stream of the living environment.

Is there any commonly agreed-to, best approach/material for this purpose? I know there are many "duct liners" on the market, but it seems you guys are using them for other purposes (walls, external to pipes/ducts, etc.). I need something that will deaden fan whine and air noise, be easily installed a duct, and yet be 100% safe to run within an air steam internal to the home (no fiberglass, no toxic/obnoxious odors) . Any ideas?

ducts. how can i treat the existing duct work to reduce sound escaping to other rooms and reduce vibrations and sound when the HVAC is running.

it is not an option to replace the runs in the HT with flex duct. is their anything simple that you all can recommend? what should i wrap the duct work with?

i did a quick search, but came up with zero.

much thanks. later.

I think most solutions require replacing a section of the existing duct with something better: a baffle, flexible ducting, etc.

Quick question for you guys - haven't seen it addressed yet in this thread:

I have a 15 cu. ft. vented, A/V equipment cabinet that, due to house layout limitations, must be exhausted into the listening room. I'm using quiet DC fans from Active Thermal Mgmt, but still want to acoustically insulate the inside of the exhaust duct (reduce fan & air speed noise). I'm concerned about using any fiberglass-based product since the deadening material will be in the air stream of the living environment.

Is there any commonly agreed-to, best approach/material for this purpose? I know there are many "duct liners" on the market, but it seems you guys are using them for other purposes (walls, external to pipes/ducts, etc.). I need something that will deaden fan whine and air noise, be easily installed a duct, and yet be 100% safe to run within an air steam internal to the home (no fiberglass, no toxic/obnoxious odors) . Any ideas?

If possible, add in lots of twists and turns in the ductwork.

If possible, add in lots of twists and turns in the ductwork.
Don't turns produce their own airflow noise?

I'm in the process of building accoustic panels, with 1x4 the panels are 4x2. I'm using OC703 2" My question is this. Should I double stack the OC703 so it's 4" thick? Is there any benefit? Should I or is there value to adding some poly batting on the front and backside of the OC703? I want to keep the fiberglass as isolated as possible.

I'm in the process of building accoustic panels, with 1x4 the panels are 4x2. I'm using OC703 2" My question is this. Should I double stack the OC703 so it's 4" thick? Is there any benefit? Should I or is there value to adding some poly batting on the front and backside of the OC703? I want to keep the fiberglass as isolated as possible.
Yes, there is an advantage to a 4" thickness. It will reach about 1 octave lower in bass, all other things being equal (which of course they never are! :D). To save money, you can use polyester batting on the backside of the panels. This should give comparable low frequency performance, though maybe not as smooth at higher frequencies. 703 fibers are pretty well bound, and I wouldn't worry about them penetrating the fabric faces of the panels.

Regards,
Terry

Don't turns produce their own airflow noise?

I'm not an expert, but not that I'm aware of unless:

1. There is a very high velocity of air, or
2. There are lots of parallel surfaces

I think twists and turns can help, but guess the ultimate solution might be a dedicated isolation baffle:

http://paulmadison.com/baffle.html

http://paulmadison.com/images/studio/baffle06.jpg

I'm not an expert, but not that I'm aware of unless:

1. There is a very high velocity of air, or
2. There are lots of parallel surfaces

I think twists and turns can help, but guess the ultimate solution might be a dedicated isolation baffle:

http://paulmadison.com/baffle.html

http://paulmadison.com/images/studio/baffle06.jpg
Cool! Which end gets the cheese? :)

Hey Folks,

Sorry if you have already covered this tons, but I just don't have the time to read through 93 pages of posts. I am having my home theatre set up next Wednesday. I didn't do any soundproofing as far as insulating the walls or ceilings in my basement dedicated room. When I was visiting with my home theatre guy yesterday he showed me these new panels that go on your walls. they are about 2' x 4' and about 3" or 4" thick. My room is about 13.5' x 10'. I am just wondering how many of these you think I would need and what sort of costs I should be paying if I was to buy them or have him install them for me. I would like to buy them myself somewhere and install them, I am just unsure about strategies which is why I hired someone to begin with. Can you guys please offer any advice and maybe mention some brands I could look at. I am just outside of Calgary, Alberta, Canada. Thanks everybody and I love this forum.

You'll find pricing all over the place. A general strategy:

Kill the front corners of the room with something relatively thick and preferably straddling the corners for bass control. The balance of the front wall should be completely covered as much as possible for a variety of reasons.

Side walls need at least a couple panels to deal with early reflections off the side wall.

Rear wall again use something thicker in the middle of the wall to help control the length related bottom end issues.

Bryan

BPape... the rear wall.... treating the middle is preferable to the corners? (for bass?)... just wanting confirmation. that actually would be WONDERFUL for me, since my entry door is in the back corner. thanks for your help.

BPape... the rear wall.... treating the middle is preferable to the corners? (for bass?)... just wanting confirmation. that actually would be WONDERFUL for me, since my entry door is in the back corner. thanks for your help.

Actually both if you can. If a door is in the way then skip it and do the back wall and the other corner.

Glenn

I am just unsure about strategies which is why I hired someone to begin with. Can you guys please offer any advice and maybe mention some brands I could look at.

There are several vendors here that sell acoustic treatment products, we've all now replied. :D

Seriously, Bryan gave you the right answer, and here's my standard reply:

Room treatment is a deep subject, and a complete answer requires far more than will fit into a single reply here. So here's the short version. All rooms need:

* Broadband (not tuned) bass traps straddling as many corners as you can manage, including the wall-ceiling corners. More bass traps on the rear wall behind helps even further. You simply cannot have too much bass trapping. Real bass trapping, that is - thin foam and thin fiberglass don't work to a low enough frequency.

* Mid/high frequency absorption at the first reflection points on the side walls and ceiling.

* Some additional amount of mid/high absorption and/or diffusion on any large areas of bare parallel surfaces, such as opposing walls or the ceiling if the floor is reflective. Diffusion on the rear wall behind you is also useful in larger rooms.

For the complete story see my Acoustics FAQ. (http://www.ethanwiner.com/acoustics.html)

--Ethan

I think most solutions require replacing a section of the existing duct with something better: a baffle, flexible ducting, etc.

I've got 20' of straight return running along the top of one side of my soon-to-be media room. It passes through the front wall back to the mechanicals room and I'm worried about vibration when the furnace kicks on.

I was going to box it out with enough room for 3" fiberglass insulation between the duct and the sheetrock. Is this going to help significantly or should I expect to need GG and a second sheet of sheetrock. Are there any other types of baffling treatments to consider? Replacing the duct is a possibility I hadn't considered. Is that far better than the insulation or GG?

Thanks.

I've got 20' of straight return running along the top of one side of my soon-to-be media room. It passes through the front wall back to the mechanicals room and I'm worried about vibration when the furnace kicks on.

I was going to box it out with enough room for 3" fiberglass insulation between the duct and the sheetrock. Is this going to help significantly or should I expect to need GG and a second sheet of sheetrock. Are there any other types of baffling treatments to consider? Replacing the duct is a possibility I hadn't considered. Is that far better than the insulation or GG?
You could use duct liner first and, if necessary, clad the duct as well.

BPape... the rear wall.... treating the middle is preferable to the corners? (for bass?)... just wanting confirmation. that actually would be WONDERFUL for me, since my entry door is in the back corner. thanks for your help.

Treating the corners is a good overall solution. If you can't you can't. Treating the middle of the rear wall is to address a more specific issue which is the potential for nulls off the rear wall based on your seating distance - and also to add some additional general low frequency control in the length dimension opposite the screen which many times can't be treated behind effectively.

Bryan

Treating the corners is a good overall solution. If you can't you can't. Treating the middle of the rear wall is to address a more specific issue which is the potential for nulls off the rear wall based on your seating distance - and also to add some additional general low frequency control in the length dimension opposite the screen which many times can't be treated behind effectively.

Bryan
When I added my first reflection point absorbers, by far the biggest difference was the panel on the rear wall (5-6 feet away). The increase in clarity from the front speakers was immense. The rear wall was causing a reflection delayed by ~12ms and really messing with my brain.

When our school (private college) was redoing the music practice rooms they lined them with a material they referred to as teknam (don't know if that's the correct spelling). It's about an inch thick, rigid, and looks like it is made up of horsehair-like fibers bound together with some hard bonding agent. Are any of you familiar with the material? I have several sheets of it. Is it more for absorbing sound or diffusing it?

I have no sound treatment in my HT which is 22 ft long and 13 ft wide. The front (without the projection screen down) is all cabinetry and the speakers are inset in the front wall on the extreme right and left). Here is a picture of the front:
http://www.krauses.net/HTFrontNoScreen.JPG

Here it is with the screen down:
http://www.krauses.net/HTRoomFront.JPG

Finally, here is a picture of the rear of the room:
http://www.krauses.net/HTRoomRear.JPG

As you might expect the sound from the mains and center is kinda muddy and I want to clean it up before I invest in some better main and center speakers.

Since there's not much I can do about the front behind the screen and removing the wains coat hardwood would negatively affect the WAF, I plan on running about a 3 foot wide strip of sound diffusing material (or would absorbing be better) at the top of the wains coat from front to back and covering the rear wall with diffusing material.

Your thoughts?

BTW - I have a recording engineer from the school coming over on Monday to give me his suggestions but I fear that all he knows about is deadening rather than optimizing the sound.

traveler:
Tectum (http://www.acoustiguard.com/interioracousticalproducts/tectum/tectum.htm)?
The first PDF on that page shows mounting suggestions -- namely to put it on furing strips in front of fiberglass.
The second PDF on that page shows absorption coefficients.

traveler:
Do you have a computer (likely, uh you're posting, but one that could be put with 20' of that HT), and a microphone/preamp with a 30' cord and mic stand(private college recording engineer), and a sound level meter (cheap)?
Do you have the DVD's: Mission To Mars, Star Wars 1 (pod race)?
Can you toe-in (turn) your left/right mains?

Some notes
- you can move the couch (modal/imaging)
- your left/right mains are against the side wall and unmoveable (3pi loading), possible PEQ
- front wall has open cupboards

How do you feel about hiring someone like UMR (http://www.accucal.org/audiocalibration.htm) to come and audio calibrate what you have now?
I don't know for sure what UMR does, but it's possibly something like this: http://www.sencore.com/newsletter/Nov03/AudioCalpart2.htm

Bob,
Yup, that's the stuff. It's actually designed to eliminate sound transmission through the wall, which is not what I'm trying to do. But, will it still work for reducing audio reflection? I don't know. The mounting directions also seem to be for reduction of sound transmission. Would it really do any good to fir out the tectum with fiberglass behind it for my application?
Now, regarding your second post, Yes, I have a computer and I certainly can get a mic/preamp and mic stand (the Media Resource Center reports to me :)) and I have a sound level meter. Yes I have Star Wars 1. No, I can't turn the speakers at all. However, once I get the room cleaned-up accoustically I plan on replacing the Left, Right, and center speakers and the L&R will be freestanding towers.

I wouldn't have a problem with hiring UMR to calibrate the room depending what the cost would be. (I work for a school, remember? That means that I get paid peanuts :)) Perhaps I'll give them a call next week and find out what they would charge.

I just saw what they charge and the travel costs alone would be prohibitive. Perhaps there's someone in St. Louis that can do this.

Bob,
Looking at your notes. Yes, the couch can move but it can't leave the room (the room was actually enclosed with the couch in it and afterwards we learned that it won't fit out the door (Doh!) The front wall does not have open cupboards (unless I removed the doors, but why would I want to do that?)

... by far the biggest difference was the panel on the rear wall (5-6 feet away). The increase in clarity from the front speakers was immense...

Wow... that was educational & enlightening. i was going to completely blow off the back wall, thought it was the least important! thanks to both of you, pepar & bpape. I may need to look into a professional calibration before i frustrate myself!

Wow... that was educational & enlightening. i was going to completely blow off the back wall, thought it was the least important! thanks to both of you, pepar & bpape. I may need to look into a professional calibration before i frustrate myself!
A pro would definitely be able to analyze and treat any acoustical problems. You'll spend more money than DIY, but it would "git 'er done" quickly without reading a lot of forum threads. :)

...
I just saw what they charge and the travel costs alone would be prohibitive. Perhaps there's someone in St. Louis that can do this.

Bob,

If that is a problem forget the search. You are very unlikely to find anyone for that price that will do a credible job. My pricing for audio is exceptionally low compared to the rest of the market.

umr,
I just sent you a PM.

Pepar:

A pro would definitely be able to analyze and treat any acoustical problems. You'll spend more money than DIY, but it would "git 'er done" quickly without reading a lot of forum threads.
I'd have worded that a bit differently.

An audio-calibrator such as UMR's technique is to use your existing room and your existing stereo-store equipment, possibly recommend additional existing stereo-store equipment (PEQ, feedback destroyers, etc) or replacement stereo-store equipment (blown speakers, bad cable), possibly moving the couch, and get the best sound with that. Similar to the sencore link I made above.

Then there's acoustic consultants like Terry Montlick (http://www.componentacoustics.com/) who do that as well, but they focus more on changing the room, especially the room boundaries, with absorption and diffusion, to get even better sound than an audio-calibrator.

The latter being more about what this thread is about.

The former being
a) pretty good (worth the cash, noticable improvement) from the various reviews of UMR's work that I've read posted here
b) perhaps really what traveler wants, given the WAF comment in the above post.

IMO, for DIY, one should look at what's coming out of their existing hardware first (check for miswiring, blown drivers, etc) because if your existing system is unfaithful, then that's your biggest bang for the buck to get it fixed, before acoustical tweaks are applied.

Traveler:

I'm not suggesting you should do these things, even if my wording/phrasing is strong. This is just the first things I thought of when I looked at your room.

Yup, that's the stuff [Tectum]. It's actually designed to eliminate sound transmission through the wall, which is not what I'm trying to do. But, will it still work for reducing audio reflection? I don't know. The mounting directions also seem to be for reduction of sound transmission.I believe it's only for reducing audio reflection, and not for 'eliminate sound transmission through a wall'.

Would it really do any good to fir out the tectum with fiberglass behind it for my application?Whether you need more absorption/diffusion is another question.

Now, regarding your second post, Yes, I have a computer and I certainly can get a mic/preamp and mic stand (the Media Resource Center reports to me ) and I have a sound level meter.
Have a look through http://www.etfacoustic.com/
RplusD (at that website) is a tool that you can use with your computer to find out what's going on. But it's just a tool it won't tell you what's going on. i.e. you have a hypothosis you want to test, you can set up experiments and use this tool to gather data to prove/disprove that hypothosis. The trick is knowing enough acoustics to use the tool successfully -- it's not that hard, but you won't do it by Monday. (BTW, you might get your computer's sound card to work, but I suggest the USB SoundBlaster is a lot easier to get RplusD to work with.)
I've used it like this
http://www.bobgolds.com/SpeakerTests/
http://www.bobgolds.com/CornerTrap/20040627/home.htm
http://www.bobgolds.com/CornerTrap/20040627/compare.htm
There are other software that do the same thing -- There's a good list somewhere.

I suspect you'll be happy with UMR, but given your job you might enjoy these books
Master Handbook of Acoustics by F. Alton Everest (http://www.amazon.com/dp/0071360972)
How to Build A Small Budget Recording Studio From Scratch : With 12 Tested Designs by Michael Shea (http://www.amazon.com/dp/0071387005)
both of which are easy to read and contain lots of stuff.

Yes I have Star Wars 1. No, I can't turn the speakers at all. However, once I get the room cleaned-up accoustically I plan on replacing the Left, Right, and center speakers and the L&R will be freestanding towers.The pod race is a good test of imaging -- at least if you've heard it in a place that has good imaging and know what to listen for. There's probably better tests, but it's one that I personally found a difference with (left speaker to right wall reflection made an acoustical imaging mess in my home).
Consider rushing out and buy a copy of Mission To Mars (2000) (http://www.amazon.com/dp/B00003CWU3) before buying a new set of speakers. At the beginning of chapter 11 from "Mission to Mars" where the guy's voice pans around the room is excellent for front-vs-rear timbre testing. I have "driver matched" speakers, yet my surrounds are quite a bit different than my mains. Fortunately my front three mains are identical (same model#, not a 'horizontal center'). Anyone with a 5.1 or 7.1 system should really try this at least once. It's an easy eye opener.

The front wall does not have open cupboards (unless I removed the doors, but why would I want to do that?)Not remove the doors; add doors or fill it with fiberglass. It looked to me like the top left cupboard was open (without door). Turn your stereo on and listen, then put your head in a 2'x2'x2' cardboard box and the same music sounds different. I believe the effect is reciprical, especially near the speaker. The effect is probably minor, but worth testing for I think. (It would be major if you had your speaker inside of a slightly larger cupboard, but you're not doing that.)

pi loading. By putting your main speakers into the front wall enclosure, what you've done is called 'baffle' mounting or 'soffet' mounting. Which is ok if your speakers were designed for it, or you've made adjustments. High frequency sound (1000hz +) is directional, mostly beaming straight out from your speaker. Low frequency sound (100hz -) is omnidirectional, going out in every direction from your speaker. Speaker manufactuers know this, and build their speakers assuming they will be out from the wall, and balance the energy between the tweater and woofer so that you get an even amount of sound from each at your listener position. If you put the same speaker against the wall (2pi loading) then the wall will have little effect on the HF, but will almost double the energy radiated forward in the LF due to the wall reflection, giving a boomy sound. Setting your mains to 'small' or other EQ may help.

3pi loading. This is similar to the above, except in addition to a single wall (as with your center), you now are in a corner (2 walls), giving an even larger bass boost.

Then there's off axis frequency response. Speakers sound different depending on the angle to which you are listening. The best is when the speaker is pointed right at you. But it changes timbre off center (off axis, left or right some degrees). The SpeakerTests link, about 70% of the way down, has some good/good/good/bad/bad/bad examples of off axis.
Anyway, becuase your left/right are
a) pointed straight out from the front wall, and
b) right against the side walls
you're probably more sensitive than most to off axis performance (comb filtering), and may benefit from a side wall absorber or toe-in (which is why I asked if you could turn your left/right mains).

BTW, I hope the top of your couch is shoulder level or shorter -- nothing near your ears. Looks like it is. But your 4 front seats look higher.

Pepar:


I'd have worded that a bit differently.

An audio-calibrator such as UMR's technique is to use your existing room and your existing stereo-store equipment, possibly recommend additional existing stereo-store equipment (PEQ, feedback destroyers, etc) or replacement stereo-store equipment (blown speakers, bad cable), possibly moving the couch, and get the best sound with that. Similar to the sencore link I made above.

Then there's acoustic consultants like Terry Montlick (http://www.componentacoustics.com/) who do that as well, but they focus more on changing the room, especially the room boundaries, with absorption and diffusion, to get even better sound than an audio-calibrator.

The latter being more about what this thread is about.

The former being
a) pretty good (worth the cash, noticable improvement) from the various reviews of UMR's work that I've read posted here
b) perhaps really what traveler wants, given the WAF comment in the above post.
My exchange was with jjacknife, not traveler, who seems to be on a different arc. jjacknife's post was simply "I may need to look into a professional calibration before i frustrate myself!" :)

Traveler:

I suspect you'll be happy with UMR, but given your job you might enjoy these books

I've exchanged several messages with UMR and may have them do some work next summer.


Master Handbook of Acoustics by F. Alton Everest (http://www.amazon.com/dp/0071360972)
How to Build A Small Budget Recording Studio From Scratch : With 12 Tested Designs by Michael Shea (http://www.amazon.com/dp/0071387005)
both of which are easy to read and contain lots of stuff.


I have the first one but it's been several years since I read it. Also, since I have a 60 hr/wk job AND volunteer my time as a pastor of a local church, I don't have a lot of free time (or cash) and most of it (both time and spare cash) is spent in the theater room. I was hoping to find here something that I could do fairly quickly without it becoming a major project.


The pod race is a good test of imaging -- at least if you've heard it in a place that has good imaging and know what to listen for. There's probably better tests, but it's one that I personally found a difference with (left speaker to right wall reflection made an acoustical imaging mess in my home).
Consider rushing out and buy a copy of Mission To Mars (2000) (http://www.amazon.com/dp/B00003CWU3) before buying a new set of speakers. At the beginning of chapter 11 from "Mission to Mars" where the guy's voice pans around the room is excellent for front-vs-rear timbre testing.

I have a 7.1 system (Lexicon MC-12B] and am amazed at the LtoR and front to back imaging I already have. In fact the first time we watched Independence Day as the coke can was shot off the spaceship and bounced around the room only to land in the right rear, both my wife and I actually turned our heads. My current concern is that the fronts sound muddy and I don't think the imaging is right so I will get a copy of Mission to Mars and check it out.

pi loading. By putting your main speakers into the front wall enclosure, what you've done is called 'baffle' mounting or 'soffet' mounting. Which is ok if your speakers were designed for it, or you've made adjustments. High frequency sound (1000hz +) is directional, mostly beaming straight out from your speaker. Low frequency sound (100hz -) is omnidirectional, going out in every direction from your speaker. Speaker manufactuers know this, and build their speakers assuming they will be out from the wall, and balance the energy between the tweater and woofer so that you get an even amount of sound from each at your listener position. If you put the same speaker against the wall (2pi loading) then the wall will have little effect on the HF, but will almost double the energy radiated forward in the LF due to the wall reflection, giving a boomy sound. Setting your mains to 'small' or other EQ may help.

3pi loading. This is similar to the above, except in addition to a single wall (as with your center), you now are in a corner (2 walls), giving an even larger bass boost.


Personally, I would never have put the speakers in the front cabinetry. Unfortunately, that's how it was when we bought the house. At the time it was open to the remainder of the basement and we simply enclosed the room to provide complete light control. I will try setting the cross-over on the fronts to a much higher point and see if that makes any difference (the Lexicon allows a lot of control of this).


Anyway, becuase your left/right are
a) pointed straight out from the front wall, and
b) right against the side walls
you're probably more sensitive than most to off axis performance (comb filtering), and may benefit from a side wall absorber or toe-in (which is why I asked if you could turn your left/right mains).


That's kind of what I was thinking. And, why I was considering doing a 3 ft high strip of Tectum from the front wall to the back at the top of the wains coat. I could cover it with material and still maintain (perhaps even improve) the WAF.

BTW, I hope the top of your couch is shoulder level or shorter -- nothing near your ears. Looks like it is. But your 4 front seats look higher.

Yep, we have direct access from all speakers to our ears when sitting on the couch (double recliner, too). The smaller chairs are for when guests come over. My wife and I, along with any children of our friends sit on the "floor rockers" while the guests sit in the sweet spot.

Thanks for your input. For now I think I will run the Tectum as I have described as well as on the entire rear wall and enclose the one open cupboard on the top left corner of the front and see what I end up with.

Pepar:


I'd have worded that a bit differently.

An audio-calibrator such as UMR's technique is to use your existing room and your existing stereo-store equipment, possibly recommend additional existing stereo-store equipment (PEQ, feedback destroyers, etc) or replacement stereo-store equipment (blown speakers, bad cable), possibly moving the couch, and get the best sound with that. Similar to the sencore link I made above.
....

I am an acoustic consultant as well as a calibrator. I am a degreed engineer unlike most in my craft.

Umr:
:)

I'm trying to decide how to acoustically treat my existing room (see my signature link to room photos).

I keep reading about traps and absorption, but little on diffusion.

I've also checked out a few sites from companies that post in this thread who sell acoustical treatments (which is probably the way I'll be going, since I'm not a DIY guy). It seems like bass traps are everywhere on all those sites (many different kinds), with little mention or discussion of diffusion.

The basic method of treatment seems to be absorption/traps in the corners and at the first reflection points.

But what if you have dipole side surrounds (actually bipole/dipole)? Shouldn't the concern for dipole surrounds be diffusion -- to spread out sound coming from them as much as possible?

I'm concerned about putting up a bunch of traps/absorbers; but then lessening the effects from my dipole side surrounds.

So what do people do who use dipoles/bipoles?

Here is an odd request.

What would happen accoustically if someone wanted to cover their accoustic panels with cowhide? Would it affect absorbtion? Too much? The purpose of the cowhide is obviously from an interior design perspective and desire.

Is it a big no no? Any technical input would be GREATLY appreciated.

Huge no-no. Don't even think about it. :)

Regards,
Terry

Terry, I thought that might be the case. Is the reason because the cowhide doesnt have the right absorbtion quality? Does it reflect more or something? Thanks, just trying to understand more.

I assume if the customer wanted cowhide accents they could simply put it elsewhere whereby it is not a part of the acoustical treatment.

It reflects a lot of mid to high frequency sound, so you are undoing much of the benefit of using an efficient panel absorber material (semi-rigid fiberglass).

Regards,
Terry

Ter, thanks bud, got it.

It seems like bass traps are everywhere on all those sites (many different kinds), with little mention or discussion of diffusion.

Diffusion is more like icing on the cake, where absorption is an important staple. Also, good diffusion costs a lot more than good absorption, so when push comes to shove and folks see the price tag, they often opt for more absorption than a less-capable mix of both. But when "excellent" is more important than "cheap," diffusion is a great choice.

Shouldn't the concern for dipole surrounds be diffusion -- to spread out sound coming from them as much as possible?

Probably not. Some of this is taste, and my preference is to absorb the rear radiation of L/C/R dipoles, and use diffusion only on the rear wall behind you when listening.

I'm concerned about putting up a bunch of traps/absorbers; but then lessening the effects from my dipole side surrounds.

I'd say the same applies there too, as least so far as early reflections are concerned. You really want to kill those reflections completely, versus scattering them around the room. But it also depends on the size of the room. A large room has much more leeway for diffusion than a small room.

--Ethan

Diffusion is more like icing on the cake, where absorption is an important staple. Also, good diffusion costs a lot more than good absorption, so when push comes to shove and folks see the price tag, they often opt for more absorption than a less-capable mix of both. But when "excellent" is more important than "cheap," diffusion is a great choice.



Probably not. Some of this is taste, and my preference is to absorb the rear radiation of L/C/R dipoles, and use diffusion only on the rear wall behind you when listening.



I'd say the same applies there too, as least so far as early reflections are concerned. You really want to kill those reflections completely, versus scattering them around the room. But it also depends on the size of the room. A large room has much more leeway for diffusion than a small room.

--Ethan

Thanks for the comments. I have some follow-up questions.

What's considered a "large" room. My room is 16 x 20 (7' 9" ceiling).

As far as dipole side surrounds (I don't have dipoles anywhere but the sides) -- I thought the point of them was to reflect the sound off the front and rear walls (as opposed to firing directly at the listener), to create an immersive diffuse sound.

So, with that in mind, if you have absorption that effects those reflections, won't that lessen the side surround sound effects? Or am I not understanding absorption? In my mind, it sounds like the sound from the side surrounds would be swallowed up, instead of the reflections reaching the listener as intended.

Thanks for the comments. I have some follow-up questions.

What's considered a "large" room. My room is 16 x 20 (7' 9" ceiling).

As far as dipole side surrounds (I don't have dipoles anywhere but the sides) -- I thought the point of them was to reflect the sound off the front and rear walls (as opposed to firing directly at the listener), to create an immersive diffuse sound.

So, with that in mind, if you have absorption that effects those reflections, won't that lessen the side surround sound effects? Or am I not understanding absorption? In my mind, it sounds like the sound from the side surrounds would be swallowed up, instead of the reflections reaching the listener as intended.
With the exception of the first reflection point on the rear wall, they are all in the front of the room. Obviously, the panels in the front will absorb sound from the dipoles, but not until it has become part of the reverberant room sound. Your sense of envelopment won't be degraded.

With the exception of the first reflection point on the rear wall, they are all in the front of the room. Obviously, the panels in the front will absorb sound from the dipoles, but not until it has become part of the reverberant room sound. Your sense of envelopment won't be degraded.

When you say they are all in the front of the room, are you excluding bass traps? As I have read that it is a good idea to put bass traps in all 4 room corners.

When you say they are all in the front of the room, are you excluding bass traps? As I have read that it is a good idea to put bass traps in all 4 room corners.
OK, I see your point. Bass traps in the rear corners will absorb some of the side dipole surround sound. Clearly, there are competing goals at play in maximizing the home theater experience and I'm not sure that there is a universal strategy that will bring them all into harmony. From my experience, limited as it is to my theater (see link in my sig) and those of some fellow local A/V enthusiasts, effectively treating the frequencies below - say - 500Hz is a primary goal and when done right greatly improves every aspect of the sound of one's theater. Perhaps you could start with traps at the three junctures in the front and see if that provides the necessary trapping?

If you are going to DIY this, then you should consider getting some acoustical analysis software and a calibrated microphone which will allow you to test, add treatments and test again. And listen.

You can ask a lot of questions here and get nearly universally good advice but, short of a pro coming in and testing your room and making recommendations, no one here can tell you with any degree of certainty to place these here and those there and you're good to go.

Have fun!

If you are going to DIY this, then you should consider getting some acoustical analysis software and a calibrated microphone which will allow you to test, add treatments and test again. And listen.



I am definitely not going to DIY. In fact, I'm concerned about my ability to correctly hang an acoustical panel that I purchase from one of the companies in this thread.

My goal is to at least do the minimum treatment for my room (which currently has none).

I am definitely not going to DIY. In fact, I'm concerned about my ability to correctly hang an acoustical panel that I purchase from one of the companies in this thread.
They're going to hang them for you? :D

My goal is to at least do the minimum treatment for my room (which currently has none).
If you are not DIY'ing and using the virtually free software available or paying a pro to come in and measure, you really should be minimalist about it. More can be added later if necessary. It is very easy to over-dampen a small room, so stick with "right-sized" 2" OC 703 (or equiv) at first reflection points. And bass traps at the three front junctures. Most of the vendors lurking on this thread can supply bass traps that are, basically, a 2x4 panel of 2" OC 703 that will straddle the corner. You will be MUCH further ahead if you can fill the cavity behind the panel with the same material. gik, I believe, sells material to do this. Maybe the others as well.

If you can afford it, before doing the above, I urge you to call in a pro with the proper test gear to check for room "issues" that the above basics will not fix.

Just my $.02.

It is very easy to over-dampen a small room, so stick with "right-sized" 2" OC 703 (or equiv) at first reflection points.



I see "large" and "small" rooms referenced alot. However, what is the definition of a "large" or "small" room. I'm not sure where my room fits in at 16 x 20 (7' 9" ceiling). Is that considered "small"?



And bass traps at the three front junctures. Most of the vendors lurking on this thread can supply bass traps that are, basically, a 2x4 panel of 2" OC 703 that will straddle the corner. You will be MUCH further ahead if you can fill the cavity behind the panel with the same material. gik, I believe, sells material to do this.

It looks like Gik has these tri corner things that sit on the floor and actually take up the whole corner (triangle shaped columns). Maybe one of each of those in each of the front corners as a minimum -- and I won't need to hang them on the wall (so even I can do that install).

What's considered a "large" room. My room is 16 x 20 (7' 9" ceiling).

I'd call that a medium size room, but in "acoustics talk" pretty much any room you'll find in a typical home is considered small. To acousticians, a large room is an auditorium.

As far as dipole side surrounds (I don't have dipoles anywhere but the sides) -- I thought the point of them was to reflect the sound off the front and rear walls (as opposed to firing directly at the listener), to create an immersive diffuse sound.

I don't have any direct experience with dipoles used for surrounds. I am not a fan of having surrounds bounce sound around the room intentionally anyway. That may be useful in a movie theater, but that's not what I'd want in my living room. I prefer "normal" speakers pointed at the main listening position as defined in the Grammy surround standards.

--Ethan

I see "large" and "small" rooms referenced alot. However, what is the definition of a "large" or "small" room. I'm not sure where my room fits in at 16 x 20 (7' 9" ceiling). Is that considered "small"?
Yes, most rooms in a residence are going to be "small." I say most because I have a 20x30x18 "great room" that, if turned into a theater (over my wife's dead body) would still not be considered "large" - think auditorium - but would not have the problems of my "small" 13x21x8 home theater.

It looks like Gik has these tri corner things that sit on the floor and actually take up the whole corner (triangle shaped columns). Maybe one of each of those in each of the front corners as a minimum -- and I won't need to hang them on the wall (so even I can do that install).
That's exactly the product I was thinking about having seen it at a show a few months ago.

I have some questions regarding my room absorbtion. If you click on the link and you will see my room.

I am going to use 2" OC703 on the side walls covered with GOM fabric and the front stage I am going to use 1" lincoustics again with GOM black fabric.

Now for the back wall, I was thinking of using Tectum panels becasue I happen to have some. However, should I just continue with the 703 on the bacl wall or will the Tectum panels better absorb and also diffuse the sound.

You can post your replies to my thread or this thread, Thank you

http://www.avsforum.com/avs-vb/showthread.php?p=12547443#post12547443

I'd agree Pepar. To really start to treat a room based on 'large room' theory, it's a lot bigger than a normal residential space.

Bryan

I have some questions regarding my room absorbtion. If you click on the link and you will see my room.

I'd use at least two-inch thick 703 everywhere, including the front wall, and at least four inches thick near all corners. I don't have the specs in front of me for Tectum, but as I recall that stuff is more like ceiling tiles than 703.

--Ethan

I'd use at least two-inch thick 703 everywhere, including the front wall, and at least four inches thick near all corners. I don't have the specs in front of me for Tectum, but as I recall that stuff is more like ceiling tiles than 703.
Not really EVERYWHERE? :confused:

Not really EVERYWHERE? :confused:Yeah. He kinda walks funny. :)

Looking for links on DIY bass corner traps. I saw a corner trap where someone just cut OC 705 into 24" triangles Not sure what type of triangles and then just stacked them all the way up. Looking for that post or similar post to get ideas for my room.

I found a local dealer that had a carton of OC 705 2'by48" and wanted to use that to cut some triangles and place them in the corners. My questions are around how to hide them.

Looking for links on DIY bass corner traps. I saw a corner trap where someone just cut OC 705 into 24" triangles Not sure what type of triangles and then just stacked them all the way up. Looking for that post or similar post to get ideas for my room.

I found a local dealer that had a carton of OC 705 2'by48" and wanted to use that to cut some triangles and place them in the corners. My questions are around how to hide them.

Looking for links on DIY bass corner traps. I saw a corner trap where someone just cut OC 705 into 24" triangles Not sure what type of triangles and then just stacked them all the way up. Looking for that post or similar post to get ideas for my room.

I found a local dealer that had a carton of OC 705 2'by48" and wanted to use that to cut some triangles and place them in the corners. My questions are around how to hide them.

I did this very thing a few weeks ago for all four corners. I must say, it turned out very professional. I attached a picture.

Basically what I did was get 1/2" plastic corner molding from Home Depot and placed a floor to ceiling strip on both sides of the corner trianges. I got it tight enough that it held the chunks in place. I think got GOM fabric and used industrial velcro to stretch it across corner. I then got a quarter round molding, painted it wall color, and pushed it against the edges to hide the fabric.

I did this very thing a few weeks ago for all four corners. I must say, it turned out very professional. I attached a picture.

Basically what I did was get 1/2" plastic corner molding from Home Depot and placed a floor to ceiling strip on both sides of the corner trianges. I got it tight enough that it held the chunks in place. I think got GOM fabric and used industrial velcro to stretch it across corner. I then got a quarter round molding, painted it wall color, and pushed it against the edges to hide the fabric.
Very nice!

I did this very thing a few weeks ago for all four corners. I must say, it turned out very professional. I attached a picture.



Very nice, please post more pictures, room dimensions, etc. This room looks like an excellent example or a small, simple, yet great theater.

Superchunk corner traps basic intro:
http://www.bobgolds.com/TrapHarder/home.htm

Cut patterns
http://forum.studiotips.com/viewtopic.php?t=535

yngdiego - you've done a nice finishing job (above).

Looks great. I just figured out that I need twice as much OC 705 material that I had thought. I wanted to do 24" triangles but I can get 8 pieces out of each 24x48" so I figured the entire box will only go abour 84" and I need 95" per cornoer. I'll need to buy 1 and 1/2 more box's of that.

Do you have an pictures pre construction? It would be great to see how it all went together. The finished product looks great.

Looks great. I just figured out that I need twice as much OC 705 material that I had thought. I wanted to do 24" triangles but I can get 8 pieces out of each 24x48" so I figured the entire box will only go abour 84" and I need 95" per cornoer. I'll need to buy 1 and 1/2 more box's of that.

Do you have an pictures pre construction? It would be great to see how it all went together. The finished product looks great.

No I don't have any pre-construction or in-progress pictures. I got 8 triangles from each piece and ended up using an extra piece or two since the weight of the pile compressed the OC703 a bit and I didn't want a gap at the ceiling.

Also, I got a $12 electric turkey carving knife at wal-mart which cut them like butter. DO get a high-quality breathing mask, wear long sleeves, jeans, and I taped around my wrists and neck to keep out stray fibers, in addition to wearing double gloves (rubber and cloth).

For the side and cloud panels I got some resin at HD and dabbed it along the edges to give it some rigidity.

Is there any reason to not use "speaker grill cloth" like this:

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=260-335

instead of GOM fabric to cover a bass trap?

Is there any reason to not use "speaker grill cloth" like this:

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=260-335

instead of GOM fabric to cover a bass trap?

I think you'll find that speaker grill fabric is too fine and loose of a weave. You'll be able to see the color of the insulation underneath, it will tear more easily, and stray fiberglass fibers may get out.

You can use black Muslin behind the grille cloth to cover the color. It's all cotton and will be fine in that application. You can't use it in front of speakers though.

Bryan

I just finished my basement theater room and I really need some advice. My room is 12'w x 22'L x 7.4'H. I have the RBH T2 speakers for L/R front and a smaller mtm for center. I have the front corners filled with some 703 , then some 1" lineacoustic panels on one side wall from floor to ceiling and 6 feet wide,and 1, 703 panel on the other wall (until I get some more.) with the subs off I get clear center info but with the subs on I get muddiness and a peak somewhere in the midrange.
Any suggestions will be greatly apreciated.
Thanks

This is a great site and has answered many of my questions as I get ready to build my basement theater.

I've found discussion about potential resonance problems but haven't been able to find a recommendation from the Pros (Dennis, Brian, ...).

What is the proper air gap between concrete walls and stud walls to reduce sound and bass transmission without creating a resonance problem?

Thanks in advance,
Eric

My room is 12'w x 22'L x 7.4'H. I have the RBH T2 speakers for L/R front and a smaller mtm for center. I have the front corners filled with some 703 , then some 1" lineacoustic panels on one side wall from floor to ceiling and 6 feet wide,and 1, 703 panel on the other wall (until I get some more.) with the subs off I get clear center info but with the subs on I get muddiness and a peak somewhere in the midrange.

WOW-- T-2s in a room that size can probably cause permenant hearing loss.:eek: My HT is a very similar demension. I was seriously considering the T-2s but opted for the RBH SI-6100s instead. I'd be interested in how you like them once you get the accoustics straighted out. In that regards, you should PM Bryan (Bpape). He is "the man" when it comes to DIY HT accoustics. Very knowledgable on HT set-up and has reasonably priced accoustic materials.:)


What is the proper air gap between concrete walls and stud walls to reduce sound and bass transmission without creating a resonance problem?

I used isolation clips to decouple the wall framing from the cement foundation. I also used these clips to decouple my walls from the overhead floor trusses. It maintains about an 1.5" gap.

http://www.pac-intl.com/decoupled.htm

On the ceiling I used a different style isolation slip. IMO these seem to work better when the load is completely vertical becuase the isolation rubber is below the load.

http://www.kineticsnoise.com/arch/isomax/index.aspx (http://http://www.kineticsnoise.com/arch/isomax/index.aspx)

If you are serious about sound isolation, I would also recommend using double 5/8" sheet rock with 3 tubes of green glue between each sheet. :D [Note: use double sheet rock on both sides of all interior walls-- those that do not back up to the cement foundation.]

Good luck. Take your time -- plannning is the most important phase of HT construction.

Hey guys,

I have been searching through the forum and can't find an answer to this one... I'm building out my basement like everyone else seems to be and I'm going to go with the GOM/Linacoustic pairing. If I'm not worried about sound bleed-through to other rooms in the basement is it necessary to put up drywall? All the construction threads seem to have drywall but I'm assuming it's only necessary for sound isolation purposes.

Thanks,
Steve

It's unclear what you mean. You indicate there will be "other rooms" in the basement. How will these be created if you don't have sheetrock walls (i.e., what kind of wall will you have)? Can you explain? Better yet, do you have any drawings of your layout?

I sorry if I wasn't clear...unfortunately, I don't have a floorplan on the computer yet to be able to share with you guys. Basically what it comes down to is I have already put up standard 2x4 walls. In any normal room drywall would then be attached, you paint, and you are done. What is usually done around here for a theater is drywall, then linacoustic, then acoustically transparent fabric over all that. That I was trying to ask was is does the drywall serve some purpose acoustically for the theater?

Hope that is a little more clear...if it's not I'll start another thread with floor plans and stuff.

Thanks
Steve

What is the proper air gap between concrete walls and stud walls to reduce sound and bass transmission without creating a resonance problem?

Anytime you have air movement in a confined space, you'll have resonance ... you just want the resonance to be inaudible. The issue of more importance however, is that the size of the air gap is going to be dictated by local building and fire codes. Typically, you'll find the framing is 1/4 to 1/2" from the foundation walls and a part of this reason is many foundation walls are not straight! Fiberglass insulation is installed between the studs appropriate to the studs you're using (2x4 or 2x6). Now, that remaining air gap will have to be closed. At a minimum at the top of the walls. In some areas, insulation will have to be placed between the back of the stud and the foundation wall (fire code).

IMO these seem to work better when the load is completely vertical becuase the isolation rubber is below the load.
Actually, makes no difference.

Hiller

As long as you are not concerned about sound being tranmitted into the adjacent rooms (including the rooms upstairs), your "standard" 2x4 sheetrock walls will work fine. You will still need to do the treatment inside the room to address the accoustics issues there.

Dennis,

According to the marketing material issued by PAC, you are correct the positioning of the PAC isolation clip should not make any difference. :)

I was just giving my own personal opinion. I have used both types of isolation clips. I prefer the Kinetic clips for the ceiling and the PAC clips for the walls. If you look closely at the PAC clip it has a metal collar inside the rubber pad, which connects the rubber to the metal frame of the clip. When the clip is nailed or screwed into an overhead floor truss the rubber pad is pointed upward and the weight of the ceiling is pulling downward. The main contact point for the load is located between the nail/screw head and the metal bracket. IMO the rubber pad will not be very effective, unless it was significantly compressed during the install. [In addition, I don't think the metal collar will allow significant compression.] With the Kinetics clip the isolation rubber is located on both the top and bottom of the hat channel. I doesn't matter if the force is downward or upward -- the rubber should minimize and vibration. The Kinetic clip also has a higher load rating, which is important when you are installing two layers of rock on the ceiling.

Hiller

As long as you are not concerned about sound being tranmitted into the adjacent rooms (including the rooms upstairs), your "standard" 2x4 sheetrock walls will work fine. You will still need to do the treatment inside the room to address the accoustics issues there.

I would respectfully disagree. From a performance standpoint, sound getting IN to the room is much more of a concern in order to keep the noise floor as low as possible.

Bryan

Bryan makes an excellent point. Sound Isolation is NOT to avoid waking the family. The lowest sound level on a movie is 22dB. The average noise floor in an urban (quiet) residence is 30-33 dB. Let's look at the impact of this two ways:

(1) If you set your reference level to 74 db, you'll need to set it for 82 (min) to hear the entire sound track. The problem with that, is the 115dB peaks will be 123 dB and it is very likely that neither your speakers, your amplifiers, or your ears will handle that.

(2) Each 3dB is a doubling of energy. So, from 22 to 25, you have 2 times. From 22 to 28 is four times, and from 22 to 31 is eight times louder.

Don't think you really want that. If fact, once you do that, you'll find the sound isolation you didn't think you'd need, you need ... or your wife will want the lawn mowed and the snow shoveled (at the same time, of course).

My bad -- I agree with Bryan and Dennis. I wasn't considering the noise outside the HT. If you are going for a reference sound level inside the HT, or if you have any significant noise outside the HT you clearly need to address sound isolation issues.

The all important WAF has appeared when it comes to putting up acoustic treatments in the still being born home theater. Has anyone used this before and/or is it okay or does the suede defeat whatever purpose the acoustic panels might serve. I am planning on 2" first reflection points along with a diffuser in the back. I will probably order some corner traps from GIK along with it. Any thoughts would be appreciated.

... Anytime you have air movement in a confined space, you'll have resonance ... you just want the resonance to be inaudible. ...

You've hit on what I was asking about. Based on all the posts I've read, for double walls, it seems that the air cavity depth that you recommend 9 inches (3.5 + 2 + 3.5).

Assuming that I get the fire-stopping right, what's the air cavity depth that I need against a concrete wall for the resonance to be inaudible? (3.5 + ??? + concrete wall) I've searched for a formula or guideline to calculate the resonant frequency and haven't been able to find one.

Thanks for all the great information on this site!

Based on all that I've found here, I'm going to build double walls on the two walls that aren't against the concrete walls. I'm going to do room-within-a-room for the ceiling by running separate ceiling joists, supported by the walls, in between the existing joists. That seems to me to be easier and cheaper than RSIC clips.

Eric

I've searched for a formula or guideline to calculate the resonant frequency and haven't been able to find one.

This is called the mass-air-mass resonance formula. Here it is for metric units:

f = 1897 √(m1 + m2) / √(D m1 m2)

f is resonant frequency in Hz, m1 and m2 are masses densities of the two wall leaves in kg/m^2, and D is their distance in mm.

Regards,
Terry

Seperate ceiling joists supported by the interior walls may actually perform better than the isolation clips for the ceiling.

Since it appears you are wanting to maximize your sound isolation, here are a few additional issues you may wish to consider:

How are you going to suport your interior walls? If you make a hard connection to the existing ceiling joists you'll be defeating the whole purpose of the "room within a room" concept. I have used the PAC isolation clips (link above) to isolate the walls in front of the concrete foundation and the inner wall of my double interior walls. I didn't use the isolation clips on the exterior double wall since it was going to make a hard connection to the sheetrock in the room adjacent the HT. Based on my review, double walls on 24" centers performed a little better than those on 16" centers.

Keep in mind, you'll probably want to install communicating doors in the double wall (i.e., two seperate solid wood or metal doors opening in opposite directions) otherwise the double wall will have a significant weak spot. You'll want heavy doors with a very good seal -- more mass = less sound transmission. They sell sound proof doors ($3000 each) -- I went with two exterior grade solid wood doors with full weather seals. You can get these for about $350 each at Lowes or HD. When ordering, keep in mind they need to swing in opposite directions. Don't make any hard connections (or anymore than required) between the double walls, especially at the door jams. [Obvioulsy both walls will touch the same slab -- unless you are doing new construction and can make two seperate slabs. Some people install chalk or rubber pad under the sill plate to increase the isolation from the slab.]

I used double 5/8 inch sheetrock with greenglue (3 tubes per sheet) everywhere! Some folks will say that the two layers should be of different thicknesses to reduce the harmonic vibrations. I spoke with the folks at Greenglue. They recommended two layers of 5/8". I heavlily chalked all of the seams on the initial layer of sheetrock and didn't mounted any electrical boxes in walls. They were all mounted in the columns, riser, stage, soffit or just surface mounted (i.e., behind the AT screen). This helps keep the number of wall penertrations down to a minimum -- basically the only pentrations are for wires and conduit for future wires. If you go with recessed lights, you'll want to install them in a soffit -- this way you will not make any holes in your ceiling.

Are you going to install a floating floor insdie the HT? I didn't. Instead I used isolation pads to decouple the riser from the slab and walls. I used GG between the two layers of plywood on the stage and riser. I have a very heavy pad under the carpet. I install isolation pads under my front row of Berkline. I installed three layers of 30# roofing felt under the stage and then filled the entire stage with (clean and dry) sand.

You'll also want to consider your HVAC and ventilation issues carefully.

Hope this helps.

I am about to mount my linacoustic on my walls. I had planned to cover the full front and then the sides to a height of 44", but only in the half where the HT is located ( the room is 38' deep, but I will only place linacoustic in the front 17'). I'm now thinking I can just mount the full width (47"), but might there be a downside to this? The other dimensions on the room are 12.5' wide and 7' tall (it's in the basement).

Thanks,

I'm now thinking I can just mount the full width (47"), but might there be a downside to this?

That's not my favorite way to treat a room because it covers places that don't need covering and ignores places that do need treatment. Much better is to treat all the corners with as many bass traps as you can manage, and treat the reflection points with absorption at least two inches thick.

--Ethan

That's not my favorite way to treat a room because it covers places that don't need covering and ignores places that do need treatment. Much better is to treat all the corners with as many bass traps as you can manage, and treat the reflection points with absorption at least two inches thick.

--Ethan

I forgot to mention that I plan to put base traps in the two corners by the screen. I will also look at putting a base trap in the one rear corner in the room. The other corner is a staggered walkway to a back room.

I will also look at putting a base trap in the one rear corner in the room. The other corner is a staggered walkway to a back room.

Most rooms have 12 corners! :D

The more corners you treat, the better. Always.

--Ethan

I apologize if this against rules but what should one pay for case of 6 of 2" OC703 (2'x4')? Maybe someone can PM me the answer. I'm in Canada and close to the border. I'm looking for a US dealer to ship to North Dakota to bypass brokerage and duties.

I apologize if this against rules but what should one pay for case of 6 of 2" OC703 (2'x4')? Maybe someone can PM me the answer. I'm in Canada and close to the border. I'm looking for a US dealer to ship to North Dakota to bypass brokerage and duties.
http://www.spi-co.com/

Thanks pepar,

You guys buy the unfaced one right?

Thanks pepar,

You guys buy the unfaced one right?

Unless your using it exclusively for mid and bass trapping. Highs will bounce right off the facing.

Bing:

This list is out of date, but it's what people posted in the past:
http://www.bobgolds.com/InsulationContractors.htm

Depending upon what you're doing, you might consider Roxul SafeNSound. Here it's available at Home Depot. It's not rigid, but it's a good density, and it's cheap and available. The 'not rigid' is why I wrote "Depending upon what you're doing".

BTW, you don't have to use 703. Anything from this page with similar absorption coefficients is probably fine.
http://www.bobgolds.com/AbsorptionCoefficients.htm

I've been searching for more info on icynene here and haven't seen a bang for buck comparison on this vs. fiberglass insulation w/ 2 layers of sheetrock w/ GG in between. Here's the info on icynene from PrarieFoam.com:

Acoustical Properties
(performance in a 2" x 4" wood stud wall @ 125 250 500 1000 2000 4000 Hz. freq.)

STC Sound Transmission Class - 37
19 30 31 42 38 46 (ASTM E-90)

NRC Noise Reduction Coefficient - 70
.11 .43 .89 .72 .71 .67 (ASTM C-423)

Back in post 459, BasementBob said:
"[Icynene] which is an open cell foam with absorbtion, in which case it's fine. Less absorbtion than some other products, but probably better air tight seal."

If the sound insulating properties are almost as good, but icynene is cheaper (considering the cost of another layer of drywall, GG, clips, my own time, etc.), I'd rather pay someone & go w/ icynene. Your thoughts?

Basement Bob:

I know about Roxul. I've built several panels out of them. It's effective but too thick visually for HF along side walls. I can't compress it down with a board and allow sound to pass at the same time. I used chicken wire mesh to keep it together but the panels are 4" thick. The rigid boards are much more manageble in terms of keeping flat, cutting to curves, etc. I'd like 2" at primary reflections and maybe 1" towards the back.

Can anyone give me some of the best websites to buy acoustic panels. Looking for panels with no fabric (will cover my own) and roughly 2 or 3 by 4 or 5 ft. Am in the Chicago area

thanks!

Can anyone give me some of the best websites to buy acoustic panels. Looking for panels with no fabric (will cover my own) and roughly 2 or 3 by 4 or 5 ft. Am in the Chicago area

thanks!
Usually, once a vendor has made a "panel" they cover it as well. You can take a section of fiberglass and cover it. GIK, I believe, sells "pillowcases" that are used to cover the sections. Size I know about is 2'x4', but there may be others. Glenn (GIK) hangs here. There are (at least) two other vendors here as well - Ethan Winer and bgape. They'll have to give you rundown on their product offerings, perhaps by PM. Downside to covering a sheet/section of raw fiberglass is lack of rigidity. Check the link in my sig for a completely DIY solution.

Can anyone give me some of the best websites to buy acoustic panels. Looking for panels with no fabric (will cover my own) and roughly 2 or 3 by 4 or 5 ft. Am in the Chicago area

thanks!

Why not just buy "raw" insulation if you are going to cover it yourself? Most acoustic panels are simply insulation with a fabric covering. Some may add some edge treatments and enhancements, but basically that is what you are getting.

Why not just buy "raw" insulation if you are going to cover it yourself? Most acoustic panels are simply insulation with a fabric covering. Some may add some edge treatments and enhancements, but basically that is what you are getting.
That is "basically" what you are getting, but purchased "panels" usually have some easy way to mount.

Thanks guys - allow me to elaborate. My wife is very particular about design esthetics but she is willing to accept my perspective that the room has to sound good (as long as it still looks good). We could debate whether I should stay married or not but it has worked out for almost 28yrs so I'm willing to compromise and find a way to make it work. So, I have 2 areas of the room (1st reflection point) where we will hang floor to ceiling curtains. I want to put acoustic sound absorbing panels behind the curtains. I am not much of a do it yourselfer -too busy with my day job - so I just want to buy panels I can mount behind the curtains. THey need to be rigid since I may need to remove them at times (the curtains hide windows and although I will place the panels so the windows are covered, my wife wants to be able to open/access the windows from time to time). So a rigid panel would work best - i would just velcro the panel corners to the wall. Can i just buy rigid styrofoam insulation or something else from a HOme Depot - or do i need to buy a special acoustic panel. At the second reflection points on the wall, there will be picture frame molding that the panel would fit into. So the panel should be about 1in thick. My wife wants the panel color to match the paint color - so she has ordered samples, will then pick the fabric and finally match the wall paint to the fabric color (did i mention I am happily married). So again I want to buy some type of rigid sound absorbing panel that can be covered and then mounted.

I appreciate your help - and pls don;t laugh too loud!

rick

Hopefully your wife is looking at GOM fabric or something similar to cover the panel -- different fabrics will have different accoustical properties. It sounds like what you need is some Owens Corning 703 1" insulation. It comes in sheets that are 2'x4'. I just bought a box (180 sg. ft) for $40 at a local insulation shop. You might find someone locally that will sell it by individual sheets (HD and Lowes don't carry it). It's fairly rigid insulation, however you may still want to build a thin wood or metal frame to make the edges hard if you think people might push on the edge of the panel. HD sells 1x1 metal edging (it looks like 24 ga) in their sheetrock section which you can easily use to make a frame. Use some heavy duty 3M spray adhesive to attach the frabic to the framed panel. Then use 1" industrial velco (much stronger than normal velco) to attach the frame to the wall. If this is too much, PM bpape. He sells the GOM fabric, OC 703 insulation and completed panels -- he can also advise you regarding the accoustical properties of the different GOM fabrics.

Good Luck

28 years is a long time! I've been married 20 years, just not to same woman. You are smart to compromise -- if she leaves, she'll get half of the toys. Trust me, I know this from experience.

rick11

Can i just buy rigid styrofoam insulation or something else from a HOme Depot - or do i need to buy a special acoustic panel.
Styrofoam is a reflector of sound, not an absorber.
Any of the materials on this page are good absorbers: http://www.bobgolds.com/AbsorptionCoefficients.htm
Notice how as they get thicker (e.g. 4") they tend to absorb lower frequencies.
Lots of other things absorb too, but mostly high frequencies: http://www.bobgolds.com/Sabin.txt

At the second reflection points on the wall, there will be picture frame molding that the panel would fit into. So the panel should be about 1in thick.I don't know of anyone selling fiberglass panels that thin, but certainly there are foam panels that thin.

http://www.realtraps.com (ethan)
http://www.readytraps.com (scott)
http://www.gikacoustics.com (bpape)
http://www.auralex.com (pretty and thin stuff)
(not a complete list)

The biggest chunk of fiberglass behind a curtain I'd ever seen is
http://www.bobgolds.com/royaldevice_SubwooferHorn_FiberglassCurtain_34a.jpg
from: http://www.royaldevice.com/custom.htm (the big floor Horn Subwoofer room with the polys everywhere)


GoM is http://www.guilfordofmaine.com
Thier 701 series of fabrics (many colours) are mostly acoustically transparent, and fire resistant.

Basement Bob - thanks for the links - this will really help me, WIll check them out tonite and over the weekend.

VA HDman - thanks and yes she has GOM samples on order. and thanks for the marriage advice - i guess my 7.1 would become 3 or 4.1 if I left .....

Since u folks are so helpful, indulge me one more questions. Do any of the websites you showed me also offer to do an acoustical design i.e. what type of panels, where in the room, how many etc. Ideally send them the room layout and they would let you know what to do. I'd readily buy panels from someone who did this.

again many thanks

rick11:
Do any of the websites you showed me also offer to do an acoustical design i.e. what type of panels, where in the room, how many etc.

All tend to recommend thier own products.

http://www.readytraps.com (scott)
does. I believe they do nice 3D drawings.

http://www.auralex.com (pretty and thin stuff)
does.
http://www.auralex.com/pcf/ <- Personalized Room Analysis Form
There's also a http://www.auralex.com/aoc/ Interactive Kit Calculator which I haven't tried.

Ethan does telephone support, but beyond that I don't know, you'd have to ask them (Ethan, bpape, etc).

(there's someone else on this forum who does nicer 3D drawings, but not acoustical analysis, just what the room layout you specify will look like)

Here's a DIY Bass Trap tutorial (http://www.youtube.com/watch?v=iyYUpkpL0gw) I created based on the StudioTips Corner Absorber that utilizes readily available materials from local sources.

These "SCA's" have been around for many years and are easy to make.


Also check out the Bass Traps Network (http://www.basstraps.net) for free acoustical devices plans and information. It is commercial free, and no sales pitches from vendors. If you have something to submit there, please do.


Cheers,


~ Joel
ReadyAcoustics.com
Come see us at CES with Scaena and Balanced Audio

Ethan does telephone support, but beyond that I don't know

Besides telephone support and advice, my associate Scott and I both do drawings when needed. I use Visio mostly, but sometimes I'll draw traps right onto a photograph etc. Whatever it takes to be sure a customer understands what we have in mind for their room.

--Ethan

bob wrote:

GoM is http://www.guilfordofmaine.com
Thier 701 series of fabrics (many colours) are mostly acoustically transparent, and fire resistant.

I most say that GOM fabric is one of nicest fabrics around. I am SO glad that Bryan (Bpape) talked me into using it for our own products. Hands down guys if you are building acoustics spend the extra few bucks on GOM.. ;):)

Glenn

Ethan - thanks. I emailed you my basement drawing - any advice is welcome

rick

I'm hanging my Stewart (fixed wall mount) screen tomorrow and it doing the fittings today I realized that I have space for 2 inches of insulation behind it.

1) Is it worth it? It's not an acoustically transparent screen... but maybe sound gets through a bit, and it would be good to absorb.

2) Being a Sunday my choices for purchase are limited. Anything at a Home Depot that is acceptable?

I have space for 2 inches of insulation behind it ... Is it worth it?

Yes, I think so. Though four inches would be better. But even two inches will help, and the lower frequencies absorbed by two-inch fiberglass will pass right through the screen.

--Ethan

That's cool. The more trapping the better.

But the downside is that means I probably DON'T hang my screen today since industrial places which could sell me something like rigid fiberglass aren't open on a Sunday :-(

I do have some old 2 inch auralex foam that I was going to use on first reflection points.... maybe I'll dump a bunch of that behind the screen, and then use fiberglass on the first reflection points where that stuff was going to go... of course, 2 inch foam doesn't do as much (especially in low frequencies) as 2 inch fiberglass....

Decisions decisions!

Ethan:

Yes, I think so. Though four inches would be better. But even two inches will help, and the lower frequencies absorbed by two-inch fiberglass will pass right through the screen.
What's he going to get at Home Depot, that's 2" thick, that won't make the screen bow? Nothing can touch the screen ever.

Well, I just got my first 2 panels of 2" in and played around with it at my front speaker reflection points and man, it really does help in my room. I cant wait to add another good 8 panels (I'll buy 2 at a time over time). The first thing I noticed was that I was able to hear the surround speakers much better.

Well, I just got my first 2 panels of 2" in and played around with it at my front speaker reflection points and man, it really does help in my room. I cant wait to add another good 8 panels (I'll buy 2 at a time over time). The first thing I noticed was that I was able to hear the surround speakers much better.
Which two points did you treat?

Which two points did you treat?

http://www.silverti.com/ht/reflections.JPG

http://www.silverti.com/ht/September%2017,%202007/DSC00496a.JPG

I dont have pics of the panel yet since its not mounted yet.

The 2 front speaker reflection points (side wall) at the point shown in my image here. The panels are 2' X 4' x 2". I laid them sideways (horizontal long). In the case of the window to the left, It’s the perfect height for me to place the panel in the window at the exact same spot as the panel right side of the room. You cant see the panel in the window since the window is covered with heavy black drapes. This worked out better then I thought it would (was worried about the window).

My plan is to get 4ish more 2" or 4" panels soon and place them behind my screen that you see there. Theres a good 6+ inches of space back there (want to put an LCD back there still).

Well, I just got my first 2 panels of 2" in and played around with it at my front speaker reflection points and man, it really does help in my room. I cant wait to add another good 8 panels (I'll buy 2 at a time over time). The first thing I noticed was that I was able to hear the surround speakers much better.
The first absorption you place in the room will make the most difference! More will help, and you have to treat at least 1/3 the room surface to really get to the point of diminishing returns.

I have heard talk of the danger of "overdeadening" a home theater room, but I have yet to encounter such a room in all of my listening and measurements. You can certainly overdeaden a recording or performance space, and this sucks the life out of it. But this is extremely hard to do for a home theater, whose role is to pass on uncolored the acoustic environment of the surround sound.

Regards,
Terry

If there's a rear wall, do that and the ceiling next.

The first absorption you place in the room will make the most difference! More will help, and you have to treat at least 1/3 the room surface to really get to the point of diminishing returns.

I have heard talk of the danger of "overdeadening" a home theater room, but I have yet to encounter such a room in all of my listening and measurements. You can certainly overdeaden a recording or performance space, and this sucks the life out of it. But this is extremely hard to do for a home theater, whose role is to pass on uncolored the acoustic environment of the surround sound.

Here's a room that's been over-deadened. (http://www.peparsplace.com/html/10.html) ;)

Usually, once a vendor has made a "panel" they cover it as well. You can take a section of fiberglass and cover it. GIK, I believe, sells "pillowcases" that are used to cover the sections. Size I know about is 2'x4', but there may be others. Glenn (GIK) hangs here. There are (at least) two other vendors here as well - Ethan Winer and bgape. They'll have to give you rundown on their product offerings, perhaps by PM. Downside to covering a sheet/section of raw fiberglass is lack of rigidity. Check the link in my sig for a completely DIY solution.

Just to clarify we DO NOT sell any kind of pillow case for DYI. We do sell GOM by the yard if someone needs it. Also bpape works with me over at GIK. :)

Glenn

Ethan:
What's he going to get at Home Depot, that's 2" thick, that won't make the screen bow? Nothing can touch the screen ever.

So the way this screen mounts, there was probably 2.3" of space so I was able to put a box of these behind the screen before hanging it:

http://www.auralex.com/acoustic_foam_dst_114/DST_114.jpg

Since I had a box of 24 (I think) I picked up "used" (never opened) in a color that the wife didn't want visible on the walls.....

Frequencies that would be absorbed by foam probably won't get through the screen (they'll be reflected) and frequencies that do pass through won't be absorbed much. 2" of this stuff just doesn't reach low enough frequency-wise. Fiberglass would have produced some results.

The screen is pretty opaque. The wedges mean there is an air gap. But I can see where high freq won't get through much and low freq won't be impacted much.

I wonder whether I should unmount the screen....and remove the panels....though MAYBE the full mass (foam + screen + draps) builds up usefully when I close the drapes over the screen for music listening.

Of course, I've ALSO used industrial strength adhesive, so removing the panels would mean not only unmounting the screen but probably pulling off the paint & plaster -- and ruining the foam.... so maybe that makes my decision for me.

The screen is pretty opaque. The wedges mean there is an air gap. But I can see where high freq won't get through much and low freq won't be impacted much.

I wonder whether I should unmount the screen....and remove the panels....though MAYBE the full mass (foam + screen + draps) builds up usefully when I close the drapes over the screen for music listening.

Of course, I've ALSO used industrial strength adhesive, so removing the panels would mean not only unmounting the screen but probably pulling off the paint & plaster -- and ruining the foam.... so maybe that makes my decision for me.
If the screen just barely touched the tips of the foam triangles, instead of the non-reflected frequencies vibrating the screen and passing through, they'd be dampened.

Fiberglass would have produced some results.

Agreed, though one way to get more performance out of foam like that is to mount it backwards, with the pointy side toward the wall. If it's not too late that's a good option. But my guess is it's too late and the stuff is glued solid to the wall, yes?

--Ethan

Yes, alas, too late. And the pointed bit is just about 1/4 inch shy of touching the back of the screen.

I'm curious: How does putting the pointy side towards the wall improve the performance of the foam? I just assumed the wedge/points was mostly a design/visual thing and that full/thick foam would actually work better -- but that by cutting it that way, they can make twice as many panels from the same amount of foam and just call it "2inch" foam, though about half of the material is actually cut away.

Yes, alas, too late. And the pointed bit is just about 1/4 inch shy of touching the back of the screen.

I'm curious: How does putting the pointy side towards the wall improve the performance of the foam? I just assumed the wedge/points was mostly a design/visual thing and that full/thick foam would actually work better -- but that by cutting it that way, they can make twice as many panels from the same amount of foam and just call it "2inch" foam, though about half of the material is actually cut away.

Most acoustic absorption material absorbs more effectively, and to lower frequencies, with an air gap behind it. Mounting it pointy side in would give you that gap, in a way.

Aren't we talking about a membrane/diaphragmatic absorber here?

Below is a bunch of guesses.

The screen is about 2oz per square foot. (That's another guess)

So, using f = 170 / sqrt(m d) = 304hz
m = surface density of the panel in pounds per square foot (2oz/16 = .125pounds)
d = 2.5 "

Sticking insulation in there makes compression isothermal rather than adiabatic, multiplying the depth by about 1.4 for whatever percentage volume has changed (not placement, volume). I figure those wedges, plus a bit of clearance to the screen, mean that half the volume is foam. So the adjusted depth would be about 3"

using f = 170 / sqrt(m d) = 277hz

In addition to lowering the peak frequency the foam would also weaken the absorption and widen the absorbed frequencies. (take a bell curve and stand on it)

I'm ignoring other effects (my bad), such as the rear wall, etc...

Aren't we talking about a membrane/diaphragmatic absorber here?

Below is a bunch of guesses.

The screen is about 2oz per square foot. (That's another guess)

So, using f = 170 / sqrt(m d) = 304hz
m = surface density of the panel in pounds per square foot (2oz/16 = .125pounds)
d = 2.5 "

Sticking insulation in there makes compression isothermal rather than adiabatic, multiplying the depth by about 1.4 for whatever percentage volume has changed (not placement, volume). I figure those wedges, plus a bit of clearance to the screen, mean that half the volume is foam. So the adjusted depth would be about 3"

using f = 170 / sqrt(m d) = 277hz

In addition to lowering the peak frequency the foam would also weaken the absorption and widen the absorbed frequencies. (take a bell curve and stand on it)

I'm ignoring other effects (my bad), such as the rear wall, etc...

Which is to say the foam MAY be helping me, if I follow you right, but it wasn't the ideal placement for them...

nathan_h:

These are not meant to be what you have, just representative of the trends I was thinking of.

This is what I think the difference in absorption would be with those wedges not behind a screen, facing either way:
http://www.bobgolds.com/Assorted/OneInch_OneInchOneAirGapAbsorber.gif

This is what I think having a screen/insulation would be like -- I'm not sure what the efficiency would be like, so there's two lines:
http://www.bobgolds.com/Assorted/MembraneAbsorber.gif

For helmholtz absorbers, I've read that putting the insulation near the front or the back, makes a difference.
But I don't know if I've read anywhere that it makes much of a difference for a membrane absorber (assuming nothing touches the membrane).

This is what I think having a screen/insulation would be like -- I'm not sure what the efficiency would be like, so there's two lines:
http://www.bobgolds.com/Assorted/MembraneAbsorber.gif



So by your estimation, his foam may be doing more harm than good, absorbing a very narrow frequency spectrum (bad, unless you know you have a room peak there), instead of absorbing evenly over a wide range of frequencies (usually, the prefered effect)?

Yes, alas, too late. And the pointed bit is just about 1/4 inch shy of touching the back of the screen.

Can't you move your screen to hang a few inches farther away from the wall?

How does putting the pointy side towards the wall improve the performance of the foam?

You are correct that removing foam material in a pattern looks nice and lets them get twice as many panels from the same piece of foam. But now there's only half as much absorbing material! By reversing it on the wall, the thicker portion of the foam slab will be an inch away from the wall, and that extends its absorption to lower frequencies. If you want a more detailed explanation, see the section Optimizing the air gap in my Acoustics FAQ:

http://www.ethanwiner.com/acoustics.html

--Ethan

For helmholtz absorbers, I've read that putting the insulation near the front or the back, makes a difference.
But I don't know if I've read anywhere that it makes much of a difference for a membrane absorber (assuming nothing touches the membrane).
For maximum effectiveness, the porous insulation should be put near the front. This is where maximum air flow occurs, both for Helmholtz and membrane type absorbers.

Regards,
Terry

Terry:

Thanks.
I have a diagram somewhere that implies that, but I still haven't read a formula for that anywhere. (Figure 6.2 on page 158 of "Acoustic Absorbers and Diffusers. Theory, Design and Application" by Trevor J Cox and Peter D'Antonio.)
RPG's Modex (http://www.rpginc.com/products/modexcorner/index.htm) seems to put the little bit of absorption in the middle -- at least according to the sales literature.

RPG's Modex (http://www.rpginc.com/products/modexcorner/index.htm) seems to put the little bit of absorption in the middle -- at least according to the sales literature.
Yeh, that's what it appears on their schematic representation. But having dissected a Modex Corner, I can state otherwise. :) They build them with the absorption in the right place -- right behind, but not up against, the membrane.

Regards,
Terry

So by your estimation, his foam may be doing more harm than good, absorbing a very narrow frequency spectrum (bad, unless you know you have a room peak there), instead of absorbing evenly over a wide range of frequencies (usually, the prefered effect)?

I'd go the other way -- putting the foam behind the screen was probably a good thing.

Having the screen 2.5" out from the wall is what makes it a membrane absorber. There are other membrane absorbers in the room, e.g. walls, leather couch.
Obviously I'm more worried about having an un-flat screen (obvious video problem) then having the screen be a membrane absorber (minor audio).

I don't know if you've ever used a kettle drum, but it has a foot peddle to adjust the tension of the drum skin, stepping on the peddle makes it tighter and the frequency of the drum goes up. The drum 'rings', there's an initial impulse when you tap it with the hammer, and the tone continues after the impulse/tap.

Membrane absorbers can also ring, and are damped by adding insulation to reduce that, but damping has other effects: lowers the height of the peak absorption, and widens the bandwidth of absorbed frequencies (while increasing the absorption at other frequencies), and lowers the frequency of the peak (not shown in below diagram, sorry). I sort of mentioned that earlier when I wrote "take a bell curve and stand on it".

In theory it's something like this:
http://www.bobgolds.com/Assorted/MembraneAbsorberInsulationAndNot.gif

Further reading:
Custom Audio Designs Membrane Absorbers (http://www.customaudiodesigns.co.uk/articles/membranes.html)
Paul White at SoundOnSound talking about Resonant Absorbers (http://www.soundonsound.com/sos/aug98/articles/practicalacoustic.html)
BBC 1992/10 Design of Modular Sound Absorber for Very Low Frequencies (www.bbc.co.uk/rd/pubs/reports/1992-10.pdf)
BBC 1992/11 Modular Wideband Sound Absorber (www.bbc.co.uk/rd/pubs/reports/1992-11.pdf)

Most interesting. Here's another tid bit. I bought most of the foam "used" for about $0.60 to $0.70 on the dollar, from a fellow on audiogon that bought it but never used it, so I'm discovering what exactly I have as I open each box. Turns out I have a second set of the wedges I put behind the screen. I could add those, inverted (mated) with what is already there, and it actually WOULD then touch the screen (in fact, maybe a little too much, I'd need to test).

It sounds like that would be a useful thing, but here are two caveats:

1) The screen is not easy to unmount & is perfectly aligned right now.
2) I could use this second set of wedges at the first reflection points on the ceiling, which are otherwise bare at this point.

Given those factors, I'm inclined to use this box of foam on the ceiling's first reflection points.

------------

File in the "what I'd do differently next time":

I bought the four boxes of Auralex foam, and six Real Traps, on the used market over the past year, and paid far less than retail.

BUT if I had just started out buying ONLY Real Traps, and got ones that work for high frequency absorption, too, the price NEW would have been only slightly more than buying "used" bass traps and separately "used" foam.

Hi, this thread is very helpful, but man 97 pages it's a lot of stuff to read. I began my room treatment last week, i completely treated my front wall, i've found my first reflection on the side walls and ceiling for 3 front speakers, i treated my ceiling. Now for the side walls i want to treat the bottom of the wall, i have 7 feets under soffit, if i put 30 inches on the bottom, and up to 6 feet where the first reflections are, is that enough cause i wonder if i put 48 inches if my room will sound dead??? I will split the panels every 48 inches with a 2 x 1 piece of wood, it will help for the GOM.

No way to know without knowing a lot of other things like:

30" of what? 1"? 2"?

How many seats in the room?

How many people?

Are you doing any 2 channel listening in there?

You're likely better off posting your own thread with some additional details to get more specific answers.

Bryan

No way to know without knowing a lot of other things like:

30" of what? 1"? 2"?

How many seats in the room?

How many people?

Are you doing any 2 channel listening in there?

You're likely better off posting your own thread with some additional details to get more specific answers.

Bryan

30" of 1"
5 seats, 3 front and 2 on riser
no 2 channel listening
usually 1 to 3 persons
i heard u better treat the room for multi channels or for 2 channels, not try to do both.

my room is 11.5' x 21' x 7.5', front wall completely treated, i found first reflexions on side walls, ceiling first reflexions treated
no bass trap since i have only 15 inches each side of my 110" screen

No way to know without knowing a lot of other things like:

30" of what? 1"? 2"?

How many seats in the room?

How many people?

Are you doing any 2 channel listening in there?

You're likely better off posting your own thread with some additional details to get more specific answers.

Bryan




Bryan is asking the right questions here. Heed his inquiry.



Joel DuBay
basstraps.net

Have you done any broadband bass absorption in the room? How did/do you plan to treat the front wall?

Bryan

There's probably 100 places to post this question, but since the question about "one inch or two" just came up here, I figure I'll ask it here ...

With regards to a blanket-type insulation (linacoustic or OC SelectSound), do two layers of 1" insulation equal one layer of 2" insulation? Or is there a boundary effect between the two layers that would prevent it from performing as if it were one homogenous single layer?

They should act the same. It's just not real fun trying to get 2 layers of Linacoustic to stay up right. It's much easier to use 2" of 703 or cotton where needed.

Also, remember that there are density differences for any areas where you may be bonding a facing to get a membrane effect.

Bryan

I'm looking to get some Owens Cornings 703, 48x24x2. Will it hurt to put it in a wood frame around the outside of the 703. I want it to hold it's shape and to help with hanging on the wall.

I'm looking to get some Owens Cornings 703, 48x24x2. Will it hurt to put it in a wood frame around the outside of the 703. I want it to hold it's shape and to help with hanging on the wall.

That's what I did. It can be tough to find straight wood planks, though. I went with pine 1x3s.

DIY project (http://www.peparsplace.com/html/16.html)

Have put up temporary treatments in my room, but am of course, waiting to secure some of them until the seating situation is worked out.

Here is some interesting data.

First, the room has very few modes? If I am reading the Bob Gold results right.

Second, according the tool on UltimateAVMag.com, I could have one row of seats essentially against the back wall, and so long as no one sits midway between the side walls, there are few problems there. (In fact, it almost looks more smooth than sitting at 1/3 the room length from the back wall, which is where the first row would be.)

Am I reading this stuff right?

DIY project (http://www.peparsplace.com/html/16.html)

Pepar... what kind of "adhesive" did you use for those?

If you want to do frames and find some straight wood - go to Home Depot and go back in with the Oak and nice clear Pine. They have Poplar craft wood back there in 1/2" thickness that is 1, 1.5, 2, 2.5, 3, 4, and 6" wide and comes in 1', 2', and 4' lengths. It's hard and straight and easy to work with. It's a bit more than pine but not much.

Bryan

Pepar... what kind of "adhesive" did you use for those?
I used a contact adhesive. I applied it to both surfaces - two coats on the mondo-porous fiberglass, let it dry until just barely tacky and then pressed the 'glass in place.

I thought it was necessary to not only have a frame, but a back as well. Aside from the routing and mitering of the frame members I had a woodworking friend do, it was a DIY project. The frame is poplar and the backer is 1/4" luan plywood.

I used a contact adhesive....

most "contact cement" are specifically for wood to wood contact. I wonder if your ceiling framed one will droop over time!?! how long has it been hanging? I'm considering trying your method with a large frame (8 ft sq?)

most "contact cement" are specifically for wood to wood contact. I wonder if your ceiling framed one will droop over time!?! how long has it been hanging? I'm considering trying your method with a large frame (8 ft sq?)
I don't recall if the adhesive was for bonding specific materials, but I can tell you that it held my thumb and forefinger together pretty well. :D

Seriously though, I believe it said "general purpose" and had a long list of materials that could be stuck together. And that is also why I slathered TWO coats of it onto the fabric covered side of Owens Corning SelectSound Black (http://www.peparsplace.com/Selectsound_bBlanket_sub.pdf). The front ceiling absorber has been in place since 6/1/05 and shows no evidence of sagging.

After 2-1/2 years, if I had it to do over again, I'd probably place diffusion there and cover it with the same black GOM (for light reflectivity reasons). My speakers - and any I'm likely to have in there - have tightly controlled vertical dispersion, so I'm probably not getting much "first reflection" from that point. I feel like I've over-dampened my room and diffusion there would address both possible acoustical reflection AND put some air back into the room.

What's diffurion? Are you saying that light is going through the GOM, bouncing off the fiberglass, and bouncing out?

... My speakers - and any I'm likely to have in there - have tightly controlled vertical dispersion, so I'm probably not getting much "first reflection" from that point...

hmm... i have Klipsch spkrs.... very directional tweets. i may begin with nothing there (9' ceiling) and see what happens. I will start my construction thread and get some more thoughts on that.

What's diffurion? Are you saying that light is going through the GOM, bouncing off the fiberglass, and bouncing out?
No, I'm saying that I'm thinking of trying diffusion on the front ceiling area instead of the 4'x8' absorber that's there now. And I'd cover it with GOM.

hmm... i have Klipsch spkrs.... very directional tweets. i may begin with nothing there (9' ceiling) and see what happens. I will start my construction thread and get some more thoughts on that.
Pls link it here. Or PM me with it.

started my construction thread... may take a couple days to get updated to the present...

http://www.avsforum.com/avs-vb/showthread.php?t=983731

No, I'm saying that I'm thinking of trying diffusion on the front ceiling area instead of the 4'x8' absorber that's there now. And I'd cover it with GOM.

Got it. I thought there was some great acoustic material that I was missing and the sucker reflected light like mad. A google search didn't turn up anything, so I had to ask.

Dedicated 2 channel room 14x12x8. Whats the word on front wall treatment?

I have a 3x5 bay window in the middle of the front wall (in-between speakers). I have 2x4x2" panels on either side of the window, 2" blinds with thin drapes over window. Thinking about adding an additional acoustic panel over window, or possibly an acoustic blanket over window.

That would be a total of (2) 2x4x2" panels and either an additional panel 3x5' or blanket 3x5' covering the 3x5' window. Does this sound like overtreatment for a 12' long wall or am I close?

For reference, I have (2) 2x4x2" panels on either side wall (14' wall) covering 1st and 2nd reflections with (2) more panels on the back wall, 3 feet behind listening chair.

Any suggestions would be appreciated.

Hi guys,

I have a basement HT and music listening room that could benefit from some sound treatment. The space is approxiimately 13 x 30, however it does open to other sections of the basement.

I would like to get the names of some experts in the Boston, MA area that would be willing to examine the room / make recommendations / sell products / and install.

Please PM me.

Thanks for your help.:)

Well, I'm no expert but I'll give you my two cents if you'd like :)

I'll be in the Boston area from March 6th - 11th.

I appreciate the offer however, I was looking for a acoustic tech/dealer/installer type.

PS...I use to ski at Pleasant Valley when I was a kid. Great little town.;)

I just moved here a year and a half a go. They must have built a gas station where your skiing hill used to be, or maybe I just haven't found it yet. God luck with the project, post pictures when you're done.

Marshall

I need some advice for a front projector home theatre room with bright sound. My receiver and speakers are bright and forward sounding in the room. Some CD's sound great, while others sound too bright and harsh. Apparently the receiver I have is revealing and my speakers are a little bright. Marantz SR9600 and PSB Image T65. I have a 11' 8" x 17' long room with a 7' 4" ceiling. Two side walls and ceiling are drywall. Floor is carpet and back wall is concrete. I am thinking of painting first and then adding some acoustic treatment.

Any idea's on acoustic panels and/or material that I can use to both soften the sound and keep light reflections low?

Have put up temporary treatments in my room, but am of course, waiting to secure some of them until the seating situation is worked out.

Here is some interesting data.

First, the room has very few modes? If I am reading the Bob Gold results right.

Second, according the tool on UltimateAVMag.com, I could have one row of seats essentially against the back wall, and so long as no one sits midway between the side walls, there are few problems there. (In fact, it almost looks more smooth than sitting at 1/3 the room length from the back wall, which is where the first row would be.)

Am I reading this stuff right?

Hmmmm. So I did some listening tests by sitting in locations that these tools would indicate are good and bad, and it appears the tools are accurate.

For example, unlike almost every other room I've been in, sitting back against the back wall does NOT create boomy bass. That's REALLY weird. Guess I should not have questioned the science behind the equations, it just flies in the face of most rule of thumb statements and my personal experience.

I am early in the design phase of a HT, and very much at the beginning of understanding acoustics, even after reading through 98 pages of posts. To make sure I at least have the basics correct, I'm hoping the folks here can confirm my understanding.

From what I've read, it seems there are two basics categories of acoustics... isolation and absorption / diffusion. It appears to me that design / build (framing and rocking) is where most isolation is done. Absorption / diffusion seems to be typically done after the room is built and you can listen to the sound produced and precisely determine first reflection points, etc.

Isolation won't be much of a concern for me (not to start a firestorm) as my HT is basically housed in a concrete bunker... floor and 2 1/2 walls are poured concrete, and the ceiling is corrugated steel and poured concrete under the garage floor. Remaining walls are doubled but separated 2x6 framing for serious load-bearing purposes (basically 2 freestanding 2x6 walls backed up to each other). HVAC will be baffled, and doors will be treated.

Since I'm early in the design stage, what I'm looking for is advice on whether there are absorption / diffusion treatments that I can build into the room design before starting construction. For example, since the room is 32 x 22 x 8 - 8.5, I'll have nice, long walls to create some serious echo. So I'm thinking about lateral (22 ft) boxed beams along the ceiling, since the steel and concrete is held up by 12" I-beams spaced every 6 feet, with the spaces between the ceiling being rocked and recessed 6" above the bottom of the beams. Breaking up the ceiling should help with diffusion, correct?

Similarly, I'm thinking about building columns that come out from the walls 4" - 6" meeting up the ceiling beams, which again should help with diffusion. The initial thoughts are decorative fiberglass or polyurethane raised panel columns... the paneling introduces more angles to the surface. And there will be soffits down the long walls for HVAC. My basic understanding is that this works like stealth aircraft... breaks in smooth surfaces scatters the signal, cutting down echo. I realize this still leaves a number of 6' x 8' flat walls, but I'm hoping every little bit helps.

Building absorbing panels into the wall instead of sheetrock isn't an option, building code requires all walls to be rocked. But are there other treatments I should be thinking about before the paint goes on the walls?

In summary, since I have an opportunity to design treatments in from the start rather than retrofitting, are there other items I should be considering?

Any help is greatly appreciated. Thanks.

- Steve.

...
Building absorbing panels into the wall instead of sheetrock isn't an option, building code requires all walls to be rocked.
Steve,

Absorption, either in the form of discrete panels of continous fabric-hidden sheets, goes over the sheetrock, not instead of it. It is always an option according to building code, even for the strictest commercial construction. You just have to assure that the materials have the correct fire/flamespread ratings.

Regards,
Terry

I've cut enough sheets of 703 to yield the triangles for the first front vertical corner. From handling them I'm wondering if settling (over time) will decrease the effectiveness of the trap? If so, should I install some sort of support to divide the stack into several groups reducing the weight on the bottom wedges? TIA!

http://www.peparsplace.com/upgrades2008 036_s.jpg

I asked the same questions a few months ago, and the consensus was NO. So I have several 8' high stacks covered in GOM with no support.

I've cut enough sheets of 703 to yield the triangles for the first front vertical corner. From handling them I'm wondering if settling (over time) will decrease the effectiveness of the trap? If so, should I install some sort of support to divide the stack into several groups reducing the weight on the bottom wedges? TIA!


I suggest you don't leave it free at the top. Add some sort of weight or pressure on top to compress the stack to begin with. In other words, stack to 8'... then push the stack down & add one more piece.

I suggest you don't leave it free at the top. Add some sort of weight or pressure on top to compress the stack to begin with. In other words, stack to 8'... then push the stack down & add one more piece.

I ended up getting 49 triangles in my corner with about 1/2" gap at the top. If you compress them too much, they will want to bulge out and depending on how you have them held in, might burst out into the room.

I ended up getting 49 triangles in my corner with about 1/2" gap at the top. If you compress them too much, they will want to bulge out and depending on how you have them held in, might burst out into the room.
Well, plus if you compress 703 too much, you will no longer have 703. As it is said to be the ideal density for bass traps, turning it into "704" may not be a good idea.

702 is the best for superchunk corner traps. You won't find 702 anywhere though.
But I think we're picking nits.(Nitpicking - the practice of meticulously searching for minor, even trivial errors)

702 is the best for superchunk corner traps. You won't find 702 anywhere though.
But I think we're picking nits.(Nitpicking - the practice of meticulously searching for minor, even trivial errors)
So, the bottom of my 703 stack even if compressed to 703.5 will perform essentially the same? Cool!

My gosh guys... This aint rocket science! bend a little... you won't break it!:cool:

My gosh guys... This aint rocket science!
Yes. Rocket science is easier. :)
If you compress 703 to half its original volume (twice the density), its acoustic resistivity increases by only 28 percent. This parameter is what largely determines fiberglass absorption, and that increase is not very large.

Regards,
Terry

Dropped a note to GIK folks yesterday but perhaps someone here knows: The GIK 244 panel and the GIK242 panel..... do they have the same broadband absorption but with the 244 going LOWER? That is, can I use the 244 at first reflection points? Or is it one of those bass traps that actually deflect higher frequencies (to avoid making the room too dead)?

I used eye screws in the floor and ceiling and stretched steel wire between them to hold my SSC bass trap in the corner.

Stacking in a corner is easy, especially one that will be hidden behind a false wall. Placing one at the corner formed by a wall and the ceiling will not be so simple. I've thought of going to a local metal shop and having some thin sheet metal bent into a 45° angle to hold the wedges in place at their two 45° corners. If the bracket is 2" x 2" with one 2" side mounted to the wall (or ceiling) and the other 2" side wrapping around the face (hypotenuse) of the wedge, will there be any reduction in effectiveness of the trap by covering 2" in from each wedge corner, i.e. 20" of each 24" face would be "open."

http://www.peparsplace.com/upgrades2008 045.jpg

I used eye screws in the floor and ceiling and stretched steel wire between them to hold my SSC bass trap in the corner.


http://www.peparsplace.com/upgrades2008 045.jpg

Great idea, thanks pepar. Do post picture on your website of your progress with the AT screen. My long term plans always included FProj, but have only started to examine AT (though I think I would really like it). Curious to see how yours goes.

Yes, I am snapping pics of everything as I go.

Hopefully, I can get some expert comment on this part of my post! TIA!!!

Stacking in a corner is easy, especially one that will be hidden behind a false wall. Placing one at the corner formed by a wall and the ceiling will not be so simple. I've thought of going to a local metal shop and having some thin sheet metal bent into a 45° angle to hold the wedges in place at their two 45° corners. If the bracket is 2" x 2" with one 2" side mounted to the wall (or ceiling) and the other 2" side wrapping around the face (hypotenuse) of the wedge, will there be any reduction in effectiveness of the trap by covering 2" in from each wedge corner, i.e. 20" of each 24" face would be "open."

I'm about ready to make my corner 'chunks' as well, and am trying to figure out the same thing...how to keep everything in place. Mine will be in the back corners of a room, 10' high, using rock wool. This is a finished, carpeted room. Crown molding and baseboards too.

Suggestions?

I'm about ready to make my corner 'chunks' as well, and am trying to figure out the same thing...how to keep everything in place. Mine will be in the back corners of a room, 10' high, using rock wool. This is a finished, carpeted room. Crown molding and baseboards too.

Suggestions?
Been to the Studiotips Forum "Treatment (http://forum.studiotips.com/viewforum.php?f=8)" section? It's all interesting and informative, but click on Studiotips SuperChunk (what we're both building) and then the link - http://www.bobgolds.com/TrapHarder/home.htm. From the forum you can follow other links and you can also google to find others who've traveled this way before.

In addition to the SSCs behind my false wall, I will be installing some in the theater itself. For those, I'd like a higher "level" of finish than on the one pictured at the Bob Gold's link. The trim in my theater is American Chestnut, so I will be designing a trim/molding that can be milled from that wood that will hold both the wedges in place and the GOM covering as well. Haven't turned my attention to that design yet.

edit: For rockwool, note the suggestion that "use rockwool at least in the 4 to 5 lbs range" . . .

I'm about ready to make my corner 'chunks' as well, and am trying to figure out the same thing...how to keep everything in place. Mine will be in the back corners of a room, 10' high, using rock wool. This is a finished, carpeted room. Crown molding and baseboards too.

Suggestions?

For my OC703 super chunks, I used 1/2" L shaped plastic molding that ran floor to ceiling. I pushed it up against the left and right edges of the stack so that it trapped it against the wall. I then nailed it to the wall every 2', stretched GOM across it using industrial strength GOM, and covered L/R outside edges with quarter round wood molding I painted to match the wall color.

IMHO, it looks great, was easy to do and did the trick.

Dropped a note to GIK folks yesterday but perhaps someone here knows: The GIK 244 panel and the GIK242 panel..... do they have the same broadband absorption but with the 244 going LOWER? That is, can I use the 244 at first reflection points? Or is it one of those bass traps that actually deflect higher frequencies (to avoid making the room too dead)?

Still waiting to hear from GIK. Left another msg on their phone line Thursday. After reading through their site more, although they don't publish the measurements of the 242 panels, they IMPLY that the 242 and 244 are the same UNTIL you get to the lower frequencies, implying I could use the 244 for first reflection points. Guess I'll try again by phone Monday.

Still waiting to hear from GIK. Left another msg on their phone line Thursday. After reading through their site more, although they don't publish the measurements of the 242 panels, they IMPLY that the 242 and 244 are the same UNTIL you get to the lower frequencies, implying I could use the 244 for first reflection points. Guess I'll try again by phone Monday.
I think it's common to use broadband absorbers at first reflection points, but not necessarily ones that extend really deep. Bass is most easily trapped in corners, so that's where I'd place "chunks."

IMHO, it looks great, was easy to do and did the trick.

... & pics would be great, i'd like to see the "how to" & the completed

thanks.

I think it's common to use broadband absorbers at first reflection points, but not necessarily ones that extend really deep. Bass is most easily trapped in corners, so that's where I'd place "chunks."

Well, in this case I've got 6 Real Traps in the corners, but I am using Auralex at the first reflection points -- which is okay, but can be improved upon (both in terms of WAF [she hates foam] and absorption [fiberglass]).

But if I'm going to hang a "2 inch" panel on the wall, I might as well hang a "4 inch" panel, if it makes it even more broadband, but doesn't sacrifice anything over the "2 inch" panel. I put the measurements in quotes because the GIK panels appear to be 1 or 2 inches bigger than the thickness of the acoustic material.

I'll be buying either their 2inch panels or 4 inch panels (preferably) once I hear from them, methinks.

Well, in this case I've got 6 Real Traps in the corners, but I am using Auralex at the first reflection points

Auralex foam is okay for reflections if it's at least two inches thick. But it's a mistake to assume that all commercial absorber panels are acceptable for that use. For example, RealTraps offers most panels in both standard and HF styles for either bass trapping or reflections. Using one of our standard panels at a reflection point would be a mistake.

--Ethan

Auralex foam is okay for reflections if it's at least two inches thick. But it's a mistake to assume that all commercial absorber panels are acceptable for that use. For example, RealTraps offers most panels in both standard and HF styles for either bass trapping or reflections. Using one of our standard panels at a reflection point would be a mistake.
--Ethan

Why? Am I missing something here? Obviously the higher frequency is the primary component as far as imaging, but what difficulty is created by more broad-band absorption?

Why? Am I missing something here? Obviously the higher frequency is the primary component as far as imaging, but what difficulty is created by more broad-band absorption?

The traditional Real Traps are designed to REFLECT rather than ABSORB high frequencies. This is because you continue to reap benefits from adding bass trapping to a room, almost ad infinitum -- but after a point absorbing high frequencies can hurt a room. So one places the traditional Real Trap in a corner, where you don't need (and probably don't want) high frequency absorption.

(I think Ethan makes a modified version for use as a true broad band absorber.

Auralex foam is okay for reflections if it's at least two inches thick. But it's a mistake to assume that all commercial absorber panels are acceptable for that use. For example, RealTraps offers most panels in both standard and HF styles for either bass trapping or reflections. Using one of our standard panels at a reflection point would be a mistake.

Yes, I haven't been too disappointed with the Auralex foam (which is their 2 inch thick panels) at the first reflection points BUT the wife hates the way they look. I was able to get "sign off" on the look of the GIKs so that is what will go on the walls. But I am wanting to make sure that the GIK 4 inch panels are NOT designed to reflect high frequencies the way the traditional Real Trap (for example) panels are designed, otherwise I should use the 2 inch GIK panels.

I'm loving the Real Traps in the corners, though because of the way the roof is conscructed, the ceiling/wall intersections are not usable. So I've got two 2x4ft Minitraps straddling the rear corners/walls, and then two 2x4 and two 2x2 Minitraps straddling the floor/wall juncture at the front of the room -- though with the ones in front I may not get to keep them at a 45 degree angle and have to place them vertical, about 2 inches off the wall.... though I have to ALSO place some 2 inch auralex on them to help deaden high frequency reflections off the front wall. (The front speakers are studio monitors on 16 inch stands.)

The traditional Real Traps are designed to REFLECT rather than ABSORB high frequencies ... (I think Ethan makes a modified version for use as a true broad band absorber.

Exactly. We offer both types depending on what's needed at each location.

--Ethan

Some 1x2's and 1/4x3's and the wall/ceiling superchunk is underway. This design is simple and cheap, though I'll need to come up with something more "finished" for the traps in the room and not behind the false wall. Next I'll install one of these on the ceiling and then "load" the chunks.

http://www.peparsplace.com/upgrades2008 059_c.jpg

hi i just finished setiting up my ht and would like to get some pannels, i would like to know what kind do i need, how many and what size? the pannels will be going into a small bedroom.

OK, here is the above mounting system in action:

http://www.peparsplace.com/upgrades2008 066_s.jpg

OK, here is the above mounting system in action:



Very nice, I'll be curious to see the final product. What's the plan, fabric soffit?

Very nice, I'll be curious to see the final product. What's the plan, fabric soffit?
No complete plan yet for the traps that will be seen. I don't like retro'ing soffits into smaller rooms; they're too encroaching. And the squared point seems "unfriendly." :)

The idea that I'm leaning toward is going to a local metal fabricating shop and having them bend some light sheet metal strips at a 45° angle. This takes the scheme I've used so far of holding the chunks in place by their corners, but eliminates the "external" fastening. A 5" wide strip bent with a 3" base and a 2" hypotenuse will allow for easy fastening to the wall or ceiling. I'm less clear on how to cover it, but molding could be screwed to the bracket and hold GOM in place.

Off to cut more wedges . . . :)

I have a long-narrow room I am in the process of setting up the room. I was hoping to put base traps on the two front corners but I only have 18 inches of space between my screen and the side walls. This is basically where my Left and Right speakers were going on stands. Would it make any difference in sound if I cut the Roxul 60 in the shape of 18" - 10" triangles and stick them in the front corners from the floor to the ceiling?

Standard chunk style absorbers are 17x17x24" - a 2'x4' piece yeilding 8 triangles that size so that would fit.

Nathan

I sent you a PM. If we've missed something, I apologize. We try to return all calls the same day. PM me with your phone number and I'll be happy to work with you to figure out your needs.

Bryan

And one 2x4 sheet of OC 703 yields 16 lineal inches of trap. A SSC-style trap between the floor and an 8' ceiling will use six sheets.

How does OC 703 and JM Linacoustic RC differ when used in corner traps like these?

Wow pepar, how many bundles of 703 did you buy?

pepar

Have you considered a cube of 703 in the corner?
http://www.auralex.com/gallery/images/a12_3ht.jpg
from: http://www.auralex.com/bass_traps_atom12/bass_traps_atom12.asp

pepar

Have you considered a cube of 703 in the corner?
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I'm not a fan of that look, but different strokes for Different Folks. Probably works great though.

Wow pepar, how many bundles of 703 did you buy?
:) Three bales consisting of twelve 2x4 sheets in each. And, believe me, my wife is ecstatic to see them disappearing from the basement. :)

How does OC 703 and JM Linacoustic RC differ when used in corner traps like these?
I would think they would perform the same if the Linacoustic is the same density.

pepar

Have you considered a cube of 703 in the corner?
http://www.auralex.com/gallery/images/a12_3ht.jpg
from: http://www.auralex.com/bass_traps_atom12/bass_traps_atom12.asp
If I do up a corner and continue across the ceiling/wall corner, I would "miter" them for a continuous appearance. Is there something gained, performance-wise, by placing a cube in the corner, or is that just an aesthetic design element?

edit: I'll bet the cube was their way of avoiding mitering . .

I would think they would perform the same if the Linacoustic is the same density.

Sorry, I should have been more specific. Does anyone know the coefficients of OC 703 that you are using and JM Linacoustic RC 1in? If so, can you post them for me or send me a PM?

Thanks,
Dan

[QUOTE=Dan Woodruff;13103372]Sorry, I should have been more specific. Does anyone know the coefficients of OC 703 that you are using and JM Linacoustic RC 1in? If so, can you post them for me or send me a PM?

It's probably in this long thread somewhere...but I'll add it if not:

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

Thank Bob Gold

Thanks for the link, two-rocks.

Pepar,
Which OC 703 are you using?

Pepar,
Which OC 703 are you using?
Dan, there's only one kind of 703. I am using it unfaced. Here's the submittal data sheet (http://www.owenscorning.com/comminsul/documents/Fiberglas700Series.pdf).

This will be my last post on this project as it marks the end of the "acoustical treatment" phase until I install additional bass traps in the theater and that is probably a month or two away.

All superchunk traps in front are complete and LCR speakers are mounted and laser-aligned. After wiring everything, I'll re-hang the 2" Linacoustic and mount the AT screen. I'll move my posts on this project to the SmX thread.

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

Dan, there's only one kind of 703. I am using it unfaced. Here's the submittal data sheet (http://www.owenscorning.com/comminsul/documents/Fiberglas700Series.pdf).

Actually there is the 1", 2", 3", 4", and 6". Which are you working with? It doesn't look like the 1" but pictures can be deceiving.

Thanks,
Dan

If I am hanging small traps from the wall to the ceiling at the sides of my front rows seating, can I place speakers nearby under them? My ceiling is 7' 6" and I am interested in placing whatever size I can fit there that may be effective but I would also like to correctly place Crystal Acoustics THX-Dipole speakers. Any other advise related to acoustics or my room I am working with while I have the available funds?

I have 12" traps in the front and back corners and areas around my room are made using fiberglass insulation and plywood. The PVC ceiling (with diffusion) is filled with fiberglass insulation and Roxul 60 above the front row. I also have Roxul 60 in the corner of the rear ceiling. I have 6 Berkline 88 leather seats. I got the result bellow after adding the traps in the corners, and before adding 6 24X24X2" Roxul panels with hardboard backing hung using Velcro in the front of the room.

http://farm3.static.flickr.com/2120/2052900626_f8fc151862_o.jpg

I was thinking of ordering 12x44x1" open back panels X 2 for the left and right walls, and 12x53x1" open back panels X 2 for the rear wall. They would be ATS panels. Will this help improve the acoustics of the room? Should I do further testing first? I hear some problems in these areas with my mains turned down.

Actually there is the 1", 2", 3", 4", and 6". Which are you working with? It doesn't look like the 1" but pictures can be deceiving.
So sorry, Dan. It is 2" 703. IIRC, 4" cost more than twice 2", and 1" not much, if any, less and w-a-y more tedious. If you look at the faces of my traps, you can see that they got more uniform as I became better with the electric turkey carver.

So sorry, Dan. It is 2" 703. IIRC, 4" cost more than twice 2", and 1" not much, if any, less and w-a-y more tedious. If you look at the faces of my traps, you can see that they got more uniform as I became better with the electric turkey carver.

Nothing to apologize for. I should have asked the thickness. Interesting idea on the electric turkey carver.

I have over half a roll of Linacoustic RC 1" left-over and am thinking of trying your idea in the front corners.

Thanks,
Dan

Nothing to apologize for. I should have asked the thickness. Interesting idea on the electric turkey carver.

I have over half a roll of Linacoustic RC 1" left-over and am thinking of trying your idea in the front corners.

Thanks,
Dan

I used an electric turkey carver as well and it worked great. The cuts weren't perfectly straight but since they aren't showing, it didn't matter. I actually got the Knauff version of OC703 and it works just fine, as well.

Nothing to apologize for. I should have asked the thickness. Interesting idea on the electric turkey carver.

I have over half a roll of Linacoustic RC 1" left-over and am thinking of trying your idea in the front corners.

Thanks,
Dan
Did you look at Bob Gold's Absorption Coefficients (http://bobgolds.com/AbsorptionCoefficients.htm)? The stuff you have tests similarly to 1" of the 703, so stacking it in wedges should give you similar performance. I have the 2" Linacoustic and will be re-hanging it behind the false wall after I wire the speakers and before hanging the screen.

I noticed the similarities. I'm not sure I'll run out and get a turkey carver but it looks like wedge cutting is in my near future.

Thanks,
Dan

I noticed the similarities. I'm not sure I'll run out and get a turkey carver but it looks like wedge cutting is in my near future.

Thanks,
Dan
I bought it for a song on eBay six to nine months ago for this project. There are a boatload of them (http://home.search.*********/electric-carving-knife_Kitchen_W0QQ_trksidZm37QQcatrefZC12QQfasiZ1QQfbfmtZ1QQ fromZR40QQsabfmtsZ2QQsacatZ20625QQsascsZ2QQsbrbinZt) there right now . . .

If I do up a corner and continue across the ceiling/wall corner, I would "miter" them for a continuous appearance. Is there something gained, performance-wise, by placing a cube in the corner, or is that just an aesthetic design element?

edit: I'll bet the cube was their way of avoiding mitering . .

That's an interesting question; given that the corner is the _one_ place where you have all three axial modes (length, width, height) there might be more to it than avoiding mitering? I'd guess (and guess it is) that the extra depth of the cube will help with more of the lower frequencies than if you simply miter.

Nathan

I sent you a PM. If we've missed something, I apologize. We try to return all calls the same day. PM me with your phone number and I'll be happy to work with you to figure out your needs.

Bryan

Thanks! Talked with Glenn on the phone for a minute. He confirmed that the 244s are not as absorptive on the high end as the 242s, by design. That makes sense.

He was also able to forward me your email which I now see was eaten by my spam filter! I've left a msg for you this afternoon to ask a couple of questions about your email.

You've recommended all bass trapping and that may be the week point in my room (about 12.5 ft by 16 ft x 7.5 tall, sealed) but I've already got six real traps, and the wife hates the look of the aurlex foam at the first reflection points, so I'm thinking I may want some 242s to replace the foam, before anything else.

Hopefully we'll connect by phone soon and we can close the deal.

UPDATE: Spoke with Bryan and he patiently worked through a scenario that will optimize my room, make use of my existing treatments, and meet my budget (by splitting up the ideal purchases into two phases). I'm actually going to start with what he called phase 2, which acoustically is less of a big impact, because it will have the highest WAF (be more visually noticeable).

OK, one last post on my superchunk bass trap installation -

The area behind the false wall is complete; the 2" Linacoustic is back up covering the entire cavity, including the newly installed chunk traps. The dual Hsu's TN-1220HO's are back in place at 1/3 the room width at that part of the room and I did a quick spkr level calibration. No screen yet, but to get audio from the BD30 I needed to fire up the video chain, too. Wanting to hear music with a solid bottom, I popped the Sade live concert DVD-Video in and selected DD5.1. It was certainly not much of a test as I could not sit back in my main listening/viewing chair due to the screen frame members lying across the back, and I wanted/expected to hear an improvement, but nonetheless I swear that I heard one - and a substantial one at that. Every bass note is now distinct, punchy and a discrete musical event. (My room was very flabby from 100Hz to 300Hz before with two serious nulls below 100Hz.) I listened to most of two or three songs before switching to my Denon 3910 and Gaucho on DVD-A. Wow! Granted, it would easier to determine if I really completely smoothed the bottom end if the bass player walked from his lowest note up the scales to his highest note, but again every note was clean, clear and oh sooo solid with no notes standing out or receding back.

When I get the screen up and the false wall buttoned up with velcro-attached panels I'll have a fellow HT enthusiast over with some audio test gear to "see" what the room's doing. I may not need to install any more chunk traps.

I have 12" traps in the front and back corners and areas around my room are made using fiberglass insulation and plywood. The PVC ceiling (with diffusion) is filled with fiberglass insulation and Roxul 60 above the front row. I also have Roxul 60 in the corner of the rear ceiling. I have 6 Berkline 88 leather seats. I got the result bellow after adding the traps in the corners, and before adding 6 24X24X2" Roxul panels with hardboard backing hung using Velcro in the front of the room.

http://farm3.static.flickr.com/2120/2052900626_f8fc151862_o.jpg

I was thinking of ordering 12x44x1" open back panels X 2 for the left and right walls, and 12x53x1" open back panels X 2 for the rear wall. They would be ATS panels. Will this help improve the acoustics of the room? Should I do further testing first? I hear some problems in these areas with my mains turned down.

Steve.

Don't know what your room is like size wise so hard to be exact. I'd recommend playing with a couple of 6" thick panels centered on the rear wall of the room to see if that will impact your bottom end response.

As for the side panels, they're important for reflection duties and general decay time. Whether they should be 1 or 2" depends on a lot of other factors.

Bryan

Bryan,

I will do more testing. I have perfect towers and it is very scientific results for any speakers I may put in there. ;) I will try with the sub only and use the SPL configuration file. I will probably end up doing the kind of traps you suggested since I read so many good reviews about them. I was looking at those last week and I could now afford those. There is about 4' 1/2" height from the rear platforms to the crown molding. I will look more into it.

1. Size

The attached SketchUp images have the exact dimensions shown. I did this after the room was built and I double (before carpet) & triple checked so I could have a nice 3d model.

2. Current room treatments

The front of my room has some of these traps I made using 4lb Roxul 60 and dowel rods covered in two layers of burlap. From the top dowel rod up, the Roxul is stacked corners, bellow it is put into the frame with the shiny looking side facing out. There are 3 cut vertical compressed with some tiny pieces behind those to fill in gaps. I forced the Roxul 60 in very tightly and during that I had to reinforce my framing with larger deck screws to keep it from coming out the wall even though I used caulk behind the furring strips. I set the dowel rods in (after testing with different configurations) using Elmers high performance wood glue and filled in the holes I drilled out on each side using wood filler afterwards. I painted the frames because I was bored while it was all drying for about a day or two.

http://farm3.static.flickr.com/2157/2045650312_f00674f7cf_o.jpg

It looks like this but I have been trying to touch up the trim using caulk more recently.

http://farm3.static.flickr.com/2108/2241618134_c0dc3cbdab.jpg

There are some in the rear of the room the same but without dowel rods being used since they were short and pretty strong to begin with. Those are between the platforms and the ceiling.

I have four 24X24X2" panels (Roxul AFB mineral wool, 1/4-inch wood back panel, industrial strength Velcro, burlap) for first reflection points I positioned using the mirror method post construction and after. I also have one just sitting behind my sub-woofer, but not the center channel. They need more Velcro. The sub is on a sub dude for isolation.

The walls are a "knock down" finish and are covered with lots of primer and paint. The walls are filled with R45 (if I remember right) and the other areas are filled using R19 that I (with help) removed the paper off of. We went through many rolls of various fiberglass insulation for the entire room. We ran out for the riser and so the center cavity is only 1/3 full. The rear wall was left uncompleted (without insulation at the bottom & drywall) to where I can stuff insulation in there later, fill with sand, or whatever I need to use to place a sub on it. The unfinished area is between the left and right rear platforms. The main reason it wasn't finished was so that I could move my wall plates later on when those go to the equipment closet.

The rear platform area is lined with the insulation but next to the wall it is not . I had nothing to put there. I put holes in the face of the plywood cavity before carpeting. I'm not sure the exact size and I haven't yet really looked into the frequency at which it resonates much. Anyone know if I should line the back wall with something or just blow in some insulation?

Hey, what do you guys think of sonex acoustic sound panels?

My testing didn't get real into much detail this time. The MACC setup on my AVR wouldn't even give me the OK for a setup even after I tried propping up the RS digital mic. I tried both left and right inputs and didn't bother to hunt down the Y connector. I thought about using REW again maybe with the correct settings at least for the program but thought it might not be worth the effort if I can't turn off bass management. I tried DVE only to find that my sub wasn't even played on the HD-DVD side, so I flipped that over and used the DVD. I ran sweeps and put the SPL meter in different locations and it looked decent. After I listened to both left and right mains in the rear of the room it all kind of just blurs together under 100Hz. Using half the spikes for each speaker to aim them seems to really hurt down low. I put the SPL meter to A weighting and checked both the front row and then the back. I checked again with the SPL meter a couple feet from the rear wall and it was really spiking from 78Hz to about 83Hz with the sub. The mains were just spiking all over the place there after about a 100. When I had the towers sitting on the side platforms even when not in use, they would make the ceiling above it rattle. I didn't check that with DVE but discovered the issue with movies pretty fast after I quit using them for 5.1 analog use. The sub seems to rattle the front tower speakers.

Does this look OK or do I need smaller? I scaled the speakers down to the correct size. I can't separate them much more or one aims directly at a beam.

http://www.avsforum.com/avs-vb/attachment.php?attachmentid=102625&stc=1&d=1203513261

Hey, what do you guys think of sonex acoustic sound panels?
Sonex panels work, but not as efficiently as semi-rigid fiberglass for the 2" variety. It may be that the contoured shape of the foam simply lowers the average thickness too much. The thick 3" Sonex performs pretty well, and the 12" thick wedges can make a nice anechoic chamber. :D

If you found a great buy on Sonex and you like the look, consider using it. One advantage is that it doesn't need to be covered with fabric to look decent. Otherwise 2 1/4 to 6 pcf fiberglass (OC 703, OC 705, Linacoustic, etc.) is the way to go, giving the most absorption bang for the thickness buck -- at least for the thinner (2") products.

Regards,
Terry

Sonex panels work, but not as efficiently as semi-rigid fiberglass for the 2" variety. It may be that the contoured shape of the foam simply lowers the average thickness too much. The thick 3" Sonex performs pretty well, and the 12" thick wedges can make a nice anechoic chamber. :D

If you found a great buy on Sonex and you like the look, consider using it. One advantage is that it doesn't need to be covered with fabric to look decent. Otherwise 2 1/4 to 6 pcf fiberglass (OC 703, OC 705, Linacoustic, etc.) is the way to go, giving the most absorption bang for the thickness buck -- at least for the thinner (2") products.

Regards,
Terry

Thanks. A guy is selling some pre-made sonex panels, so I was curious. Of course, I can always get some sonex myself, and there is the other stuff you mention, so I'll look into it....and I'll check out your site too :)

thanks,

:)

Steve

Any uninsulated wall should be done. Blown in is fine but fill it up.

As for the panels on the back, that can certainly help. I was suggesting just trying to sit them there as a test.

Bryan

I spoke with Bryan the other day. I decided to try the GIK 244 Bass Traps on the back wall. I will also test them on the front wall but I only have 19" between the traps and the screen so I would require custom sized ones there later on if I find them to help. It would be nice to cover up those speaker plates. The LCR are 8' from the middle seat, and the towers are about 1' 10" from both walls in the photo. The center channel is about 3" from the wall from where it's bass ports are sticking out the back. I could place some under the screen and behind the center channel maybe also. I got set straight about the ATS bass traps and a few other issues. It gets very confusing sometimes. Thanks Bryan! :)

http://farm3.static.flickr.com/2255/2280853173_206180ec43_o.jpg

Sonex panels work, but not as efficiently as semi-rigid fiberglass for the 2" variety. It may be that the contoured shape of the foam simply lowers the average thickness too much. The thick 3" Sonex performs pretty well, and the 12" thick wedges can make a nice anechoic chamber. :D

If you found a great buy on Sonex and you like the look, consider using it. One advantage is that it doesn't need to be covered with fabric to look decent. Otherwise 2 1/4 to 6 pcf fiberglass (OC 703, OC 705, Linacoustic, etc.) is the way to go, giving the most absorption bang for the thickness buck -- at least for the thinner (2") products.

Regards,
Terry


Any idea where I can find Linacoustic or any of the other products online or otherwise? I am in Toronto, Canada.

thanks,

:)

I'm trying to figure out a good way to mount 2x4' OC703 panels diagonally along the sides of the room where the wall meets the ceiling. I got some Rotofast cloud hangers that worked well for my horizontal clouds.

However, trying to use them for a diagonal mount isn't working too well. I put two U shaped hooks in the ceiling near the wall and ran some string through two sets of two cloud mounts up to the hooks, forming a triangle for each support. However, trying to get the string length just right so the panel is snug against the wall/ceiling is tough. Plus, it's pulling the Rotofast anchors at weird angles and I fear they will pull out.

So now I'm thinking about a couple of small but deep brackets/hooks that would go on the wall under the bottom to support the weight, and some type of hook deal in front of the panel on the ceiling to hold the top up.

The panels are just plain OC703 which I covered in tan GOM. So there's no real structure to the panel that I can anchor from behind. I'll go to home depot tomorrow, but wanted some input first.

Thanks!

I'm trying to figure out a good way to mount 2x4' OC703 panels diagonally along the sides of the room where the wall meets the ceiling. I got some Rotofast cloud hangers that worked well for my horizontal clouds.

However, trying to use them for a diagonal mount isn't working too well. I put two U shaped hooks in the ceiling near the wall and ran some string through two sets of two cloud mounts up to the hooks, forming a triangle for each support. However, trying to get the string length just right so the panel is snug against the wall/ceiling is tough. Plus, it's pulling the Rotofast anchors at weird angles and I fear they will pull out.

So now I'm thinking about a couple of small but deep brackets/hooks that would go on the wall under the bottom to support the weight, and some type of hook deal in front of the panel on the ceiling to hold the top up.

The panels are just plain OC703 which I covered in tan GOM. So there's no real structure to the panel that I can anchor from behind. I'll go to home depot tomorrow, but wanted some input first.

Thanks!
You may not judge this method suitable for locations that can be seen, but here is my post from earlier in this thread (http://www.avsforum.com/avs-vb/showthread.php?p=13083785#post13083785). The "finished" result is pictured some posts after it. It is extremely simple and inexpensive.

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.

I posted photos in my dedicated construction thread -- http://www.avsforum.com/avs-vb/showthread.php?p=13216725#post13216725 -- but since one thing I couldn't find when planning to order some panels were good CLOSE UP photos of them, I'm cross posting those photos, here.

They are black, but the flash washes out the color and shows through the GOM fabric (an upgrade) to the structure underneath. Even under direct sunlight you cannot actually see anything under the GOM. I'm not sure what the default GIK cloth looks like. I decided I wanted to get the "best" covering right out of the gate, in order to make sure I please "she that must be obeyed."

I may try out the standard fabric on the next order and see what that is like and whether she likes it.

The picture hanging wire on the one where you see the back hasn't been tightened on for use, yet.

(For the record: The Auralex foam is slowly be sold on craigslist. Two boxes were never even mounted! But she hates foam and that was the biggest complaint from her about the whole theater... not the black room or anything else. And the Real Traps were sold not because they were ineffective -- far from it -- and of course they are built like tanks -- but because she prefers the "all fabric" look. Almost think I should have just covered the Real Traps in some GOM but it's too late now.)

http://i208.photobucket.com/albums/bb269/nathan_h_photos/IMG_6905.jpg

http://i208.photobucket.com/albums/bb269/nathan_h_photos/IMG_6906.jpg

http://i208.photobucket.com/albums/bb269/nathan_h_photos/IMG_6907.jpg

http://i208.photobucket.com/albums/bb269/nathan_h_photos/IMG_6908.jpg

I have two unopened bales of the 703 material in the one inch variety. I have enough room in the theater that I could literally just sit them in the corners of the room as dense absorbers? Would that be productive, or does the material only work if it's had a chance to expand to its unpacked dimension (2x4x1inch) If I do unpack it, my read of the thread is that there isn't a reason, other than aesthetics to go with angled 'chunks' rather than a cube?

Thanks.

I have two unopened bales of the 703 material in the one inch variety. I have enough room in the theater that I could literally just sit them in the corners of the room as dense absorbers? Would that be productive, or does the material only work if it's had a chance to expand to its unpacked dimension (2x4x1inch) If I do unpack it, my read of the thread is that there isn't a reason, other than aesthetics to go with angled 'chunks' rather than a cube?
I don't think there's much to be gained by having a BIG square column from floor to ceiling over having a half-as-big TRIANGULAR column from floor to ceiling. And there's TWO of the latter in the former.

that makes sense, twice as much material for the same amount of money and a triangle isn't half as effective as a cube, so why not. I guess I was trying to avoid having to make lots of cuts, but the electric knife idea is a good one, maybe I'll try that.

I actually used two electric turkey knives. The first one I used was from the 1950's - 1970's and ran for less than half a minute. The second "good turkey knife" started getting dull after about a third of the way though and was no longer cutting as well. I used the good ones for the corners and used my scraps elsewhere.

I actually used two electric turkey knives. The first one I used was from the 1950's - 1970's and ran for less than half a minute. The second "good turkey knife" started getting dull after about a third of the way though and was no longer cutting as well. I used the good ones for the corners and used my scraps elsewhere.
My new knife got very warm and smelled a bit almost immediately. I pressed on and cut about a one and a half bales of 703. Got some good wrist workouts in the process.

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?

My new knife got very warm and smelled a bit almost immediately. I pressed on and cut about a one and a half bales of 703. Got some good wrist workouts in the process.

I used a cheapo $15 one from Wal-Mart and I cut two bales without issue. It did get somewhat warm, but never smoked and I didn't notice it getting dull.