Acoustical Treatments Master Thread - Page 78

If the fabric is mounted as a wall or ceiling covering, as specified in International Building Code 2003, section 803.4, then the fabric only is required to have been tested and given a Class A rating according to ASTM E 84. This will be true for typical permanently-installed fabric -- stapled over furring strings, or attached via a track fabric system.

If the fabric is mounted otherwise, as covering an acoustical panel, then NFPA 701 testing applies instead the the ASTM testing. That's where the "701" comes from in "Guilford FR701®," which is used a great deal for commercial acoustical panels. The entire assembly must be tested under NFPA 701, unless it covers less than 10% of the room wall and ceiling area (which would qualify it as a "decorative finish"). Technically, acoustical panel manufacturers must provide proof of this testing.

Regards,
Terry

Terry:

Interesting--that original fabric I was looking at says "Passes California Bulletin #117; ASTM E-84 adhered method Class I; NFPA 260, UFAC Class I. "

How does "Class A" compare to "Class I"?


Thanks.

Different beasts entirely. One cannot substitute one for the other. ASTM E-84 is for building material flame spread and smoke development. NFPA 260 is for upholstered furniture fabric ignition from cigarettes.

Regards,
Terry

I asked this question in another thread, but I will repeat it here, where the acoustic folks hang! MY HT is a basement build, with 2 of 4 walls being concrete outside walls. In the rest of my basement that is finished, walls are first covered with a permeable foam board, which is sealed to the concrete, then a 1" air gap, then the 2x4 wall with R-13 fiberglass. I plan the same technique here. Since these walls are against concrete, do they need the whole DD+GG treatment? Any sound that "gets through" will then have to go up and through the floor upstairs to be heard. The joist will be filled with fiberglass insulation 1' thick, plus another 2" below that(ceiling will be suspended with the 2" RSIC clips). Just curious what the latest is on these basement walls.

I can get this locally:

http://www.jm.com/insulation/perform..._microaire.pdf

How good would this material be compared to the popular OC703 for both treating first reflection points and making bass traps? It's type 475 and comes in 4x10x1" sheets with FSK. The absorption coefficients look close, but I couldn't find the density spec.

Type 475 = 4.75 pcf. This is about midway between OC703 and OC705, and should work fine for both functions. For early reflection and wideband absorption, you definitely want to have the FSK side so that it is not facing the room.

Regards,
Terry

We added several bags of insulation behind the scrim wall. Used the auto equalization feature of the Lexicon. Ouila! Great bass! It is better near the microphone location,but functional in most seating locations.
I really like the Lexicon Eq feature. It makes us look good.

Hey guys, I just bought some owens corning ductliner, type 150 for use in my HT. I hope this stuff will work ok, I live in a small town and it is the only thing I could find. So from my reading I've concluded that I should cover the entire front wall with this stuff. Now the sidewalls I've read 42" and down. Would this be true for a 10' ceiling also? What about the back wall and the ceiling. Should anything be done there?

I also want to look into bass traps, is this something I need in each corner of the room? I generally see them placed up high in the corners, is there a method to determining where the traps would go?

All corners are viable - where two walls meet, where a wall and ceiling meet, and even on the floor at the bottom of a wall. Three-way corners are especially prized. I have many traps in wall-floor corners.

--Ethan

This is somewhat on the low density side. I wouldn't use less than a 2" thickness.


Yes, 42 is the answer. Don't forget to bring a towel!

Seriously, different rooms need different treatments. I routinely use side wall absorption right up to the ceiling. And of course the standard poly batting "diffusion" for the upper wall is really absorption anyway.

Regards,
Terry

Well, its what I've got to work with at this point. I am not going for a THX theater here I just want it to sound alot better than it does with 4 bare walls like I currently have. Plus I think the look of it really adds to a dedicated room. I guess I'll staple it up and do some sound testing.

Couple more questions..

I plan to have 2 rows of seating, the back seats on a riser (which I have not built yet), so should the side walls be treated higher near the back to compensate or will 42" accrost the board be good enough?

Next question, should any of this stuff go on the back wall at all or do I want to leave it untreated?

If you have depth on the front wall, a few inches of fiberglass thickness will do double-duty for reflections and bass absorption. I have also used the rear wall for bass absorption, but not without verifying that the back of the room will still be sufficiently "live" for the surround channels.

The thing about bass absorption, be it in the corners or on the walls, is that you need to cover a substantial area with the absorber. Little tri-corner absorbers won't make much difference.

Regards,
Terry

Terry, what do you mean if I have depth on the front wall? My room is 22x17x10.


If I use the stuff I bought, owens corning 150, and build 4 traps like the ones on this web page, will that help?

http://www.runet.edu/~shelm/acoustic...html#BassTraps

Only that you will need 4" or more of depth from the surface of the absorber to the wall for significant bass absorption. With screen and seating requirements, this is sometimes too much to ask for.


Yes, it should make a significant difference! Floor to ceiling corner bass absorbers give you lots of depth in otherwise unused spaces. The WAF can be rather low, though.

Regards,
Terry

I don't have to deal with WAF, I have the luxury of having the GFDWIW (girlfriend does what i want) factor.

I am the king of my castle! But my castle lacks sound treatment and a moat! Sound treatment first, the moat is still being dug out, 1 shovel full at a time. Anyways, thanks for the help, Im going to get started today. Wish me luck!

Luck!

- Terry

Well I did a quick calculation and the amount of material I have would only only me to do the front wall, side walls, and 2 traps if I built them like the above link. I'd have to buy another 400 sq/ft roll just for 2 more traps. So, would 2 traps be ok or pointless?

What If I framed up the corners for a triangle and just shoved in whatever leftovers I have left, would that work or no? And lastly, I have a huge amount of pink wall insulation left over from building my house, could I utilize it in the traps or is it not dense enough?

One thing you can do is use (unfaced) fiberglass batting to fill space behind your more dense fiberglass. This often gives very good results. It alleviates the frequency "ripple" that you can get if you have just an airspace behind a layer of fiberglass absorption.

- Terry

I've started putting the stuff on the front wall. Wow what a difference already in echo reduction! How do you guys fasten this stuff to the wall and keep it smooth and flat without any dents? I've tried screws but they either create a dent or the head sticks out to far.

I also have a question about treating the side walls. I've been planning on ear level down but then I read about batting above that. What is that for? I would like to leave the top portion of the wall untreated for asthetic reasons. Will this still work ok?

Look at impaling cleats for hanging the fiberglass on the walls. They're flats of metal with screw holes and spikes on them. You screw the metal flats onto the wall, and impale the fiberglass on the spikes.

I've had mixed success with those, especially with thicker panels. My preference is to use these: http://www.rotofast.com/

Screws seem to be working ok if I drive them half way into the duct liner. If I get enough screws I don't think it will go anywhere. Plus the fabric will hold it on once up anyways i think.

New question, It looks like I'm going to have enough left over to cover the back wall from ear level down also. Asthetically this would look nice I think. Any positives or negatives to doing this vs leaving the wall drywall?

New question if I may (just posted this in the main forum but realize it is better suited here).

During really low bass moments I always hear rattling coming from my basement windows. Upon further investigation I see that it is the slats in between the panes of glass that are causing the rattle.

Since I can't really fix that short of getting new windows does anyone have any suggestions on how to dampen the bass hitting the windows?

I have heavy theater curtains covering the windows and bass traps in the corners with GIK panels on the walls already.

I was thinking of buying some OC703 insulation (4 inches thick?) and covering that with fabric - sort of like a big pillow and stuffing that into the window opening. Would that be effective in dampening the bass from reaching the window?

Any other suggestions would be much appreciated.

I am in no way an expert on sound but I do know somethings about construction and I'm guessing its the base on the walls that are vibrating the walls and causing your windows to shake. Kinda like when you slam the door and the window behind you rattles. I would think filling in the window with sound obsorbing material might stop the rattle sound from reaching your ears, even tho its still rattling. Maybe some ductliner or a whole bunch of wall insulation compressed together and fastened into the window frame?

Just a thought, maybe one of the pros can recomend a doodaddogimmic that will work better.

Hardax,
Think of your window like a drum set. If the tones hits it then it will vibrate (raddle). If you put 703 on it then the raddling should stop.

Glenn

Thanks drunkpenguin and Glenn. Looks like we are all thinking on the same level.

One other question Glenn (or if Bryan is reading). Do I really have to worry about the material I use to cover the 703 in this application? I have some basic black fabric (old curtains) that I could use but wonder if I would be messing anyhing up acoustically?

Also, I am sure it has been covered here before but can anyone tell me where to get OC703? Searches seem to be coming up short.

Many sharp shoppers buy their acoustical insulation from this company. These materials are generally made for insulating/quieting HVAC ducts and the best prices can always be had when one buys close to the source. All of the commercially available acoustical absorption products for home theater start with these materials.

The fabric can make a difference acoustically. Tight-weave fabrics can reflect high frequencies, making them less able to pass sound through to be absorbed. You are then reducing the absorber's efficiency.

On the other hand, some highs will get through virtually any fabric, so it is a matter of degree. If you don't know what fabric you have, you are taking pot luck.

Regards,
Terry

I'm using Felt over my 2" rigid fiberplass panels. Do you find that acceptable? I originally used Muslin, but felt (pun) it was ugly, so I changed it to felt. It could be me, but it appears that I don't have as much absorption now as when the Muslin was over the panels. I'm wondering if Felt is acceptable, or if I should re-wrap my panels (located at the 1st reflection points) with GOM?

You might have increased absorption at some lower frequencies by adding a "diaphram", but felt is NOT acoustically transparent, so you've decreased the overall effectiveness of your absorbers. Why not just bite the bullet and buy the RIGHT product for the job - Guilford of Maine FR701???