acoustic treatment - the more foams the better?

95bcwh · « **on:** 31 Jan 2006, 01:52 am »

All,
I have a seriously crap room (3m x 3m x 4.5m) with carpet which I wanted to treat, a friend of mine recommended getting 4" foams from this website:

http://www.foamandupholstery.com/Noise_Control_Products%20.htm

I am absolutely new to the topic of room acoustic. I wonder if someone can advice me whether the more foams I place in the room (covering side walls and ceiling) the better?

I am also thinking of getting rolls of fiberglass insulation from Homedepot and stack them up at 4 corners. This, together with lots of foams, will it be sufficient?

Thanks for your opinion.
RV

woodsyi · « **Reply #1 on:** 31 Jan 2006, 02:13 am »

RV,

You can't be married if you are thinking of doing this!

Check though some threads on the Acoustic Circle and you will get some ideas on commercial products and DIY solutions that may have a tad bit higher WAF. Good Luck.

P.S. Some (falsely advertised) foams are no better than packing foam as I found out the hard way.

Make sure your acoustic foam comes from reputable source if you go with foam.

warnerwh · « **Reply #2 on:** 31 Jan 2006, 04:26 am »

The more foam does not equate to better. If your room is 3mx3m and 4.5m high then you have a significant problem. A square room. This amplifies the room modes. Some foam on all first reflection points as well as some behind the system is a good place to start. What you're really going to need the most is bass traps. These can be purchased from people like Realtraps or diy. Either way you need to read up on room acoustics. You'll get very good performance with good acoustics no matter your system.

A very expensive system with poor room acoustics will usually not sound near as good as a much less expensive system with good acoustics.

95bcwh · « **Reply #3 on:** 31 Jan 2006, 05:57 am »

Thanks guys!

oops..sorry.. I meant to say that my room is 3m width, 3m height, and 4.5m length. I realize that I will need bass trap... I don't want to pay over the top for bass traps, the last time when I check, one tube of bass trap is costing like $200. With that money I can buy plenty of foams and plenty of fiberglass rolls to fill up my room.

Yeah, I've been doing some reading...however, I have not been able to find any proven formula, I think I will space out the foams and bass traps all over my room to start with, and then move these materials around to see the difference they make.

Jon Risch was suggesting wrapping up fiberglass with a layer of polyster batting so that it will absorb both high and low frequency. I will try that too.

95bcwh · « **Reply #4 on:** 31 Jan 2006, 06:06 am »

woodsyi
I m married with one kid, but luckily I have an extremely obedient wife..I'm sure this room will look like a junk hole with all these quick&dirty DIY stuff...she will not like it, but no one has to enter that room except me.

I feel more sorry for my little kid, he will lose one of his many playgrounds..

JLM · « **Reply #5 on:** 31 Jan 2006, 10:34 am »

Whatever you use for absorbent panels, think of them in terms of "colors of sound". In other words, just as different materials are seen in particular colors (based on what they absorb and reflect), the same can be said regarding what frequencies of sound are absorbed or reflected.

Most foam only works on mid/high frequencies. High density (around 6 pounds per cubic foot) fiberglass works well across a wide frequency range. This stuff can be bought in bulk but GIKacoustics.com prices for finished panels, for the amount you'll probably need, is hard to beat.

Realtraps.com explains the value of locating treatments in the corners. 8th Nerve (with their own circle below) emphasises corners too and provide a lower visual impact.

Glenn K · « **Reply #6 on:** 31 Jan 2006, 11:33 am »

Quote from: 95bcwh

All,
I have a seriously crap room (3m x 3m x 4.5m) with carpet which I wanted to treat, a friend of mine recommended getting 4" foams from this website:

http://www.foamandupholstery.com/Noise_Control_Products%20.htm

I am absolutely new to the topic of room acoustic. I wonder if someone can advice me whether the more foams I place in the room (covering side walls and ceiling) the better?

I am also thinking of getting rolls of fiberglass insulation from Homedepot and stack them up at 4 corne ...

Be very careful with foam. Ethen Winer from Real Traps did some lab testing with FBM (pretty much the stuff you are looking at) and the numbers FBM published where fraud.. I know that is a harsh word but the are.. Stick with rigid fiberglass, you will thank me at the end..

Glenn

bpape · « **Reply #7 on:** 31 Jan 2006, 02:16 pm »

Glenn is absolutely correct. I believe the foam you have listed is the same entity.

If you're going to do foam, stick with Auralex. If you want to explore other options, rigid fiberglass, mineral wool, and acoustical cotton of the appropriate densities for each application can provide you with much better performance for less money.

In addition, all of the materials listed above are class A fire rated materials where even the good foam is at best Class B, some is much worse or not fire rated at all.

Bryan

95bcwh · « **Reply #8 on:** 31 Jan 2006, 03:22 pm »

Thanks for all your suggestions...I bump into this on ebay.. I probably won't buy them since I want to stick with fiberglass, but just wondering if these type of material is as good as they claimed?

http://cgi.ebay.com/Acoustic-Acoustical-Panel-for-Recording-Studio-No-Foam_W0QQitemZ7385023169QQcategoryZ3278QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Glenn K · « **Reply #9 on:** 31 Jan 2006, 04:08 pm »

Quote from: 95bcwh

Thanks for all your suggestions...I bump into this on ebay.. I probably won't buy them since I want to stick with fiberglass, but just wondering if these type of material is as good as they claimed?

http://cgi.ebay.com/Acoustic-Acoustical-Panel-for-Recording-Studio-No-Foam_W0QQitemZ7385023169QQcategoryZ3278QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Here is the problem I have with these panels.. They have a 1/4" wood backing on them.. The back of the panel needs to be open for it to work right...
This really gets to my point about products that are not tested, that I am screaming about all time..

Watson · « **Reply #10 on:** 31 Jan 2006, 04:16 pm »

Quote from: Glenn K

Here is the problem I have with these panels.. They have a 1/4" wood backing on them.. The back of the panel needs to be open for it to work right...

Why does the back have to be open for it to "work right"? It's going to be mounted against to a solid wall.

richlo · « **Reply #11 on:** 31 Jan 2006, 04:38 pm »

Quote from: Watson

Quote from: Glenn K
Here is the problem I have with these panels.. They have a 1/4" wood backing on them.. The back of the panel needs to be open for it to work right...

Why does the back have to be open for it to "work right"? It's going to be mounted against to a solid wall.

Actually for the panels to work effectively - they need to be mounted off the wall so that sound travels through the back and sides...this is by far more effective..in most cases, if not all cased, HUGELY ..so you can not cover the back with something dense- this defeats the purpose..If the panel is 2" thick then it should be mounted 2" off the wall...I will let the PROS here better explain..

for what its worth it is not a huge investment...it might be worth it for you.

Glenn K · « **Reply #12 on:** 31 Jan 2006, 07:08 pm »

Quote from: richlo

Actually for the panels to work effectively - they need to be mounted off the wall so that sound travels through the back and sides...this is by far more effective..in most cases, if not all cased, HUGELY ..so you can not cover the back with something dense- this defeats the purpose..If the panel is 2" thick then it should be mounted 2" off the wall...I will let the PROS here better explain..

for what its worth it is not a huge investment...it might be worth it for you.

You are right on the money sir.. If you want some idea of how much better it is, go to our lab report and look at the panel "A" mounted (flat against the wall) compared to "J" wall mounted.. Much better.. Our panel has a 2" space on the back anyway, so the number would be even worse with a flat wood back.. Honestly, I think you would be better off with making something yourself.. Boy I hope I don't sound like I am trying to put down a company

, just hate to see things done wrong..
Glenn

_scotty_ · « **Reply #13 on:** 31 Jan 2006, 07:12 pm »

Mounting the panel on the wall with an air space behind it greatly improves it's performance below 250Hz. The longer wavelengths travel through the panel and are reflected from the wall behind and have to travel back through the panel to get back into the room. In the process sound wave has to make a transition through the boundary from the fiberglass to air and back into the fiberglass which aids in dissipating the acoustical energy present.
Owens Corning 703 semi-rigid fiberglass is the gold standard for sound absortion efficiency.
Scotty

Ethan Winer · « **Reply #14 on:** 31 Jan 2006, 08:45 pm »

Scotty,

> The longer wavelengths travel through the panel and are reflected from the wall behind and have to travel back through the panel <

Sure, but just to clarify, this happens whether there's an air gap or not. The real issue is that rigid fiberglass and other "porous" absorbers operate on wave velocity. The velocity is zero at the wall, and increases to a maximum at 1/4 wavelength away for a given frequency. So for, say, 100 Hz the ideal air gap is 34 inches. Of course you don't need that much gap to make a big improvement! As we all know, even a few inches can make a big difference.

--Ethan

Glenn K · « **Reply #15 on:** 31 Jan 2006, 09:07 pm »

Quote from: _scotty_

Mounting the panel on the wall with an air space behind it greatly improves it's performance below 250Hz. The longer wavelengths travel through the panel and are reflected from the wall behind and have to travel back through the panel to get back into the room. In the process sound wave has to make a transition through the boundary from the fiberglass to air and back into the fiberglass which aids in dissipating the acoustical energy present.
Owens Corning 703 semi-rigid fiberglass is the gold standard for sound absortion efficiency.
Scotty

Scotty you are right, but it also helps A LOT with the high end.. Sound is able to come in from the sides so it picks up more of the sound reflections.... Space is your friend..

Glenn

95bcwh · « **Reply #16 on:** 1 Feb 2006, 06:26 am »

Thank you all. I have one last question, according to this excellent acoustic panel DIY website:
http://www.angelfire.com/sports/RCcars/acoustic_panels.htm

The author clearly said that a panel won't fix frequency below 80Hz. To do that we need a bass trap.

Now, I have read from various website that a quick and dirty DIY bass trap can be made by stacking up rolls of fiberglass bought from homedepot, keep them in their plastic bags, wrap one layer of poly batting around them and then covered with burlap. The result is a tube-shape that can be placed at 4 corners of the room.

But, these are made of the exact same material as the acoustic panels! What will make them trap more bass than the panel?

Appreciate your comments.
RV

Glenn K · « **Reply #17 on:** 1 Feb 2006, 12:01 pm »

Quote from: 95bcwh

Thank you all. I have one last question, according to this excellent acoustic panel DIY website:
http://www.angelfire.com/sports/RCcars/acoustic_panels.htm

The author clearly said that a panel won't fix frequency below 80Hz. To do that we need a bass trap.

Now, I have read from various website that a quick and dirty DIY bass trap can be made by stacking up rolls of fiberglass bought from homedepot, keep them in their plastic bags, wrap one layer of poly batting around them and then covered with burla ...

I would say that panel on the link would maybe work for first reflections but it really is not a good design at all... You do not want peg board on the back and if making a panel it is best to use rigid fiberglass..
I think if you took rolls of fiberglass and stacked them from floor to ceiling in all corners then built a wall out of fabric in front of it, you would be much better off..

Glenn

bpape · « **Reply #18 on:** 1 Feb 2006, 12:48 pm »

Reasons the roll will work better....

- It's thicker so more and longer waves can exist inside it at one time.
- it's leading edge is farther from a boundary
- it's more dense since in the packaging it's compressed more
- it has no back so waves can use the space behind to enter.

Other than that, they're about the same

gonefishin · « **Reply #19 on:** 1 Feb 2006, 03:53 pm »

Quote from: bpape

Reasons the roll will work better....

- It's thicker so more and longer waves can exist inside it at one time.
- it's leading edge is farther from a boundary
- it's more dense since in the packaging it's compressed more
- it has no back so waves can use the space behind to enter.

Other than that, they're about the same

Hi bpape,

- If it is simply thickness that you going for, why not double up the 2" 703 or 705 board? That's what's really recommended when making the high density fiberboard bass traps anyway. Leaving it at 2" is recommended for reflection points, not bass traps.

This would leave you with the recommended 4" of high density bass traps, as opposed to the 3 1/2" r-13 bass traps.

- It's leading edge would be further out in the room if you use the recommended 4" of high density fiberglass as opposed to the 3 1/2" of r-13.

- Are you saying that r-13 is more dense than high density fiberboard (such as 703,705)?

- A great way that DIY'ers could be saving money, is to buy non-backed 703,705 (and knauff equivalents) when they don't need it. The non-backed cartons of high density was a GOOD deal cheaper per carton. So if you don't need the foil skrim backed...don't buy it.

thanks,

dan