Differences in foam?

[Schwarzwald]

I'm going to be making some sort of vocal booth/bass traps/whatever comes to mind this weekend, and I'm wondering, does the foam you use matter? I got inspired by someone how made a Reflection filter out of stuff they found at home depot, using mattress pads for acoustic foam, is this just as good?

Has anyone ever questioned the differences in foam?

[Jens Eklund]

The single most important figure is ”flow resistivity” (Rayls/m or kPa*s/m²). Once you know this value, you can simulate the effect of it using different thickness and air gaps using this free calculator:

Porous Absorber Calculator V1.58

[Richie]

make sure it is fire resistant, foam can be very combustible. You can spray any foam with a product called "Inspecta Shield" or something like that. It may change the character of the foam, but worth it if your using off the shelf stuff.

[Sebg]

There is also a difference between polyurethane polyester foam and polyurethane polyether foam. One is more prone to absorb moisture over time and turn into a fine crumbly powder...

Precision Foam Pty Ltd - Foam Applications

[T800]

Originally Posted by Jens Eklund

The single most important figure is ”flow resistivity” (Rayls/m or kPa*s/m²). Once you know this value, you can simulate the effect of it using different thickness and air gaps using this free calculator:

Porous Absorber Calculator V1.58

I prefer using my ear to determine which absorbers sound and perform better. Because in the end - that is the final gauge - so i skip right to it. I have a good feel for these kinds of things anyways.

[Jens Eklund]

Originally Posted by T800

I prefer using my ear to determine which absorbers sound and perform better. Because in the end - that is the final gauge - so i skip right to it. I have a good feel for these kinds of things anyways.

... ok.

[Glenn Kuras]

Not all foam is made the same so stick with true acoustic foam (or better yet ridged fiberglass). Ethan did some tests of Foam By Mail (they go under a lot of different names) and found there stuff to be totally fraud. Did not work at all.
BBW!

[T800]

Originally Posted by Jens Eklund

... ok.

Sorry, "feel'" was the wrong word, i meant i have a good "ear" for these things. As do most people who have experimented alot in treating rooms. You can tell if an absorptive material is working or not by listening to the response of the room. you hear out whether you have the same resonances and mode problems with your ears - or whether the room has been balanced out and treated properly. If you know what to listen for, then its rather quite easy - you should try it sometime. Because thats what matters at the end of the day. So assuming a person is trained in what to hear and spot, and how to judge if a room is acoustically proper, at a certain point, quantifying everything down to audibly insignificant data becomes pointless. And also, as a result of test data that all these entry level people look at - the owens corning test data you guys all refer them to towards 703 - they then believe they need 703, and not realizing that 705 and 707 are the proper industry standard boards used in the real studios. So we have an example right there of test data misleading people - perhaps even faulty test data. who knows. Therefore, just in case the test data is faulty - this is why the ears are always the best measuring and testing tool (and it helps if the person is experienced with many different absorbtive materials and has been at it for a while.)

Its like music, many musicians can create amazing music without studying theory or notes, just like others can create acoustically amazing rooms without using the ETF or other testing programs or devices. Alot of experience and trial and error and simply knowing where to put things. The mirror trick is also a great one.

[T800]

Originally Posted by Glenn Kuras

stick with true acoustic foam (or better yet ridged fiberglass).

By the way - industrial and commercial grade acoustical panels use OC705 and OC707, and the flimsy OC703 boards are not for pro studio applications as you guys mistakenly believe. Please see Pilchner and Schoustal. Its all 6pcf 705 or even the 7pcf 707 boards.

Ethan did some tests of Foam By Mail (they go under a lot of different names) and found there stuff to be totally fraud. Did not work at all.
BBW!

This is a highly dubious claim. Since the majority of people say that it does work to some degree, but that is just does not work as effective on lower frequencies as auralex and primacoustic do. But it is still acoustic foam that does work to some degree and is worth the low price - to make up for the more poor low frequency performance go with 4 inch colored wedges - as the color is an injected dye that increases the rigidity and density of the foam and it does perform better than the charcoal. Therefore, their calling it Acoustic Foam is not fraudulent. Because it is acoustically absorptive. But its just not too effective. But more effective than putting egg cartons up on the wall.... (even egg cartons are a little bit acoustically absorptive, just not too great at mids and zero effectiveness at lows - but works on some high mids and some highs - but too many potholes in the absorptive character over the frequency spectrum).

[Jens Eklund]

Originally Posted by T800

Sorry, "feel'" was the wrong word, i meant i have a good "ear" for these things. As do most people who have experimented alot in treating rooms. You can tell if an absorptive material is working or not by listening to the response of the room. you hear out whether you have the same resonances and mode problems with your ears - or whether the room has been balanced out and treated properly. If you know what to listen for, then its rather quite easy - you should try it sometime. Because thats what matters at the end of the day. So assuming a person is trained in what to hear and spot, and how to judge if a room is acoustically proper, at a certain point, quantifying everything down to audibly insignificant data becomes pointless. And also, as a result of test data that all these entry level people look at - the owens corning test data you guys all refer them to towards 703 - they then believe they need 703, and not realizing that 705 and 707 are the proper industry standard boards used in the real studios. So we have an example right there of test data misleading people - perhaps even faulty test data. who knows. Therefore, just in case the test data is faulty - this is why the ears are always the best measuring and testing tool (and it helps if the person is experienced with many different absorbtive materials and has been at it for a while.)

Its like music, many musicians can create amazing music without studying theory or notes, just like others can create acoustically amazing rooms without using the ETF or other testing programs or devices. Alot of experience and trial and error and simply knowing where to put things. The mirror trick is also a great one.

Originally Posted by T800

By the way - industrial and commercial grade acoustical panels use OC705 and OC707, and the flimsy OC703 boards are not for pro studio applications as you guys mistakenly believe. Please see Pilchner and Schoustal. Its all 6pcf 705 or even the 7pcf 707 boards.

First of all, I have little or no respect for people that claim to be able to acoustically treat a room (to high standard) without making measurements.

Secondly; all too often, I see people buying wool that has way too high flow resistivity for the intended purpose. Usually rigid stuff and unfortunately, this misconception is so widely spread that you might be correct in that it has become the “standard”. Too bad then, that the “standard” is resting on false promise. If you still do not believe that a relatively low FR is what you want in studio design (booth for insulation but especially absorption if not very thin absorbers but this is not common if proper studios and correctly treated), just check it up with any calculator using the Delany-Bazley or Miki model and please note that these are empirical models:
http://www.gearslutz.com/board/6863157-post6.html

I cannot speak of OC since I actually do not know the FR of this product (I’m in Europe) but when I give recommendation related to these things, I always just point to the importance of the FR value and to a freeware calculator (PAC).

[Glenn Kuras]

By the way - industrial and commercial grade acoustical panels use OC705 and OC707, and the flimsy OC703 boards are not for pro studio applications as you guys mistakenly believe. Please see Pilchner and Schoustal. Its all 6pcf 705 or even the 7pcf 707 boards.

We don't use OC at all, but 703 is used in million dollar studios every day. As a bass trap gets thicker it is actually a better choose. This is well documented, but you are right that when making thinner broad band traps 705 is better.

[EricF]

Originally Posted by T800

I prefer using my ear to determine which absorbers sound and perform better. Because in the end - that is the final gauge - so i skip right to it. I have a good feel for these kinds of things anyways.

Yeah. Don't let all that pesky math and test result stuff get in the way. Jens and Glenn are total noobs and have no idea what they're talking about.

[aackthpt]

Is this the return of The Wizard??

[Rod Gervais]

Originally Posted by T800

Sorry, "feel'" was the wrong word, i meant i have a good "ear" for these things. As do most people who have experimented alot in treating rooms.

I find myself curious......just how many studios have you experimented with?

You can tell if an absorptive material is working or not by listening to the response of the room. you hear out whether you have the same resonances and mode problems with your ears - or whether the room has been balanced out and treated properly. If you know what to listen for, then its rather quite easy - you should try it sometime. Because thats what matters at the end of the day. So assuming a person is trained in what to hear and spot, and how to judge if a room is acoustically proper, at a certain point, quantifying everything down to audibly insignificant data becomes pointless.

This is a very serious question - so please don't blow it off........

Would you explain to me just how it is that your ears can hear the depth of a null?

And just what level of sensitivity hear are we talking about - can you discern a 3dB variance? If not 3dB - just what exactly is your level of sensitivity?

I find it totally amazing that you're so much better than the group who you say design the only world class studios (that would be Pilchner and Schoustal) - they actually have to test their rooms the way the rest of us do...... perhaps you should apply for a job with them - you could save them a ton of money in room testing.......... bet they would pay you big bucks for that.

And also, as a result of test data that all these entry level people look at - the owens corning test data you guys all refer them to towards 703 - they then believe they need 703, and not realizing that 705 and 707 are the proper industry standard boards used in the real studios.

Just so I can keep this straight - you're saying that Galaxy - Avatar - Power Station NE (just to name a few) are NOT world class studios? I just ask because most people in the industry think they are - good that you're hanging around to straighten the rest of the world out.

So we have an example right there of test data misleading people - perhaps even faulty test data. who knows. Therefore, just in case the test data is faulty - this is why the ears are always the best measuring and testing tool (and it helps if the person is experienced with many different absorbtive materials and has been at it for a while.)

No, actually what we have here is a lack of knowledge misleading people - this even though you really do think you know what it's all about. You started here in this thread - and then moved on to another - in both cases spreading bad information - making claims that (on the face of them) you cannot back up with any data - simply with a claim of "I can tell it's right".

Its like music, many musicians can create amazing music without studying theory or notes, just like others can create acoustically amazing rooms without using the ETF or other testing programs or devices. Alot of experience and trial and error and simply knowing where to put things. The mirror trick is also a great one.

And just who is it that foots the bill for all of this trial and error?

All of these materials are expensive - so just pick up a pile of crap and start playing with it without even understanding the basics? And then when it doesn't work pick up a bunch more crap and start playing with it?

Listen up - there is a reason that people who want to build good rooms actually pay people like us (and this includes the company you apparently think are the only ones who know what they're doing) huge chunks of money to design their rooms and oversee the construction - and that's because what you believe to be real is in fact a fantasy........ if it was really as easy as you believe then we would all be out of business.......

For the rest of you folks......... I don't usually bother responding to posts this old - however - I have a real problem with finding something like this and ignoring it - this because there will eventually be some newbie visiting this place that will view it as "the word" if it isn't openly challenged.

Have a great day,

Rod

[jhbrandt]

+1 Great post Rod.

I concur wholeheartedly.
John