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Discussion Starter · #1 · (Edited)
Hello All,

I purchased some 2" wedge foam from Noble Product Line. Not only did I go cheap, I bought B stock as well. This was a 4'x6' sheet of 2" foam for $40 shipped. More here:

http://www.nobleproductline.com/2-Wedge-Style-Acoustic-Foam-B-Quality-p/wc2r.htm

After reading all of the not so hot information about Foam By Mail (FBM) and the testing Ethan Winer has done with Auralex and FBM I decided I would run some very basic tests. I tested by using an iPad 3 and AudioTool's FFT (hi-res RTA) with the built in speaker, noise generator, and mic. I was 4 inches from the wall for all tests with the back of the iPad facing the wall and ran the test for roughly 10 seconds using averaging. I know this device is not accurate, however it should show the relative differences.

As you can see in the picture below the panels are 2'x4' and covered in black muslin. I should mention that I tested two of the 2'x4' panels and did not test the superchunks made of solid rockwool that are also in the picture.

I believe based on the 3 tests shown below that the Auralex and Noble foam are much more similar than they are different.
Pic 1 Auralex,
Pic 2 Noble
Pic 3 Bare wall
I have REW if anyone has testing suggestions. Thanks!

Comments?
 

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Does that make either one of them good? Looks like neither did much of anything below 2kHz.

In all fairness, you need to look at thicker material, lower frequencies, and decay time, not just frequency response to draw valid conclusions Not saying I would recommend either one but just trying to be fair. I wouldn't expect much of any product that's only 1-2" thick to do a lot in the mid and bass.
 

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Discussion Starter · #3 ·
Does that make either one of them good? Looks like neither did much of anything below 2kHz.

In all fairness, you need to look at thicker material, lower frequencies, and decay time, not just frequency response to draw valid conclusions Not saying I would recommend either one but just trying to be fair. I wouldn't expect much of any product that's only 1-2" thick to do a lot in the mid and bass.
Mr. Pape, it's nice to have an authority on the subject. I have a few comments, and would expect you to correct me if I am wrong.

I believe that Auralex has been measured to be "effective" down to ~500 Hz. Obviously that term effective is up to each person's interpretation. I would consider an absorption coeffecient nearing 1.00 to be considered effective. For others, that may not be acceptable.
http://www.auralex.com/testdata/test/2wedge.pdf
http://www.realtraps.com/data.htm

My point was about the similarity of the two products.
If (that's a big if) one finds the Auralex panel acceptable, might they consider the Noble Product Line foam?

I have measured the result of my room response, waterfall plots, ETC, and the like, with and without all of the panels, and enjoy both the sound and measurements with them. However, I am not sure how to easily measure a single panel versus another. Ethan suggested speaking directly into the panel "Testing 1, 2, 3" on another forum where he is active. I tried this and the result was inconclusive. Therefore I made my crude test, which I also believe to be inconclusive. Both of which are far superior to a bare wall. Do you have suggestions for a slightly better crude test?

I have a few more first reflections to tame from my rear and side speakers requiring a significant amount of absorption, and I am on the fence if I should continue down the road of inexpensive foam or plunge into rigid fiberglass. My waterfall plots and RT60 would indicate that these first reflections are worst above 500Hz. Could I benefit from additional bass traps? Couldnt we all? I would rather build large super chunks made of rockwool for that and really dig down deep (64Hz is my problem spot). While taming the first reflections as cost effectively as possible.

Thank you for your comments and contributions here.
 

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Mr. Pape, it's nice to have an authority on the subject. I have a few comments, and would expect you to correct me if I am wrong.

I believe that Auralex has been measured to be "effective" down to ~500 Hz. Obviously that term effective is up to each person's interpretation. I would consider an absorption coeffecient nearing 1.00 to be considered effective. For others, that may not be acceptable.
http://www.auralex.com/testdata/test/2wedge.pdf
http://www.realtraps.com/data.htm

My point was about the similarity of the two products.
If (that's a big if) one finds the Auralex panel acceptable, might they consider the Noble Product Line foam?

I have measured the result of my room response, waterfall plots, ETC, and the like, with and without all of the panels, and enjoy both the sound and measurements with them. However, I am not sure how to easily measure a single panel versus another. Ethan suggested speaking directly into the panel "Testing 1, 2, 3" on another forum where he is active. I tried this and the result was inconclusive. Therefore I made my crude test, which I also believe to be inconclusive. Both of which are far superior to a bare wall. Do you have suggestions for a slightly better crude test?

I have a few more first reflections to tame from my rear and side speakers requiring a significant amount of absorption, and I am on the fence if I should continue down the road of inexpensive foam or plunge into rigid fiberglass. My waterfall plots and RT60 would indicate that these first reflections are worst above 500Hz. Could I benefit from additional bass traps? Couldnt we all? I would rather build large super chunks made of rockwool for that and really dig down deep (64Hz is my problem spot). While taming the first reflections as cost effectively as possible.

Thank you for your comments and contributions here.

From Auralex test data:

The overall dimensions of the specimen as measured were 2.44 m (96 in.) wide
by 2.74 m (108 in.)


It might go down to 500hz with a piece that big, but the panel size most will use will not render this specification.

Always read the small print.
 

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Discussion Starter · #5 ·
I believe that is normal for a test lab to use a large sample.
I don't believe a larger coverage area will effect the frequency response if the thickness is not changed. Those that have hired labs may be able to chime in.
 

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That's correct. For a proper lab test, there is a minimum sample size required in terms of square footage.

Bryan
 

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The important fact isnt that tests have large sample sizes, its that the size of the panel your using must be large enough to capture the wavelength of the frequency your trying to treat.

1k = 13.5"
500hz = 27"
300hz = 45"
250hz = 54"

Most audio folks say you should absorb evenly down to 250-300hz. Obviously, a panel 24" wide isnt going to get the job done even if the published figures say it will.

Even if Auralex does absorb evenly down to 500hz, which I doubt given ive owned and tested the stuff, this isnt the frequency you should be aiming for.
 

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Actually for every room volume and usage has a target decay time curve that goes all the way down to around 60hz.
 

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Actually for every room volume and usage has a target decay time curve that goes all the way down to around 60hz.
I was speaking of the kind of targets used for 1st reflection points. Certainly when you consider the overall picture, bass trapping must deal with whats below 250hz, and coinciding with that are decay times, true.
 

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Yes - and you'll have SBIR problems from side and ceiling reflections that can go down into the low 100's.

Bryan
 

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Discussion Starter · #11 · (Edited)
The point of this thread was to point out the difference, or lack there of, between Auralex and Noble. We've strayed a bit, which is fine. It looks like the preferred discussion is about the low frequency capabilities of foam, or lack there of.

My goal is to treat my room as cost effectively as possible.

Reflections
Therefore I've used affordable 2" foam that is very effective from 400Hz on up and still helpful from 300Hz - 400Hz. This is not broadband absorption, nor was it ever intended to be. However it is effective at handling reflections.
Bass Trapping
I'm using super-chunk bass traps full of rock wool. Of course these are placed in the corners where bass as high as 400Hz builds up. I still have 3 more to add, but the two I have in place are working well. I have 7 corners available in total.

This causes me to wonder why so many here discount foam as worthless due to its lack of usefulness at 250Hz. Bass traps that are full of rock wool or pink fluffy are great at the bottom end. Why concern yourself with frequencies below 300Hz when choosing first reflection panels on a budget? It seems I'd rather use two specific cost effective treatments to do their specific duty, and add more of each to taste and to maintain a balanced decay.

Are some rooms in need of more trapping than all available corners, so broadband absorption is desired all over?
 

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The point of this thread was to point out the difference, or lack there of, between Auralex and Noble. We've strayed a bit, which is fine. It looks like the preferred discussion is about the low frequency capabilities of foam, or lack there of.
Neither product is recommended.


My goal is to treat my room as cost effectively as possible.
2" foam isnt effective IMO

Reflections
Therefore I've used affordable 2" foam that is very effective from 400Hz on up and still helpful from 300Hz -
I cant agree with this statement.


This causes me to wonder why so many here discount foam as worthless due to its lack of usefulness at 250Hz. Bass traps that are full of rock wool or pink fluffy are great at the bottom end. Why concern yourself with frequencies below 300Hz when choosing first reflection panels on a budget? It seems I'd rather use two specific cost effective treatments to do their specific duty, and add more of each to taste and to maintain a balanced decay.
Most discount foam as worthless because it absorbs unevenly beginning at 600hz or higher. Your claim that its effective at 400hz is not shared by most.



Are some rooms in need of more trapping than all available corners, so broadband absorption is desired all over?
Bass trapping in all the corners is the very beginning or minimum, not the finished product or complete treatment necessary for most rooms.
 

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If you consider 4-500Hz lower limit as effective at treating reflections, then your assertions are true. That said, damaging frequency response problems from side wall reflections can be down in the lower 100Hz range. This requires more thickness, more effectiveness, and larger surface area to address.

Bryan
 

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Again, it all depends on how you want to look at reflections. From an SBIR stand point (which are indeed reflections) it will go much lower as I identified. Purely for mid and high frequency reflections and comb filtering, sure.

Just as an aside, I used to moderate the MusicPlayer acoustics forum for Ethan before I started working for GIK.

Bryan
 

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Discussion Starter · #16 ·
Again, it all depends on how you want to look at reflections. From an SBIR stand point (which are indeed reflections) it will go much lower as I identified. Purely for mid and high frequency reflections and comb filtering, sure.

Just as an aside, I used to moderate the MusicPlayer acoustics forum for Ethan before I started working for GIK.

Bryan
Very cool. Thanks for the update and explanation. I'll be ordering some rock wool to insert into my panels as a replacement for the foam.
 

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4" panels work pretty well for side walls or even thicker if you can tolerate it. Don't get hung up on density - 3-4lb will be just fine. No sense in spending money for the 8lb.

Bryan
 
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