For those contemplating such devices, take a look at the "non-linear absorption characteristics" that such devices introduce into your listening room. While most people install these thinking that they are going to help the sonics out, all they do is create even greater irregularities in terms of what you hear. Chances are, not only do you have a screwed up room to begin with, you've now introduced even more irregularities into the equation as frequency changes.
Take a gander at this and then come back and read the rest of this post. For most installations, you'll want to look at the green line on the chart.
RPG Pro Foam Absorption coefficientsIf any of you saw that and thought that it looked like a mess in terms of frequency response, think again as it is even worse than what you think. Rather than providing you with room acoustics that would resemble what is provided on that chart, you have to flip it upside down to see what the in-room response would be like. This is due to the fact that they are showing you how much absorption takes place at a given frequency, not the actual "frequency response" that you would hear.
Once you look at it upside down, you can see that these "acoustic treatments" create a very big "suck-out" in the 500 Hz to 1250 Hz range and reduce all frequencies above 1250 Hz to a very noticeable extent. Most everything below appr 400-500 Hz passes through untouched.
As such, the very "life-blood" aka midrange of the music is damped / absorbed and all the artifacts of treble reproduction ( air, spaciousness, harmonic structure ) are reduced. On top of this, the rate of attenuation is NOT linear across the band so you end up with peaks, valleys and ripples as the signal is spread out across various frequencies. Since bass is not affected in the least, the warmth region and bottom end remain consistent with what you had before installing these devices, but now everything sounds thicker, more distant with less "sparkle" up top. Tonal balance has shifted drastically and NOT in a linear manner.
As such, the end result is that you've created another form of acoustic non-linearity in your room and paid $150 for $5 worth of "flimsy molded foam". If you keep spending at this rate and buying devices like this with no real plan of attack or understanding of what you are trying to achieve, your system should be completely unlistenable in no time flat.
Rather than throw your money away on J-U-N-K like that, invest in a book or two by
F. Alton Everest and look at your room like you would your system i.e. as a WHOLE. Once you have a better understanding of what is going on, visiting such sites as those put together by
Jon Risch for DIY room treatments and acoustic engineers such as
Rives Audio will give you the ability to do things yourself and / or get professional help to diagnose what you really need to do. Rather than throwing money away in a random fashion and creating new problems to deal with, you can get to the root of the problem much simpler, faster and cheaper without as many drawbacks or side-effects taking place along the way.
I hope this helps some of you to realize that "audiophile approved" items are not necessarily "good" and that, many times, you can learn / do / build something better yourself for a LOT less money. As i've said before, there IS a place for "specs". That is, so long as one knows how to interpret them AND the manufacturer has presented them in an honest fashion. Sean
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PS... I think that Agon member
"Tom_nice" has various plans for bass traps, room treatments, etc... that also work quite well. You might want to try contacting him for further info. Hopefully he doesn't mind me doing this, as he's offered th same thing himself several times in other room acoustic related threads. I also know that Tom is a "fan" of Everest's books too, as they are about the best that you'll find on the subject for the amount of money spent.
