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How to "mount" acoustic foam ?

My main system is in my partially unfinished basement.
While I have finished the ceiling and have nice floors / rugs - I do like the industrial / rough look of the concrete walls....I just finished painting them but don't want to install any sheetrock / finishing material.
Instead I want to buy acoustic foam (2inch depth squares) and mount them to the walls - front / back and sides
And here are my questions:
1. Should I just use glue and apply the foam squares directly to the wall ?
 - IF YES - what glue should I use? I know there is the special construction glue for laying floors etc..... I now they sell it also for concrete and stone application - sold in caulk like tubes 
2. Should I first apply the foam  to a plywood / wood and anchor that to the floors ?
 - IF YES - I would imagine a few concerns: 
-  Will that wooden structure bring about sound resonance that I am actually trying to control ? (Wood isn't as bad as concrete but still....) 
-  Will I have to add a layer of caulk or similar filler between the wall and  the wooden panel? Obviously the concrete walls are not super smooth so the wood panels will not be in perfect and uniform contact. They will be held rigid with the specialty screws drilled into the walls....but still 
- What type of panels should I use....I was thinking anything from very thin cardboard like materials (to minimize any resonance from wood) to 1/2 inch plywood for rigidity.
IN SUMMARY: 

 I am leaning for the 1/8inch thick boards - In my mind it would provide smooth surface to mount the foam onto, retain the acoustic profile of the foam, and then just hold it all in place up on the wall with 4 bolts (each corner)

Anyhow....Any other tips and advice about proper installation would be appreciated.

Thank you!! 
ether
geoffkait's avatar
geoffkait
23,365 posts
 
gdhal
“Moreover, the overwhelming majority of music that I listen to (and collect) is Grateful Dead http://halr.x10.mx/shows.html For those familiar with their music, I’m confident they would agree that (a) much of their live recordings are excellent quality sound boards and (b) more so than any other band, they often sound fantastic irrespective of the who, what, where, when, why and how of the playback mechanism.”

Anyone else feel just a little uncomfortable about that paragraph? Not the Grateful Dead part -well, maybe a little 🤡 -but that the playback system/room doesn’t really matter? Whoa! This appears to be a perfect example of what I like to call Stove Piping, which is what happens when audiophiles work in a vacuum of sorts, on concentrate on a relatively narrow range of music or whatever and develop systems and concepts in a (limited) “stovepipe” fashion, without the benefit of shared knowledge and experiences. No wonder many audiophiles have such widely diverse opinions and conclusions about just about everything.
jafant
18,997 posts
 
Laughing....
gdhal's avatar
gdhal
1,641 posts
 
Laughing....
@jafant 

Unclear to me me what you find humorous, nevertheless, in the case of my posts, the information I've provided herein is true.
noromance's avatar
noromance
9,574 posts
 
Per @slaw and @geoffkait , I removed the 4 x 24x48x2" acoustic foams I installed a few weeks ago. When first installed, there appeared to be an improvement in control of the music with better depth. However, after some further listening tests, I have to agree. While the sound is a little "wilder", it is freer. The music breathes, is louder, more dynamic. The foam basically killed the music. I have found the same effect with some mats. Damping can be deleterious. 

geoffkait's avatar
geoffkait
23,365 posts
 

noromance
Per @slaw and @geoffkait , I removed the 4 x 24x48x2" acoustic foams I installed a few weeks ago. When first installed, there appeared to be an improvement in control of the music with better depth. However, after some further listening tests, I have to agree. While the sound is a little "wilder", it is freer. The music breathes, is louder, more dynamic. The foam basically killed the music. I have found the same effect with some mats. Damping can be deleterious.

>>>>>Thanks for posting your results. What I think happens is that the foam changes the nature of the acoustic wave traveling through it. Obviously the acoustic wave actually travels though the foam twice, once through the foam to the wall then back out again to the air. So any effect the foam has on the acoustic wave is doubled. As I intimated earlier ANY foam in the room has a similar deleterious effect on the sound, for example the IKEA Poang Chair that has foam seats and backing. Just when you thought it was safe to go back into the water. 🦈 Effective, non-interfering acoustic solutions such as Michael Green Echo Tunes and panels, Tube Traps, Skyline diffusers and others do not (rpt not) contain foam.

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