Room Acoustics - Absorption Panels Behind ML's

[Leporello]

acoustic treatments should ideally be a solution to a specific problem. Will this IKEA thing do, what it advertises? Probably yes.

will it make your system sound better? Maybe yes, maybe not.

A specific problem could be a strong specular reflection from the surface behind the speaker ("front wall") in which case, it might help. What would be ideal, in many situations, would be to stochastically diffuse the rear wave, such as with a QRD. But those tend to be pricey, and don't fit all decors.

Any sound that radiates from the speaker, bounces off a surface and reaches the listener's ears a short time after the direct wave is bad for stereo imaging. As Denis points out, stat panels are good for suppressing that kind of early reflections from the floor and side walls. But the fact that you have a nearly coherent wave coming from both the front and rear of the panel can be problematic when reflected from surfaces directly behind the speaker, or directly behind the listener. Frequency response correction (Audyssey, etc.) will not help. I agree that you don't want to try to "correct" the panels' frequency response. Below 100hz, bring it on.

If you succeeded in completely absorbing the wave coming from the rear of the speaker, it may be more "objectively right" in terms of lessening indirect sounds and standing wave modes, but tends to make the speakers sound dead. If they're more than the recommended 3' from the "front wall" (confusing term IMO) the reflections are no longer "early reflections" and not problematic in terms of soundstage.

Small midrange frequency wiggles are not so objectionable subjectively. Trying to correct them e.g. with Audyssey may cause more problems than it solves.

 

[Mirolab]

My SL3 panels are 28" from the front wall, and that is not really ideal. You can see that I have about 3" thick absorption behind the speakers, which i find beneficial to whatever speakers I am using. Without the absorptions, the SL3s do sound more open, but also a bit phasey and unfocused. I think the ideal solution would be to have combination diffusion+absorption, but i've been very happy with this setup for many years. The top 12" of my panels do not have absorption directly behind... so 'some' of the rear wave does get bounced off the wall.

Please don't criticize my idle 801's in the corners. Yes, the system does sound better when they are not there.

 

[Tmort]

A lot depends upon your room, if you have a large enough space and can get the stats out from the from the walls sufficiently then absorption on the front wall may not be completely necessary…but like many, my space constraints put the stats closer to the front and side walls than ideal. In this case front wall and first reflection sidewall absorption delivered awesome results.
GIK Acoustics 244 or 242 panels work very nicely. Built well, some nice fabric options and not terribly pricey.
Sidewall panels not in this image.

 

[kach22i]

A lot depends upon your room, if you have a large enough space and can get the stats out from the from the walls sufficiently then absorption on the front wall may not be completely necessary…but like many, my space constraints put the stats closer to the front and side walls than ideal. In this case front wall and first reflection sidewall absorption delivered awesome results.
GIK Acoustics 244 or 242 panels work very nicely. Built well, some nice fabric options and not terribly pricey.
Sidewall panels not in this image.

In my current room I started similar to where you are, and ended up completely blocking the window up with old acoustic ceiling tiles and foam rubber flooring (covered in felt). Then I took my tall equipment rack out, firstly by using an older low rack center stage, then again moving the equipment to a side wall (below ear level). Then I moved the equipment even further back along the side wall to avoid the first reflection point. And then treated the first reflection points on the sides and then the ceiling (floor was already double carpeted).

In short, Martin Logan's don't like company and want all the front stage space to themselves - the selfish gimps.

EDIT:

There is a quote in post 2,177 which is curious, maybe windows are not the devil?

https://whatsbestforum.com/threads/ron’s-new-system.35810/page-109

The glass between and behind the speakers is a nice thing to have.

The video in link above (post 2,172) does show a very open front wall/front stage and is a professional installation.