Room treatment for rear firing soundwaves for CLXs & MLs

[peacefulcargo]

Hi What do you recommend to place on a rear wall with the speakers one metre in front. Acoustic foam like the attached ? or nothing. Does it improve the sound ? This is a new area to me . Found this site which seems good https://www.customaudiodirect.co.uk/swell-acoustic-foam

 

[GW1800]

I think you mean the front wall or the wall behind your CLX which are 1 M front it right? I have a very similar situation but a bit closer. I was skeptical what treatments would do. My dealer loaned me some old ones and I was impressed. I ended up with a RPG Bad Arc panels 3’x5’ directly behind the speakers. They absorb and deflect at the same time plus they have an arc to the outer surface not flat. All I can say is it’s a game changer and I consider a must do. Ideally you should be at least 4’ or more is better from the front wall.

Also I see we have similar tastes in cables. Nice!

 

[Brad225]

I have the entire wall covered with absorption panels, as is the entire room. All of the panels are 2" Owens 705 fiberglass with either FRK or craft paper over the fiberglass and under the Gulf of Maine fabric covering them. The purpose of the FRK or craft paper is to reflect some of the higher frequencies while absorbing the bass.
The only exception to that is the panels directly behind the speakers that don't have FRK or craft paper to absorb the entire rear wave. That has always been my preference with any stats.

Recently I tried a small amount of diffusion on top on the absorption panels behind speakers and smaller yet in the center of the wall between the 2 panels. All 3 of the diffusion panels are vertically centered on the speaker panel itself. I can move them side to side and up and down with it having an effect on the image and tone.

I must say I was quite surprised that I liked what changed when I tried them. YMMV

To answer your question, I have not used foam so I don't have a good answer for you. I would think if the provide documentation of its ability to absorb it would probably work. $.02

 

[peacefulcargo]

Thank you both, great insight.

 

[JonFo]

Foam only absorbs a limited range and therefore will skew the frequency balance of the rear wave. So it's not recommended, I know, been there, done that, didn't work.
Best to do what Brad and GW1800 recommend, and use either commercial products that are broad-range absorbers (or abfusors if you want to preserve some reflected, yet diffused energy).

I recommend what Brad did, and build your own treatments customized to your room and speakers. It does not have to be complex to build, as you can just build out a frame over the wall with fabric insertion tracks (like I used on my sidewall treatments) and then just stack whatever OC 705 batts or diffusors you want and they will be hidden by the Guilford of Maine acoustical fabric put into the tracks.

I also recommend that the absorption placed directly in the path of the rear of the panel have zero reflective elements, pure absorption only. Otherwise, comb-filtering occurs. If you want to add some diffusion later, do ensure it redirects the sounds away from returning back through the panel.

 

[RDC]

Great advice as always from the guys above. But every room is different and in my situation I chose to opt for a row of 30x94" 3.5" thick absorption panels behind and above the main listening position and a row of 24x94" diffusers (vertical and horizontal slots) behind the MLP at ear height. Both are 40" behind the MLP.

For the front wall I experimented with absorption panels directly or in between the loudspeakers. Absorption dulled the music too much for my liking. So I ended up with using only diffusion panels behind the speakers. Horizontal slots, as vertical placement made the center soundstage to wide and out of focus. It kept the energy I liked and at the same time the room sounds larger than without diffusion, i.e. expanded soundstage.

In my experience it seems that experimentation is the best thing to do, and the most fun, as it is very surprising what (a little) absorption of diffusion can do in a room. All my panels are DIY, apart from the cheap ready-made diffusion panels.

 

[sleepysurf]

Another "creative" solution for ameliorating the rear wave, without adding any room treatments whatsoever, is to position the speakers with greater "toe-in" than typically recommended. That will cause the rear wave to reflect at > 30 degrees off the front wall, thereby minimizing interference with the front wave. That can also widen the sweet spot, and improve off-axis imaging, albeit giving up a little in overall detail/image precision. I've been experimenting with this lately, and feel the benefit (at least in my setup) outweighs any negatives.

 

[peacefulcargo]

Another "creative" solution for ameliorating the rear wave, without adding any room treatments whatsoever, is to position the speakers with greater "toe-in" than typically recommended. That will cause the rear wave to reflect at > 30 degrees off the front wall, thereby minimizing interference with the front wave. That can also widen the sweet spot, and improve off-axis imaging, albeit giving up a little in overall detail/image precision. I've been experimenting with this lately, and feel the benefit (at least in my setup) outweighs any negatives.

I actually was wondering about this . I also came across this site https://www.customaudiodesigns.co.uk/rpg-harmonix-diffuser.htm