Question: Sound Treatment behind the Listener?

I have treated the 1st and 2nd reflection points and I have sound panels between my speakers. I also have tube traps in all 4 corners, but I am not sure what (if any) should be done with the wall behind the listener.

That wall presently has a DIY rack system that holds about 5000-6000 cd’s. I believe it helps scatter the sound. But I’m not sure if that is the right approach.

So, what are you guys using on that wall? Diffusion, Absorbtion, Reflection? Anything else?

I would appreciate your thoughts.



You think I will still need the 6" absorption panels even if I use the Stillpoints Aperture’s?

Here is what Stillpoints Aperture Panels claim:

"The Stillpoints Aperture is the only acoustical product that will give you both absorption and diffusion at the first reflection points of a system. And you want both!"

  • The Aperture’s unique trapping system captures an area of waveform much broader than its small surface area would suggest.
  • The Aperture can be used to trap waveforms either facing the wall or, facing away from the wall.
  • The Aperture effectively increases soundstage width and depth. This is especially true for smaller rooms. (See the Michael Fremer review in Stereophile, Feb 2016.)
  • The Aperture will increase the dimensional perspective of the image structure.
  • The Aperture focuses music and voice without room boundary.


I believe if you place one Stillpoint Aperture II on each side of a 6" thick absorption panel that is set directly behind your listening seat on the back wall you will be set perfectly and won't notice the CD racks as being missing. Mount them so the centers are in line with your ears. The sound probably will be even better. This assumes you have those bass traps in the corners of the back wall.

Thank you that is very good advice.

You are right on. I like the sound I have but am concerned that when I remove the Cd's/rack the sound may change.

What about Stillpoints Aperture ll's. I already have 6 in the room, would a couple more of them behind me work well?


Sounds like you have a lovely space and you have treated it nicely. Do not over dampen the room.

Do you like the sound you are hearing? Do you believe there is an issue or are you thinking that if you remove your racks you just might create one?

Diffusion is already working on the rear wall due to the CD rack so I believe that is the direction to start with.

I would suggest a 6” thick 2x4 panel directly behind you flanked with two panels specifically designed for diffusion. Diffusion is best when they are placed approximately 8 feet from the listener which it appears you will have slightly more so they will work great there.

If I understand correctly the back corners have bass traps all ready so you should be good after the three panels are installed.

Enjoy and don’t over think this since it appears you already have a very nicely treated room.

Live End Dead End treatment works great in a recording studio when you are near field. I have found in my space if the front wall is too dead so is the music. I have bass traps in the from corners, absorption in the middle and diffuser panels directly behind the speakers. Works very well. My speakers are 55 inches out from the front wall measured from the front of the speaker and the speakers are rear ported so the diffuser panel scatters the sound from the port. Just one way to handle a front wall, there are many others, but the key is don’t over deaden the room.

It is a amazing that turning the ASC tube traps how it can affect the center image.


Ozzy, you may want to measure your room. If you don't have any WAF considerations and can treat as you please I would measure. 

My GIK rep had a great point which is that, although he rec that I measure my room to see what I'm working with - because it is the LR and I'm WAF limited, that it is less important. This is because even if the measurements call for certain treatments, if they don't look like they will look good in our LR, I'm not buying it.

That said, I'm not tech savy at all and every time I start watching a youtube vid on REW my brain turns to mush. Also, I don't have streaming so I don't have a good way to hook up my laptop to my integrated amp (Primaluna). Someday I'll make the effort when I have more time, but I don't now - but again, it won't make much difference anyway since I'm for the most part limited to panels with Guliford fabric (and not ones with diffusion over top).

Art Noxon is the founder of ASC (Acoustical Sciences Corporation).

I learned a lot by reading his technical papers.


Thank you, you are too kind.

BTW, my Westie is named Westy. He really loves to lay between the speakers in the sweet spot.

The cd’s are arranged irregularly by the artist. Some groupings have many cd’s, some not so many and there are spaces between artists.

I have the speakers about a 1/3 out from the wall and I sit about 1/3 back from the speakers and then the chair is also 1/3 back from the rear wall. Although, that was mostly just a starting point until I dialed everything in.

This whole thought occurred to me because I really don’t listen to the cd’s anymore. so, I was wondering what to do with that wall if I removed them. I appreciate the very good suggestions that have been made by the community.


I read with great interest your situation. I also have a lumin x1. The footings are interesting

I think all the CDs should be arranged irregularly to improve diffuser capabilities. Do you have lots of sound treatment stuff in the room. I would remove it all and see what the furniture in the room is doing which is extremely important and always never really discussed.

You sit really far from the back wall which is ideal, no doubt the speakers are pulled forward.

No doubt you’re Westie offers invaluable diffuser and absorption benefits.

Don’t overthink it it’s not rocket science

Love your system

Since you are familiar with ASC tube traps, take a look at Art Noxon’s suggestions.

I believe a couple tube traps with silver buttons facing the listener is what he would recommend behind your listening position. 

I have a 48x56" Rockwool sound absorption panel installed into the wall behind my listening chair. Covered by a print of the Grand Tetons taken at 10,000' . 

In another room I was forced to vacate I had a closet the length of the wall behind. I put absorption on back wall of it and removed the doors. That extended the size of the room and the distance behind the listening chair. It was probably the best sounding dedicated room I have used.

I do have 4- 20" ASC tube traps in the corners. I also have 7 Stillpoint Aperture 2's.

So, do I really need to absorb the bass frequencies further?



Thanks. Good info. I think you are mixing up me and the OP though, just fyi. My rear wall has 4 ASC sound planks on it directly behind my seat (6" apart) and is open on one side to the rest of the house and the other is curretnly (!) drywall. I'm discussing w/ GIK about that now and a few other things. He is suggesting thick bass absorbsion with deflection on the rear wall also. One issue is that I can't go more than 4" since that is also essentialy the wall to the hallway to our bedroom and can't stick out too much.

The good part is my room is very close I think to where I want it - just need to tame some highs.

I honestly have no idea.  The Podiums maybe help with vibrations, but I don't think it would help with bass?  But I am not an expert.

If you think the bass sounds good from where you sit, I would just not worry about it.  In the end, do you enjoy listening to your system?  That's all that matters.  

You may not need any (or you may need a lot?) of extra bass absorption.  It really has to do with your room geometry, where the speakers are placed, and where you sit.  The guy from Acoustic Insider always suggested figuring out where the best place to put your speakers and the best place to sit is the first step in "treating" your room and that is free.  

If you are sitting in a null, you won't hear much bass and if you are sitting in a node, the bass may sound too loud or weird, so you'd move your seat up or back to see if that helps.

Your original questions was about if you need to do anything behind your listening position.  The challenge with your CD wall is that it could be very reflective and late reflections from that back wall could cause some issues.  If it sounds good to you right now, again I wouldn't worry.  If you want to experiment, try something behind your listening area that is not super expensive (couch cushions?  Thick blankets?  I don't know....) and, if you feel it helps, then consider purchasing or making something more permanent.   

I have a window behind my seat (about 5 feet behind me) and I have two 4" panels on stands that I just put in front of the windows.  To me, it helped a LOT.  It was probably one of two room treatment things that made me go "yeah, I can tell a difference".  But that was when I had no other treatments up at all.  You already have a room that is treated so your experience may be different.  

@charliech , do you think having Townshend Podiums would reduce the need for so much bass absorbsion? I still need to measure my room but when walk around the room I don't sense that much bass pretty much anywhere. That said, I still feel it in my listening chair when rocking out.....which is a good thing for ....for me anyway.

One of the things that I consistently hear in my research on acoustic treatments is that you can never have too much bass absorption. The problem is that you need really thick panels to get into the lower frequencies. If you use thinner panels, they will just absorb the higher frequencies (which has its place in making a room less reverberant or maybe comb filtering) but won’t help you with bass nodes or standing waves.

Even if you get thick absorption panels. they still absorb the top end so the theory is that you should just have the thickest absorption panels you can so that you get as much bass absorption as possible.

So if you decide not to get the Alpha 6s, try to make sure you make your panels as thick as you can. The Alpha 6s are six inches in depth with a scatter plate so the theory is that they would absorb the lower frequencies while providing diffusion for the upper frequencies.

And, in my experience, it’s so hard to tell. I mean, while I get controlling excessive reverb and reflections makes total sense on paper, there are so many options and so many people (including me!) who just repeat what they’ve heard without direct scientific experience it’s frustrating. But you have time. And it never hurts to try the free or cheap route and work your way up to more expensive things.

Good luck on this journey!

Thank you, I will check out those sites.

It sounds like GIK wants me to get 6 of the Alpha 6's. I'm not sure if $1500 would better the sound that I have now with the cd rack.

I may try some convoluted foam I have behind me first just to see if absorption is where I wanna go.


I have found the Acoustic Insider channel on YouTube to be a good source of information around treating your room.  He mostly discusses treatment for small home studios, but the theory still applies to a listening room.  

As far as I can tell, he's not selling anything.  He does reference a document you can download, and I have no idea if he charges for it or if that is a gateway to purchase other stuff, but I've never looked into that.

Thanks Vinyl Shadow for the info.

I'm getting some advice from GIK but also just started a dialogue with Jeff at HD Acoustics who I found when searching here. It won't be free but it will (should?) be unbiased and sounds like he knows what he is talking about....because I don't w/ acoustic treatment on the rear wall.

I use Rockwool @ 35Kg per M3 floor to ceiling in height as a Absorption Room Corner conditioners. Directly behind and spanning between the Speakers I use a Diffusion Panel.

Each Side Wall has a diffusion pane.

The Rear Wall has a Aborption and Diffusion Panel set at a height of the listeners ears.

The sound is managed in a manner that has improved attraction with these measures in place.

Would it be identified as a accurate treatment using tools the can measure room modes is an unknown for me. 


I'm not sure how many of the Alpha 6a's would need to be acquired. 3 of them with shipping is $763.


@ozzy  makes sense I think. You have a decent size room so they’re recommending abfusors.
FWIW, for my room, which is smaller, Mike recommended absorbers on the sides for early reflections and tri traps with range limiter in corners behind speakers. 

Got a reply from GIK. I need more info.

"OK, yeah that's a fair amount of space to work with. It will really come down to tolerance of thick panels and of course budget. If you can fill the entire wall with sound blocks that will work very well but that's a bit of a space commitment. 

If not getting Alpha 6As for that wall will help quite a bit still, and take up less space. 

We can also mix things up a bit, using Range Limited bass traps low near the floor and high near the ceiling, with the Diffusors (Alphas or others) in the middle at ear level."


People often seek to apply a solution when they don't know what the problem is. Diffusion and absorption each help resolve different issues applying the wrong one makes them worse. 

@ozzy Give GIK a few days. Their recommendation for my room was pretty accurate. 


How many of the GIK 6A Alpha diffusor/absorbers did you use?

I haven’t heard back from GIK yet, but Stillpoint’s says behind the listener treatment is not really necessary.


BTW, the cd rack has many spots where there are few/none cd’s which creates alot of voids etc., in a random manner.



I have open book shelves on my back wall. They hold my technical books and years worth of audio magazines. Also a few diffuser/absorption panels and record cabinets.This has worked very well for me. I will add 2 bass tube traps soon. At the moment I prefer diffusion on my back wall. I’m 99% done with my room, not sure when I’ll get to the last 1%.

My head is 6 feet from back wall.

Maybe repositioning your CD’s in a random pattern might help? 6000 CD’s my goodness. Good for you.

Joe Nies

The best situation is to have no wall behind the listener. An open concept situation open to the rest of the house. The rear is then open between various rooms. This keeps reflections as late as possible and fractured as much as possible. 

@ozzy I'd be curious to hear what GIK says. That's a great service they provide - it was somewhat of an education to me in terms of the information they provided (and why). 

With approximately 8' behind you to the wall, the sound level is only attenuating 3.52dB, plus whatever the absorption coefficient of the building materials (ie CD cases are which is probably very low), and another 3.52dB attenuation on the reflection. I do not believe that is near enough. I would be shooting for no less than 10dB if not 15dB. The only options are increasing the distance (which is probably not an option), or adding sound absorption material0, which can achieve that.

There is a rule-of-thumb (a formula in acoustical engineering terms) for how far one must be from the wall behind the listening position when using diffusion rather than absorption. I didn’t bother to memorize it, as it told me I couldn’t use diffusion on that wall, my currently situation requiring me to sit too close to be able to do so. I'll bet a Google search will lead one to the answer.

I ended up going with GIK 6A Alpha diffusor/absorbers to go behind my listening position. Granted, my room constraints necessitated something that would work relatively nearfield which these do. Highly recommend these.

Well, I submitted the form to GIK. Before being able to submit the form, I must say the constant need for showing that I am not a robot is annoying. Especially so for the GIK website. Why is that necessary?


That youtube vid posted earlier is excellent. I'm thinking about ordering  2D / GIK polys to put next to (new and larger) GIK 242 panels on my side walls. 

I just need to take a smidge of treble energy out of the room - not much but some - well quite a bit for some recordings but none to very little on others. Resisting buying an EQ.

Perfect, thanks. I'm thinking about moving my 242s to the rear wall but they don't have scatter plates - maybe I can buy those sep and then pull the staples out of the fabric and put those in and restaple. I'd probably make a big mess of things though.


I put up 3 square 242 Acoustic Panels With Scatter Plate (+$30)
Pure White Fabric (standard) to better blend into the white wall.

They are about 18" above and behind my head evenly spread out with about 2" in between them.


Also, the ceiling in the room has acoustic tiling glued and stapled over the drywall and there is 6" insulation in the jousts. There is no slap echo at the back of the room.

I was ok with the sound with the Cd’s/rack combo, just thinking of removing it now that I don’t play the CD’s.

I have already in the room Stillpoint Aperture 2’s at the 1st and 2nd and center points, perhaps adding a couple more of these in the back? I also will check out the GIK and see what suggestions that adds.



Timely thread as I'm looking into this as well - absorbsion and/or deflection on the rear wall. @vinylshadow  , which GIK panels did you put up? Thanks.

I did reach out to Mike at GIK. Sent him pics of my listening room. 

He suggested, and I bought, 3 acoustic panels to go on the wall up and behind my listening position. Which was on a couch with a wall right behind it. 

@ozzy why not reach out to GIK Acoustics

I’m working with Mike Major to finalize everything I need for my room and I find Mike to be very knowledgeable. Provide your room dimensions and photos and see what they say. 

You will get some reflection from the back wall but it will be low intensity as those waves will have travelled some 20 feet before they reach you.

Being of a practical disposition, I suggest you hang some heavy blankets on the wall behind you and listen to see how the presentation has changed and whether you like it.  If that may be too much damping try it with thin cotton sheets.  You will be able to gauge what is required and what suits your tastes.



How you treat your room is somewhat based on what type of speakers you have, monopole, dipole, omni. For example, a “dead” front wall is not ideal for dipoles. 
To your OP, we typically suggest wide-band absorption at the middle of the back wall about 4’ wide (maybe wider) with diffusers flanking left and right. 

I found In my rectangular room 12" of the wall and 12" of the ceiling full length of the rear wall and corners with absorption panels sounds the best. Like yours, my rear wall also has household objects that act as diffusion. +1 curiousjim... the clap method was how I arrived at my room correction. My system is very lively and this final treatment went a long way in taming Klipsch Heritage speakers at the higher volumes I prefer. Good luck.


When you stand in the back of your room do you  hear any echo? Clap your hands, can you hear a reflection? If you hear anything then yes, some absorption and maybe something in the top corners as well. 

Ozzy, Live end/dead end is a credible notion for set up. Speakers on dead end. listeners chair on live end. This has been around for years. Obviously how well it works depends on your room and how its executed.

For OP, if you feel you must, I'd recommend diffusors on the wall behind you, but personally I think your CD storage if they are spaced irregularly would be better than a flat surface and all you need unless you are pretty anal.  Spend some time with experiments  and see what you can actually hear as opposed to 'theories'. For example take down your CD's, what to your hear? Place a heavy wool blanket on the wall, what do you hear? As Ozzy suggested, think live end/dead end and experiment with deadening some, or a lot, of the rear and side walls relative to speaker placement. FWIW I use room furnishings to solve reflection problems not only because they look better (to me of course) but they make reflections less uniform, which I think is good, but I realize others may disagree and want to have identical reflections thinking that they will increase depth of image, etc.  That said, speaker and chair set up can go a long way in solving a lot of 'room' issues. For example, bass issues, I see folks trying to kill excess bass with corner traps when the problem is that the listener chair is in a bass node and all they have to do is move the chair a tad (out of the node) or that they measure bass in the corners where it always dwells and conclude that by killing this bass (which they can't do by using domestic bass traps). I guess the message is to solve actual, extant, problems, not theoretical ones. Have fun but take your time. :-)