[Housteau]

Lets first assume that we are using the speakers firing into the longer length of a room and the listeners seat is away from the rear wall 7-9 feet or so, give or take.  Lets also assume that the front area of the room is properly acoustically treated and the speakers are optimally set-up.

I have read in different places that with either a complete LEDE set-up, or with a properly designed reflective free zone in the front of the room, the back wall is best left to be highly diffusive as opposed to being absorptive.  In rooms such as this a row of 5 - 6 foot tall book cases, album storage and/or CD storage is often recommended as a natural way to accomplish this.

Alternatively I have read when it is more desirable to use absorption instead, just like what was used in the front areas of the room to control those reflections.

Most rooms naturally mix diffusion with absorption to some degree anyway, just by the very nature of what we often have in them.  So, which way is best for the rear wall directly behind the listener?  Would a wall of album and cd storage be ideal, mixed in with some other home made, or professionally designed diffusers.  Instead, would a simple set of absorption devices do the trick, or should we mix and match.

[azryan]

You kinda answer this question yourself.

'It depends'. Typically on preference mostly. You'll probably get more answers like you've gotten in the past.
'Do it like this'
'No, do it this way'

Technically getting the most accurate output from your speakers to your ear means eliminating the room as totally as you can.
Almost no one believes that this sounds good though.

But headphones inherently act as totally room absorbing anechoic chambers like this.

There's no 'right'.

I think the first step in room treatments is to identify the problems you have in your room.
You might have none and be 'done' without doing anything.

Typically it doesn't work out THAT easy though.

For your specific question of what to do about the rear reflection...

Someone with the back of their room open to another room is basically 'done' without doing anything and is getting a fairly 'absorbed' sound.
Or maybe a little loooong delayed and low db echo which is sort of a 'diffused' effect.


In your room I'd suggest you try absorbing the rear reflection with a big quilt and seeing what happens -'cuz it's fast, easy, and cheap to do.

Scattering the sound (diffusing) with bookshelves and assorted bits/stacks of 'stuff' should help if you have an echo problem from that wall.
Not quite the same things as prefessionally made diffusor panels though.

Depends on your listening distance and dist. from the wall behind you and your speakers.

If you totally dampen out the speaker end of the room (live end/dead end), sound can't echo back and forth so a live untreated bounce from behind you might sound best to you.

I personally tend to lean towards hitting the first reflections and then tracking down any other probs. 'if' your room has 'em -and trapping corner built bass modes (but that's a whole 'nother issue really).

[Ethan Winer]

Housteau,

> which way is best for the rear wall directly behind the listener? <

The rear wall and rear corners are the perfect place for serious bass trapping. That's the main "wavefront" direction for sound leaving the speakers, and the rear wall is the primary cause of response-skewing low frequency reflections.

--Ethan

[Housteau]

In my example room above, I was planning on bass trapping for all 4 corners and several of the ceiling wall intersections as well.  The space between the speakers along the front wall could also be a combo of bass and higher frequency absorption.  My thought was that the other areas dedicated to bass trapping would leave the higher frequencies basically alone.  Although the areas of primary reflection would be absorptive to those higher frequencies.

However, lets also say that this example room is of a size and the speakers placed within in such a way that the primary reflections would be at a distance away from the listener where they would not have as strong an influence.  It may be that the higher frequency absorption in those areas would really not be needed to be there for that reason, but would help in balancing the room out from being too lively.

If bass trapping is placed behind the listening seat as well, there is still the option of having it absorptive to the higher frequencies or not.  I guess that would be set to more a matter of taste, as suggested, rather than an acoustic absolute.  I suppose what I would do if given the opportunity to build such a room, would experiment mixing the centered rear wall bass trapping surrounding it with book shelves and media storage, including the walls to the side and behind the listener.

[redbook]

 Lately I have placed a heavy drape fabric over the 50" flatsceen ( between the speakers) with a degree of better soundstage.... It is also more interesting to look at than my reflection from the screen   LOL. Any way it is a positive effort.........

[bpape]

With that much space behind you, you can have both bass control and diffusion by using diffuses that are light mass which will diffuse from say 3-400Hz up and then pass lower frequencies to be absorbed by the panels behind.

If you don't have significant bass problems related to the rear wall, then pure diffusion would be fine. You can also use diffusion on the rear portion of the side walls and (pending good off axis response) at the side wall reflections.

Bryan