[Housteau]

I ran across this interesting site on speaker and listening room interactions:

http://www.immediasound.com/Speakersetup.html

I found it interesting in that some of what is perscribed is contrary to what many others in the know often recommend.  I was curious to see what this fine group thinks about it and the math that forms the basis for the theory.

Dave

[RickRichardson]

Sorry I can't comment on the math or science regarding this approach, but I have tried it very successfully.  I had a pair of Audio Physic Libra speakers and set them up according to the suggestions of Immedia.  The room was 26 X 15 and I had the listening position on one of the long walls.  I was amazed at how wide the spread of the speakers could be without losing the center image.  I ended up with the speakers about 70 degrees apart and about 1/3rd of the way from the front wall.  The imaging was amazing with a huge and deep soundstage.  The bass was controlled by the speaker location.  The drawback is that this setup is very intrusive and makes other uses of the room potential problems.  I ended up putting small pieces of thread in the carpet to be able to relocate the corners of the speaker to the sweet spot.  Most of the time the speakers were close to the wall, but for really music listen were moved to the optimal location.  I am sorry to have moved to a new house where I can't duplicate this set up.  It is worth experimenting with if you can deal with the set up downsides.

[Housteau]

Yes, this kind of arrangement does work well as I have been using it for years now.  However, I was not fully aware of why it was working so well.  I had originally set things up this way having my room built after visiting and spending time in a friends purposely built listening room.  I was truely amazed at the sound in his room and so I basically had it duplicated.  I did this before I had the knowledge I do now about acoustics and speaker - room interactions.

This paper on the Immedia site is the first explanation that I have run across that really describes nearly exacly what I have done and actually says it is the right thing to do.  Normally what I read on room acoustics and speaker placement has had me wondering and second guessing myself over the choices I have made.  I guess it was a good feeling to finally see something in print that assures me that I was not such an odd duck after all.

With that said, there are still some things mentioned on that site that I am still not so sure of.  For instance, it shows the center of the room as a bass reinforcement zone.  I had always thought it as being more of a null and believe I read that here in this forum as well.

Dave

[Sedona Sky Sound]

This seems to be a somewhat over symplistic version of a whitepaper originally done by John Dunlavy. If you do what it says, you should get good sound but far from the best possible sound you can get. There is just no substitute I know of for well placed room treatment.

Having your seat directly against the back wall reduces the smearing effect of late transients but you are going to miss out on mid and high level detail since the re-enforced bass is going to cover it up to some degree. This may be prefered in a Home Theater or if you are using monitors (since more bass may be a good thing) but will severly degrade the overall sound with many full-range speakers.

Having your seat 3 feet from the back wall is almost always a bad idea unless you have serious absorption on your back wall. In my experience, 6 feet is usually the minimum to reduce transient smearing from the back wall (since it now had a 12 foot reflection path that provides suitable delay from the direct radiated sound).      

On the Internet, there are many recipes for getting good sound. Unfortunately, very few of them go into enough detail to explain what compromises are being made. Where most people mess up is that they combine "good idea A" with "good idea B" to create "crappy sound C". If you want "great sound" and don't want to spend the $$$ to hire a true professional (and there are VERY FEW of these in the world), then there is no substite to reading all 598 pages of "The Master Handbook of Acoustics". I think I have read it cover to cover about 4 times (and some sections 20  or 30 times) and learn something new every time.  

Julian
www.sedonaskysound.com

[ekovalsky]

Dunlavy's paper

There are significant differences from the Immedia paper.  Dunlavy recommends LEDE room treatment, listening very close to the rear wall (1ft), speakers close to front wall (1-2ft) and further from side walls (3-4ft), speakers facing shortest dimension of room, and listening arc of 60-100 degrees.

Here's my current room layout

[Housteau]

"This seems to be a somewhat over simplistic version of a whitepaper originally done by John Dunlavy. If you do what it says, you should get good sound but far from the best possible sound you can get. There is just no substitute I know of for well placed room treatment."

Agreed, and my room has proper treatment, but it's amount has been minimized by the distance between wall and speaker interactions.

"Having your seat directly against the back wall reduces the smearing effect of late transients but you are going to miss out on mid and high level detail since the re-enforced bass is going to cover it up to some degree. This may be prefered in a Home Theater or if you are using monitors (since more bass may be a good thing) but will severly degrade the overall sound with many full-range speakers."

The bass is reiforced by the rear boundry, but not in a large or overbearing sort of way.  I have bass control and treatments set-up in other areas of the room which seem to smooth things out nicely.  The actual reason I have my seating position where it is has more to do with the rest of the musical spectrum and the overall presentation of space and depth I get.  My rear wall is not just flat and reflective though.  It is lined with book cases and has other areas creating diffusive and dispersive effects.  There are some baren areas though and one is directly behind my head and near ear level.  I have tried adding absorption and dispersive elements there, but have not noticed any change and so I have left that space alone.  I have also tried moving my seat further away from the wall and did notice changes, but not really for the better, just different.  

"On the Internet, there are many recipes for getting good sound. Unfortunately, very few of them go into enough detail to explain what compromises are being made."

Very true.  I am running across them constantly and we have had discussions about them before here on this forum.  What I think is needed and could prove to be quite useful and interesting, would be for someone to gather up all of this diverse data and methodology on listening room acoustics and present an organized paper, or even a book regarding it.

I am going to look into "The Master Handbook of Acoustics".  It looks to be full of the right information.  

Dave