how far off the wall


I undesrstand that a speaker should be given some room to breath, that is to pull it a couple of feet of the wall. With my kef reference fours I found this to be simple. The speakers are enclosed and so i measured the disstance from the back of the speaker to the wall behind it, and advanced it the need distance. With the Martin logan vantage should i measure from the woffer enclouser or from the electrostatic surface. thanks,cj
cj1capp
Go to the Martin Logan Club for more info.

http://www.martinloganowners.com/~tdacquis/forum/index.php?
Besides saying 5' off a wall tehre is a formula out there to help avoid standing waves and all sort of issues that place your speakers based on room size. The speaker in general should be measured from the middle of the cone not the enclosure.

To tell you a story though I had a really good guy came in and tune my room. He started by the book placement, then tewwkwd to his sound meter and in the end did slight tweeks based on ear.
Far enough out to reduce the chances of non-modal peaks and nulls being introduced...modal peaks and nulls are another story and problem...although the two tie together overall.

Non-modal peaks and nulls are caused by a freq's wavelength and in relation to it's distance from room boundaries. Bass wavelengths are very long so reach all walls within the room.

Odd points: 1/4-3/4-5/4...ect,ect cause nulls
Even points: 2/4-4/4-6/4...ect, ect cause peaks

As you move the speaker out...and away from the wall you will pass through these wavelength points. The important part for bass in many rooms is usually to get out past the first 1/4 wavelength (null) but maybe not into the 2/4 wavelength (peak)...somewere in between these two first measurement points may be fine also.

If we use 100hz as an example:

2 ft 10 inches is the 1/4 wavelength for that freq...null

5 ft 8 inches is the 2/4 wavelength for that freq...peak

Of course all the other bass freq's have a different wavelength so have different measurement points in relation to the wall for their peaks and nulls.

5 feet (or so) works so well because it's far enough away to clear the first null for almost all of the lower bass points.

These same problems effect the listening position in relation to room boundaries...I'm sure you have read at this or other forums advice for placing a subwoofer at the listening position while you crawl around the room listening for the best bass...and then swapping those points between yourself and the sub.

I'm not the best at explaining things... even a worse writer, so sorry if this is somewhat unclear.

Dave
Duke - I am currently researching diffusion options for some planar speakers I currently have 4' from the wall (Quad 988's). There are cheap diffusor options (Auralex), but the reasonably priced ones are either limited in depth (2-3 inches) or complexity (and randomness) of form. Then there are the more expensive RPG and Auralex forms, but that will cost a bunch to cover maybe 3'x5' behind the Quads. Do you have any recommendations for diffusor options?

Thanks, Peter S.
Sogood51, my head is about to explode. No i did not know to crawl around the room listening for the best bass. Could you our one of the members here suggest a entry level book on audio setup. thanks so much