Near field listening and speaker placement


We have a large music room (20x30) with a cathedral
ceiling and front outside wall angled out at 105 degrees,
(typical contemporary) with a tall bank of windows. In
order to avoid interaction with the glass, speakers must
be placed along short (20FT) axis of room. The room is
live (hardwood floors), although we have thick wool 9x12
rug in front of speakers

We would like to use a near field listening configuration,
and have several questions:

1. We assume nearfield listening is an attempt at zero
interaction with boundaries so that only direct path sound
arrives at the ear. Is this the consensus, or have we
overlooked something in the definition?

2. Speakers are placed 6 feet from the "back" wall. What
is the result of eliminating the back wall from the
listening equation?

3. In order to minimize interaction with the floor (the
closest boundary) should we worry about carpet on the
sides and behind, not just in front of our speakers?

4. Are there a canonical set of rules for spatial
optimization in near field set ups?

Guidance from the experienced is much appreciated.
hindemith
I think your questions are impossible to answer over the net. Like a Dr. ( I ain't no Dr.) trying to diagnose over the phone, But:

1) Yes that's the idea but there is always reflected sound. And you will not "aviod" interaction with the glass in a room that size no matter what the placement. You can reduce it.
2) See articles mentioned below
3) Will take experiments but probably yes.
4) Yes, See Cardas article below and Art Ludwig's site.

There are lots of theories on placement but all of the people I have talked to indicate that it is very room, taste, and system specific. Even with the best theory it takes a lot of moving stuff around.

You will definately have to work on the hardwood floor and glass with coverings if the entire floor is hardwood and the windows dominate a wall. I have heard some really nasty systems in this kind of room if not damped (Sorry). A very good short explanation of the classic "near field" set up by George Cardas is at www.audiolinks.nl/speakersetup/speakersetup.htm

A short piece by Joachim Gerhard (audio physics) is at www.speakerbuilding.com/content/1039. Gerhard suggests placement more toward the middle of the room than the classic placement that is described at the first site mentioned.

There is a wealth of information and recommended reading on this topic at Art Ludwig's site. www.silcom.com/~aludwig.

Good Luck

Sincerely, I remain
jfrech, ivanj, Creeper, Rosstaman, Clueless,

So much, to the point, so promptly. Thanks for the
guidance and websites.
One thing to keep in mind--If you have large speakers where the drivers are spaced relatively far apart they may not be suitable for nearfield listening as the drivers might require some distance for their sound to mesh into a coherent whole. Just another thought.

Tim
Was about to state Soix's point.
I listen to 3-ways in a 7.5' triangle in a 14x24 room.
The speakers are 8' out from the front wall.
I tried several serious 3 ways (N803, N804, Ariel 8, Revel F30, VA Fidelio) before deciding upon my choice (Parsifal Encores).
The Ariels and ESPECIALLY the Nautilus' had SERIOUS problems in the nearfield due to lack of coherence. The Revel F30 was pretty darn good, but my wife hated the California moderne looks. The Fidelios didn't work because their rear-firing woofs needed boundary reinforcement, and 8' is WAY too far away. So this can get tricky unless you take the easier route with excellent two-ways or at least 3-ways with a low cross.
Damping the room much more than you have is my strong preference, but you may be able to get decent sound in the nearfield. Controlling sidewall splatter with toe-in and speaker selection for off-axis response characteristics will be important. (You DON"T at all have to have a headphonesque stage...quite the contrary.)
I'm fortunate that my 7.5' triangle throws a stage about
12' wide and easily 10-15' deep!---WAY beyond the speaker positions. I use stuffed sofa and chairs with throw pillows
propped on top of them where windows and fireplace are at first reflection points. Wall-to-wall with pad is HIGHLY recommended, and a cross-beam ceiling doesn't hurt either.
By contrast my 14x14 cathedral-ceilinged hardwood-floored, multi-windowed familyroom system sounds like crap!...but it sure plays loudly! For TV that's fine...makes the "action" seem bigger, and for 2-channel HT that's ok.
But for serious music reproduction deader is better, and to repeat, ultra-coherent speakers in the nearfield just improve your odds of aquiring a stage and frequency-response
close to the designers' intent.
Good luck.
You also don't want a flat wall behind your speakers no matter how far out they are, I put 3 fig trees between and behind the speakers for dispersion and the soundstage and imaging improved...