Speaker Imaging - Do you hear a line, or do you hear an arc??

Before room treatment-
     Definitely an arc.
     Center image not settled in the center.
     Little or no depth of soundstage.
     Images seemed to be easily perceived from left speaker, area 
     between the speakers, and right speaker, ie- the speakers did not 
     "disappear".
After room treatment-
     Front line well established.
     Sides of soundstage extending beyond the edges of the speakers.
     Nice depth of stage extending beyond front wall (the wall behind
     the speakers).
     Center images well-established, solid and 3-dimensional.
     Soundstage is now taller, wider, and deeper and appears more
     of a box instead of an arc.
     Front of stage either appears in front of speakers, in line with
     speakers, or behind speakers, depending on recording.
     All images seem more 3D, more round, less flat.
     Speakers disappear convincingly.
Room treatment on all four walls plus ceiling.
Dedicated listening room.
Dedicated AC line to room.
All gear plugged directly into wall.
Speakers are Vandersteen 2Ce Sig IIs.
No rack between speakers.
No TV in room.
Dire Straits and Pink Floyd always sound very well recorded, as do most classical and jazz.
Most rock and pop sound surprisingly good now that the room and setup were established for best sound to "play the room".

Tom

     

pretty much what Eric [bdp24] said.
System: BiWired Spica TC-50 polyprop recap. Lead shot filled spiked stands. Speakers attach to stands w 4 Isolate It 50 Duro 0.25 x 2.25 circular pads. Kimber 2.5m BiFocal-XL. cd6006, passive LC1, passive XO1. 2x ML 800x w 10kg anti-skating.

Specifics:
Test discs never told me anything well recorded program couldn't tell better. Attend plenty of live acoustic music, get the image right for a well recorded large orchestra at full steam in a good hall and everything else is a doddle.

On a well set up system depth should approximate the space, be it hall or digital. It should draw you into the music as if you could walk up on stage.

An excellent set of a wide variety of well recorded material in good halls with a fairly consistent sonic is Louis Frémaux - The Complete Birmingham Years. Of course you have to like French music in English halls.

Note also, when a sound seems to be coming from farthest away, it’s pretty much always centrally located (center back).

IMO, this is a system failure. Back in the 90's, we did tests with 32bit digital processors, adding even or odd harmonics @ the CD 16bit bit 0 level. Even harmonics spread the backstage and push the image back, odd bring the image forward and triangulate it back to a point. The even push back can be solved by speaker placement, the odd triangulation cannot.

Other failings, mostly time coherence, cause the image to be too tall, tilted fore or aft.

IMO, a great many systems AT ANY PRICE are incapable of any semblance of correct imaging because their time coherence is non-existent.

Some people dont believe time cohesion is real

Tom:
Good point. Very good point. I haven't had a great listening room in ages. :(

Erik