what speakers do the best "disappearing act"??

Two of the three best disappearing acts I've heard were by speakers that are no longer in production.

The first was the Meridian M2. This little beauty used a pair of 5 1/2" KEF woofers and a 2" (that's not a misprint) KEF dome tweeter. This was an active system using an MTM driver layout (well before Joseph D'Appolito's landmark article in SpeakerBuilder), with fourth-order Linkwitz-Riley filters, delay-compensation in the crossover, and a sixth order (assisted) vented alignment. All this back in 1981! This little beast was absolutely holographic - the sound field extended way beyond the plane of the speakers in width and depth. I haven't been the same since.

The next speaker that did an amazing disappearing act was the Snell Type A, not sure which version (again, early 80's). This was a brilliantly designed speaker with the best anti-diffraction baffle ever made. The baffle was a two foot wide, three foot tall totally smooth surface that gently curved back from the drivers, and more or less approximated a large spherical surface. The Type A's were intended to go flush up against the rear wall, not normally a location associated with decent imaging. But on a good Sheffield Lab recording, the room seemed twice as deep. And unlike the little Meridians, the Snells had a very natural tonal balance.

Plato, there is one line of electrostatics that has very uniform dispersion with respect to frequency and a correspondingly wide sweet spot. That line is the Sound Labs, in particular the full sized models. I'd be happy to explain why if you would like.

Which brings me to the third speaker that really surprised me with its disappearing act - the Sound Lab Ultimate 1's. These huge, rigid metal-frame electrostats replicated and perhaps even surpassed the vanishing act of the little Meridian M2's. Once again, there was no sense of room boundaries, much less of speakers in the room.

To put things in perspective, I do not place holographic imaging near the top of my list of priorities. If I had to choose, I'd much rather a speaker get the timbre of instruments right rather than their position. But holographic imaging can be a lot of fun, especially when combined with correct timbre.

Honorable mention for disappearing acts goes to the Martin Logan CLS, the MBL Radialstrahler, the Spica TC-50, and the Quad 63.

Excellent points on quality control, Subaruguru!

Ultimately, I found driver-to-driver inconsistencies to limit what I could accomplish on my own during my years as an amateur speaker builder.

Now that I think about it, the three speakers I mentioned above all excel in this area. The active Meridians used individually-tweaked amplifiers to set the exact levels of each driver, and if memory serves me right, when ordering replacement drivers they would ask for the serial number because they matched the replacements based on their database at the factory.

You mention Snell as a company that pays special attention to driver-to-driver matching, and in retrospect I'd have to credit the Type A's excellent imaging in part to this.

The Sound Labs have a bias control for each panel that allows precise level matching. I have found that sometimes, especially with tube amps, one channel may be a tiny bit louder than the other. By tweaking the bias controls on the Sound Labs I can dial that vocalist right in to dead center, and the result is much more three-dimensional than using a balance control in the signal path would be.

Fcrowder, I remember well the way the Meridian and Snell placed the analog noise at the speakers, instead of back in the sound field. This made it much easier to ignore the ticks and crackles, much as it's easy to ignore minor audience noises at a symphony concert because they are not spatially intermingled with the music.

You also spoke about being able to move around in the room and have the location of the instruments remain stable. This is something a line source inherently does better than a point source, because the decrease in volume with distance is much more gradual with a line source than with a point source. Of course the speaker would need a wide, uniform radiation pattern to give decent soundstaging from well off-axis. Also, a tall line source will have the same tonal balance whether you're sitting or standing, which I think is kinda neat.