Quote Originally Posted by skeptic
"and of course the drivers are closely matched which no speaker using a metal tweeter can ever be unless the woofer is metal too "

To truely match a woofer and tweeter, the first thing that would have to happen is that they should be mounted coaxially. If they are not, the mere fact that they are at different locations would mean that there would be interference patterns at every point in any room in the general frequency range where their respoinses overlap. Secondly, the faster driver would have to be fed a time delayed signal so that the two drivers produced vibrations that exactly coincided in time and space. To do that, the system would of course have to be biamplified and the faster driver fed with a delayed signal preferably frequency compensated. I do not know of a single example of any loudspeaker commercially available configured this way. On the bright side, as far as I know, nobody has ever demonstrated that this would yield a better or more accurate sounding speaker.

That would be the Thiel 6 with the new coaxial mid/tweeter driver.

http://www.thielaudio.com/THIEL_Web/Pages/cs6.html

Thiel lives on thier engineering. I've heard the 3.6's and I was impressed, and I've been told that the the 6's were incredible. The crossovers they use are a work of art to bring the phase responce to within a few degrees. The drivers are also precision time aligned.