ATC active vs. passive

There isn’t a single dealer in the northeast that has ATC SCM50 or higher.
I’ve auditioned most other brands ranging from 10-300k, none of them had the dynamics, timbre and accuracy of ATC except Avalon acoustics Saga. Those are the very best I’ve heard but the price is out of reach. 

I auditioned SCM40 active and passive. The active demo was controlled by ATC preamp. The passive was driven by North Moon 641/681 DAC ( this DAC was also the source for the active setup)

I preferred the passive setup; I ended up purchasing the passive SCM40 v2 to use with moon 761/791. Super happy. These speakers have taught me a lot regarding natural sound and high performance. I understand why there is so much praise for ATC.

@ei001h 1. is it possible to self modify Active into passive down the line if get tired of active and would like to try other amps ?  Is it possible to purchase passive crossover and swap them at home? 

NO this is not possible due to the calibration necessary to set individual driver loves to build cohesive anaphase linear system.  Theoretically you could purchase an ATC passive crossover (for the model you have). Installing it would not be something to do at home.  You'd have to remove most of the drivers to get inside the box. 

2. 150 is considerably wider baffle than 50. How does this affect the imaging and the ability to disappear. Logically, 150s should be much harder to disappear.  The wider baffle is of course to fit an 15 instead of a 9 inch woofer.   The waveguide on the midrange and tweeter do not allow the drivers to depend on the baffle for pattern control;  the dispersion pattern from these drivers is less than 180 degrees.   I have heard the 150s sound as good as 50s but with more low end due to the larger woofer.  Doug Sax, mastering engineer extraordinaire, (now passed) used 150s installed in a soffit to get the ideal, bass is now working into half space instead of full space. So no I don't think this baffle width is a major factor in comparing these two models (although I will ask engineering about it).  In 20_ years I have never had anyone note this or say they can hear this difference.  Rooms are such a major factor influencing imaging and the ability of the  speaker to disappear.  1st reflection problems can dramatically affect this aspect of speaker performance.         

@theophile 

+1 and excellent post.

I have passive 40s V2, driven by an older solid state Musical Fidelity amp. When I got a streamer and a DAC with warmth—in both cases—everything became a little bit tubier. I’m very happy with my system now. You can definitely warm up solid state power with your source and your DAC.