ATC scm 19 vs ATC scm 20SL?

With ATC its a simple to understand their line up. There are passive 2 ways and three ways; there are active versions of some of the 2 ways and all of the three ways.

The three ways add ATC's proprietary mid dome, now copied by a lot of others, dropping midrange distortion by a LOT. This is what makes them so popular in recording studios. With the three ways, you choose how loud you want them to play and how low you want them to go (woofer size). Other the bottom end, all the three ways sound very very similar to each other, enough so that you can use larger ones in front and smaller ones in back in the typical multichannel 5.1 or more rig. Pink Floyd Dark Side 5.1 was mixed like this by James Guthrie, with 150s in front (15 inch 3 way) and 50's on rear (9 inch three way).

Brad

I own an ATC SCM20 SL since 1992. It is the oldest piece in my chain. I had a love-hate relationship, but I am glad I kept them. While they provide a rather dark, mid-hall sound, they brutally reveal any weakness in the chain. They are especially sensitive to any sibilance and "digitits".
I modded them heavily, with all Duelund crossover components, ring radiator tweeter and C37 lacquer. They are unique in combining intimacy with force. The Quad ESL63 had a similar "intimacy", while seriously lacking force.
I am happy now, driving them with Nuforce 9V3 SE, Metrum Octave dac, Audiophilleo2 and ASI liveline cables.
My dream amps would be Spectrals though...

How can you do a driver swap without destroying how they were originally voiced? I don't want to sound too critical as I have done this very same thing with 1985 vintage ProAc's. The tweeter replacement was from the Response series (i.e. one silk dome for another).

@ Linkster
The two tweeters (Vifa D27TG and Scan Speak D2905/9700) share the heritage, and the impedance curves are almost the same. So it was a drop-in, besides adjusting for the slightly different sensitivity. This was also confirmed by a professional who designes Xovers for loudspeakers. I was never very impressed by the sound of the original, cheap Vifa tweeter, and I never regretted the exchange. ATC seems to have recognized the weakness of the original Vifa tweeter as well, as newer models use a much better Seas tweeter.