ATC SCM20, Wow what sound..

The 20 is a "pro" number in the US, and home audio model is called the SCM 19.  Active is called the SCM 19A.  

The SCM 19 and SCM 20 pro are voiced differently, in both active and passive versions.  The 20 is brighter and set up for highlighting flaws in mixes, where the 19 is warmer and nicer to listen to.  Both use the same drivers, but different crossovers in passive form and different amplifiers in active form.  Most people do not know this.

Brad
Lone Mountain Audio consumer
TransAudio Group Pro
Importers to the trade

Except there’s also the "SCM20" from the home classic series with the detachable baffle: http://atcloudspeakers.co.uk/hi-fi/loudspeakers/classic-series/scm20/

I’m not clear how the 19/20/Pro can be voiced much differently if the crossover point is exactly the same at 2.8khz (well, before they introduced the ATC tweeter...with the 19s and 20 Pros now at 2.5khz) and if they use the exact same drivers in more or less the same cabinet. I think the crossover caps are different (Bennic in the 19s, Ansar in the 20 Pros), which might do it. Otherwise, there’s only resistors and coils left.

Great speakers,  must have equally great ancillary equipment for them to really shine.   ATC speakers are used in studios all over the world.   Based on my limited short term listening , if you don't like how they sound it's probably not the speaker's fault.   For some contemplating amplifiers, active ATC s are the way to go if you can spend the $$$