I sort of asked this question of Richard Newman - engineering manager for ATC when he gave me and my wife a tour of their factory, while waiting for my 50 actives to be manufactured, this a couple of months ago.
The answer was they were continuously being improved for both quality and ease manufacturing.
We saw this through the tour with the staff showing both he and us the effects of various minor adjustments, some good, some indifferent and some not so good. What was good to see was that the staff felt comfortable to poke fun at the ‘not so good’ with comments like I told you so!
The areas of refinements were almost microscopic but the results were measurable, all very impressive.
What Richard did say was that when we received our 50 actives they would be the best 50 actives that ATC had ever produced.
Loving ours with the NC222.
Hope this helps, Paul.
I have no special insights, but I don’t think a pro version of the SCM 40 is very likely. The pro range have SL drivers and whilst there are SL versions of the tweeter and midrange dome, I don’t think there’s a pro version of the 164mm woofer. So ATC would have to design and build a new driver and tweak the active crossover for a model that’s probably going to end up fairly close in price and performance to SCM 50s.
What they might possibly consider is a wider range of veneers on the current cabinets, perhaps with some premium offerings. But I guess that would need to be negotiated with their suppliers. It’s an intriguing thought, though.
Roger
Yep. They are my spare. I used them in my office and then for a TV viewing before I went to WATT6. I sure had a great fun using different amplifiers over the years with the pair. I used them with Krell 300i, JRDG Concentra, Nagra MPA and Primare 30i, EAD Theatre Ovation ( for TV ) .
I even tried them with a KT90 push pull valve amp ( Art Audio Concerto ) and they sounded great! ( KT88 did not do it )
Once out of curiosity I tried them with a Nait 3R. I only got a peep out of the speakers. 
These ATC SCM7’s are in my three season porch paired up with a Sonos Amp. I also have a Concept One AV setup which use the same speaker for the front channel. Great little speakers!
Many thanks for the insight, Paul. Sorry for the late reply. Nice touch with the ongoing improvements. I was also thinking if there was a specific year the 50s changed drivers, like the tweeter, or something more fundamental, that could be classified as “mark II”. I know ATC started to produce their own tweeter for the SCM40, and I guess it is the same for the SCM50. This is mainly information for when looking for 50s second hand. At the moment I eye a pair from 2014.
regards
Hell @Patu - I’m glad you did! Lovely indeed. I’m curious. What are those two Chinese looking audio products on the middle shelf? Come to think of it, what are the three components on the middle shelf too? 
Thanks! It’s Holo Audio Spring 3 DAC and their Serene preamp on the middle shelf. Top shelf has Holo Red streamer and English Electric 8Switch with a linear PSU for it. Holo Audio is a Hong Kong based brand and quite well known these days.
Which PSU do you use with EE?
It’s just a Topping P50. Probably the cheapest possible option but it’s actually very well built and an improvement over iFi iPower2 I used before.
I read other people using the Forester F1. Apparently it works well
Ah yes. I nearly said are they Holo Audio. They measure very well indeed from what I’ve read. And some reviews state that their DACs are best in class! Nice!
Don t know if already mentioned, fan ATC article from fidelity mag germany.
Quick UP for this thread so it won’t die 
50ASL’s singing as beautiful as always here.
hi
I bought atc scm 100 aslt . I’ll use with my naim 552
wich cable do you use with atc active and naim 552 power supply : xls with din naim ? or other brands ?
thanks for your response
Mogami for me. Amazing sound
thanks teslik and which mogami you you use with your atc ?
best regards
I wrote a long reply about xlr-cables before I realized you obviously need din-xlr.
Maybe ask designacable if they’d make you din-xlr cables from Belden 8402? Great cable for the price, I keep a pair around as my reference cables.