@david_ten
I have used extensively since ’95 ATC speakers. SCM 20, SCM 20SL, SCM100A and their C6 subwoofer and even their largest active centre channel.
They all sound very similar even active vs passive.
As you go larger and go active the clarity and distortion drops while the SPL capability increases to truly incredible dynamic levels.
Recently I simplified to their active 150 elliptical design which has a 15" woofer. If you are a stickler for precise timbre of sound for percussion, vocals, piano and pretty much anything at live music levels then you can’t go wrong with ATC - especially the larger models - no speaker I know of has better driver integration or such extremely low distortion at high SPL than a large ATC. The sound is neutral and precise and totally natural/realistic.
My speakers and class A to 2/3 power active discrete component amps are entirely made in the UK by ATC. All three drivers are entirely made in house by ATC. The tweeter is a new in house design and has no Ferrofluid - it has a double spider - perhaps the only tweeter using this design. As others have mentioned, the magic is in the bass and mid range with ATC - the bass and mid range are so clean and tangible that this is immediately easily noticeable versus other speakers. The new tweeter is designed and built in house by ATC (like all their drivers) and is only available on very recent models and it is outstanding but the tweeter improvement vs other speakers is not of the same order of magnitude noticeable significant improvement as the bass and mid range.
Active is such a no brainer - it allows amps to work within a limited bandwidth and without the heavy load of a passive lossy crossover - the design is just an order of magnitude better than the traditional approach in terms of low distortion and driver integration (provided active is done well as it is possible to mess up any design approach).