ATC scm 19 vs ATC scm 20SL?

I think BongoB and Kinn got most of it covered. The 19 uses the same SL woofer/midrange driver so apart from a slight difference from the better tweeter extension (2.8Khz and up) they should sound pretty much the same. I have not opened a 19 up so I am not sure if they use the same good quality supersound polyproplene caps and air core inductors in their older models but I expect they do.

Judging by looks of the cabinet it has been engineered/designed to be mass produced at lower labor cost compared to the intricate work on the SCM 20SL. The 19 can be used without grills due to the rounded edges. The standard domestic 20SL needs grills installed to help reduce edge diffraction.

Since the SCM19 is cheaper i'd say it is better value but apart from that you are talking about substantially the same speaker.

I've never heard an ATC (but would love to someday).

Bob it is true that diminishing returns are reached quickly in small active monitors (much quicker than passives). Veneer and good looks do add significantly to the cost and these are real cost factors not markup - although they do nothing to improve the sound. Provided one accepts a near field position and does not demand realistic live SPL then the choices multiply.

The big ATC's are kind of mind blowing but they also suffer from diminishing returns because the SCM20 is already very good (even the passive version). It is a matter of degree - the smaller speakers simply cannot do large orchestra or big band with quote the same aplomb - so they are not quite "you are there" - the dynamics from percussion is not quite what you get from a real drum set. The larger ATC speakers get you all the way there (a point where you simply cannot imagine better other than a live band or just a slightly different but equally good presentation) - but the extra cost is almost certainly into diminishing returns.

Bob,

IMHO, it is the the extended bass (down to 40 Hz) that you get with the bigger models. A large woofer will pressure up the room. It may be something we not only hear but feel. In any case you can definitely achieve similar results with a sub and smaller monitors. And yes a subwoofer has a ridiculously difficult task. Finding a sub that is powerful enough to play as low as 25 Hz with 115 db SPL and very little distortion or heavy compression is as rare as a needle in a haystack (ATC make one but it costs nearly 10 grand). Nearly all subs start to distort/compress at about 105 db SPL at 20 Hz (yes - I am even referring to the big big expensive ones)