cattie15 posts 12-19-2009 10:12pm
Cost no object, ATC SCM 50 is the choice. This is because SCM 50 uses the audio grade dome midrange (part number SM75-150s) while SCM 40 uses the public address grade dome midrange (part number SM75-150). That's explained the difference in price and sound quality.
The SM75-150 used in the SCM40 has a less powerful magnet system than the 'S' version used in the bigger classic/tower and pro series monitors. This would mean less efficiency and output capability, but I doubt SQ has been seriously compromised since that isn't the ATC way. More likely the lower efficiency mid dome was appropriate for the lower efficiency sealed '40.
I think the fact that SQ is pretty consistent across models is evidence of this lack of compromise.