I worked in a Munro designed room with a pair of Munro enclosures using
the ubiquitous 75-150 soft dome mid unit and a pair 10" bass drivers, the Vifa tweeters eventually failed and seas replacements where fitted after morels where tried and rejected.
They may not be the best sounding speakers but they might be some of the most accurate mixing speakers I have tried. The smaller SCM 20 is very good but its that soft-dome midrange unit in the larger ones covering from as low as 300 Hz all the way up to 5000 that makes ATC's so special for me.
The only thing that comes close for broad flat agile midrange IMHO is a pair of huge wooden VitaVox 220Hz 15 cell horns with Coral M104 drivers and Meyer after market JBL 2425 Diaphragms.
But thats just because I am a very horny old engineer.