Some years ago I had to replace a different dead (& no longer available) Martin Eq unit. The Martin replacement was a bit on the pricey side, so we used a TC X024 speaker management unit, & adjusted it by ear.
I think the M1 was also superseded a while back, but if you have access to test gear* you could sweep the input with a tone-source & measure what comes out of the outputs, which will at least tell you what Martin intended. *If not, there's an excellent phone app called AudioTool, which has all you need.
Interestingly, the venue where I still dabble has a mainly ICT300 rig, with a bit of low-level buzz on 1 speaker-pair. We've always assumed that it's a dodgy jack-socket on the PO-style jackfield, but maybe I'll try swapping M1's around to see if the buzz moves.