I had my first rehearsal using the M20 last night. It's a four-piece folk/acoustic lineup. We're using two LD MAUI11 compact line arrays for speakers, and overall the sound was excellent.
One particular problem I had was with the feedback reduction. We use a DPA 4099 clip-on condenser mic on the violin, which can sometimes be a challenge with feedback. In the past I've successfully notched out the worst frequency with the parametric EQ on a Bose T1 mixer, but I was looking forward to seeing how much better the automatic reduction would be on the M20.
Sadly, it completely failed to deliver. I auto-trimmed the input gain, and then cranked up the master. Very loud feedback ensued, at multiple frequencies. The FBS was on, and I tried resetting it and switching between vocal and universal setting. After trying for some time, it hadn't found a single frequency. My ears did though- it was very loud, with very easily discernible individual frequencies. A bit later it did pick out a couple of lower frequencies (ie the red lines appeared on the chart), but it made no noticeable difference to the feedback. As it stands, this renders the DPA mic completely unusable, which is hard to take since the per-channel FBS was the main reason I went with the M20 in the first place.
I also tried this same operation earlier with an AER acoustic amp and an SM58 with basically the same result. No apparent attempt from the M20 to cancel any feedback frequencies.
Am I missing something? Is anyone else having problems or could my unit be faulty? It has the latest firmware.