It depends on your room, speaker/sub placement, etc. The m3's are rated as follows:

Freq Resp +/-3dB: 60 - 22 kHz Graph
Freq Resp +3dB- 9dB: 50 - 22 kHz

I would say 80hz would be a good starting point.

M80s VP180 4xM22ow 4xM3ic EP600 2xEP350
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