Hello Scott,
How would you describe the difference between the D2 and 4" Be ?
How did you EQ them? Did you look for an identical response curve between the two?
This could help with room modes, at least.
Integrating a helper woofer in the M2 design is pretty straightforward if using an identical volume/tuning (~280L total!):
- change the LF shelving to -2dB instead of -8dB
- increase the Q/slope of that shelving a bit (IIRC in rephase I had to go from 0.6 to just under 1.0 when doing the simulation)
- lower gain by 6dB
- duplicate these LF settings for the helper woofer
- add a 1st order low pass at 95.5Hz for that helper woofer ( 135Hz/sqrt(2) )
Steps 4 and 5 could probably be replaced by a
line-level passive 1st order filter in front of the amplifier for the helper woofer, in order to save a DSP channel (unless you are using crown amps with integrated DSPs that is...)