Ian, thanks for the test results and also for again making the point that "Lots of things are measurable but not audible".

The measurements are consistent with the mid-woofer rolling off below about 150Hz at 12dB/octave. As you indicate, it's in "its own very small enclosure inside the M60 cabinet". In effect it's a sealed speaker and as such would be expected to roll off at 12dB/octave below the tuned frequency even in the absence of a separate high-pass filter(which some critics appear not to have noticed). Without the Theile-Small parameters this can't be calculated precisely, but with a driver Fs of around 60Hz being sealed in a sub-enclosure of possibly 6"x6"x4" these are the sort of results that would be expected. Congratulations on a design which achieves fine audible results in the real world, while also being cost-effective.


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Enjoy the music, not the equipment.