Bandpass subwoofer design & simulation with Eminence Deltalite 2512, looking for comments!

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I'm trying to figure out a high efficiency bandpass subwoofer design
(dual parallel) and am looking for any pointers. The aim to be
lightweight, *efficient/loud* and small enough to be hauled by a
bicycle!. Sound quality is not paramount, but it must be half-decent
playing house or maybe some reggae. It will probably be driven by a
150-350 watt class D amp.

I've been looking at the Eminence Deltalight 12" driver and have tried
to model it with WinISD beta, have a look at these screen shots of the
simulation:


1) Relative gain
http://www.biggerbyfar.com/subwoofer/bandpass_box_sim1.gif


2) Phase plot
http://www.biggerbyfar.com/subwoofer/bandpass_box_sim2.gif


3) SPL @ 100watts @ 1m
http://www.biggerbyfar.com/subwoofer/bandpass_box_sim3.gif


4) Group delay
http://www.biggerbyfar.com/subwoofer/bandpass_box_sim4.gif


The gain seems good, but I'm not sure about the group delay - is it
normal for a bandpass??
All comments appreciated, the more in depth the better! Is this a
suitable driver for this or have I gone up the wrong path. The Qts is
0.39 which some people seem to think is ideal.


Cheers!


Paul.