El: You should start studying Walsh "Bending Wave" technology. It doesn't suffer from all of the problems that most conventional dynamic drivers that you have described do. No whizzers yet you can get very reasonable high frequency extension, excellent horizontal dispersion, gobs of surface area for good low frequency extension, etc... Using this approach though, one is still limited in SPL range though.
As to more conventional designs, Nelson Pass' latest DIY speaker effort is published in AudioXpress this month. Making use of a Lowther DX55 in each HUGE and highly technical cabinet, the results are staggeringly non-linear and completely lacking in bass. After applying equalization circuitry and running a completely out of the ordinary amplifier design that is the reverse of what is commonly bought and used, the end response doesn't look bad at all. The fact that it took someone like Nelson Pass, a huge cabinet, custom built electronics and this much work to get the speakers to flatten out says gobs about where this type of driver is at in the grander scheme of things. Sean
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