They've got a fair amount of VC inductance(Le is 1.6mH) so don't work up very high at all. I'd only use them to 150-200hz at the most. I'll be crossing them around 40-50hz so its a non issue.

Subs rely less on fancy materials and more on sheer mass, stiffness/rigidity, heavy bracing and damping. The idea being to shift the resonances up higher with a narrow Q so that they're out of the subs passband.

I'd completely agree if we're talking about a midrange enclosure but MDF has a good low end resonance profile with the more major problems at 400, 700 and around 1Khz. Its ideal for subs in other words.

The panel thickness came about through the desire to sub divide the larger panels into many smaller ones that had higher resonance frequencies. This required the use of 'skinning' techniques whereby you have a cabinet within a cabinet.

All this is just another way that works well, with a minimum of fuss. Scott(who drew up the rough idea) originally wanted a cabinet with a 4" cavity all the way around which was filled with kiln dried sand and a 3" thick concrete baffle. I'm quite sure that that would have been *the* most inert cabinet but the fact was that it took up 170ltrs with a 63ltr internal volume!