It would be interesting to hear the two drivers, loaded in small sealed subs, with identical resultant alignments, side by side for tonal comparison. A scenario whereby the actual tonal characteristics would be in full evidence when driven at or near their limits. Obviously, the operational drive levels that would be governed by the thermal limits of the 5100. The drive voltage could be backed off somewhat, maybe 2-3db for additional thermal stability. EQ/LT both systems flat and either minimize the impact of the room, or conduct this test outdoors. Now if the room is well mannered wrt modal behavior, and it allows for a decent system representation, go for it.
At this point the tonal characteristics of the two should be able to be delineated. Everything from their different motor structures, and Bl curves, their much different suspensions, cone shape and material, and perhaps their compression behavior, either magnetic or thermal, would differentiate the two. And ultimately, the sum total of all the distortions above, and their over-all self noise, then one could get a good idea side by side and would determine their ultimate sound. Then, one could determine the difference and attempt to attribute a relative subjective
difference in character between two of the finest LF transducers in the world.
As well as the above, small sealed alignment, limited by thermal constraints. One could attempt to perform the same tests in an IB alignment, and allow excursion to be the final limiting factor. Comparing the two alignments, small sealed and IB, where the limits are likely different.
Nathan, have you, or anyone for that matter, ever performed anything like this? Not IB, just some measure of a side by side? Would the suspension differences change the over-all sound at the drivers limits? If you EQ'd them at 75db, how significant would their tonal characteristics be at other operational levels? I know Bosso posts that we listen to the FR of a system. EQ them identical, then they sound identical. However, what's always bothered me is dynamics in general. More specifically, compression effects; to a lesser degree instantaneous magnetic, and a greater degree thermal over time. With radically different motors, equally different suspensions, and some measure of in-equality in the VC/former (2x power handling), I would put forth the supposition that these two would possess different tonality, .... even if EQ'd identically.
I'm fine with modeling etc., but the totality of it all is the final arbiter.