Al vs Be cones, or did you do that already and I just missed it?
I think Aluminum is heavier for the same stiffness, so it should dig a bit deeper on the bass (i'm not sure about Gene's "more output" comment. *shrug*)
Since Be is lighter but retains the same stiffness, it should be more efficient, and thus i'd imagine easier to drive / more dynamic for the same stiffness?
The real advantage of Be seems to be that with the same stiffness of cone, its main breakup peaks may be around two octaves higher in frequency.
The result is, say the 4" aluminum cone breaks up at 10khz, and the 4" Be cone breaks up at 20khz. So at 3khz, the aluminum cone probably has a peak in its 3rd order distortion profile, while the Be cone has nothing unless you look at the really low order stuff, like 5th order, which should already be around 70-90db below the fundamental tone.
That also means you can get away with a simpler crossover, so no possible "ringing" at that same 10khz from a 2nd order crossover.
I don't know if it's a meaningful difference, but just being able to tell myself I have a Be mid is awesome
This is the one I got. The shipping was fairly quick, it took about 11 days total for it to get here.
Did you really need a 50 watt amp for two feet away? Lol.