beryllium vs diamond

ScienceCop, how many loudspeakers have you built? 6dB is a huge difference in power and volume. The anomalies you mention will have less effect on the sound than the phase shift from a higher order crossover. Burn that tweeter out? Your ears will burn out long before that tweeter will get even just a degree warmer. I suggest you go pick up a copy of loudspeaker design for dummies. 

Stereophile has an interesting paragraph on the  Magico Be-Diamond tweeter:

"A beryllium dome is both light enough and stiff enough to behave pistonically, and was used in the Magico Q5, which Michael Fremer reviewed in November 2012. Applying a layer of diamond to the metal, Tammam explained, results in a dome with a more homogeneous surface, which both reduces intermodulation distortion and results in a more benign harmonic-distortion signature that is less like that of a metal dome. I asked why they hadn't gone all the way and used an all-diamond diaphragm. It turned out that, yes, diamond would produce a very stiff diaphragm, but the required suspension would raise the tweeter's low-frequency resonance from the desired 500Hz or so to about 1.3kHz. This, in turn, would mean that the tweeter would have to be crossed over to the midrange drive-unit at too high a frequency. Beryllium's lower mass ensures that the resonance frequency is close to 500Hz, but the diamond layer raises the dome's stiffness to extend the high frequencies."

@mijostyn
Do you even understand what a 6db XO is? How about breakup modes? The geniuses you are, you surly understand the difference between a 6db electrical XO (simple - but unless the frq. response of the driver is flat, which is not in this case, not phase coherent) and 6db acoustical slop (very complicated - phase cohere). Or did you not get to this part in your loudspeakers 101? There is nothing simple about building loudspeakers. That is why simple minded people should stay out of it. The speaker you are proposing will not be phase coherent, will sound horrible due to the fact you didn’t suppressed the breakups, and will not play loud at all (yes, you will blow up the tweeter in no time). 

Sciencecop, I hate to say this but you have no idea what you are talking about and you are having trouble applying the manufacturer's  data to real life performance. Those frequency response graphs you are referring to are take under static conditions. Music is not. It is dynamic. Whether or not a cone "breaks up" depends not only on the frequency but on the volume and duration of the signal.  I know from experience that I can apply certain drivers that way in that format with insanely good results for a point source speaker. 

Oh and Sciencecop, I can digitally emulate any crossover you can think of and on the fly bi and tri amping. Making analog copies is child's play.