AJ,
Lighten up my friend, it was just a joke. That's why I used the laughing emoticon. But... fair enough questions none the less. Should have known I couldn't leave it at that. My bad.
OK...pure opinion here - haven't done the quantitative analysis to back it up. Nevertheless... I've NEVER heard an aluminum dome dome that I liked. Why? Probably because of their "oil can" resonance right above 20KHz. Virtually all of them have so much mass that the driver designers are barely able to push that huge, high "Q' resonant peak up out of the pass band. So what, it's stilll beyond audibility - right? Yep. But the sub 20KHz intermod products that result from the beating of that resonance with audible band tones sounds like crap - clearly audible IMHO. You (the system designer) can't put a high enough order filter above 20KHz to knock that resonance down either - to complicated, too sensitive to component tolerances and too many parts. A lower order filter would just roll off the top end. You're screwed. You live with the ringing and the resulting IMD and hope nobody can hear the difference.
Fact here: Check Amphion's frequency response. Look for the dip at crossover. Most likely their tweeter/waveguide's roll-off slope before any filters are applied is 3rd order. Can't use a simple first order electrical in series to achieve a 4th order alignment to net the resulting ideal "in phase" summing with the woofer. Why? Not enough protection for the tweeter. Could use a 1st order higher up but then that would raise the crossover frequency too high. That would then waste most of the waveguide's advantage. Could use a series 3rd order electrical to achieve an acoustical 6th, but that's a bit sensitive to component values - the production engineer would hate your guts - and has more parts/costs more anyway.
Whaddaya do? Get funky with some screwed up "Q" version of a 2nd order electrical to try and minimize the dip in the response and then live with whatever dip that remains. If only their waveguide had more acoustic gain at the low end such that they started out with a 2nd order roll-off. Then they'd get perfect phase summing with the woofer like we do. Too bad. There are so many possible variations to the waveguide you go nuts trying to find the right combination. Close enough is close enough. Get on with production and start making $$$.
Then check out their crossover frequencies. Anywhere near 600-700-800 Hz? Nope. They're lucky to hit 1KHz. Why? re-read previous 2 paragraphs. Then...
Thankfully... they never optimized their waveguide to extract the full potential waveguides have to offer.
Why not?
That probably because they don't know my secret. aa
So...there's my argument. Not as flippant as you might have thought, eh?
I always have a reason. I just may not give it out right at first.
Thanks and take care,
-Bob
