Re: Sundown X, technical question about output, cone area/excursion
Usable piston diameter consists of the cone plus ~1/3 to 1/2 of the surround. So when you look at cone area, envision that half of the surround is also a part of the piston area that actually moves air.
To my knowledge, the X isn't over sized. I haven't used them but I've used the SA and Z series and they're the same physical dimension at the mounting ring and I can't imagine a manufacturer making a mid line sub larger than its top line.
But back to piston area... a low powered 10 with little xmax will usually measure 8-8.5" of piston area. A high powered, high xmax 10 will usually measure 7.75-8.25" of piston. So for the low powered speaker (using the larger of the numbers) you have 56.75inⁿ of piston area and with the high powered one you have 53.46inⁿ of piston area.
To begin with, that's not much of a difference. But then if you consider that the low powered sub has ~11mm of xmax (just under ½") while the high powered sub has ~22mm (about 7/8"), you can see that the high powered driver will displace a lot more air.
The reason.... you have 6% less cone area with the high powered driver but, you have 100% more xmax, so the loss in cone area is more than made up or by the amount of travel that smaller cone has.
And please understand, I'm not quoting specific speakers or making a claim that ALL low powered drivers are this large or have that much xmax. The numbers I used are averages.
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