like everyone else said, sensitivity is mostly a moot point. it DOES have some effect on overall output but in general it wont make that much of a diference, at least in subs. for mids and highs sensitivity is something to consider. of the subs ive owned(about a dozen or so) my favorite has been the JL W0. now before everone starts ranting i ONLY liked that sub so much because it was cheap, sounded nice, and took vitrually 4X its rated power before it complained. and when it finally broke, JL sent me a replacment for free and paid for me to ship the one i fried in to them. the tinsel leads broke, and the new W0's have woven tinsels/bigger tinsels.
if you go with sundown or DD, you cant loose. i have also heard very good things about SSA and ID subs. but at the same time my dad has been running the same JL W3 for over 10 years, and it still works great.
So when you say power handling and spl aren't necessarily the same thing, how is that so? I mean, I know there's a lot of factors that come into play from cone mass to surface area and especially the box, but if you took an sa12, put it in the optimum spl box for that sub on 900wrms, and then took one of those pioneers and put it in it's own spl ideal box for 900wrms, efficiency and such aside, why wouldn't the pioneer be just as loud?
I appreciate you answering my questions though. Im glad to learn this stuff.
For car audio specific topics high sensitivity isn't necessarily a good thing as a high sensitivity woofer actually has less output in a small sealed box than a less "efficient" woofer.
Both of these images came from the Technical section of one of my web pages (Stereo Integrity). Here are two completely different woofers in the same size box. One woofer is 84 dB efficient and the other one is 97 dB efficient. The first graph will be of the two woofers in 1 ft^3 sealed:
The second graph is of both woofers in 3 ft^3 sealed:
Notice I haven't told you which woofer is which plotted line yet. :) The blue plotted line is the 97 dB woofer and the black plotted line is the 84 dB woofer. Notice that in 1 ft^3 below ~45 Hz the less efficient woofer has more output compared to the other woofer that has a +13 dB higher efficiency! In a small enclosure (which all car audio alignments are) a "less efficient" woofer will actually have more actual output where it matters than a higher efficiency woofer. If you want to listen to kick drums all day long then a much larger sealed, or vented, alignment coupled to a higher efficiency woofer might be a suitable option for you. The point is that if you are looking for woofers that have upwards of 90 dB efficiency ratings you must be ready for a large enclosure in order to get the benefits from it.
ok, if you go to walmart and get a "1000W" amp. that is most likley peak power. but if you look at the RMS it may say 500W or so. now if you take that amp and put it in your car assuming you will get 500W you will most likley not get that. most amps are measured at 14.4V instead of 12V. and since W=V X A you get less power if ur amp only gets 12V.
but thats not all! even if you DO have 14.4V steady power to that amp, there is a VERY high chance that the "500W" of power will not be clean. "dirty" power will kill woofers fast under the right circumstances, and under others it will just make ur system sound like ****. if you get an amp from a good company, and do the big 3 power mods, you will be fine.
some amps even have a build in "power amp", so to speak. it takes your cars whatever volts and puts out AT LEAST rated power. unfortunatly the only amps i can think of ATM with this are the JL Slash amps. they put out more than rated power at virtually whatever voltage you give them. but these type of amps can be BAD for your car.