four good 8" subs, given enough power, should technically sound better than two equally good 12"s because you have four motors pushing less cone mass vs. two motors pushing more. this should result in the 8"s having better control, lower distortion, etc.
however, the cone area of four 8"s is about the same as two 12"s, so with all else being equal, it would be a close comparison. whether you could hear a difference or not is debatable.
one thing's for sure: four 8"s would be more expensive than two 12"s in order to sound as good. installation, enclosure design, wiring, and amplifier requirements would be considerably more for the eights, as well as the higher cost of the drivers themselves. but...
you could say you have four 8"s, which is kinda cool in itself.
True but i can always make the box taller, cant make it any deeper, seat wont go up anymore. Thought about 4 8W3v2 which need .50 cu ft per sub. I can get 4 of those in with indivual chambers and be ok. Also thought about 4 S8L7
i use a single S8L7 powered with 200 watts and can't complain a bit. if you had four of them you'd definately know it.
the L7s are going to outperform the W3v2s because they have a higher power handling, larger xmax, and greater cone area. there are some that say the L7's sound quality isn't good, and others say they aren't reliable, but i just don't buy all that stuff. mine sounds very good and has lasted me a year so far. sure, there are better subs in the world, but the L7s are one of the better 8"s.
what kind of truck are you driving? i have 2 12" VMAXs behind the seat of my 91' reg cab GMC pickup..the box was custom built but it fits perfect w/ just the right amount of airspace. how much depth do you have to spare? you might want to look at a few 10" models as well, many have shallow mounting depths and take very little room to preform. im not sure if anyone asked, but what exactly is your budget?
Also using the whole 7 inches is pushin it, another reason i was looking at 8's is because there xmax is lower, meaning its less likely to be hitting the back of my seat and causing self damage correct?
there are others out there, just aim for something that can make 900 watts rms @ 1 ohm.
regarding your xmax requirements, you may want to rethink using 8W7s. their cones will move nearly a full inch out of the enclosure. the S8L7s have a smaller throw, so may be more suitable for your application.
truck boxes (at least ones that are behind reg. cab seats) are normaly angled, going from large to small as they gain hieght. if you find a box that has a bottom depth of 7inches, no doubtably the top depth would be closer to 4.5 - 5inches. the subs would be angled as well which would help prevent them from hitting the back of your seat. but never the less, 4 8's would be one hell of a system. good luck and let us know what you end up deciding on!
roger has got a good point. i was in fear of the same thing you were Kebo. i bought a couple sub grills and they work great. they dont come close to the subs excursion but i also havnt pushed them to the max or even close to it yet (still breaking in) but they are a great investment. being that the subs will angle in the truck box, im sure that youll have enough room for the grills and if not, you can always go down to 2 or 3 tens which would have less xmax but still pound like crazy.
That's what I was going to recommend. There are several companies that make shallow mount subs. I believe they are more for underseat applications, but they would work in this application also. I've never heard the ones above, but I am partial to them, but I run a pair of the earthquake tremor 12xr's. you might ask Jonathan or Glass, about the others that make the shallow mount subs. This was just posted a few weeks ago, but I can't recall the others that make them. But again the earthquakes are great subs.