12 vs 15

I am currently running 2 15in Kicker XPL's in a sealed enclosure and wanted to know what everyones opinion was on whether to use 12's or 15's. I am running my subs through a gen XI zues amp and I listen to a lot of rap and some country(I know rap and country what a combination). I was thinking of going to 12's because the 15's don't seem to have that tight bass that you can feel in your chest. Any opinions out there would be helpful

Are you underpowering the 15's? Most people do not power their subs correctly, Generally speaking the larger the driver, the more energy it takes to move the larger, heavier sub, this eats up a lot of power that should be produced as sound. !5's can wail you in the chest, really damn hard, if they are matched together correctly  -subs - amp - box, screw up on one of these and it's all over. Personally I do not like 15's, they move alot of air, lots of bottom end but I like the sound of a pair of 10's or 12's, depending on the vehicle. The smaller driver is much easier for the amp to control the motion of the driver and yield the results that I need and want. There are lots of routes to get deep, tight and loud bass, it depends on which route you want to take to get there.

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Top Secret, I can tell you but then my wife will kill me.

I am pretty sure there is enough power the Hifonics Zeus genXI is rated at 350X2 @ 4ohms and the only thing it is powering is the subs. the XPL's are rated at 300w rms 600w max. They are in a sealed enclosure(which XPL's call for) that is around 2.30CF and the call for 1.8-2.7cf. They are in the back of my blazer, if there is any thing else that can be making it seem flat let me know. Thanks

I couldn't find the info on your amp, can you send me a link where the info is. It did not list any info for the gen xi series of amps on their website. This is a big amplifier (surfboard size dude) to 350w x2 rms @ 4ohm @ 12v. The biggest 2 channel I stock is rated at 150w x2 rms @ 4ohm @ 12v, it has 4  - 25 amp fuses in it. What are the sizes of the fuses for your amp? What cd player are you using? The more info you can post up, the more information people will be able to give to you. There are a lot of really knowledgeable people out here that can give you multiple opions, some of them will probably be the same, some radically different, but all are trying to get you the results you want.

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Top Secret, I can tell you but then my wife will kill me.

Hifonics took the GenXI off there site because they are updating to the GenXX. Here is some of the specs that I found in the manual. If you need more info let me know what you need and I will try to find out.
Amplifier - 350x2 @ 4ohm - 1200 watts RMS total
350x2 @ 4 Ohm (stereo)
550x2 @ 2 Ohm (stereo)
600x2 @ 1 Ohm (stereo)
1100x1 @ 4 Ohm (bridged)
1200x1 @ 2 Ohm (bridged)

it has 2 70 amp fuses
This one is not the Zeus series of amps that they sell it is a zeus amp. the zeus series starts with a z followed by some numbers Below I will list what I have installed.

JVC headunit kd-sh55 cd player
JVC cd changer
Hifonics zeus series Z6400(running components)
Hifonics GenXI zeus (running Subs)
2 Kicker XPL 15"
2 sets of Polk db6500 component sets
Monster cable RCA's

Your choice of an amplifier seems fine. It should provide loads of power. Have you tried adding a line driver to your system? Audio Control makes a really good little add on  (the matrix) that will probably help out your system quite a bit. I would use this myself in your system, but to get the "tightness" you want, a quartet or pair of 12's may be the answer. I would give a good hard look at a pair of Eclipse aluminum 12's.

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Top Secret, I can tell you but then my wife will kill me.

I am already running a line driver on the sub amp. the eclipes are a little pricey right now(wife nagging about what it cost so far). Any other brands that might not be so expensive that you can recommend?