Let me start off by saying that this is one of the most potent subwoofers i have ever worked with. Besides getting great reviews from Car Audio magazine and various other writers, i personally give it an A+. Its a woofer where the marriage of SPL and SQ are perfect. The box i used was a 1.25 1" thick MDF enclosure, port tuned to 33 htz. Not only did it hit 148.2 in a trunk of an Accord on a new AC mic, but sounds sweet as well. I will compare it to the 12W7 just because that seems to be the sub most people are familiar with.
Ease of installation is about the same. With the w7, you have the overroll surround, which can be a pain but gets easier the more you work with them. The H2 has more screws than other subs that have to be predrilled exactly, but it also becomes easier with experience.
Sq. I would have to say that the W7 is probably my favorite sub when it comes to SQ, but the H2 is an extremely close second. Higher frequencies hit harder with the H2 than the W7, as well as the low end, but i feel that the overall spectrum of SQ as a whole is a little clearer than the W7, but again, not by much.
SPL. Destroys the W7. Much higher power handling due to its Dual Gap Geometry. Sensitivity on the H2 is higher than the W7, which i know doesnt mean much, so we swapped out the H2 box with a W7 box, and the difference was about 3.4 DB less with the W7.
This was a test run for me to see if i wanted to do the 15H2, and it seems that i am going to. Time and time again i have had loud systems in my car, but since it is my daily driver, i would always get pissed off when i tried to listen to normal music. The H2 gets loud, stays loud, and responds well to all types of music. Pricing is good too. the 12H2 retails for 599, as opposed to 749 for the W7.
I would recommend the H2 to anyone who has the money to afford it. There are other subs that are cheaper that can play in the same ball park, but as a total package ive never been more impressed.