Doesn't sound good to my ears in a sealed box
I immediately broke the sub in by playing it free-air at its resonance frequency at full excursion(just shy of mechanical noise) using a 2500 watt pro amp. Next I installed the sub into a .34 cubic foot sealed enclosure. I bridged my HiFonics Pluto amp to deliver 120 watts rms to the sub and always set gain with 10dB of gain overlap. I always had to turn up the sub gain on the head unit in order to balance out the sound with a pair of Alpine 6-1/2" coax. I also noticed mechanical noise when turned up close to max volume on certain frequencies although the woofer didn't appear to be reaching xmax. I removed the woofer and applied Dynamat to the two plastic pieces that are attached to the voicecoil since this is where I determined the noise was coming from. I also concluded that either the box volume is too small and causing compression or that I needed more power. I replaced the HiFonics amp with an Alpine MRP-MR350 to provide 200 watts rms. Better but the bass still sounds too compressed. Removed the woofer and installed my old school JL Audio 8W1-4 and the bass QUALITY immediately improved. The JBL is clearly made for bass quantity. The cone is more like a 6-1/2" cone with a big surround, and a lot of xmax. I haven't given up on the JBL though. I believe it would be better suited for the twice as big ported enclosure that JBL recommends so I'll be building one and reviewing it again. Let's face it. It's an 8" so don't expect much bass below 40Hz unless you use multiple subs.
Pros: Good value. A lot of xmax.
Cons: Recommended sealed volume is very inefficient and suffers from compression. Built for SPL not SQ.