Active Subwoofer Recommendations

3rd the Rythmik L12.  They stand out in sound quality at this price.  The only other subs I would consider at the price point are HSU.  

Before you can enjoy it all, you have to integrate the subwoofer with rest of your system, and how you connect a subwoofer to the rest of your home theater setup depends on whether it is Passive or Powered. That’s how we do in our management setup. حسين البداد

I use two subs — left and right — powered 8”   Velodynes. The bass is utterly awesome. It is almost as if the room shakes. 😁

+4 on the Rhythmik L12.  Down 3dB at 18Hz for about 500 bucks -- that's just nuts.