I watched a review of Beale Street Audio 6" and 8" subs. They come with an enclosure and use a transmission line design, ported out the front though several slot ports.

Havn't used them my self but the reviewer said they had very little vibration which he attributed to the energy being redirected out the ports.

I have tried their 6" and 8" in ceiling speakers and was very impressed so I'm hoping to try the subs soon. They're a Vanco product so which ever disty you deal
with that has Vanco should have them. Mine lent me a couple pair of speakers to try. Perhaps yours could too.

Craig