Basically they're bass drivers that make no noise. They get bolted to a couch or chair frame and connected to an amplified source. So, during heavy bass scenes.. it feels like more bass.... puts you in the movie more.
It sounds gimicky, but it really helps those who have HT's in the basement or on a concrete slab and they're missing that "oomph" when watching Jurrassic Park.
I just ordered up two pair of those yesterday. I plan to install 2 on each futon in my theater. I'm not really lacking bass from my 15" Tempest Sonosub I just want more. I'm going to test them out with my current subs amp and see how well they work before buying another amp for them.
When you started this thread you mentioned "Buttshakers". There is a brand of tactile transducers called ButtKickers. This brand is rather powerful. Obviously the amount of transducers you need to install will depend on how powerful they are, and how heavy your seating platform, seating and people will be. Two ButtKickers are powerful enough to be attached inside the platform rather than to the seating. Since they are rather large chances are you wouldn't be able to fit them inside a chair anyway. Other brands of smaller, less powerful types of tactile transducers might be able to fit inside a chair.
I built a seating platform that I estimate weighs about 400 pounds. The four cinema recliners probably weigh an equal amount and I guess on the average four people weigh an other 600 pounds. The ButtKicker folks have released a new amplifier which when connected to two ButtKickers in parallel will deliver about 2,200 watts of power. That is enough to do a good job of shaking the platform. Each ButtKicker is like a speaker in that it has a positive and negative wire. So for two ButtKickers the two positive wires are connected to the positive terminal on the amplifier and the two negative wires are connected to the negative terminals.
If you click on the link in my signature and then click on the Photograph link, you will see a picture of one of my ButtKickers attached inside my platform. There is also a brief description.
If you want to install them, but don't want them on every time you watch a movie - Would you install a switch in the circuit? Or are they driven by a separate amplifier that you could just turn off when you don't want to use it?
I have 4 bass shakers installed in my theater. They're powered by a seperate 150 watt amp that I purchased from Parts Express. You can always turn the amplifier off, as well as adjust the volume down too.