1. I would go with 3 or 4. I have 3 mounted directly (1 per chair) and they that is about sufficient but I would imagine a platform will need even more.
2. Buttkicker has the following piece in their FAQs. I think you will find it helpful:
"Many home theaters have more than one row of seats, with the second and third rows being built upon risers. These risers, for ButtKicker transducer applications, have two purposes; raise and support the seats and occupants, and allow vertical platform and seat movement.
Height for the ButtKicker brand transducer:
ButtKicker brand transducers can be mounted above or below the top surface of the riser. If above, consider people traffic, furniture placement. If under the surface, some simple framing can be done to avoid the extra room needed under the riser. As always, keep in mind any maintenance that may become necessary.
In essence, you're constructing a floor above the room's floor. Build the riser similar to a suspended wood joist floor to give the riser its greatest low frequency response.
The major differences between a riser and real floors are the suspension points and tie points (to other external structure). The riser should be free floating (not tied into any adjacent walls), and suspended by short sides only. Use vibration isolators on the short dimension to support the riser from the room floor. Some customers have even used coiled automobile springs for suspension with great results.
The greatest flex of the riser will be along its long dimension, the riser's short dimension will offer much less low frequency flexibility. Therefore, when possible, avoid any support along the long dimension."
Originally Posted by panino
I'm looking to place one or two buttkicker LFEs in a riser and need some advice.
The riser is going to be about 6.5'x 12'. I'm planning on running the riser joists parallel to the long side of the riser to maximize the low frequency response. The riser will be isolated from the floor with U-boats or a similar isolation mechanism. I thought I'd place 1 or 2 buttkickers mounted inside to the riser framing for a cleaner look. Probably have access panels in the riser floor for future access (just in case).
1) for this size riser is 1 Buttkicker LFE enough or do I need 2?
2) what would be the optimal placement if I end up with 2 of them in the riser? Can they be in adjacent joist compartments for easier access with a single access panel or should I spread them out as much as possible? I assume the latter is preferred with attachment to different joists to maximize the vibration.
Thanks in advance!