Esta es la solución que ponen en la pagina web del fabricante:

Home Audio System Installation Guide
To add bass shakers to your home theater system, they need to be powered by an amplifier and receive the same signal as your powered subwoofer.

Here's how you add bass shakers to your home theater system:

1. Find the variable low-level RCA output for the subwoofer (LFE) channel on the rear panel of your AV receiver and disconnect the cable going to your powered subwoofer.
2. Connect a RCA Y-cable to the subwoofer output on your receiver.
3. Connect the cable from your subwoofer to one end of the Y-cable.
4. Connect a cable to the remaining unused end of the Y-cable to an input on the amplifier being used to power the shakers.
5. Connect the shakers to the output of the amplifer.
6. Set the relative level of the shakers by adjusting the volume control on the amplifier driving them.