Hmm.. don't know if this would work, but you could try generating particles and then replacing the particle objects with copies of the speaker. Don't know if this would respect the motion animation or not though - plus you'll lose the control over placement.
Another option would be to look at the plugin hdinstance (
http://www.happy-digital.com/instance.asp) that might do what you need (if you're using LW9 however, check first whether it is compatible - I've heard rumours that it crashes in 9)