[sdiy] Slightly OT: really loud but light weight speakers

[Joris]

Together with a friend I'm building a remote controlled combat robot
with built in sample player, amp and two speakers.

The speakers should be as loud as possible (the battle arena is noisy)
and still weigh very little (there is a weight limit for the bot).
We've reserved 2 kg (4.4 pounds) for the pair of speakers. We're
planning to filter out the low frequencies and use some kind of
speakers intended for mid and high frequencies.

I don't know much about speakers though... in our previous robots
we've used car speakers but they tend to be either too heavy or too
quiet. Any suggestions would be much appreciated!

Joris