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

[Peter Grenader]

What you are looking for is called a mid-woofer. I would stick to something
around the 5-6 inch range.  As far as the low's, you can do anything you
want with a passive crossover - but most of these will become pretty
inefficient under 80 hertz. For 4 inch, don't expect anything good to come
out below 120 Hz.

Also, 8 ohms obviously will require half the power from your amp than a 4
ohm speaker, so stick to 8's to keep the unit's weight down.  As far as the
loudness, there are a number of thing that come into play, the most critical
being the efficiency rating of the speaker (basically how much current is
required to drive it), which is directly related to the size of the magnets
and coils, so the larger the megnets the better, but this will cost you
weight obviously.

The efficiency rating of a speaker is a measured (in non-THX standards) in
DB when it's driven by 1 watt or power, measured from 1 meter away.  This
also determines the listening range, as you will lose 6 dB each time you
double your distance (2, 4, 8, 16 meters etc = 1 6dB each increment).

You probably knew all this stuff, but if not - hope this helps.




> 
> 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
>