AW: [sdiy] what exacly is "audio" in electronics terms?

[Czech Martin]

The fun thing is (I never thought about that before) that nearly all
amps are voltage sources. In order to move the speaker it should be
a current source. And further: not the cone position, but cone velocity is
needed to create air pressure.

Keeping this in mind it is surprising that conventional dynamic speakers
fed with voltage sources work so well. I think the reason for that is
that the coil has very low impaedance so that the actual coil
current is determined by the amplifier voltage minus the induced
coil voltage, that is proportional to coil celocity.
Here we get it. For some frequency range the coil velocity must follow
the amplifier voltage, or large currents will flow to make up for that.

So, we finally get U ~ v which is demanded.

m.c.

> "It" becomes real audio when the electrical energy forces the speakers
> coil to move. The speaker moves when the current, that runs 
> through the
> coil, is changing. So you might say it is current. But the 
> current won't
> change as long as the voltage on the coil does not change.
>