At 06:33 PM 7/29/01 -0400, Olin Lathrop wrote:
> > It always mystified me why we drive a device that converts current into
> > sound pressure, with a voltage waveform.
>
>I thought that too a long time ago -- until I tried it.  It didn't sound as
>good.  Then I did some measurements and found the frequency response was
>worse than when driven with a fixed voltage.  Then the obvious finally
>became obvious to me as to why this is.
>
>True, the force pushing the center of the speaker cone is directly
>proportional to current, not voltage.  However, you hear the result of the
>displacment of the whole speaker cone, not the force applied to it.  The
>mechanical system has relative resonances and dead spots a various
>frequencies.  When a resonance occurs, the speaker's impedance goes up, and
>the inverse happens at a dead spot.  With constant current drive, when the
>impedance goes up, more power is delivered, thereby exaggerating these bumps
>in the frequency response.  With a constant voltage drive, the power goes
>down as the impedance goes up, which compensates a bit for the bumps.
>
>Sometimes the road less traveled is less traveled for a reason.

Interesting.
I must have lucked out with my speakers.

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