Re: Speaker Response?

[mjmahon@aol.com (MJMahon)]

Colin Klipsch wrote:
> 
> Greetings.  I have an obscure question about the Apple II's speaker
> behavior.  (This would be the speaker found on the 8-bit Apple IIs, not
> the //gs.)  I've searched through the on-line technical notes and was
> unable to find the information I'm after.
> 
> I'd like to know the speaker "latency" -- the time it takes for the
> diaphragm to move from one extreme to the other, after a reference to
> a $C03x I/O address.  Let us assume that the diaphragm was already
> resting at one extreme, and that no $C03x address is touched again
> during the ensuing movement.
> 
> Perhaps this information is hidden in the Apple ][ Reference Manual ....

"Latency" is not the usual way to characterize transducers.  In the
case of the Apple II speaker, one could talk about the "time constant"
for speaker cone motion, which would be very closely related to the
high frequency response.

My own experiments indicate that the audio output of the little speaker
is still going strong at 11 KHz, but has dropped off significantly by
22 KHz.  (This is why my DAC522 sampled sound player has no
audible "carrier"--it's at 22 KHz and both the speaker and most human
ears are many db down at this frequency  ;-)

High frequency response tailing off between 11 KHz and 22 KHz would
indicate that the time constant for cone movement is on the order of 
75-100 microseconds.  (Meaning that the cone settles to within 30%
of its final position in that time.  In fact, I'd be amazed if the cone is
critically damped--it probably oscillates some around the final position.)

You've made me curious about what you're doing that depends on this!


-michael

 Email:  mjmahon@aol.com
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