Re: Speaker Response?

[rubywand@swbell.net]

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 ....
>

     This is not very likely. Apple intended the speaker to, mainly, sound 
the system BEEP tone. Small size and low cost were more important than 
frequency response.

     One way to check the speaker's response is to use a program which 
outputs tones at selected frequrncies. A decent mike attached to a meter 
or 'scope will supply a measure of loudness. Start at 100Hz and move up in 
50Hz steps noting the output on your meter or scope. Chart the results and 
you should have something like your speaker's actual response curve.

     As for "latency", my guess is that it would be reflected by a peak on 
the curve. That is, your speaker's resonant frequency should be a function 
of latency. If this is the case and, say, output peaks at 500Hz, then your 
'charicteristic latency' would be somewhere around 1/(2*Freq.) or 1 
millisecond.

     If you do a response curve on your Apple ]['s speaker, be sure to 
post the results!


Rubywand