[Milsurplus] LS-3 Speaker

[jhhaynes at earthlink.net]

On Sat, 24 Jun 2006, Al Klase wrote:
>
> A PA-system line-to-voicecoil xfmr is a good bet.  (Radio Shack used to have 
> these.) Connect the speaker to the 4 or 8-ohm tap.  The "highest-power" 
> primary will be about 500 ohms, and the lowest will be about 10K, with a 
> number of taps in between.  The best match will give you the loudest output.
>
The primary taps are marked in watts, which means the watts that will
be delivered to the speaker when the primary is connected to a 70.7
volt line.  Since power = e-squared over R, and e-squared is about 5000,
a 10-watt tap will transform to 500 ohms.  The lowest power tap on the
sample I have is .62 watts, which works out to about 8000 ohms.  This
is on the transformer which Radio Shack used to carry but may have
discontinued.