in the PA speaker
In the September 1996 issue of SILICON
CHIP there was a project for a "high-quality loudspeaker for public address".
The specified speakers (P17WG-00-08 and AD11600/T8) are hard to find now. Do you
know of equivalent speakers that are readily available? (S. P., via
tweeters are now unavailable and the Vifa woofers are also hard to get. However,
the designer of the project has since made an equivalent PA speaker using four
C3086 165mm woofers and four C3003 25mm dome tweeters, from Altronics in
The design is similar to the original but with the following
changes: First, the box is changed from 750 x 370 x 460mm to 800 x 440 x 440mm
for a nominal internal capacity of 100 litres using 18mm MDF. The spacing
between woofers and tweeters is 150mm; tweeter-to-tweeter spacing is 55mm;
woofer-to-woofer spacing is 185mm. Port to tweeter spacing is 55mm.
The ports require a 65mm hole while the tweeters require an
80mm hole counter-bored to 104 x 4mm deep. The woofers require a 150mm hole
counter-bored to 175 x 4mm deep. The two speaker ports are each 50mm in diameter
and 200mm long.
The crossover arrangement is as per the 1986 design, with the
two 3.2μF capacitors each used for the high-pass and the low-pass filters
changed to 4.7μF. The inductor for the woofer crossover is changed from 0.82mH
to 2.7mH. The inductor for the tweeter crossover is changed from 0.82mH to
The 10μF/12ω ohm shunt network across the woofers becomes 10μF
and 8ω. The attenuators for the tweeters change from 3.9ω and 10ω to 3.9ω and