Thursday, March 10, 2016

Pioneer CS-88A Loudspeaker - The Crossovers Recycled

Here is a Pioneer CS-88A I found at the local transfer station a few months ago.  There was a pair of them but one had the woofer missing.  Some of the tweeters had gone "open circuit" and one of the crossovers needed some repairs.  The cabinets were in good condition, particularly the wood grilles.


Pioneer CS-88A Loudspeaker
Pioneer CS-88A Loudspeaker
Before taking the CS-88A apart, I decided to test the response in the bass region using the SWTP function generator and the iPad Air running an FFT app.  Here is the setup for testing.

Pioneer CS-88A Loudspeaker - Bass Response Test Setup
Pioneer CS-88A Loudspeaker - Bass Response Test Setup
 During this testing, I could hear buzzing from the woofer at several test frequencies.  Tapping the bass cone gently stopped the buzzing temporarily.  Apparently, the voice coil is rubbing the pole piece intermittently.  The only drivers working perfectly in this speaker are the two midrange drivers and the "super" tweeter in the upper right.  The bass output of this loudspeaker rolls off below about 70Hz while placed at the floor boundary.  It would probably have more bass placed in a corner.

These Pioneer cabinets have a removable back panel making it easy to get them apart.

Pioneer CS-88A Loudspeaker - Back Panel Removable
Pioneer CS-88A Loudspeaker - Back Panel Removable
 Here is the back panel removed.

Pioneer CS-88A Loudspeaker - Back Panel Removed
Pioneer CS-88A Loudspeaker - Back Panel Removed
 Here is the four-way crossover.  This one appears to be in good condition.  I had to replace a 3uF capacitor and solder a couple of high-wattage resistors back into the crossover I removed from the other speaker.

Pioneer CS-88A Loudspeaker - The Four-Way Crossover
Pioneer CS-88A Loudspeaker - The Four-Way Crossover
I have already tried these crossovers out on the New Folded Corner Bass Horns.  They work really well.  Essentially, I am "bi-amping" through the low pass woofer network in this crossover, which appears to cut off at about 300Hz, to remove midrange and treble from the signal applied to each of the New Folded Corner Bass Horns.  With this setup, I can adjust the level of the bass region separately.  The Klipsch Shorthorns are powered with a separate amplifier.  A preamplifier feeds both of the power amplifiers so, once the balance is set, it remains in effect and "tracks" according the preamplifier volume level.

The Sound Transformer Pair and the New Folded Corner Bass Horn put out significant acoustic power down to about 45Hz.  This is with the amplifier(s) set for "flat" frequency response without any bass boost.

I think bass players would be flattered to actually hear how their playing sounds when played back through a horn-loaded system like the Sound Transformer Pair or the New Folded Corner Bass Horns.

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