Forty years ago, I had built from scratch a version of the Klipschorn folded corner bass horn. I modified an Allied or Electro Voice 15TRXB tri-axial speaker by removing the horn tweeter. This, I installed as a bass driver in the big plywood horn. This seemed to work quite well. I had the high frequency horn tweeter from the 15TRXB. What I needed was a midrange horn to go with it. I tried layering up a polyester resin and fiberglass horn over a wood mold but ran into trouble when the mold would not fully "release" from the horn. I had to destroy the fiberglass horn in order to remove it from the mold. I still have the original mold with resin stuck to portions of it.
|Midrange Horn Mold #1|
|Midrange Horn Mold #2|
The big folded horn appears in this old photograph center right in the corner between the barn and the house. You can see how big the horn is by comparing the size with the two red cars, the 544 Volvo and the 142 Volvo, at about the same distance away in the photo.
|Listening to music through the big folded corner horn|
Well, I had to let the big folded horn go during a move. I dropped it off at the Boothbay Transfer Station on Country Club Road at some point during the 1980s. I hope that someone recognized it for what it was and rescued it from the construction demolition grinder. I held onto the two plywood midrange horns.
A few years ago, I removed a couple of 2 1/2 inch speakers from small plastic computer speakers that used to come with desktop pc computers. Recently, I was cleaning up my shop and found the pair of small speakers and thought it might be interesting to see how they would work as drivers for the old plywood horns. The speakers have rubber surrounds and 1/2 inch voice coils and seem to be pretty well made.
First, I made a couple of new plywood flanges for the horn throats. To prevent the rubber surrounds from hitting the flange, I carved a circular groove out of the flange. Using the special mounting hardware that I had saved, I installed the speakers on the horn flanges.
|Plywood horn with new flange and wired for testing|
|Benjamin Miracord Turntable|
At about this time, I became aware of the Class D 12 Volt amplifiers made under the Lepai brand. The sound of these horns through this amplifier is about as clean as I can recall ever hearing.
|Lepai amplifier with "Poor Man's Horn Driver"|
Compression drivers can be quite expensive. The "poor man's horn driver" I have stumbled upon is definitely "under-engineered" and perhaps even "heretical" in that it appears to "get around" an apparent cost barrier to the enjoyment of high end sound reproduction.
Now, I really need a couple of bass horns to go with these plywood horns. The next project I will undertake is an improvement on the Klipschorn folded corner bass horn.