I have decided to convert some alnico jbl driver to field coils. I thought I would document my travels on here. I'm doing both 15" woofers and 2440's. I started by taking apart the magnet assembles and taking measurements. From there I calculated to size of the coil. I'm going for a middle of the road approach and I'm using 18 gauge wire. After I had the magnets out I started machining the pole pieces of the 2440. I attached a pic. This was kind of the point of no return, LOL. Once the material is off I cant put it back on.
I'mIm going to analyze some of the shavings to get the chemical composition of the steel using. Luckily I work in a metallurgical lab and I can do that kind of stuff.I'mIm going to use 1018 steel. Steve Schelrecommendeded 12l14 steel but after looking at mill certs I decided to use 1018. It has less alloying elements in it. The carbon is about the same as 12l14 too. Plus its a little cheaper.
I hoping to buy a 11 pound spool of 18 gauge wire this weekend so I can start winding coils for the woofers. The woofer coils will be 1 1/2" tall with an outer diameter of 5 1/8". The inner diameter is 3 1/8". It will be about 1000 turns of 18 gauge.
Now Im sure some of you guys will give me a hard time for this. But remember, the change over to perminent magnets was for cost reasons and not quality. Plus I find it fun. The drivers are d130's and if I recall, the first d130's were filed coil drivers. But I am going to do some experimentation with different cones, voicecoils, and spider. Just to see what ts parameters I get.
More to come as I proceed.
Nick
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