.Just a batch of notes and pictures right now..more to come (maybe)
1. Cut the housing from 2" by 3" rectangular tubing. I got a 5-foot cut-off piece from Potomac Steel in Alexandria, VA for about $20--enough to make about 16 tweeters (or one very massive line array).
2. Cut slots in the front face using a table saw with a 7" metal cutoff blade (fiberglass material?). Actually, I just let the blade make a bubble on the inside of the tubing and then cleaned out the slot with a Dremel tool and fiberglass cutoff wheels
3. Clean-up sharp edges, sand down the tubing and clean with solvent. Spray with a rust-proof primer. The cleaned-up tubing will look like this:
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4. Make a pole piece. Size and shape will depend on the size and shape of the magnets. I used a piece of 3/4" square rod. A 3' piece cost less than $2. You need to cut slots in the rod to vent the back of the diaphragm. I used alternating angles for the slots, but there are many ways to do this. Sloppiness is not a problem--just need enough steel to conduct the flux.
5. Glue the magnets to the pole piece with urethane glue (magnets should be series parallel so they all add):
Slide the pole piece into the tubing. A couple of drops of urethane glue or super glue will keep it fixed in place:
Another view:
Forcefield at http://www.wondermagnet.com has a good stock of NIB magnets (Neodymium-Iron-Boron). An even cheaper source, with a great selection, is Rattlesnake magnets. Contact is Dale Young at 520-282-6277 (P.O. Box 1770, Sedona, AZ 86339). Email is dennis@sedonastarlight.com. I found him on eBay, and his auctions "come and go"--keep checking or send him mail. The magnets shown above are .75" by .3" by .5". Each was $4.50, so the four magnets for one Heil cost $18. These are potent 13,000 Gauss magnets (grade 38)!.
I had no trouble ordering a pair of diaphragms from ESS. They don't take credit cards, so send a cashier's check. $30 apiece plus $6 handling per order.
The address is on the package:
The double sided tape used to mount brackets is almost thin enough to be perfect to position the diaphragm in the magnet structure. If someone finds something a little thinner, please tell me.
Install the tape on either side of the diaphragm and peel off the protective plastic
Center it and press in place. The excitement should be getting to you by now. Hook it up with a series capacitor and make sure it works.
Add wool or your favorite acoustic dampening material. I used some wood blocks to help hold the end caps, which are cut from 1/8" hardboard. Purists may want to use 1" MDF, but it REALLY isn't necessary here.
I like the urethane glue (Probond) for filling in voids around the edges of the end cap
It only takes about an hour to make a circuit board for the electrical connections, and you get to write your initials on it. Lots of ways to do this...
Sounds very good. Send enough money for me to buy Ravens and I will tell you how they compare.
Definitely an above-average computer speaker!
The tweeters in my old computer speakers started to deteriorate (DIY Heil diaphragm got brittle). Also, they were a bit too heavy for the wall, since the tweeters themselves were well over 20lbs. The following pictures might explain the weight:
22"! Gotta be a joke here somewhere.
The Alnico slugs were scavanged from Magnetrons. Each is 1-1/2" in diameter and a little taller than wide. The steel was all hand-cut with a low-budget circular saw, so it's not particularly neat. The diaphragm took many hours to lay out and many more to fold. This is a great project to recommend to your worst enemy.
