Since I seem to have poked the hornet's nest over in the Tube 101 forum, I'll try testing the waters over here. I'm a DIY type of guy so I'm always looking for other DIY'ers to share ideas with. When folks suggest to me that they are into building their own speakers my naive and delusional mind assumes that they are building their own drivers. Then they have to explain that what they really mean is that they enjoy building boxes and putting store bought drivers inside them. OK, fair enough.
What I'd like to offer up is a way to make your own drivers. The kind that I prefer to build and listen to fall under the rubric of planar magnetic dipole radiators. Besides their unsurpassed sound quality they also come with the blessing of not having to build an enclosure for them. All that's needed is a rigid panel to support them in any configuration that pleases you.
The photos are of a sample prototype of one of the HF drivers that I designed and built way back when. The unit is now about 25 years old and shows some of it's age. It still works fine, though! The current project that I'm working on is a new form of driver that will have an unprecedented VC resistance of several K ohms. The reason for this high value is that when I get the 'Hot Rod 26' tube finished it will need to have a proper load to drive if I want it to be a useable output tube. I want to have the tube's plate directly drive the VC w/o the need for any transformer. This driver design will require a lot of thinking outside the basket (speaker pun). I'll use the diaphragm and frame of the planar tweeter as a testbed for the high impedance VC. I have some extra parts around here somewhere that will reduce the amount of new machining that will have to be done.
The diaphragm is .6 mil (.0006") polyester film. The original voice coil is one turn of 30 microinches (.000030") of copper with a resistance of 2.0 ohms. These were used in line arrays and the sum of the VC resistances could be added for whatever value was desired. Since the VC is only 1 turn and sits above the magnet in the focused fringe gap, it's impedance is basically a purely resistive load in the audio frequency range up to 40 Khz or more. A multi-fiber damping arrangement negated the need for electromagnet damping. These drivers make excellent tweeters in a 4 way system using active filters in front of each power amp. The companion midrange and upper bass drivers are larger versions of similar design.
I'll have to wind some high resistance test VC's for prototyping. To try and keep this project's description semi-coherent, I'll just give a quick explanation of where things started and where there headed. It'll take a couple of posts to get up to date.