DIY 802 field coil drivers may be a reality!!

[LowOhms]

I don't understand this "bucking" either. Jeff, can you give us a detailed explanation of what your referring to?
As I understand it, a FC motor uses a strong electromagnet fed with a robust, filtered and regulated DC voltage. There is no ripple or any disturbance in the field coil gap either from the DC power supply or induced by the voice coil. As long as the DC power supply is working properly, there is never any change in the magnetic flux in the gap surrounding the voice coil. It remains the same from day one to the date that the system is retired.
That is very unlike alnico magnets that are always loosing there magnetic field strength due to aging, a well documented problem. Not to mention that over powering an alnico driver will also substantially damage the magnetic fields strength. Also well documented. And that may be the weakness in alnico or any permanent magnet structure. If playing a strong signal through a voice coil can damage the alnico magnet, what is a weaker signal doing to the magnetic field in the gap? It may be causing distortion of the signal being reproduced.
Think about it.

BillWojo

On Edit: Steve, I want to thank you for your explanation, it gives one enough to calculate the coil specs.

Hi Bill,

Decent question, nicely put, thank you Bill..

I will not be able to help you, the way you would like. Mine were listening observations, between myself, and a close friend who spent his lifetime in the movie theater service and ownership business. The listening covers literally hundreds of movie-quality field coil speakers between us, mostly Western Electric, RCA, and some modern ones. He is far far more experienced than me. I only "audiophile" owned 13 of the RCA Mi-1428B or 1443 field coil drivers.

One can ascribe "reasons" for one technology being better than another, as you do, and you nicely discuss, in this exchange between us. It is called theorizing. Nothing wrong with that. I did the same thing 25 years or so ago, when I was using field coils. The main thing in audio to me is " how does it sound??"" It seems, if I read Elitopus correct, he tried a 802 field coil recently and reported his " first listening impression was - it was not High Fidelity, but OK for Musical Instrument or Guitar reproduction. " if I were " hot to trot " on 802 field coils as you are, I would be questioning him further, as he seems to have direct 802 experience.

As for me, and what I hear in 2017, I still feel (a) amplifier implementations, (b) system wiring, and (c) capacitor choices, make far greater performance differences, and offer room for real improvement, than any of these speaker ( alnico / ceramic / or field coil ) topics one may discuss. The better ALTEC drivers, are NOT the weak link, but I find from my own building and experimenting, and LISTENING, (a ) though (c) certainly are.

Have fun, enjoy the hobby, I do ! Lately, I have been trying to mentor others, privately. Its a good thing to do, some lovely people did so for me, when I was younger. We had a Type 46 Direct Coupled two stage DHT amp " born " this afternoon, ( first fire-up) and the DIY builder seems very pleased. That is exciting, it was my own, from-scratch design.

Low Ohms ..... Jeff Medwin