That is true. We do know though that the magnetic field sags when current is put through the voice coil. So is the gap still saturated?What difference would it make if the source of MMF is a coil or a PM? The pole piece & iron around the gap should be saturated, and once that's achieved, it would make no difference how it got that way.
If you hit the gap with a strong enough field so that the voice coil field generated during loud playback cannot pull the gap metal out of saturation, then yes. With inadequate MMF in the gap metal parts, then it would be possible for loss of saturation to occur due to large voice coil excitation currents. So, it's design-dependent.That is true. We do know though that the magnetic field sags when current is put through the voice coil. So is the gap still saturated?
Exactly.If you hit the gap with a strong enough field so that the voice coil field generated during loud playback cannot pull the gap metal out of saturation, then yes. With inadequate MMF in the gap metal parts, then it would be possible for loss of saturation to occur due to large voice coil excitation currents. So, it's design-dependent.
Are we still discussing advantages of field coils? I would have thought that the mutual induction of a field coil loudspeaker's two electromagnetic coils means that it will also "react to current in the VC".I think most people assume that magnets don't react to current in the VC which isn't the case.
Personally I think there is a real risk of the Class A Amplifier Effect taking hold. Namely, just because someone can describe a technical advantage (for Class A, no switching of the output devices and no crossover distortion), then suddenly in demo rooms around the world we start 'hearing' them as superior.Based on my subjective evaluation of dozens of speakers/setups at a recent major audio show with hundreds of exhibitors, I have to say that the Songer field-coil speakers were in the top three. The clarity and full-range coverage of the demo setup incl. model S1 speakers were unbelievable and rivaled those of a setup spec'ed at almost $900k+. A result of 6+ years of R&D, the rep said. And it shows. Have started saving money now to get to the ~$37k MSRP (with the requisite PS).
I would have thought that the mutual induction of a field coil loudspeaker's two electromagnetic coils means that it will also "react to current in the VC".
Apparently we are. A regulated supply solves the 'react to current in the VC' thing. I think a constant current supply is better, but the point is its regulated.Are we still discussing advantages of field coils? I would have thought that the mutual induction of a field coil loudspeaker's two electromagnetic coils means that it will also "react to current in the VC".
Field coils tend to be a pretty constant load for their power supplies- only changing as the coil slowly heats up. Regardless of program material, I've not seen the current change with it.Absolutely. After all, some servo subwoofer use an additional coil as their sensor.
A well designed field coil driver should include at least one feedback loop of some sort. Most (if not all?) of the modern field coil implementations I've seen seem to use a simple "dumb" DC power supply as the driver, and that's just, well... dumb.
Oops, I just discovered this thread. Is the photo from you? Have you been there?The switch from AlNiCo to ceramic for magnets was driven by the Cold War and the use of cobalt in other technologies (not so hifi-friendly ones) and supply constraints that also had geopolitical underpinnings.
The ability to make more or less arbitrarily powerful electromagnets is at least possibly a "plus".
Your high field FFT NMR instruments, e.g., use superconducting electromagnets. Could audiophile drivers be too far behind?
From ASR's perspective, field coil (electrodynamic) drivers probably make no sense.
Not everyone shares the canonical ASR perspective, though.
Make it yer own Tungar Supply
Went to the "Secret Land of Walter" last weekend to have some fun with some friends. On the agenda for the weekend were some Tungar Supplie...hifiheroin.blogspot.com
Low voltage, high current power supplies for field coil drivers using Tungar tubes.
View attachment 259979
This appears to be the audiophile Rolls-Royce of field coil drivers from Voxativ https://voxativ.berlin/products/acx hopefully not "dumb"!Absolutely. After all, some servo subwoofer use an additional coil as their sensor.
A well designed field coil driver should include at least one feedback loop of some sort. Most (if not all?) of the modern field coil implementations I've seen seem to use a simple "dumb" DC power supply as the driver, and that's just, well... dumb.
I also always wondered why nobody AFAIK has implemented a modulated field coil drive, modulating the DC current with a scaled copy of the momentary VC current. When dialed in properly, this could reduce significantly force factor modulation BL(i).A well designed field coil driver should include at least one feedback loop of some sort. Most (if not all?) of the modern field coil implementations I've seen seem to use a simple "dumb" DC power supply as the driver, and that's just, well... dumb.
Only 14 grand? Get a couple for the kids!That driver uses a simple field coil like the rest of them. Its not a bad driver but it certainly doesn't do 20Hz!
LOL (You are right!)Only 14 grand? Get a couple for the kids!
Yes, my photo.Oops, I just discovered this thread. Is the photo from you? Have you been there?
Some of old audio friends I know use such Tungar PSU for their Western Electric Horn speaker systems, obviously it must be so to sound right. I may still have photos I took of it. I must have a look in my photo archives.
HaHa, they shine beautifully blue.My eyeglasses should attenuate most incident UV (most plastics are not very UV transparent) -- but, yeah, vision (eyesight) isn't something to gamble with.
^^^ Here, e.g., are a couple of 866jr tubes from the power supply of Gary Kaufman's 211 amplifier.