This was a good read.
High Efficiency Speaker Asylum
Steve, thanks so much for the info and the links. That's the sort of real, practical info I'd love to see on the thread over at DIY. I despair that may never happen.
This was a good read.
High Efficiency Speaker Asylum
My take on ALNICO & PM drivers; The VC AC flux modulates the PM maginetic field which causes back EMF and higher distortion levels...non-linear maginetic flux...
My take on Field coil drivers; Back EMF in the field coil due to modulation of the Field coil magnet would be minimized as these currents would be shunted through the Field coil power supply....
My conclusion is that a Field coil driver should sound better..... But JBL came up with a
mod for PM drivers, A shorted turn to shunt the back EMF and reduce non linear flux ....This would be an interesting research project.....................My 2 cents......GC
Yeah, cradeldorf, that thread was interesting.
One great point was that field coil does not automatically make a speaker good! So true. Most of them are junk, or at best nothing special.
But some real good drivers only came out in FC versions, so how can you know if it is the FC making them good?
The comment about the negatives of humbucking coils was interesting also. I recently dismantled a Jensen 18" Auditorium speaker and a WE TA-4181 18" driver. Since the WE unit was OEM Jensen or at least Jensen parts, the metal parts and construction were identical. The same replacement cones fit both units. However, the Jensen had a humbucking coil and the WE did not. That was the only visible difference.
Well gotta get off the computer and finish packing. Leaving for the Munich High End show in the morning, where I will be hearing field coils for a week, 10 hours a day...
PS: Here's some pics of the inside of a TA-4181. Scary looking ancient stuff!
Great info and read Craddledorf, but now I am a little perturbed, there was a company in europe selling new repros of 16" 604's in a field coil design. At a price tag of around 7000 a pair I thought it was a little extreme, but maybe I was wrong!!!! Now I cant find the company.........
I remember seeing something on Ebay about totally rebuilt 604's. It was a company/Person in Germany. They had pictures of one completely stripped down and sandblasted. I remember they were priced way up the scale from the normal prices but I don't recall anything about it being converted to a field coil.Originally Posted by juniper
A604 | Kilimanjaro-Series | Wolf von Langa
Maybe Joe will run into this fella at the Munich show, and can give us some insight.
Not all vegetables make good leaders.
Yup I was going to suggest this too. Trumped by that Chevy guy again !
I'm particularly interested in the A284 & the A416 . Hope you get to hear the Wolf Von Langa FC's.
http://www.kilimanjaro-series.com/En...ries/a284.html
http://www.kilimanjaro-series.com/En...ries/a416.html
Cradeldorf, I have intended to conduct experiments to test for the superior quality of field coil magnetic circuits, but to date I have failed to do so. The prevailing theory is that field coil motors resist flux modulation by voice coil currents better than permanent magnet motors do, providing better fidelity to the driving signal. A permanent magnet structure is provided a magnetic charge from a momentary infusion of energy. This charge can be momentarily or permanantly altered by voice coil currents. An elecromagnet is connected to a DC power supply which is capable of providing current to maintain the magnetic circuit under dynamic conditions. The subjective results of field coil operation are of control of the moving mass, providing great fidelity to the audio signal. The results are similar to a good Alnico motor, but a bit better yet.
This all begins to be a religion after a while, like triodes vs. pentodes, tubes vs. transistors or you-name-it. Most field coil advocates have reached their preference after numerous convincing listening sessions. We are all allowed our preferences, and field coil advocates enjoy the sound of their drivers. A field coil cannot make a flawed speaker great, like a 6" cone trying to operate full range. Electromagnets do seem to provide benefits though, at least to their adherents. "Nuff said.
Some people allready have a business in FC conversions. On the bottom of this page //www.ch-audio.com/CH288287.html there is a measurement comparison between a stock alnico and a fieldcoil converted 288 driver. Clearly the field coil is smoother and more extended, surprisingly (or not?) most at the bottom of the FR. I would expect more difference at the top end if the differences where only due to the FC having a stronger field.
As least as interesting is that the driver has a very straight FR from 150-15kHz! Very nice for any full range driver. Now you just only need a suitable horn, like an WE-15A.
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