Forums - Rewind Voice Coils?

Brian

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Rewind Voice Coils?
07/25/20 at 06:20:06

I recently read a comment on listeners preferring JBL professional speakers over residential models when the driver compliment was the same, and the cabinet was the same, except the drivers in the pro models had 16 ohm voice coils, while the home models had 8 ohm.

The commentor said:
"In my opinion 16 ohm components carry less current for the same efficiency and the overall current related flux modulation distortion is lower in the Studio Monitor series, therefore they sound cleaner and more civilized when compared to consumer grade speakers."

This is fascinating to learn. It reminds me of reading that the old field coil electromagnet speakers of the 1920s & 30s were often listed as 500 ohm. I sometimes come across a reviewer saying: after hearing field coils he is never going back to permanent magnets ever again.
I have wondered what made the field coil speaker sound superior, I now wonder if this business of less current related flux modulation distortion is the answer.

This all leads me to ask:
Can voice coils be rewound to greater resistance? Is there typically room on the VC former for the extra windings? If the magnetic gap is too tight for adding windings, perhaps whittling out a new former on the lathe is not difficult. I don't know. I imagine it calls for a machinist's metal lathe instead of a carpenter's lathe to get the precise dimensions, even though the VC former is not made of metal.

Brian

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4krow

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Re: Rewind Voice Coils?
Reply #1 - 09/06/20 at 17:37:36

This is fascinating to me also. Thing is, I would wonder how a typical power amp would deliver to higher impedances. If an amp were rated at 100wpc into 8 ohms, and 200wpc into 4 ohms, then I expect that it would be drop in power at say 16 ohms, like 50 watts. And how this might relate efficieny of the driver itself in that if it were rated at say 95db sens., then there wouldn't be much of a problem with lower powered amps. Now, as to the sound, I wouldn't have a clue, but surely I would expect a change at least in character.
The field coil speakers were a really good idea because the power of the eletromagnet could be varied, resulting in a difference in the bass as I understand it. Of course, the permanent magnet driver was very much leass expensive to make, and that seems to always rule when it comes to consumer products. Just think of the power supply needed to make such a magnetic field coil design. Lots of current.

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Brian

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Posts: 903

Re: Rewind Voice Coils?
Reply #2 - 09/07/20 at 03:01:30

Thank you for the reply 4Krow.
I would like to hear an 8 Ohm speaker changed to 16 or 32 Ohms, to hear if the difference is as that reviewer said. Changing to as much as the 500 Ohms of the field coil is probably excessive. I would not try that, but I would like to try the other values.

I don't know how much of a do it yourself community is currently here on the Decware forum. Perhaps there is no one here who could wind a coil.

Brian

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Donnie

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Re: Rewind Voice Coils?
Reply #3 - 09/07/20 at 04:02:21

So what would it take to wind a coil?

Could you use a lathe to do it, rotate the spindle and match the IPR (Inch Per Rev, the amount that the carriage moves every revolution of the spindle)

Doesn't this stuff get into flat wire and how closely the wire can be wound, and the gage of the wire?

Sounds complicated, I like to make complicated things real easy.

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Brian

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Posts: 903

Re: Rewind Voice Coils?
Reply #4 - 09/08/20 at 04:24:47

Hi Donnie,
It may be complicated. I don't know. I would guess it is something a Handyman - Mr Fixit sort of fellow could do. It would require building a winding apparatus, but I would think that is fairly simple. Something like the level wind mechanism on a fishing reel.

Making a new bobbin may not be necessary. The one pulled out of the speaker would presumably have enough wall thickness to allow trimming it to a reduced diameter to make room for the extra windings.

I don't know what else would be involved.

Brian

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4krow

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Re: Rewind Voice Coils?
Reply #5 - 09/12/20 at 23:30:05

The closest that I ever came to winding wire like that was for an antique house fan. Worked fine when I completed it.

For one thing, it may be a longer run of wire than you think. More importantly, I wonder if the coil would be wound in perfect layers. Lastly, I personally would want square wire to wind, because it would make a more efficient 'motor'.

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Decware 34I.3 integrated amp/Forte' 3 bass amp/Velodyne SMS-1 bass mngmnt system/Decware ZOB speakers/Audio Nirvana 8" bass drivers/Xiang Seng DAC/ LR Audio Computer/Rega Apollo R CDP/Emotiva ERC3 CDP/BPT 3.0 power cond.

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