Field Coils for Audio Systems

[cal3713]

I'm sure Bill and some others have already seen this content, but since this thread is a place to collect valuable information on field coil design:

https://www.facebook.com/ProjectRyu/ & https://projectryu.com/wp/ & https://www.diyaudio.com/forums/multi-way/212953-project-ryu-diy-field-coil-loudspeaker.html

I've been trained by Audiogon to only provide links... here's an image of his field coil motors to entice link clicking:

 

[Audiophile Bill]

I've been trained by Audiogon to only provide links... here's an image of his field coil motors to entice link clicking:

View attachment 79448

I was telling Marc to consider these. Only issue with them is slightly lower sensitivity than some other full range drivers.

 

[morricab]

I can also confirm that John uses JBL for his FC operation. I spoke to him about Hartsfield reproductions a few months ago.

I would love to hear those Hartsfield reproductions as well. The originals with supertweeter sound fantastic and I like horn bass better than any kind of vented box.

 

[jeff1225]

He

I would love to hear those Hartsfield reproductions as well. The originals with supertweeter sound fantastic and I like horn bass better than any kind of vented box.

actually uses a field coil 18" JBL in the Hartsfield. I think it could be quite special.

 

[morricab]

He

actually uses a field coil 18" JBL in the Hartsfield. I think it could be quite special.

The original was a 15 inch driver, wasn't it?

 

[morricab]

He

actually uses a field coil 18" JBL in the Hartsfield. I think it could be quite special.

Website says 15 inch bass driver

 

[Atmasphere]

The original was a 15 inch driver, wasn't it?

Yes. He used to use a 15" FC driver that he made (IIRC, a modified JBL driver) but he built an 18" FC driver for his T-1 which really works nice. I'd not seen that it had found its way into the Hartsfield though.

 

[jeff1225]

J

Website says 15 inch bass driver

Just talked to him on the phone.

 

[Atmasphere]

J

Just talked to him on the phone.

Dang! He keeps pushing the LF cutoff of that speaker down...

 

[bonzo75]

I've never seen an Altec that didn't use Alnico

Sorry I don't know where the word pre came from in my text, must have been some autocorrect. Edited.

Btw they did use field coil on early Altec 284 And on the 515 woofer

 

[Atmasphere]

Btw they did use field coil on early Altec 284 And on the 515 woofer

I'm sure those go for a nice price

 

[the sound of Tao]

 

[dcathro]

Field Coils are another element that add complexity and cost.

Just trying to imagine a Field Coil version of the Wilson Wamm, requiring 16 power supplies.

 

[Atmasphere]

Field Coils are another element that add complexity and cost.

Just trying to imagine a Field Coil version of the Wilson Wamm, requiring 16 power supplies.

Yes. In a portable radio that would be a problem. In a high end speaker its not. If using FC drivers, the Wamm probably wouldn't need so many

 

[K3RMIT]

My reason was not just regulation but induction interactions based on varying frequencies. even harmonic noise back into psu. Like diodes do to power supply transformer.

 

[K3RMIT]

Field Coils are another element that add complexity and cost.

Just trying to imagine a Field Coil version of the Wilson Wamm, requiring 16 power supplies.

I don’t know enough to say it’s better , and I agree more complex. I think horns have the need based on a nostalgic look

 

[Audiophile Bill]

My new motors are ready for shipping hopefully tomorrow. It took a little extra time as I had some custom thread made on the permendur pole so I can use any manner of phase plug that I make depending which driver I use.

 

[Atmasphere]

My reason was not just regulation but induction interactions based on varying frequencies. even harmonic noise back into psu.

If the power supply is properly regulated this is no concern at all.

I think horns have the need based on a nostalgic look

Horns and high efficiency are about a lot more than just nostalgia! Controlled directivity is really helpful in smaller spaces like a living room (less short delay reflection problems with side walls means a smoother sound as the ear interprets short delay times as harshness) and high efficiency in general is paramount to keeping distortion down in all amplifiers. Efficiency is helpful to prevent thermal compression which is problematic of all lower efficiency loudspeakers. Put another way if you want to experience the actual dynamic contrast in any recording (especially if bass notes are involved) then you need high efficiency.

Computer optimization has made it possible to rid horns of artifact.

You do run into other issues, such as noise floor but they can be dealt with.

 

[cal3713]

My new motors are ready for shipping hopefully tomorrow. It took a little extra time as I had some custom thread made on the permendur pole so I can use any manner of phase plug that I make depending which driver I use.

View attachment 79471

What a fun tool Bill. Can't wait to hear about the comparisons. Congrats!

P.S. You are certainly much more skilled than I, but the thought of removing the permanent magnets from your AER drivers gives me nightmares.

 

[Audiophile Bill]

What a fun tool Bill. Can't wait to hear about the comparisons. Congrats!

P.S. You are certainly much more skilled than I, but the thought of removing the permanent magnets from your AER drivers gives me nightmares.

Ha. Already done it before but yet I took a few deep breaths due to the cost of those BD4s