field coil speakers

[mekr]

i would like to have members opinian regarding field coil DIY speakers,cogent are the best but too expensive,which other drivers like suprravox ,fertin and fostex or any other make reach the heights

[scott fitlin]

Your in an area which ALL the products are VERY expensive.

[kevinkr]

I have heard a system using RCA field coils, fun, but I think unless you are very well healed the money can be spent better elsewhere. If you have access to a decent machine shop perhaps you could convert some compression or FR drivers.. It's going to take some work. I would aim for a low voltage field coil set up both for safety and to make winding the coils relatively tolerable. The RCA drivers I have seen run ~ 13V @ 1.2A. (Don't recall the exact numbers.)

[NKF]

i would like to have members opinian regarding field coil DIY speakers,cogent are the best but too expensive,which other drivers like suprravox ,fertin and fostex or any other make reach the heights
I am a new member to this site as of today. I am going to be auditioning a pair of classic Audio's new field coil drivers on Bruce Edgar's tractrix horns. I will let you know how they sound compared to my mint JBL 375's

NKF

[scott fitlin]

I am a new member to this site as of today. I am going to be auditioning a pair of classic Audio's new field coil drivers on Bruce Edgar's tractrix horns. I will let you know how they sound compared to my mint JBL 375's

NKFNKE, HELLO and WELCOME to THE FORUM!

I use JBL 2441J comp drivers, and LIKE YOU I am VERY interested in your direct A/B comparison of both drivers. I am EXTREMELY interested in your subjective opinion of HOW the field coil driver with it's Be diaphragm sounds at it's lower operating frequencies.


:bouncy:

[NKF]

NKE, HELLO and WELCOME to THE FORUM!

I use JBL 2441J comp drivers, and LIKE YOU I am VERY interested in your direct A/B comparison of both drivers. I am EXTREMELY interested in your subjective opinion of HOW the field coil driver with it's Be diaphragm sounds at it's lower operating frequencies.




:bouncy:


Thanks, the diaphragm seems to have a coating on it. I will let you know my findings.
I too have a set of 2441's but they are in need of a re-mag so the 375's seem to sound a little better. I know how good the 2441's are.

Nick

[scott fitlin]

Thanks, the diaphragm seems to have a coating on it. I will let you know my findings.
I too have a set of 2441's but they are in need of a re-mag so the 375's seem to sound a little better. I know how good the 2441's are.

NickYou already know the 2440 and 2441 ( 375 and 376 ) are the same motor and phase plug, it's the diaphragm that is different.

I have been looking at the CLASSIC AUDIO's drivers and of course, I lust for them. But for me, on the right horn, the JBL drivers magic is in it's LF performance, NOT the upper end of it's operating limit. And, to add my own take on things, although FIELD COILS are quite a bit before my time, and I have heard one set of OLD field coil speakers, I do not know that much about them and their sound, other than what I know and understand about the principles of field coil operation. I AM, however, a BIG fan of ALNICO magnets. Other than what FIELD COILS are supposed to sound like, and the one time I heard a set of Western Electric FC speakers, I have yet to find a sound I prefer over alnico motors, i.e.; ceramic ferrite or neodymium.

CONGRATULATIONS on your acquisition, I look forward to reading your opinions and testimonials! :D

[NKF]

You already know the 2440 and 2441 ( 375 and 376 ) are the same motor and phase plug, it's the diaphragm that is different.

I have been looking at the CLASSIC AUDIO's drivers and of course, I lust for them. But for me, on the right horn, the JBL drivers magic is in it's LF performance, NOT the upper end of it's operating limit. And, to add my own take on things, although FIELD COILS are quite a bit before my time, and I have heard one set of OLD field coil speakers, I do not know that much about them and their sound, other than what I know and understand about the principles of field coil operation. I AM, however, a BIG fan of ALNICO magnets. Other than what FIELD COILS are supposed to sound like, and the one time I heard a set of Western Electric FC speakers, I have yet to find a sound I prefer over alnico motors, i.e.; ceramic ferrite or neodymium.

CONGRATULATIONS on your acquisition, I look forward to reading your opinions and testimonials! :D

The 2441 has 3 different versions of phase plugs depending on the years made. When I fisrt found my pair, the plugs were very differnt and the drivers would not image properly. I have since found a match to the better of the first set. I'll remag and see how they sound.

Nick

[scott fitlin]

Yes, I know there were some revisions down through the ages. I didn't know they did exactly three phase plug changes, though. I use the six 2441J,s that we bought BRAND NEW with six 2395 lens horns in 1979-80, and I had them all remagged 5 years ago.

I have another two 2440 drivers and the 2395 lens horns, these came out of West Point Academy, they are dated 1972 and say West Point, and I have tried them, with the 2440 and 2441 diaphragms, and these two drivers have a slightly wider gap than my later 2441 drivers, and YES they do sound different as well.

I am good, I simply use my set of six 2441,s together, they all have the same aging on them, and were re-gaussed together, and they play properly together. :D

[kevinkr]

My understanding from people who own both 2441 and 2440 is that the phase plugs between these two drivers have always been different. I own a pair of 2440 but have not seen a pair of 2441 apart.

Does anyone know of a relatively local outfit (Boston area) that can remag JBL alnico drivers? Mine don't appear to need it, but it would be handy for future reference and in the event that I acquire other drivers that do need it.

[scott fitlin]

My understanding from people who own both 2441 and 2440 is that the phase plugs between these two drivers have always been different. I own a pair of 2440 but have not seen a pair of 2441 apart.

Does anyone know of a relatively local outfit (Boston area) that can remag JBL alnico drivers? Mine don't appear to need it, but it would be handy for future reference and in the event that I acquire other drivers that do need it.No, it is the DIAPHRAGM that is different, the phase plugs are the same.

The 375/2440 uses a phragm with a half roll surround. The 376/2441 uses a diamond pleat surround to extend frequency response. I have a 2440 right here in front of me, and I opened it up, again, and the phase plug is exactly like my 2441 drivers.

[jcrobso]

You need to wind the coil very tight, you need to get the correct # of wire turns.
The formula for flux is amps X the number of wire turns=flux.
There are a lot of variables in play here, what wire gauge, how many turns, what voltage and the resulting current needed to get the SAME flux density as the Alinco magnet provided. Oh yes, you do have to dismantle the driver and remove the magnet not a easy thing to with our degassing the magnet first.:eek:
Then you have to make a steel coil form the exact height as the old magnet so the gap lines up correctly & the phase plug fits correctly.:crying:
If you get all the above done correctly you need a VERY stable and CLEAN DC voltage source.
To do all of this will cost BIG $$$.

[NKF]

My understanding from people who own both 2441 and 2440 is that the phase plugs between these two drivers have always been different. I own a pair of 2440 but have not seen a pair of 2441 apart.

Does anyone know of a relatively local outfit (Boston area) that can remag JBL alnico drivers? Mine don't appear to need it, but it would be handy for future reference and in the event that I acquire other drivers that do need it.

JBL alnico drivers displace 1% of there magnet strenght every year and more if they have been dropped or over heated. Orange County Speaker in CA does re-mag. $25.00 per driver. Pack them well.

Nick

[yggdrasil]

JBL alnico drivers displace 1% of there magnet strenght every year and more if they have been dropped or over heated.
This topic have been discussed at several occations - here's a really qualified answer: http://www.audioheritage.org/vbulletin/showthread.php?10280-Recharging-Alnico-Ferrite-magnets&p=110522&viewfull=1#post110522

[kevinkr]

No, it is the DIAPHRAGM that is different, the phase plugs are the same.

The 375/2440 uses a phragm with a half roll surround. The 376/2441 uses a diamond pleat surround to extend frequency response. I have a 2440 right here in front of me, and I opened it up, again, and the phase plug is exactly like my 2441 drivers.

I stand corrected.. :D I have not seen, nor compared the phase plugs in the 2441 with the 2440. Thanks for setting the record straight as I was mis-informed. I did know about the diaphragms..

[kevinkr]

JBL alnico drivers displace 1% of there magnet strenght every year and more if they have been dropped or over heated. Orange County Speaker in CA does re-mag. $25.00 per driver. Pack them well.

Nick

Yeah, I was aware of Orange County Speaker, unfortunately the round trip shipping charges from Boston, Ma. would be prohibitive for something the size and weight of a 2440 and I really wanted to find an outfit within an hour's drive of Boston that could do it. That said they would be a good option for something smaller. Anyone?