Field Coil Speakers?
Moderators: pompeiisneaks, Colossal
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- Posts: 369
- Joined: Thu Oct 24, 2013 7:22 pm
- Location: Las Vegas, NV
Re: Field Coil Speakers?
dorrisant,
That number AO-21055-(2 or Z) looks very familiar from my research and from what I've found (and you likely will also) is that it has a 1.75" voice coil and will accept a cone kit for most of the G12 series of Celestions.
An ohm meter on the 2 different coils would be a good starting point. If neither coil is "open" or shorted, it would seem that one of the next steps would be to figure out how to best fire up that amp, possibly a slow Variac fire up to gently/hopefully "reform" the caps a little and hopefully be able to test voltages without having to do a pile of repairs on the amp! I'm not well versed on the reforming process, but there are likely some smarter guys than me here who can give us a little guidance. Once we know what voltage is used to energize the field coil, we're "OFF TO THE RACES!"
Also identifying the amp, possibly finding a schematic for it would be helpful. It would be interesting, out of curiosity, to see if the field coil power is taken from it's own B+ node or if it shares a node with other parts of the amp.
I'm a fairly rabid search monster and if you can get some numbers off the amp, I can likely track down some info. Remember that while firing up the amp, you need to have a suitable impedance load on the output transformer.
Once we know the voltage we're dealing with, we can either build or acquire a similar voltage power supply in a variable form. I would suggest that for initial testings, we use a really low, 5 or so, watt amp to avoid smokin' the voice coil!
Sorry for the long post, but I'm pretty stoked about this! I'll PM my contact info for you to use at your convenience. I have a good friend, amp builder in McCordsville (North East of Indianapolis) who may be able to help out with some components, etc.
Thank You Sir,
Gene
That number AO-21055-(2 or Z) looks very familiar from my research and from what I've found (and you likely will also) is that it has a 1.75" voice coil and will accept a cone kit for most of the G12 series of Celestions.
An ohm meter on the 2 different coils would be a good starting point. If neither coil is "open" or shorted, it would seem that one of the next steps would be to figure out how to best fire up that amp, possibly a slow Variac fire up to gently/hopefully "reform" the caps a little and hopefully be able to test voltages without having to do a pile of repairs on the amp! I'm not well versed on the reforming process, but there are likely some smarter guys than me here who can give us a little guidance. Once we know what voltage is used to energize the field coil, we're "OFF TO THE RACES!"
Also identifying the amp, possibly finding a schematic for it would be helpful. It would be interesting, out of curiosity, to see if the field coil power is taken from it's own B+ node or if it shares a node with other parts of the amp.
I'm a fairly rabid search monster and if you can get some numbers off the amp, I can likely track down some info. Remember that while firing up the amp, you need to have a suitable impedance load on the output transformer.
Once we know the voltage we're dealing with, we can either build or acquire a similar voltage power supply in a variable form. I would suggest that for initial testings, we use a really low, 5 or so, watt amp to avoid smokin' the voice coil!
Sorry for the long post, but I'm pretty stoked about this! I'll PM my contact info for you to use at your convenience. I have a good friend, amp builder in McCordsville (North East of Indianapolis) who may be able to help out with some components, etc.
Thank You Sir,
Gene
Re: Field Coil Speakers?
I would just do the coil as B+choke like in the old organs. If you want to knock off SPLs, Eminence is working on a variable gauss speaker, not sure when it will be out, but it should be priced more reasonably.
Re: Field Coil Speakers?
The Reignmaker is already out. I have one over a year now. It does work, but there is significant tone change too.
John
John
Do not limit yourself to what others think is reasonable or possible.
www.johnchristou.com
www.johnchristou.com
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- Posts: 369
- Joined: Thu Oct 24, 2013 7:22 pm
- Location: Las Vegas, NV
Re: Field Coil Speakers?
Well Folks,
I found a guy who has 4 speakers, identical to the one Tony posted pics of. He says they are perfect working order and will let me have them for the cost of shipping! For the time being, I'm just getting one of them for experimentation and will grab the rest if all pans out. I will naturally throw him a few extra $$ for his efforts, generosity, etc!
Once I receive the speaker, all I need is to figure out what voltage range to start with and then it is, as they say, "Off To The Races!"
Any Help & Thoughts Are Appreciated,
Gene
I found a guy who has 4 speakers, identical to the one Tony posted pics of. He says they are perfect working order and will let me have them for the cost of shipping! For the time being, I'm just getting one of them for experimentation and will grab the rest if all pans out. I will naturally throw him a few extra $$ for his efforts, generosity, etc!
Once I receive the speaker, all I need is to figure out what voltage range to start with and then it is, as they say, "Off To The Races!"
Any Help & Thoughts Are Appreciated,
Gene
Re: Field Coil Speakers?
Maybe I can help you guys out? I bought 3 vintage field coil speakers to experiment. Two of them are Jensen F12N and one is a Rola 12 inch. They all have 1.75 inch diameter voice coils. The field coil DC resistance for each is in the range of 680-700 ohms, and they all came from a Hammond organ. Hammond used 100 volts DC to power the field coil, so that's a good upper limit for your power supply voltage. Fluxtone uses a much lower voltage supply for safety reasons, so they wind their own field coils to suit the lower voltage. I didn't want to rewind the field coils, so I stuck with a 100 volt variable power supply. I bought 100 watt voice coils, Grey Wolf cones, large H-screen dome dust caps, and spiders from Weber, and reconed the speakers. I reconed the speakers to be sure that they could handle high power. The speakers turned out to be very efficient and sound good to my ears. The power supply can be adjusted between 7 and 100 volts, and can be used to cut the volume down. I found however, that the speakers start to get a lot of compression and low note distortion at low field coil voltage. I don't hear this happening on the Fluxtone videos with their speakers. I'd be very interested in hearing back from anyone that's tested the Fluxtone speakers - do they compress too at low voltage? Any excess distortion on the low notes at low voltage?
Re: Field Coil Speakers?
A little more information on the field coil voltage supply. I used a Hammond step down transformer 166G80, and then this adjustable DC voltage module that is based on the TL783CKCSE3 linear voltage regulator - AudioWind Electronics-Salon Model SP-4.
http://www.audiowind.com/pdf/sp-4.pdf
http://www.audiowind.com/pdf/sp-4.pdf
Re: Field Coil Speakers?
Bit of a tangent but I looked up Audiowind found their ebay store and saw this. Real mad professor. I want one!
http://www.ebay.com/itm/Audio-Power-Amp ... 2ed2a30f7f
http://www.ebay.com/itm/Audio-Power-Amp ... 2ed2a30f7f
Re: Field Coil Speakers?
Nice door pull to the Mancave.
John
John
Do not limit yourself to what others think is reasonable or possible.
www.johnchristou.com
www.johnchristou.com
Re: Field Coil Speakers?
!!!!!Cantplay wrote:Nice door pull to the Mancave.
John
- dorrisant
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Re: Field Coil Speakers?
You could warm 'em up real good for when the revenuers come a knockin'.
Tony
Tony
"Education is what you're left with after you have forgotten what you have learned" - Enzo