field coil speakers

[freak scene]

anyone know any good companies that still manufacture these?

[Mark Hammer]

I don't mean to be snotty, but why would anyone want to?  There may be some old ones that sound decent as speakers, but the advantages of using a permanent magnet instead of a created field are patently obvious to any manufacturer.  It's not just the cost of producing the speaker, but the cost to the OEM manufacturer of having to provide the additional supply current to produce the induced field in the speaker.  If someone IS still turning out these behemoths, chances are you will need to spend a huge chunk of change to get one since I can't imagine they have many customers.

[freak scene]

well i just bought an old gretsch amp with a field coil speaker, i wanted to replace the speaker so that i would have the original in tact and not have to worry about damaging it.  i also didnt want to mod the amp and possibly mess something up. 

any suggestions?  is there an easily reversible way to mod an amp to run off of regular speakers?

the amp in question is a late 40's(?) gretsch electromatic with tremolo.

[cx_deluxe]

Sounds like a nice amp.  I don't know about modifying things so much yet.  I'm really in the "collecting all the bits stage".  That said, field coil speakers aren't that hard to come by.  I guess it depends on what you need, but there are A LOT of old radios out there that have one.  If it were me, I'd go to flea markets and look for old cabinet radio/record players - particularly the ones that don't work and have beat up cabinets, heh.  Also check out radio swap meets, thrift stores, even the local "specializing in radios" antique store...  you'll find what you're looking for.  Its pretty unlikely that you'll be able to buy a new one.  Come to think of it, I think I saw one on ebay recently.

Good luck.

[cx_deluxe]

Ok so I just looked on ebay.  What am I talking about "I think I saw one"! 
There's TONS of them on there right now.  Prices anywhere from 10 bucks to $500.  I'm sure you'll find one. 

[freak scene]

right on, yeah i saw a bunch on ebay last night, i was just curious about current manufacturers or mods. 

i also saw a hammond tube amp and field coil speaker kit that looked like it could be fun.   

[petemoore]

  Besides all the 'practicality' matters...
  Functionally, did these field coil systems offer some type of advantage or another?
  Or were they just a 'novel' approach that had a run of popularity?
  Extree Troublesome to be sure..is it truly fair to think that permanent magnet speakers are just plum 'better'?
  Maybe they can be used in a totally unorthodox manner...say using a tube output to speaker intput, the otherwise unconnected field coil connections would have a signal output

[Mark Hammer]

I don't know that field coils are sonically better OR worse.  What they are is simply one more headache to have to design/build around.  Ultimately, as a moving object, the sound of any speaker is as much a property of the cone, suspension, and other mechanical properties it possesses, as it is a property of the coil and magnets.  A good *physical* design is not necessarily ruled out by field coil use, nor necessarily implied by use of a permanent magnet.  True, it is technically possible to vary the properties of the magnetic field using a field coil approach, but quite frankly it has gotten easier and easier for manufacturers to identify the properties of aged magnets and optimum megnets and simply have them made.

If one's goal is to maintain the authenticity of something from a bygone era, then naturally you use what was used then, and the issue of what "sounds best" is set aside in favour of what sounds authentic.

[puretube]

The field coil is the L part of the power supply LC-filtering, most of the times!

[puretube]

try to find a suitable (x mA)  choke to replace the fieldcoil, when useing "normal" speakers.

[petemoore]

  I don't know that they ever got or ever will get the same attention to myriad design targets speakers and tube amps of the permanent magnet got, for the extre trubbles, it'd have to be some cool 'authentic' vibe, or quite measureable 'improvement' or alternate 'function'..the next point of inquiry
  Could some kind of cool phase shift be imparted to the induced field to create a 'new' effect, when combined with a speaker and channel which is in phase 
  WHo knoes Who Cares...I pity the fool who dares !!

[freak scene]

here is the amp in question for those curious.

its... relic-ed... heh.

[runmikeyrun]

cool amp!!

if you're worried about vintage value and having the original speaker for some day down the road, you would need an exact replacement, because anything else would require drilling new holes to mount it, plus the mod of adding a choke coil.

I'd stick w/ what ya got and just take it easy on the volume knob.

[puretube]

that amp loox cool!!!

of course - given that the field coil of the ancient speaker is still OK:

you can go and just use an external speaker instead of the built-in old one (concerning the voice-coil),
and leave the old speaker`s field-coil-choke as a "dummy".

petemoore:
I`m sure there must be some magic voodoo concerning "sag"/"compression"/"mains-hum modulation" with those electrodynamic speakers!
but at the time I played around with them, it was all about "radio", so-called "hifi",
and trying to achieve an S/N ratio of over 50dB @, <10% distortion @ 1W from 300 to 4.500 Hz,
so I don`t actually remember if they really were "better"...

[Ge_Whiz]

Wow! The original Orange amp!

[gez]

There's a novel that follows the life of a Stradivaris violin over the centuries.  It made me think what sort of life this little gem has seen...but on reflection probably just a load of drunken slobs in smoke-filled bars! 

Nice find!

[Paul Perry (Frostwave)]

As a child, I got a hell of  a boot off a field coil speaker... who would have thought that there would be 380V DC on a wire going to a speaker?? then again, what was I doing behind the wireless....