field coil speaker

[baddog]

I just picked up a jensen F15N concert series speaker out of the trash. where can i find info on this speaker and would it make a good tube guitar amp speaker? I tested the voice coil at 10ohms and the field coil at 2,500 ohms.

thanks
keith

[cbarrow7625]

Ampage Archives.

http://archive.ampage.org/threads/6/..._anyone-1.html

[6267]

It would be perfect for a blues amp…You'd want to redesign the powersupply of the amp to use the field coil as a choke, or at least come up with a nice 100v DC supply to run through it. Field coil speakers can also be wired for additional humbucking by playing with the polarity of the coil. They have excellent bass in my experience as well. Killer for harp amps too.

[baddog]

field coil speaker

The speaker needs roughly 239 v to operate properly(i have the old amp with the schematic on it) , i just have to order the parts to make the amp to power the field coil. Im modifing a valve junior and plan on using the speaker with it.

thanks
keith

[6267]

I think you'll be happy with the sound, it may be tricky or not (not having looked at a valve junior schematic) to use the choke/field coil in the powersupply…

[baddog]

field coil speaker

I built a power supply for an old 12" magnavox speaker i removed from an organ and it sounded ok . A little tinny when over driven with my valve junior. I just have to order a different zener diode to add to my existing power supply to make it compatible with the Jensen . I found the schematic for the power supply at Weber Speakers .com
I was wondering if the speaker would work in a closedback cabinet or if they are designed for openback only? Any thoughts

thanks
keith

[6267]

I haven't had good experience with overdriven field coil speakers either. I imagine it varies from speaker to speaker though. I am sure it'll work with a closed or open back, the only real difference is how the magnetic field is created. That being said, I've never seen a closed back field coil speaker.

[thetechguy]

Jensen 15n "mains energised" speaker.

Thetechguy--(Paul). The speaker that was removed from a defunct jensen,is known as (in u.k.)a "mains-energised" type speaker. It would ideally connected in a 15 watt (r.m.s.)tube amplifier,the field winding should be connected in place of the h.t. smoothing choke--after first discharging h.t.,then disconnecting the smoothing choke,then wiring in the field coil. DO NOT COMPLETLY REMOVE THE CHOKE,BECAUSE IF THIS SPEAKER WERE TO FAIL,EVERYTHING CAN BE REWIRED BACK AGAIN.

[baddog]

I think you need a certain DC voltage for the fieldcoil to operate properly. 2500 ohms is a little big for a choke . Most chokes are 100 to 200 ohm if im thinking wright. Just my thoughts

[Enzo]

Field coils were designed into the circuit. Not all that odd to find 2500 ohms in a B+ string. SOme FCs are in series with the B+ load, while others are across the B+.

[baddog]

Field coils were designed into the circuit. Not all that odd to find 2500 ohms in a B+ string. SOme FCs are in series with the B+ load, while others are across the B+.

Hey Enzo

I was thinking about building a fender champ and using a Jensen field coil speaker Im not sure if its possible What do you think? Can it be done?

Baddog

[ThermionicScott]

Hey Enzo

I was thinking about building a fender champ and using a Jensen field coil speaker Im not sure if its possible What do you think? Can it be done?

Baddog

Depends on the specs of the FC you have on hand, but it's very doable. If it's a high-resistance choke, you might put it between the plate and screen, rather than as a CLC filter before the plate. Unless you need to drop a bunch of voltage anyway.

- Scott

[Prairie Dawg]

Depends on the specs of the FC you have on hand, but look at some of the early Champs and Princetons -- they did it.

- Scott

Gibson and Supro used them plenty and the schematics are all around us. Particularly Gibson.

[Enzo]

No reason in the world you couldn;t do it, but as Scott points out, you need some idea of the FC characteristics of your particular speaker.

When I was a kid, I came up with a field coil speaker from some old record player or radio, and I build a plywood box for it and used it as a speaker for my own record player. I built a little DC power supply inside it for the coil, so this speaker had a power cord trailing out and an on/off switch.

[Prairie Dawg]

No reason in the world you couldn;t do it, but as Scott points out, you need some idea of the FC characteristics of your particular speaker.

When I was a kid, I came up with a field coil speaker from some old record player or radio, and I build a plywood box for it and used it as a speaker for my own record player. I built a little DC power supply inside it for the coil, so this speaker had a power cord trailing out and an on/off switch.

Ted Weber was working on a field coil project last year and has a schematic for a power supply to run them. I think what makes them interesting, though, is the connection between the field and the B+ supply. There's got to be some interaction going on there. Seems to me I've seen a schematic for an old Danelectro circuit that actually modulated the field coil to produce a vibrato effect.

The field coil will suck up a lot of voltage that could be going to the plates.