need help with figuring out the connections on an old speaker

yourownfree · 07:03 AM

I have a 12 inch speaker. What it came off of I don't know. I am assuming it is from the tube era. I am guessing by the grill cloth at least 50's era or earlier.
It has a transformer attached to the outer part of the speaker rim, with three connections on the primary and two on the secondary. Actually more on the secondary but only two are used. I am assuming that transformer is made for a push pull amp. The weird thing for me is that it has not only the voice coil but two separate coils on the magnet which is round and about two inches in diameter and about three inches long. Starting with the secondary of the transformer, one side goes to the voice coil directly. The other side of the secondary goes to one of the windings on the magnet and the other side connects back to the other side of the voice coil. My thought is this is a bass speaker and that coil is to change the response of the speaker to the low freq. range by adding inductance. So what is the other coil for? It goes to a harness which at one time went to a plug (still attached) back to the amp. (The amp does not exist). What did it connect to, back at the amp or what is it for? Remember this coil is also wound on the magnet and not another voice coil. I am stumped on this one.
I am sorry about placing thread in wrong place, too late for me to change it.

planet10 · 19th December 2009, 07:23 AM

picture please.

dave

Mooly · 19th December 2009, 07:38 AM

Anything along these lines,
Mains energised speakers. - UK Vintage Radio Repair and Restoration Discussion Forum

godfrey · 19th December 2009, 07:38 AM

Are you sure there is a magnet?
The "other coil" could be a field coil to magnetize the core.

See here for an explanation:
Antique Electronic Supply - Speakers

dhaen · 19th December 2009, 07:56 AM

Speakers with a field coil rather than a permanent magnet (called "mains energised" in the UK) sometimes had 3 windings:
1.voice coil (a few ohms), 2. field winding ( a few hundred ohms) 3. a hum cancellation winding. I can't remember the resistance of the hum cancellation "dinger" coil.
On this type the field winding would double as a choke in the HT or +B supply. The ripple would cause hum in the speaker which would be cancelled by out-of-phase current though the "dinger" coil". I think the "dinger" coil was on or near the voice coil and was connected in series with the field winding.
We're going a long way back here...

planet10 · 19th December 2009, 08:33 AM

Quote:

Originally Posted by godfrey

Are you sure there is a magnet?
The "other coil" could be a field coil to magnetize the core.

This is where a picture would be worth a 1000 words.

dave

dhaen · 19th December 2009, 08:51 AM

After a quick google, it seems there are some modern "field winding" speakers.
I wonder if this is the way to go? After all it's easier to produce high quality, high power DC for the field winding, than to produce high quality, high power audio for the voice coil.
In other words: why not increase speaker efficiency by this method, so as amplifier power can be reduced...

yourownfree · 19th December 2009, 11:55 PM

Here are some pics of the speaker. the coils are 2.5 inches across and 2 inches high. The speaker is a 12 inch. It might not be a magnet at all on there as I don't really know. The pics are from camera with 480x640. if you need better resolution the best I can do is 1 meg, but I can get as close as you need.
thanks.

jleaman · 20th December 2009, 12:47 AM

Quote:

Originally Posted by yourownfree

Here are some pics of the speaker. the coils are 2.5 inches across and 2 inches high. The speaker is a 12 inch. It might not be a magnet at all on there as I don't really know. The pics are from camera with 480x640. if you need better resolution the best I can do is 1 meg, but I can get as close as you need.
thanks.

the transformer might look like it step's up or down voltage to create a magnetic coil,

dhaen · 20th December 2009, 08:47 AM

It's all clear now:
There is a big field coil and a smaller hum coil on the same core. The field coil is fed directly and doubles as a choke. The hum coil is connected in series with the voice coil to cancel some of the AC component.
There is a conventional output matching transformer, it's secondary being connected to the voice coil via the hum coil. Both secondary connections are sent back to the amp for negative feedback.

19th December 2009, 07:00 AM	#1
yourownfree diyAudio Member Join Date: Apr 2008	need help with figuring out the connections on an old speaker I have a 12 inch speaker. What it came off of I don't know. I am assuming it is from the tube era. I am guessing by the grill cloth at least 50's era or earlier. It has a transformer attached to the outer part of the speaker rim, with three connections on the primary and two on the secondary. Actually more on the secondary but only two are used. I am assuming that transformer is made for a push pull amp. The weird thing for me is that it has not only the voice coil but two separate coils on the magnet which is round and about two inches in diameter and about three inches long. Starting with the secondary of the transformer, one side goes to the voice coil directly. The other side of the secondary goes to one of the windings on the magnet and the other side connects back to the other side of the voice coil. My thought is this is a bass speaker and that coil is to change the response of the speaker to the low freq. range by adding inductance. So what is the other coil for? It goes to a harness which at one time went to a plug (still attached) back to the amp. (The amp does not exist). What did it connect to, back at the amp or what is it for? Remember this coil is also wound on the magnet and not another voice coil. I am stumped on this one. I am sorry about placing thread in wrong place, too late for me to change it. Last edited by yourownfree; 19th December 2009 at 07:03 AM.

19th December 2009, 07:23 AM	#2
planet10 frugal-phile(tm) diyAudio Moderator Join Date: Oct 2001 Location: Victoria, BC, NA, Sol III Blog Entries: 4	picture please. dave __________________ community sites t-linespeakers.org, frugal-horn.com ........ commercial site planet10-HiFi p10-hifi forum here at diyA

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19th December 2009, 07:38 AM	#3
Mooly diyAudio Member Join Date: Sep 2007	Anything along these lines, Mains energised speakers. - UK Vintage Radio Repair and Restoration Discussion Forum

19th December 2009, 07:38 AM	#4
godfrey diyAudio Member Join Date: Nov 2009 Location: Cape Town	Are you sure there is a magnet? The "other coil" could be a field coil to magnetize the core. See here for an explanation: Antique Electronic Supply - Speakers

19th December 2009, 07:56 AM	#5
dhaen diyAudio Moderator Emeritus Join Date: Jun 2002 Location: U.K.	Speakers with a field coil rather than a permanent magnet (called "mains energised" in the UK) sometimes had 3 windings: 1.voice coil (a few ohms), 2. field winding ( a few hundred ohms) 3. a hum cancellation winding. I can't remember the resistance of the hum cancellation "dinger" coil. On this type the field winding would double as a choke in the HT or +B supply. The ripple would cause hum in the speaker which would be cancelled by out-of-phase current though the "dinger" coil". I think the "dinger" coil was on or near the voice coil and was connected in series with the field winding. We're going a long way back here...

19th December 2009, 08:51 AM	#7
dhaen diyAudio Moderator Emeritus Join Date: Jun 2002 Location: U.K.	After a quick google, it seems there are some modern "field winding" speakers. I wonder if this is the way to go? After all it's easier to produce high quality, high power DC for the field winding, than to produce high quality, high power audio for the voice coil. In other words: why not increase speaker efficiency by this method, so as amplifier power can be reduced...

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