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Post subject: mystery speakers...?
Posted: Sun Sep 11, 2011 6:09 am
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I don't know much about speakers, and I have 2 questions: 1 - I have a 10" speaker in an old amp. Every speaker I've ever seen in a guitar amp has a magnet that looks like a flat disk - this one looks more like the speakers you'd see in an old radio - the magnet is like a metal bracket with a cylinder inside it. Is this an alnico magnet? It's very heavy and isn't the original speaker. 2 - I have a pair of 12" speakers in a very nice cabinet that did come from an old radio/record player. I'd love to use them for something, but it looks like their magnets are powered by current from the radio/amplifier(?) Is this possible? If so, can they ever be used with a regular amp?


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Post subject: Re: mystery speakers...?
Posted: Sun Sep 11, 2011 7:00 am
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Yeah the first speaker sounds like an alnico magnet speaker,and the other speakers,I don't know for sure,there is such a thing as field coil magnets,but they're older style and not a good fit for most amps now days,that could be what those are....I would just buy a good replacement speaker for whatever it is that you need...lots of times,old no name speakers are just junk.


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Post subject: Re: mystery speakers...?
Posted: Sun Sep 11, 2011 7:01 am
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Red F (love that name--- conjures up fast cars).... What you prolly seen is a speaker with a Field-Coil magnet. Back before they had the technology to make permanent fixed alnico (Aluminum-Nickel-Colbalt) or good ceramic magnets, manufacturers used an electromagnetic, driven by part of the power tranny, to magnitize bigger speakers. The voice coil is activated, as usual, by the AC signal coming off the output tranny.


See link:

http://www.ebay.com/itm/VINTAGE-JENSEN- ... 588d91dc7d

So, the circuit of the amp would need to include HV taps off the PT to activate the speaker's magnet. To use these speakers you would need a separate tranny to drive them. And the knowledge of how many VDC and amps it takes to keep them activated.

http://www.tubesandmore.com/scripts/fox ... HSPEAKER01


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Post subject: Re: mystery speakers...?
Posted: Sun Sep 11, 2011 9:04 am
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BMW2002Ti wrote:
Red F (love that name--- conjures up fast cars).... What you prolly seen is a speaker with a Field-Coil magnet. Back before they had the technology to make permanent fixed alnico (Aluminum-Nickel-Colbalt) or good ceramic magnets, manufacturers used an electromagnetic, driven by part of the power tranny, to magnitize bigger speakers. The voice coil is activated, as usual, by the AC signal coming off the output tranny.


See link:

http://www.ebay.com/itm/VINTAGE-JENSEN- ... 588d91dc7d

So, the circuit of the amp would need to include HV taps off the PT to activate the speaker's magnet. To use these speakers you would need a separate tranny to drive them. And the knowledge of how many VDC and amps it takes to keep them activated.

http://www.tubesandmore.com/scripts/fox ... HSPEAKER01


+1

Good call, Steve.

Today the only real appeal for FC speakers is among hi-fi purists and fans of antique radios who enjoy restoring and owning old gear. While there were a few guitar amps early on using these, most were equipped with "permanent magnet" alnico drivers. The FC types did exact a toll on an amp's power supply and presented a hazard because of their high-voltage requirements.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: mystery speakers...?
Posted: Sun Sep 11, 2011 9:38 pm
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FYI: There is at least one company that still makes Field-Coil speakers, Lowther. And they are quite good speakers (for hi-fi use). But, if you have to ask the $$$...

http://www.ebay.com/itm/Lowther-field-c ... Subwoofers


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Post subject: Re: mystery speakers...?
Posted: Sun Sep 11, 2011 10:02 pm
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BMW2002Ti wrote:
But, if you have to ask the $$$...


(heh heh heh......)

:mrgreen:

Arjay

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Post subject: Re: mystery speakers...?
Posted: Tue Sep 13, 2011 8:28 am
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I'm thinking of replacing these speakers with new replacements - what would be good, fairly inexpensive 12" speakers to hook up to a low powered '70's vintage stereo tuner/amplifier. There would be no high frequency speakers - the two 12"s would be it.


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Post subject: Re: mystery speakers...?
Posted: Tue Sep 13, 2011 4:54 pm
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Red F--- any good full range speaker with fixed magnet would due the trick. One issue, if you are using the amp which the original FC speakers came off of.... you'd need to apply a load to the PT tap that fed those original speakers. The power tranny was designed to "see" that field coil magnet. Without the load---you run the risk of damage.

See the link to AES (tubesandmore.com) in above link, to calculate the load.


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Post subject: Re: mystery speakers...?
Posted: Wed Sep 14, 2011 6:56 am
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Yeah, the amp/radio that powered those speakers is long gone. I'll be using a '70's vintage Pioneer stereo amp that uses regular speakers. Most 12" speakers I can find seem designed for guitar amps - would they sound okay? How about a pair of inexpensive Weber or Jensen speakers?


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Post subject: Re: mystery speakers...?
Posted: Wed Sep 14, 2011 9:54 am
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No. Guitar amp speakers aren't good for hi-fi use. They have too lightweight speaker cones and thus too limited frequency response. Plus the cone is designed to enhance the those wonderful harmonics, which isn't too wonderful for hi-fi.

In fact a car speaker would be better. There are a lot of good 8-inch ones on the market.

The full range hi-fi speakers that I'm familar with are high end stuff. You wouldn't want to ask the price...

Good luck!


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Post subject: Re: mystery speakers...?
Posted: Wed Sep 14, 2011 1:20 pm
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Something like this might be just the ticket for stereo/hifi playback......

http://www.ebay.com/itm/Matched-number- ... 3cbbe0f5c1

HTH

Arjay

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