Re: Field coil blast from the past with a nifty suspension . . . - Steve Schell - High Efficiency Speaker Asylum

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Re: Field coil blast from the past with a nifty suspension . . .

Steve Schell

In Reply to: Field coil blast from the past with a nifty suspension . . . posted by Christopher Witmer on March 13, 2007 at 05:13:59:

Hi Christopher,
As I understand it, Messrs. Rice and Kellogg of General Electric developed a moving coil cone speaker, and Mr. Kellogg applied for U.S. Patent #1,707,617 in January 1925. Mr. Paul Voigt in England had the same idea, but filed for a British patent about three weeks after Mr. Kellogg. I have also heard that Messrs. Jensen and Pridham had invented a moving coil cone speaker in California as early as 1915, but apparently did not attempt to patent the idea.
These G-2s are built to the typical Rice-Kellogg recipe for the earliest consumer moving coil cone speakers, which I believe began with RCA's Radiola 104 driver in 1926. They all seem to feature a generous field coil motor, center suspended 6" to 8" seamed paper cone, and soft fabric or leather outer suspension. These were installed in open backed console radios with often all DHT amplifier circuits. Live broadcasts came sailing in over uncrowded airwaves. No wonder folks sat transfixed in front of the family radio in those days!
I haven't examined a G-2, though I have a pair of G-3s enjoying a looooong wait for new cones. Most of these speakers have a riveting, lifelike sound, with the basic characteristics that attract the full range, open baffle folks these days.
Despite the hefty motors, most of these speakers have a wide voice coil gap and only about 6 to 10 kilogauss flux density. Still, they work great.
When RCA designed their first theatre compression driver in the mid 1930s (which I am fond of, as you know), they retained major elements of these speakers: big motor, cone diaphragm, center suspension, cloth surround. Basically they shrunk and stiffened the cone, tightened the gap and put on a phasing plug with high compression ratio. Yum.
There is a steady parade of these old radio speakers on ebay, often selling for less than $10. I may have seen this very pair of G-2s a while back, selling for a fraction of the current asking price. I think that in general these old speakers represent a huge bargain, especially for those with repair/rebuilding skills. They're field coil, they sound great, and they're cheap!

Rice-Kellogg patent (Open in New Window)

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Follow Ups Full Thread

Topic - Field coil blast from the past with a nifty suspension . . . - Christopher Witmer 05:13:59 03/13/07 (5)

Re: Field coil blast from the past with a nifty suspension . . . - Steve Schell 12:36:06 03/13/07 (3)

Thanks for pointing me to the patent - Christopher Witmer 17:23:50 03/13/07 (2)

Re: Thanks for pointing me to the patent - Steve Schell 11:44:30 03/15/07 (0)

Re: Thanks for pointing me to the patent - Dominic 20:53:08 03/13/07 (0)

Re: Field coil blast from the past with a nifty suspension . . . - chopper87@aol.com 07:58:15 03/13/07 (0)

Follow Ups

Re: Field coil blast from the past with a nifty suspension . . . - Steve Schell 12:36:06 03/13/07 (3)

Thanks for pointing me to the patent - Christopher Witmer 17:23:50 03/13/07 (2)

Re: Thanks for pointing me to the patent - Steve Schell 11:44:30 03/15/07 (0)

Re: Thanks for pointing me to the patent - Dominic 20:53:08 03/13/07 (0)

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