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Old 24th Jul 2020, 5:22 pm   #1
RadioHist
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Default Oliver Lodge moving coil loudspeaker 1898?

I'm working on upgrading a presentation I made some 30 years ago on the history of the Magnavox Company, Oakland, California. Local (USA) dogma has it that founders, Pridham and Jensen get credit for bringing the first moving coil loudspeaker to market in 1915. BUT I come across a few "spoiler" references saying they were not the "first". Several Internet references drop the name of Oliver Lodge as having British Patent # 9712 granted in 1898 for a moving coil loudspeaker.

However I cannot find that patent disclosure on the Web.... Has anyone seen that patent and even better, provide a copy? And, of course, was there any practical use made of this moving coil loudspeaker invention prior to 1915 by Lodge or anyone else for that matter.

Thanks,
Robert
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Old 24th Jul 2020, 6:06 pm   #2
Robert Gribnau
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Default Re: Oliver Lodge moving coil loudspeaker 1898?

Looks like this is the one:

https://worldwide.espacenet.com/pate...3DGB189809712A

Greetings,
Robert
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Old 24th Jul 2020, 6:37 pm   #3
GrimJosef
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Default Re: Oliver Lodge moving coil loudspeaker 1898?

There's a lovely line at the top of the second page of the 'original document' in that patent entry, following the description of a series of moving coils connected up as microphones and speakers to make an amplifying chain. I quote:

I call it a bellowing telephone because a gentle tone at one end of the series becomes a shout at the other end



In his book Loudspeakers Wharfedale's Gilbert Briggs writes in 1948

... the first ever moving coil invention must have been the Ernst Wermer patent, filed by Siemens on December 14th 1877 ...

He also says that Lodge's original device was then in the Science Museum but goes on to state that in 1898 there wouldn't have been sufficient power available at the required impedance to operate a moving coil driver .

Cheers,

GJ
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Old 25th Jul 2020, 11:10 am   #4
Robert Gribnau
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Default Re: Oliver Lodge moving coil loudspeaker 1898?

It looks though that Oliver's bellowing telephone did work; it was demonstrated successfuly in a patent battle in 1927:

https://cite.case.law/f2d/20/150/

But maybe the successful demonstration was made possible because of supporting technology from that time.

Last edited by Robert Gribnau; 25th Jul 2020 at 11:16 am.
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Old 25th Jul 2020, 2:46 pm   #5
RadioHist
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Default Re: Oliver Lodge moving coil loudspeaker 1898?

Robert & Grim,

Thanks very much for taking the time to find the Lodge patent and the 1927 case law. I was on Espacenet yesterday but got the formatting of my query wrong. (I'm a complete novice at patent search.)

So it does appear that Lodge had a moving coil circuit operating in a strong constant magnetic field. The coil being attached to a lever and fulcrum arrangement by which the coil motion could be conveyed to a panel flexible enough to vibrate, a cone?, diaphragm or electrical contact. It reads to me that he saw the most value of his invention as a mechanical amplifier of weak currents. Similar to the later S. G. Brown amplifiers using a reed actuator in a changing magnetic field.

It would be great to have a definitive statement as to whether his patent principles were practically applied prior to 1915 to make a loudspeaker.

Peter Jensen had been an assistant to Vlademar Poulsen as early as 1902 and was completely familiar with attempts to modulate small arc transmitters with high current carbon microphones. The Magnavox public address systems pre-vacuum tube/valve era used carbon mikes with a nominal 4 to 6 Amperes supplied from a 6 to 12 volt storage battery/accumulator. So applying this technology was equally important to their success in making a practical PA system....

Again thanks for your comments.
Robert
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Old 25th Jul 2020, 2:51 pm   #6
mark_in_manc
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Default Re: Oliver Lodge moving coil loudspeaker 1898?

I can't quite remember where Rice and Kellog come into all this.

Chapter one of Hunt's book 'Electroacoustics' is a great summary of everything from Benjamin Franklin up to state of the art in 1954. It's a good read if you're interested in the history of all this. Somewhere he shows how Pulse Code Modulation was first mentioned at the end of the 18th century
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