RCA Sounds / Recordings / Samples II

From here (http://www.thereminworld.com/forum.asp?F=1&T=4233&cmd=p&p=3)

On the topic of the RCA Radiola speaker. One thought that has been in the back of my head is that I believe it was an electrodynamic (field coil, no permanent magnet) speaker.

Anyone care to comment on how that may have affected the sound/tone?

Yes, the RCA-106 loudspeaker (like the Hammond M3 organ) has an electrodynamic speaker. I doubt the electromagnet will have any significant effect on the sound other than a little extra hum...and a lot more hum when things are not working as well as they should. That said...

EVERY different speaker (driver) will impart its own unique character to the sound produced. This will depend on materials, voice coil design, compliance, resonances, dampening, etc...
Frequency response graphs will tell part of the story, but coloration is best determined by ear.

Ideally in loudspeaker design cabinet resonances are kept to a minimum. Obviously, resonances are an integral part of acoustic instrument design. The Ondes Martinot is one rare exception being an electronic instrument using loudspeakers with resonating elements.

I actually just got an email today from an old radio guy who has a couple of speakers from the 106. He did have two complete cabinets but sold them.

I was toying with the idea of building a (sort of) replica 106 cabinet, anyway. Although more utilitarian, without the fancy woodwork and embroidery.

I haven't heard back yet as to the price or condition. If they are usable and not to expensive I might have to pick one up for fun. I figure I can always just put a different speaker in there if need be.

If anyone has any thoughts regarding feasibility this hair-brained project, let me know.

I believe one has to plug in the speaker to operate the field coil. Could it be as easy as "mount speaker, plug speaker into wall, hook amplifier output to speaker". I'm sure there's is something there I'm missing.

"Could it be as easy as "mount speaker, plug speaker into wall, hook amplifier output to speaker". I'm sure there's is something there I'm missing."

Absolutely not!!! You ARE missing somthing. The electromagnet of an electrodynamic speaker operates with DC current. Plugging it into 120V, 60 Hz AC mains current will produce a very loud 60 cycle hum at the very least.

The two cylindrical objects on either side of the speaker's field coil are the disc rectifiers of the full-wave bridge.

On the RCA-106, the voltage across the field coil should be about 95 volts DC without the speaker and about 80 volts DC with the speaker.

If you send me your email address, I can send you JPEG's of the wiring diagram and schematic which should clear things up for you.

Those schematics could be handy.

I figured it needed DC. In the photos I've come across it looked like it had a plug coming out from somewhere. I was guessing it had a means of converting the AC power (all depending on if everything still works of course ;)

Thank you for any info.