OT: very early outdoor FC unit

[Alien_Shore]

Check this out...

Vintage Speaker with Cast Aluminum Enclosure No Reserve | eBay

Looks like garden speakers for the victorian-era playboy...




{edit}: looks like this is a late 1920's RCA model 100-A. Restore site here.

[Phil-G]

would make a great headstone. put a motion sensor in it so it plays music, funny messages, or talks when someone walks by.

[Steve Schell]

Alien_Shore that driver isn't field coil, it's even older than that. The drive unit is called "moving iron" or "reed armature" and predates moving coil cone drivers. The cone is driven by a small rod or needle at its apex, which is attached to a thin reed suspended between magnetic poles. Two coils with thousands of turns of tiny wire and thus several kilo-ohms of resistance are driven in opposite polarity by the output tube and the reed is moved in a push pull manner and so moves the cone. I've got a few of these oldies and the vocal range can be pretty darn good though the bass is very limited due to the limited excursion of the reed. Overdrive one of these and the reed goes BRAAAAP! The moving coil cone speaker replaced these in no time beginning in 1925 as much larger cone excursions (bass!) was possible for the first time in consumer gear. A modern amp can drive a reed unit by using a single ended tube output transformer connected backwards: secondary to the amp terminals, primary to the high impedance coil leads.

[bowtie427ss]

Alien_Shore that driver isn't field coil, it's even older than that. The drive unit is called "moving iron" or "reed armature" and predates moving coil cone drivers. The cone is driven by a small rod or needle at its apex, which is attached to a thin reed suspended between magnetic poles. Two coils with thousands of turns of tiny wire and thus several kilo-ohms of resistance are driven in opposite polarity by the output tube and the reed is moved in a push pull manner and so moves the cone. I've got a few of these oldies and the vocal range can be pretty darn good though the bass is very limited due to the limited excursion of the reed. Overdrive one of these and the reed goes BRAAAAP! The moving coil cone speaker replaced these in no time beginning in 1925 as much larger cone excursions (bass!) was possible for the first time in consumer gear. A modern amp can drive a reed unit by using a single ended tube output transformer connected backwards: secondary to the amp terminals, primary to the high impedance coil leads.

Seems the basic mechanics are an adaptation of how most mechanical phonograph reproducers work.

[VolvoHeretic]

I wonder if that enclosure rings like a bell?