[Hallicrafters] Headphones

[Langston, Mike]

Well, I started with some low impedance (8 ohm) Yaesu phones (Model
YH-55). Unbelievable HUMMMMM when plugged into my SX-101A and worse on
my SX-96. Neither of these rigs have HUMMMMM when using the speaker (3.2
ohm). Then I tried the Califone 2924 AV (600 ohm) recommended by someone
on the Hallicrafters reflector. Much better, but still so much HUMMMM
that I would rather use the speaker. Then I found this old set of phones
that got thrown in with some other purchase I had made that I had never
put a plug on. Guess what? No HUMMMMMMM and they sound great. Now I'm
curious what these are. Here's the identifying info:

 

Alnico Magnetic

No. 25

C. F. Cannon Co.

Springwater, N.Y.

 

The headpiece is a metal frame with padded springsteel, the earpieces
appear to be bakelite and they have black rubber covers (not the kind
that cover the entire ear, just cushioning for the ear resulting in
plenty of background noise getting through), the cord is flat 2
conductor, brown in color and where the cords from each earpiece meet
(about 18 inches) there is a brown plastic looking junction (riveted
halves) with only one cord leaving the junction and on to the plug. The
earpiece cover unscrews and there is a thin metal disc (starting to rust
a bit) that can be removed revealing two oblong magnets with wire wound
around them. Here's my questions, can anyone tell how old these things
are and maybe what impedance? Can anyone explain why these work so well
with the old receivers compared to the modern 600 ohm Califone?

 

Thanks,

Mike KL7CD

Dallas-Ft. Worth