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Author Topic: Old headphone technology  (Read 4592 times)
N3QE
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« on: March 25, 2012, 02:11:17 PM »

When I was a kid 35-40 years ago I had a large assortment of old headphones to play with and they were far from new back then.

They had cloth covered cables with pin tips on the end, and each earpiece had a metal diaphragm underneath which there was a small permanent magnet and a coil wound with a lot of skinny wire.

In some cases the earpieces exterior were maybe bakelite but in other cases they were clearly metal and in any event they were always quite heavy. Sometimes they had little binding posts for wire attachment on the outside, in others these were hidden under a removable cover.

Is there a generic term or some brand names for this style of headphones? I know they were not crystal. Were they high-impedance magnetic headphones?
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AC5UP
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« Reply #1 on: March 25, 2012, 02:58:08 PM »

Were they high-impedance magnetic headphones?

Yup. With a typical impedance of 2,000 Ohms IIRC.

What made them interesting to the hobbyist was that at 2K they could be driven directly from the plate of many audio amplifier tubes. If someone slapped a dual section tube like a 1U5 (diode & pentode) right behind a crystal set front end they'd have a not-terrible receiver for local stations........
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KS2G
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« Reply #2 on: March 25, 2012, 08:19:07 PM »

I believe one of the brand names was Clevite-Brush.

73,
Mel - KS2G
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N3QE
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« Reply #3 on: March 26, 2012, 03:42:24 AM »

I believe one of the brand names was Clevite-Brush.

The Clevite-Brush headphones I remember were crystal headphones. But I googled some pictures and yeah they externally looked similar to the ones I got to play with as a kid.

The ones I'm remembering definitely had a metal diaphragm, and underneath that a small PM and lots of turns of skinny wire. Looking back... the metal diaphragm seems a bit odd, unless maybe it was steel and supposed to be magnetic? I remember as a kid pulling the diaphragm off after unscrewing the cover, and seem to recall it being "stuck" by the magnet's pull. Either that or decades of age.

I don't remember a lot of hi-fi listening to these but I'd guess that they must've sounded pretty tinny when I tried them out against old radios :-).
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N3QE
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« Reply #4 on: March 26, 2012, 03:44:58 AM »

Yup. With a typical impedance of 2,000 Ohms IIRC.

What made them interesting to the hobbyist was that at 2K they could be driven directly from the plate of many audio amplifier tubes. If someone slapped a dual section tube like a 1U5 (diode & pentode) right behind a crystal set front end they'd have a not-terrible receiver for local stations........

You are definitely right... I remember doing stuff like that after I got beyond finding some B+ batteries that worked!

Trying to relive my childhood... is there a generic name or a brand name for this type of headphone so I could ask around and find another set? Just "old high impedance magnetic headphones"?
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WB4SPT
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« Reply #5 on: March 26, 2012, 07:36:47 AM »

Yes,  2000 ohms and a dynamic steel diaphragm.   I drove mine from a 1T4 tube.  The name might be "radio headphones".  You might need to weed out several hundred stereo headsets before you find the right one!
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KD0REQ
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« Reply #6 on: March 26, 2012, 01:39:08 PM »

basically they were called "magnetic headphones" in the day.  Brush also made 8 and I think 50 ohm jobs, the single-earpiece ones were common in radio studios.  awful sound compared to the monitor speakers on the wall, but you did surely hear your sidetone.  the amount of "squawk" in the Brush would let you ride voice over instrumentals and you didn't have to look at the VU meter to do it.

Philmore probably still imports some headphones, web 'em.
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K3WEC
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« Reply #7 on: March 26, 2012, 06:25:39 PM »

I found this very old writeup on this type (I think):

http://decodesystems.com/help-wanted/headphones.html
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N3QE
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« Reply #8 on: March 27, 2012, 12:08:10 PM »

I found this very old writeup on this type (I think):

http://decodesystems.com/help-wanted/headphones.html

Thank you! With this info, I can do a google search on "Brandes headphones" and turn up many examples including some for sale. This way I can have the same style headphones I played with when I was in 2nd grade, maybe reliving my childhood in a way!

Luckily none of the hi-fi nuts have latched onto these so they sell for reasonable prices :-)
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KAPT4560
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« Reply #9 on: March 28, 2012, 12:41:54 PM »

 Another brand name was E.F. Cannon of Springwater, N.Y.
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K1ZJH
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« Reply #10 on: March 29, 2012, 07:51:08 PM »

Biggest problem with many of these, and there were hundreds of manufacturers, is the
loss of magnetism in the armature winding metal core. That reduces the maximum
volume before distortion sets in.

Pete
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W8AAZ
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« Reply #11 on: March 30, 2012, 07:55:01 PM »

If you want the most sensitive of the prewar headphones, going back to at least the early 20's, look for a good pair of Baldwin's. They are more sensitive than the average Brandes or just about any of the old metal diaphram types, for that matter.  I have 3 pairs and if working right, are best for xtal sets.  As you get into tube radios or anything with gain, alot of the advantage is eliminated, but they still are louder with a one- tube regen. type radio.
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K2OWK
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« Reply #12 on: March 30, 2012, 08:36:58 PM »

Also able to operat directly from a crystal radio with no amplifier. IE Philmore.

73s

K2OWK
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N7AG
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« Reply #13 on: April 09, 2012, 09:23:29 AM »

I have such headphones:  Army NOS 1966.  N7AG  Bill
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