The high impedance phone that came with the crystal radio that I had when I
was a kid in the 50's had a large stationary coil wound around an iron core.
The sound was produced in a steel disc suspended over the iron core.
Because the coil was stationary and its mass did not have to move, it could
achieve the hi-z by adding many turns. Phones of 2K or higher can be
driven directly from the plate of a vacuum tube circuit. Is that the
context of your question? You could use a modern lo-z phone in such a
circuit with a matching plate-to-voicecoil type transformer.
Ray
"Watson A.Name - Watt Sun" wrote in message
m...
In article ,
mentioned...
"Paul Burridge" wrote...
What differentiates the internals of hi-z headphones from those of say
the 8 ohm type. I mean, how is all that extra impedance achieved?
I see that you're crossposting to a ham group, which adds a twist to the
discussion, because at least 25 years ago when I last paid attention to
ham
radio, the kind of headphones used in ham sets were different than the
kind
used these days for listening to music. Hams used 8 ohm dynamic phones,
or
they used hi-Z crystal phones.
I disagree. They used 2000 ohm variable reluctance headphones.
http://www.audiosears.com/acoustic/2444.html
http://www.audiosears.com/acoustic/ears.html
The phones used for music listening these days are generally in the
range of
30 to 100 ohms, with some oddballs around 600 ohms. They are dynamic,
that
is, they use electromagnets rather than piezo crystals. I don't know
how
they pack that much wire into 'em (although some do have two diaphragms
in
series, for each ear), but I think the basic idea is that where a
loudspeaker has a heavy magnet and relatively few turns of wire,
headphones
work the other way - light (and weak) magnet, lots of turns.
--
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