[ARC5] Headphones H-43 B/U

[Dennis Monticelli]

Richard,

>From a standpoint of power sensitivity, which are the best of the
headphones?  I heard that the Baldwins are very sensitive.

Dennis AE6C


On Tue, Mar 25, 2014 at 9:04 PM, Richard Knoppow <1oldlens1 at ix.netcom.com>wrote:

>
> ----- Original Message ----- From: "Dennis Monticelli" <
> dennis.monticelli at gmail.com>
> To: "Kenneth G Gordon" <kgordon2006 at frontier.com>
> Cc: "ARC-5 Maillist" <ARC5 at mailman.qth.net>
> Sent: Tuesday, March 25, 2014 6:56 PM
>
> Subject: Re: [ARC5] Headphones H-43 B/U
>
>
>  Ken,
>>
>> I am back from my business trips and can now report on my measurements
>> from
>> a few years ago.  I too found a sealed and boxed H-43B/U at a local flea
>> market.  The mil seller must have had 30 of them.  I paid $2.
>>
>> DCR = 4550 ohm
>> AC impedance = 21K at 1KHz  (cans wired in series?)
>> 1mV drive at 1KHz plainly audible.  That equates to 50 pico-watts!
>> With proper impedance matching, these could be used in a crystal set.
>>
>> Dennis AE6C
>>
>
>    Scott shows a couple of H-43B/U phones from different manufacturers at
> http://oldheadphones.com/crystal/gallery/gallery2.html
>
>    Most phones are connected in series.  These are probably a variation of
> the Western Electric type 509W. The DC resistance sounds a bit high but the
> impedance of magnetic phones is usually about 5 to 7 times the DC
> resistance so its probably correct.  These are at the high end of the
> impedance range. Phones like these were intended to work from high
> impedance sources such as crystal detectors and low level tube plates.
>  They are ideal for crystal sets except for the lack of fidelity. Most
> magnetic phones are resonant around 1 khz.  About the only phones with
> higher impedance are Brush crystal phones which have an impedance of around
> 100k. I challenge you to find a pair that works:-( I have maybe half a
> dozen individual Brush phones and only one capsule is not trash. FWIW,
> brush phones are connected in parallel so the wiring harness can't be used
> to replace the more common series type.
>    Somewhere along the line I started collecting headphones, I have no
> idea why. I measured a number of them on a General Radio bridge. Impedance
> (not DC resistance) varies from around 50 ohms to around 25K ohms.  The
> military standardized on impedances of about 8K and about 500 ohms. The
> moving coils headphones for aircraft use ANBH-1 and ANBH-1A are 500 ohm
> (connected in series) and are quite high quality.  The ANBH-1A were
> military equivalent of the Permoflux commercial phones. The first stereo
> recordings I ever heard were played over a pair of split Permoflux phones.
> If these phones are in decent condition you got them at a steal.
>   OK enough on something thats probably OT and a bore.
>
>
> --
> Richard Knoppow
> Los Angeles
> WB6KBL
> dickburk at ix.netcom.com
>