[ARC5] Headphones H-43 B/U

[Dennis Monticelli]

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


On Sun, Mar 16, 2014 at 11:04 AM, Kenneth G. Gordon <
kgordon2006 at frontier.com> wrote:

> Thanks for the info below, Dennis. I am certain you are correct. 20K
> impedance, 3K resistive. Makes sense to me.
>
> Now to see how I can get the best "action" out of these.
>
> Mine were also hermetically sealed when I bought them. They were sealed
> up in a heavy plastic envelope. Even so, although my hearing is
> "unbalanced" in that I hear better at some frequencies from one ear than I
> do
> the other, and vice versa, I am suspicious that one of the elements is
> defective. One seems "quieter" than the other.
>
> Ken W7EKB
>
> On 16 Mar 2014 at 6:45, Dennis Monticelli wrote:
>
> >
> > I measured my phones at 1KHz using a generator and the max power transfer
> > method. They are indeed 20K and they are magnetic. Must be mighty fine
> wire and
> > thus subject to corrosion damage. Good thing mine came NOS in a sealed
> airtight
> > pouch.
> >
> > I won't be able to dig up my sensitivity measurements until the next
> weekend.
> >
> > Dennis AE6C
> >
> >
> >
> > On Sun, Mar 16, 2014 at 1:32 AM, mac <w7qho at aol.com> wrote:
> >     Ken,
> >
> >     OK, think we're talking about two different things here, d.c.
> resistance and
> >     audio impedance the latter which, of course, is frequency dependent.
> Note
> >     that TM-11-487 uses the term "impedance" not resistance in the H-43
> B/U
> >     description. Looked back in my 1942 Radios Master and found that most
> >     headphone manufacturers of the era specified d.c. resistance only,
> typically
> >     1000 or 2000 ohms d.c. and generally described these as "high
> impedance "
> >     types. Only found Cannon listing both d.c. resistance and impedance
> figures
> >     together -- specifically 10,000 ohms at 1000cps for their 2000 ohms
> d.c
> >     headphones and 15,000 ohms at 1000cps for their 3000 ohm d.c. units.
> This
> >     would reasonably seem to square with 20,000 ohms IMPEDANCE and 3000
> ohms
> >     d.c. RESISTANCE for the H-43 B/U.......
> >
> >
> >     Dennis D. W7QHO
> >     Glendale, CA
>
>