[ARC5] Headphones H-43 B/U

[Kenneth G. Gordon]

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