[ARC5] Headphones H-43 B/U

[Dennis Monticelli]

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
>
> ***************
> On Mar 15, 2014, at 11:03 PM, Kenneth G. Gordon wrote:
>
>  On 15 Mar 2014 at 20:55, mac wrote:
>>
>>  Dennis,, Ken, et-al,
>>>
>>> 20K sounds awfully high for a magnetic headphone.  Crystal unit
>>> maybe?  "Scot's Headphone Museum Gallery" lists the H-43 B/U at 3000
>>> ohms see <http://oldheadphones.com/crystal/gallery/gallery2.html>
>>>
>>
>> Yes. I saw that. But when I bought them off eBay the seller was certain
>> they
>> were 20K ohms AND, besides, I found this:
>>
>> http://www.liberatedmanuals.com/TM-11-487M.pdf
>>
>> which lists a bunch of military audio components, like loudspeakers,
>> headphones, etc.
>>
>> That document says the H-43-B/U is 20 K also.
>>
>> I guess I'll have to test them out to see.
>>
>> Ken W7EKB
>>
>
>