[ARC5] Headphones H-43 B/U

[mac]

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