[TenTec] 565 Low level audio on headphones

Jim Brown k9yc at audiosystemsgroup.com
Tue Mar 19 16:20:44 EDT 2013


On 3/19/2013 1:03 PM, Wade Staggs wrote:
> Are some of the Heil Headsets and Microphones still using Hot Glue to hold
> the Elements in place?

It's been a while (2004) since i took it apart, so I don't recall 
details, but it was REALLY mickey mouse. :)

> As for the Impedance Issue, just from my experience ... Higher
> Impedance headsets seem to need more voltage to produce the same amount of
> volume. I believe that once again Bob/K4TAX is correct in saying that Lower
> Impedance Headphones should have greater sensitivity or louder output.
> These are my beliefs. Your mileage may vary.

While this is approximately true, there's quite a bit more to it than 
that. The difference is EFFICIENCY -- how much POWER is needed for a 
given loudness. And, in general, the transducer designer must give up 
some efficiency to get smooth frequency response and lower distortion. 
In addition, the impedance of ANY magnetic transducer is FAR from being 
constant with frequency. There are many electromechanical resonances 
that show up in the equivalent circuit. Headphone and loudspeaker 
impedances are specified at their minimum value in the audio midrange 
(think 500 Hz - 4 kHz for headphones).

73, Jim K9YC



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