[CW] A note on headphones

[Richard Knoppow via CW]

----- Original Message ----- 
From: "Ken Brown via CW" <cw at mailman.qth.net>
To: <cw at mailman.qth.net>
Sent: Sunday, October 26, 2014 4:28 PM
Subject: Re: [CW] A note on headphones


> If you do the math, you will see that the higher impedance 
> phones will always get a larger percentage of the voltage 
> produced by the generator than lower impedance. If you 
> used a smaller series resistance the difference will not 
> be as great, yet the higher impedance ones will still get 
> the highest voltage across them. What kind of source are 
> you using for your tests? An audio signal generator with a 
> 600 ohm source impedance? Or something else? Have you 
> tried different sized series resistors, including none at 
> all?
>
> DE N6KB
>
    I think I was  not very clear. I used a high source 
resistance to try to duplicate the conditions presented by a 
crystal detector. If I compare phones connected to a low 
source impedance of course the lower impedance ones will be 
louder. I have phones with impedances (per pair) from about 
25K ohms down to about 50 ohms.
    The true sensitivity could be calculated from the power 
input compared to the acoustical power output but the latter 
is not trivial to measure.  It would also be interesting to 
calculate the motional impedance. Of course, I am 
re-inventing the wheel here but its an interesting 
excercize.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com