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Subject: Re: audio line specifications
References: <3DEE2757.EE79B063@crf.canon.fr> <email@example.com>
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Date: Sat, 07 Dec 2002 21:48:20 -0500
NNTP-Posting-Date: Sat, 07 Dec 2002 21:48:24 EST
Organization: Bell Sympatico
On 7 Dec 2002 15:52:52 -0800, firstname.lastname@example.org (Ben
>In sci.electronics.design, John Woodgate
>>I read in sci.electronics.design that Vlad wrote
>>) about 'audio line
>>specifications', on Fri, 6 Dec 2002:
>>>Isn't the quality of the sound that feeds the headphones important ?
>>Yes, but the frequency responses of moving-coil headphones are NOT
>>affected by source impedance.
> FWIW, I have Sony MDR-7506 headphones (I have no doubt these are
>moving-coil - they're definitely not electrostatic) and the frequency
>response most definitely IS affected by source impedance.
The source impedance affects harmonic distortion, intermodulation and
response the same way it does to a speaker . The ratio between the
impedance of a speaker or a headphone and the source impedance is
called "damping factor"
A pair of headphones or speakers connected to a an impedance of the
same value . Example a 8 ohms speaker connected to an amplifier with
an output impedance of 8 ohms has a damping factor of 1 and that is
consider a very low quality system by today's standards.
You only find that on low quality devices were maximum transfer of
energy or spurious low frequency resonance is desired
A good system today has a damping factor close to 100 .
Yes, the output impedance of the amplifier is 100 times lower then the
impedance of the speaker or in this case the headphones that in the
majority of the cases are only miniature speakers.
>>They are not like miniature loudspeakers;
>>the mechanical resistance dominates the motional impedance.
>>Regards, John Woodgate, OOO - Own Opinions Only.
>>Interested in professional sound reinforcement and distribution? Then
>>PLEASE do NOT copy news posts to me by E-MAIL!
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