> Headphone efficiency clearly has other dependencies than
> impedance.
Yes, there are other dependencies like the weight and "stiffness"
of the diaphragm, the strength of the magnet, the coil geometry,
etc. However, there is still a strong correlation of efficiency
with impedance in well built headphones.
73,
... Joe, W4TV
On 12/29/2015 4:55 AM, Barry N1EU wrote:
Jim, I think it would be great if you would clarify your comment to
Steve. I've looked at the data sheet and everything Steve said seems
correct to me???
And I'm not sure I'm willing to totally buy (per Joe) that there's
necessarily a proportional relationship between headphone impedance
and efficiency that makes up for the inverse relationship between
output power and load impedance. I just don't observe this efficiency
rule consistently in my collection of headphones with varying
impedance. Headphone efficiency clearly has other dependencies than
impedance.
73,
Barry N1EU
On Tue, Dec 29, 2015 at 6:46 AM, Jim Brown <j...@audiosystemsgroup.com> wrote:
You clearly don't understand what you're reading on that data sheet, nor the
design of audio output stages. I refer you to my earlier posts, and to those
by W4TV, W2RU, and W3FPR.
Those numbers you quote are NOT the output impedance, they are the minimum
LOAD impedance that the output device is designed to work into. Modern
output stages are essentially constant voltage sources. That's what Bud is
telling you with his discussion about damping factor -- the output Z (source
Z) is typically 50-100 times the load Z.
With headphone amplifiers, a good designer will add some small value of
resistance in series with the output to prevent the output stage from
failing if a short is connected to its output (which could occur when a plug
is being inserted, or with an improperly wired plug). Line level outputs use
a series output resistor to prevent the output stage from seeing the
CAPACITANCE of a long cable, which could, by interaction with the feedback
network, cause the output stage to oscillate.
Executive summary -- simply buy good quality headphones, and don't worry
about impedance.
73, Jim K9YC
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