Re: Speaking of audiophools

Ban <bansuri@xxxxxxxxxxxx> wrote:

mc wrote:
For a nominal 8 ohm speaker expect the impedance to vary between 5
and maybe as
much as 100 ohms.

[...]
But this is not the whole lunch. The speaker has a complex impedance and a
real resistance in series will not only affect the volume level, but the
resonance frequency(lower) and especially the Q at the resonance, which
will increase. This might really be audible. The speaker is a motor and
relies on its back-EMC being shunted by the amplifier.
If an amp has a "damping factor" of 400, it means its interiour resistance
is 8/400= 20mOhms and this is augmented to 520mOhms. If there is little
mechanical damping as you find with high quality speakers mounted in
bass-reflex enclosures, the misalignment will result in a different, more
"boomy" bass response. In expensive speakers a lot of money is spend for
very low ohm air coils, which is wasted in this case.

This isn't the whole lunch, either. Consider that the voice coils
(usually) are wound with copper wire, whose resistivity increases by
~0.39% per degree C. It has been shown (by me and others), that the
temperature of the voice coil easliy reaches 150 degrees C or more
during "heavy" playing. This means that the resistance of the voice coil
can easily reach up to ~150% of it's nominal (20 degrees C) value... Put
these figures into the calculations of (bass reflex or closed)
loudspeaker boxes and passive filters (and don't forget that midrange
and tweeter enclosures are (in most cases) closed loudspeakers, too) --
and the sub-ohmic differences between various speaker cables will no
longer look *that* impressive.

--
http://www.flexusergroup.com/
.

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