Stewart Pinkerton wrote in message news:WitYb.51895$uV3.103980@attbi_s51...
On Mon, 16 Feb 2004 18:18:27 GMT, "Wessel Dirksen"
wrote:


This is what I was referring to with the "ask an amp guy" line. And may
perhaps explain why beefing up the ground connections to a loudspeaker
driver tends to improve overall damping properties.

This is not true - I'm an amp guy......... :-). Electrical damping is
only of relevance *below* the fundamental resonance of the system,

No, this is most certainly not true. Damping is most significant
AT fundamental resonance. Why? Because this is the point where
the system is storing the most energy, it is the frequency at
which the total system losses are most significant, since it is
those losses (all of them) that determine damping. Above resonance,
the system is mass-controlled. Below resonance, the system is
stiffness-controlled. At resonance, it's resistance controlled.

Now, that being said. the notion that "beefing up the ground
connections tends to improve overall damping properties" simply
does not hold at all under scrutiny, UNLESS the ground connections
are som abysmally bad as to be a significant source of the total
system loop resistance to begin with. And, if that's the case, the
system is broken.

TO explore this requires us, once again, to dispell the myth of
"damping factor." The damping of the system is essentially a
measure of the energy stored to energy dissipated through loss
mechanism. That energy storage is greatest at resonance.
Remember that the energy stored in the moving mass goes as
velocity squared which goes directly as frequency below
resonance, and as the inverse of frequency above resonance,
and in a stiffness, it goes as excursion squared, which is
constant below resonance, and goes as in inverse square above
resonance: combine the two, and we find that energy stored is
maximum AT resonance.

There are three basic means of dissipating this energy, removing
it from the resonant system and thus damping the system: energy
can be removed through the resistive part of the radiation
impedance, i.e., we do work on the air and it makes sound. It can
be removed through mechanical friction in the surround and spider,
or it can be dissipated in the effective total series electrical
resistance. I state these in increasing order of importance: by
far, the LEAST amount of energy is dissipated by producing sound,
typically less than 1% in direct-radiator loudspeakers. The
mechanical damping comes next, and is on the order 5-25% of the
total damping. By far, the largest portion of the energy dissipation,
or damping, in speaker that have any pretentions is electrical.

Now, that may SEEM to be arguing FOR "beefing up the ground
connections" and rewiring the two feet of wire between the
crossover and the driver, BUT, such notions ignore the fact
that BY FAR, the single LARGEST resistance in the ENTIRE loop,
by an order of magnitude and most often much greater, is the
simple DC resistance of all that wire in the voice coil.

Unless those whimpy ground connections and that awful ordinary
wire from the crossover to the drivers has a total loop resistance
that is significant compared to the DC resistance of the voice
coil, beefing them ground connections and replacing that awful
wire, WILL NOT change the system damping in ANY significant fashion.

I now realize that I had given the wrong impression in this thread in that I
never intended to imply that there was any kind of voo-doo involved, only
that electrical conduction is more that just connecting the dots and
measuring the impedance factors between those dots. I was not under the
impression that electrical conduction was actually measureable at this level
yet.

Actually, it's been measurable at this level for more than 30 years.

Try twice that long!