Low damping factor but fast& high current SS amps?

In a dynamic system, I rather doubt you can have one without the other.

That the speaker generates the energy which damps its motion is without question.
And, since speakers store energy for later release, I'm not too uncomfortable calling it back EMF.......

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In a dynamic system, I rather doubt you can have one without the other.

It is very easy to have EMF without a magnetic field. Voltage without a path means no current. No current means no magnetic field.

Since the impedance is very low the current is higher and the EMF very low (ohm's law). Again, it is the field created by the current doing the work, not EMF.

I'm not too uncomfortable calling it back EMF

Comfortable or not, it is wrong. EMF is voltage. It is not voltage that damps the motion, it is a magnetic field.

This is physics. There are precise definitions for these terms and the science behind how they interact is well defined and understood. Since you are comfortable using them incorrectly there is no point in further discussion.

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There is both some conceptual as well as terminological confusion here.

All this talk of damping factor without a single tip of the hat to the 'q' of the speaker.
Critically damped speakers...Q-0.707 need much less amplifier damping.
Hi Q speakers can benefit from higher amp damping factor, but only to a point

The total Q of the driver/enclosure together (which is the figure to which you're referring) is VERY much dependent on the source impedance the driver sees . . . in the Thiele/Small equations, this is reflected through the driver's electrical Q (Qes).

Generally, drivers with a high Qes (especially with a low resonant frequency Fs) are more suitable for sealed enclosures, which (again, speaking generally) tend to work better with amplifiers that have a low output impedance. On the flip side, if you're designing a reflex loudspeaker with a Q of 0.707, the cabinet volume needs to be larger, and the port tuning lower, to acheive this with a higher source impedance (that is, a lower damping-factor amp). So for a given loudspeaker, the total system Q goes up as the source impedance gets higher, usually causing a mid-bass peak.

I'm of the opinion that the subjective sound of this mid-bass peak is the true source of the term "damping factor" for an amplifier, not for the literal mechanical damping of the woofer cone itself, or especially "damping" in the sense of classical Control Theory. Also, this peak can be frequently tamed by increasing absorption losses in the cabinet . . . that is, to add "damping material" (to offset the lack of "damping factor").

Comfortable or not, it is wrong. EMF is voltage. It is not voltage that damps the motion, it is a magnetic field.

I think that a frequent point of confusion is between the acronyms EMF (electromotive force), EMI (electromagnetic interference), and EMP (electromagnetic pulse) . . . the error is in assuming that "speaker back EMF" refers to "electromagnetic force" . . . which if these terms are used precisely, it doesn't.

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Kirkus, good point, I didn't occur to me that somebody might be confused if they picked the incorrect meaning of EMF.

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09-12-11: Herman.

Liguy, did you cut and paste that from a tech for dummies web site?

No, I did not. I tried to explain it in the most simple terms I could.