Low damping factor but fast& high current SS amps?

Why do you want low damping factor? The damping factor of an audio amplifier is unrelated to the slew rate or speed of the amplifier. An audio power amplifier's damping factor is defined as the ratio of the load impedance to the output impedance of the amplifier.

Loudspeakers have the tendancy to continue vibrating after the signal is gone due to inertia. Suppose the incoming signal is a "tight" kick drum with a short attack and decay. When the kick-drum signal stops, the speaker continues to vibrate so that nice, snappy kick drum turns into a boomy throb.

When the loudspeaker cone vibrates, it acts like a micro-phone, generating a signal from its voice coil. This signal generated by the speaker is called back EMF (back Electro Motive Force). It travels through the speaker cable back into the amplifier output, then returns to the speaker. Since back EMF is in opposite polarity with the speaker's motion, back EMF impedes or damps the speaker's ringing. The smaller the amp's output impedance, the greater is the effect of back EMF on the speaker's motion. An amplifier with low output impedance does not impede the back EMF, so the back EMF drives the loud-speaker with a relatively strong signal that works against the speaker's motion. When the speaker cone moves out, the back EMF pulls the speaker in, and vice versa. In short, the loudspeaker damps itself through the amplifier output circuitry. The lower the impedance of that output circuitry, the more the back EMF can control the speaker's ringing.

I would think you would want an amplifier with a higher damping factor. I am curious why you want one with a lower damping factor?

It's very simple to add a resistor in series with the output of an amplifier with a high damping factor (a.k.a. low output impedance) to get whatever damping factor you desire. The resistor value can be calcuated by dividing the nominal speaker impedance by the target damping factor value. So if you wish to have a damping factor of two, and your loudspeakers have a nominal impedance of 8 ohms . . . then placing a 4-ohm resistor in series will acheive the desired result.

Most audiophile parts suppliers have an assortment of resistors of the proper value - a non-inductive wirewound type is ideal, and a power rating of 20-50 watts will be more than adequate for the overwhelming majority of domestic applications.

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

I think it is a rather poor explanation because it is the magnetic field which damps the motion, not back EMF.

The amount of force it takes to move a generator (ringing speaker in this case) is proportional to how low the load is.

The lower the impedance the speaker sees looking back into the amp the more current it generates with its motion.

The more current it generates the stronger the magnetic field it generates which pushes back against the speakers magnetic field.

That's why speakers are often shipped with shorting straps across their terminals. This short allows a lot of current to flow when the speaker vibrates and dampens it. If you ever turned a hand generator you will find that the harder you crank and the lower the load the harder it gets. Not because of any back EMF, because the magnetic field from the current flow pushes back.

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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.

Electricity and magnetism are interchangeable. Think of a shorting strap as an amp with low resistance to the back EMF generated in the speaker.