Damping Factor

The Damping Factor Debate See Below:

http://www.lansingheritage.org/html/jbl/reference/technical/damping-factor.htm

One of the problems with determining how important is a high damping factor is the "all other things being equal" problem.  You never can achieve all other things being equal, so it is hard to say if any difference is attributable to damping factor.  Also, there are some systems where low damping factor does indeed alter the sound, but, it can be for the better.

How high damping factor is achieved matters a lot to me.  Throw in a lot of negative feedback and you can get spectacularly low source impedance (high damping factor) but those designs tend to sound dead, or "sterile" to my ears.  I recall when Halcro amps came on the market and audio magazines went nuts raving about them.  They measured spectacularly--ultra low distortion, utlra high damping factor, etc. and I did not like them on any of the speakers I heard them playing.  A friend of mine said that he had tears in his eyes when he first heard them play because of the nostalgia it provoked--it reminded his so much of the first time he heard a Phase Linear 700 amp (i.e., he thought it sounded awful too).

The last time I shopped for speakers, I visited a dealer to audition (if my memory serves me) a pair of Magico S5's.  The salesman initially drive them with a very powerful, very high damping factor solid state amp and it seemed like the S5's it didn't have much bass.  When the "high end" listening room became available, he powered the S5's with Audio Research tube power amps and the bass was dramatically more prevalent and musical.

It's kind of like a wet.....well, you ,know. Someday you'll understand. 

Basically all high damping factor (DF) tells is that the amplifier has very similar voltage output into an 8 ohms resistive load and into a a no-load (aka infinite resistance load).

There are loads of conjectures on how a very high DF affects sound quality, but such conjectures are severely restricted to closely identical topology and loudspeaker loads. For example, when a specific solid state circuitry's DF is 20, and it's improved to with minimal alterations to its topology to 200, there is a noticeable improvement in bass performance when driving low efficiency, current hungry loudspeakers. The applicability of DF-centric paradigm / observations are restricted to this playing field. The actual DF count means something very different for a class D amplifier than a class A single ended amplifier, the numbers are not comparable, as their voltage / current generation and handling mechanisms are very different.

In general, DF is provided for an 8R purely resistive load at 1kHz frequency. (Unless otherwise specified.)

However, to make DF useful, (whether it helps you or not), you need to know what the DF is in the actual region where it has significance: the 20Hz-100Hz region.

A DF of 1000 at 1kHz is useless when the DF at 20Hz is only 20. (However, it is unlikely to have super low DF at 20Hz when DF at 1kHz is very high, but it's not guaranteed.)

Even worse, the DF has to be recalculated for YOUR LOUDSPEAKER to tell how your amplifier is handling the Loudspeaker. How it handles a nominal resistor is fundamentally different from how it handles a loudspeaker.

My experience:

-Solid state amplifiers are kings to handle resistors, but they don't do so well with loudspeakers.

-Tube amps do not do so well with resistors, but do much better with loudspeakers, provided that loudspeakers are a match to them. (Neglect impedance matching = failure.)

DF in the marketing literature: we are measuring a phenomenon at the wrong frequency and with the wrong type of device. 1kHz instead of 20Hz, and with 8R resistor instead of an actual inductive loudspeaker. This is like measuring a swimmers performance doing squats in the locker room, instead of actually clocking his swimming....

Coming back to applicability: high DF counts when driving low efficiency & current hungry speakers, which need tremendous control over the cone, as the energy required to reach the same spl can be x100 or greater than with a high efficiency speaker.

Briefly: if you can see the cone move, you need high DF. If the cone does not move, DF is almost irrelevant.