Damping factor can equate to less bass ?

[otiake]

I'm not sure everyone here has grasped the complete picture. Most manufacturers test and define their DF with resistive loads under test bench conditions. Large numbers impress and with lots of system negative feedback largish numbers can be produced easily. It doesn't mean it sounds good, and often high DF systems using excessive feedback to reduce steady state distortion often suffer from transient response issues.

Loudspeakers are reactive, the effective loop inductance a complex result of device geometry, amplifier phase margin and connection series resistance, not to mention any passive crossovers. While the DC resistance of a crossover and associated wiring may well be milliohms, to be effective as a crossover it needs significant impedance at the crossover frequency. Cored inductors may be smaller with lower resistance but inductance is inductance regardless of the construction.

The net complex impedance from all this can range from 0.1ohms up to many ohms at crossover frequency. Consequently effective DF can drop off to near nothing.

Whether there is "less bass" or "more bass" depending of the DF is really a function of the speaker acoustic loading and natural resonance.

I recall a time 30 years ago when I produced an amp for personal use but some colleagues thought it was pretty good and it ended up in the local audiophile store being compared with the latest and greatest. It scored a first equal with the comment "bass a bit tight". If I recall, the output stage used multiple feedback paths with a DF around 50 at 1kHz into a resistive load with exceptional transient response. It was also excellent with reactive loads. I wound up a couple of 300uH chokes and put them in series with the speaker leads. The results were a "warmer sloppier bass" (to my ears) which those listening thought was "perfect". Equivalent DF at 150Hz was around 5.

[DF96]

Originally Posted by otiake

The net complex impedance from all this can range from 0.1ohms up to many ohms at crossover frequency. Consequently effective DF can drop off to near nothing.

I think you may be confusing resistance, which provides electrical damping, with total impedance. Reactance does not provide damping, so the fact that a crossover inductance has high reactance does not affect damping. Away from the bass resonance electrical damping has little effect anyway.

It is true that the DC resistance of crossover inductances can limit effective DF. Cable resistance does this too. For these reasons there are diminishing returns as the bare amp DF goes much above 20 or so.

[max_cwb]

The best bass I've ever heard came from a push-pull tube amplifier with five dumping factor. Must be why Sakuma uses the 300B push-pull section to feed the bass ...

[DF96]

"Best bass" or most bass? Low DF means, other things being equal, a large bass resonance; sometimes known as 'one-note' bass. Superficially impressive, but you can end up hearing the speaker resonance rather than the music bass line.

[Charles Darwin]

The best bass I've ever heard came from a bjt ss amp with a damping factor of >400.


A question: I understand DF is frequency dependent (some manufacturers state a DF of X at 100Hz, others at 1000Hz), is it possible to guesstimate what it would be at a frequency other than the one chosen by the manufacturers?
In other words does it vary at a roughly predictable rate?

[AndrewT]

I don't think so.
The output impedance is affected by the circuit itself and the filters added to the output to help with stability.

[DF96]

The raw DF for a typical SS amp is likely to fall with frequency because of the loop gain. This raw value will be modified by any output network and the cable. A simple rule of thumb is not really possible.

[Charles Darwin]

Thanks guys!

Only asked because in my youth I read a german HiFi rag and they tested for DF at three frequencies: 100, 1000 and 10 000Hz.
As far as I remember it was always higher the lower the frequency so I was just wondering as it would make comparing specs (for what they are worth) easier.

[Carloshenri]

There's a LOT of different information, experiences, and opinions in the
Audio Industry, aren't there? Well... MY experience, and my opinion, about DF's is the same about every other aspect of this wonderful arena: It's ALL about the synergy of the components involved, the macro components and the micro. Change the amp output filters, 2 lil resistors and a tiny cap: you’ve altered the sound of the entire system. It’s the synergy of combining energies and types.

I personally like the well rounded sound and feel of the bass my tube amp gives my tuned port speakers vs. the bass from my SS amp.