Damping Factor?

[docmd2010]

When considering amplifiers, how important is the stat of the "damping factor" to the overall quality of sound and the amplifier?

[PHC1]

Certainly not a sole criteria by which one should select an amplifier.

It's a bit much to type to go into detail but there are other factors at play such as the ultra low output impedance of an amplifier which produces high damping numbers (damping factor is amplifier output impedance to speaker impedance ratio) Such amplifiers often use tons of negative feedback which in itself is a whole other can or worms...

Then there is that whole thing of what I hear and prefer vs what you hear and prefer. Some will find an accurate bass "dry"... Others will find a tuneful, analog like bass bloated...

What do you have in mind more specifically?

[docmd2010]

Well I have noticed that some manufacturers display this number and some don’t. To my understanding it is a quantitative assessment of how well the amplifier controls the driver once the signal stops. To my understanding, this basically equates to how well the amplifier controls the woofers.

[PHC1]

Originally Posted by docmd2010

Well I have noticed that some manufacturers display this number and some don’t. To my understanding it is a quantitative assessment of how well the amplifier controls the driver once the signal stops. To my understanding, this basically equates to how well the amplifier controls the woofers.

In a nutshell, yes, however... That damping figure in itself is not indicative of anything other than how low the output impedance of the amplifier is and the resistive impedance of the speaker used. How that damping factor was achieved as I already mentioned, can be more of a detriment. Certainly tube amplifier can hardly match Solid State with tons of negative feedback and very low output impedance.

I personally never liked amplifiers with very high negative feedback, (or at least I have yet to hear one) in general and comparing to amplifiers that used zero negative feedback and not nearly the same damping factor, the later sounded much more analog and natural when it came to bass response. Of course the speaker itself plays a significant role here.

The damping factor is akin to the total harmonic distortion numbers that some manufacturers tend to boast... We all know that is certainly not the most important factor.

Here is a brief article that may shed some light on the topic for you. http://www.butleraudio.com/damping1.php

[PHC1]

From the article above:

"When I get a letter from someone who is worried about buying a certain amplifier because it has a specified damping factor of "only" 15 to 16, I can't help but remember an old, old joke. It goes like this:
A scientist is giving a public lecture. During the course of his speech, he predicts that in 100 billion years human life will become extinct. A man in the audience, obviously upset, asks the lecturer to repeat the statement.
"I said", quotes the professor, "that in one hundred billion years, human life will no longer exist."
"Oh, thank goodness", replies the man, much relieved, "I thought you said one-hundred million!".

[W9TR]

Well stated Serge! Mostly damping factor (amplifier output impedance) isn't really relevant.

There is one sonic artifact of really low damping factor (high amplifier output impedance). Some loudspeakers have very large impedance swings themselves. One example is electrostatic loudspeakers whose impedance at high frequencies can dip below 1 ohm. In this case an amplifier with a low damping factor (high output impedance), typically a tube amplifier, would sound dull or rolled off driving this type of speaker.

Some conventional speakers have big impedance swings as well, so using a tube amplifier with these speakers can act as a sort of tone control.

This is one of the reasons why amplifiers that measure the same can sound different driving real world speakers.

Tom

[PHC1]

Originally Posted by W9TR

One example is electrostatic loudspeakers whose impedance at high frequencies can dip below 1 ohm. In this case an amplifier with a low damping factor (high output impedance), typically a tube amplifier, would sound dull or rolled off driving this type of speaker.


Tom

Sometimes, that is a blessing in disguise. Being oblivious and enjoying music thinking it is non fatiguing, inviting, lush, musical... Then finding out and saying "oh, so that's what's going on.. It's rolled off!!! Oh my, the horror..."
Worse yet, making a switch only to be dissatisfied because the magic is suddenly gone but hey, it's all about being faithful to the recorded music... Sometimes being a "purist" just doesn't pay off.

[docmd2010]

Thanks for the response guys. I was being led in the wrong way about this damping factor business.

Thanks for the clarifications!

[PHC1]

Originally Posted by docmd2010

Thanks for the response guys. I was being led in the wrong way about this damping factor business.

Thanks for the clarifications!

Looking for another amp for the inbound Magico speakers?

[tdelahanty]

Lets pretend a large kettle drum was hit very hard. A large positive pulse, from the amp, pushes the woofer forward (out). As the pulse subsides and the woofer returns to resting an equal and opposite pulse is generated. The amp must absorb this equal and opposite pulse, here is the relevance of damping factor. Very interesting and useful scientifically not that big of a deal in our world. Happy tunes.