damping factor

[Rob41]

Yet, it is a static measurement.

Where DF counts is not a static situation. It's an environment where power and acoustics(acoustic load and cabinet tuning) play a significant, and reactive role.

I'm glad you brought that up. It seems to me that a sealed enclosure would produce greater damping than a similiarly sized ported cabinet, as does cone weight and cone surround stiffness to mention just a couple variables.

From my very limited understanding, I see the above examples as mechanical damping. If a woofer is very heavy with a stiff surround the mechanical damping can shorten the ring of the drum beat eliminating a small bit of the recording. It's been my understanding that the additional damping provided by using an active crossover with one amp per set of drivers delivers greater cone control but without cutting off any of the original material but rather keeping the cone from getting out of control. Does that make sense?

 

[ken kantor]

A good thread... once quick note:

Amplifier-related damping will only have an effect for a speaker system that has a relatively high Qms. A driver with a low Qms is likely to be more dependent on mechanical damping. (IIRC)

-k

 

[atmasphere]

One thing not brought up so far is what is the damping factor at the frequency extremes. Quite often it is different than what it is at 1KHz, for example even if your DF is relatively high, if lower at 20Hz you will hear anomalies.

FWIW it is possible to build a tube amp wherein the DF at 10Hz is the same as it is at 1KHz.

Here is an article by the head engineer of Electro voice. In it we see that no speaker needs more than 20:1, and some need quite a bit less:

http://www.paulspeltz.com/tomcik/index.html

One reason DFs of large values (+20:1) is not really a good thing is that a lot of feedback is required to achieve the figures. The feedback introduces distortions that were not present in the input signal (see Norman Crowhurst). Nelson Pass wrote an interesting article about this:

http://www.firstwatt.com/pdf/art_dist_fdbk.pdf

Were that the end of it! But its not. Traditional uses of feedback rarely meets all the requirements for successful application. The result is a compromised amplifier. For example, feedback in an amplifier often introduces RF to the input of the amp, which is never a good thing. Open loop bandwidth plays a bigger role than is seen at first blush, for more on this topic here is another great article:

http://www.normankoren.com/Audio/FeedbackFidelity.html

My opinion is that DF is overrated (we see that in the first article- some speakers are easily overdamped, causing them to loose resolution and of course, bass impact). Flat output impedance with respect to frequency is IME more important. Of course, you might expect that from a tube amplifier manufacturer...

 

[Jeffery]

One thing not brought up so far is what is the damping factor at the frequency extremes. Quite often it is different than what it is at 1KHz, for example even if your DF is relatively high, if lower at 20Hz you will hear anomalies.

FWIW it is possible to build a tube amp wherein the DF at 10Hz is the same as it is at 1KHz.

Here is an article by the head engineer of Electro voice. In it we see that no speaker needs more than 20:1, and some need quite a bit less:

http://www.paulspeltz.com/tomcik/index.html

One reason DFs of large values (+20:1) is not really a good thing is that a lot of feedback is required to achieve the figures. The feedback introduces distortions that were not present in the input signal (see Norman Crowhurst). Nelson Pass wrote an interesting article about this:

http://www.firstwatt.com/pdf/art_dist_fdbk.pdf

Were that the end of it! But its not. Traditional uses of feedback rarely meets all the requirements for successful application. The result is a compromised amplifier. For example, feedback in an amplifier often introduces RF to the input of the amp, which is never a good thing. Open loop bandwidth plays a bigger role than is seen at first blush, for more on this topic here is another great article:

http://www.normankoren.com/Audio/FeedbackFidelity.html

My opinion is that DF is overrated (we see that in the first article- some speakers are easily overdamped, causing them to loose resolution and of course, bass impact). Flat output impedance with respect to frequency is IME more important. Of course, you might expect that from a tube amplifier manufacturer...

Oh lord, not feedback again. You'll never get away with posting anything Pass without the obligatory Bruno Putzeys declaration that There is no such thing as too much feedback

 

[racca]

Oh lord, not feedback again. You'll never get away with posting anything Pass without the obligatory Bruno Putzeys declaration that There is no such thing as too much feedback

Ooh, do I get to make the obligatory "Putzeys says that because he designs digital amplifiers that rely on massive amounts of feedback to function" comment?

 

[ken kantor]

Ooh, do I get to make the obligatory "Putzeys says that because he designs digital amplifiers that rely on massive amounts of feedback to function" comment?

Regardless of his motivation or methods, Putzeys is absolutely correct.

Negative feedback is extremely well understood, very beneficial to both sound quality and measured response, and exhibits none of the notorious problems that certain reviewers and manufacturers claim it does.

-k

 

[mhardy6647]

I think the issue with NFB is all about the implementation (not the technique per se).

 

[E-Stat]

...and exhibits none of the notorious problems that certain reviewers and manufacturers claim it does.

None? Others measure (creates more complex spectra) and perceive differently.

Audio Distortion and Feedback

 

[racca]

I think the issue with NFB is all about the implementation (not the technique per se).

This, but regarding just about everything in home audio reproduction. Differing design goals, etc.

 

[ken kantor]

I think the issue with NFB is all about the implementation (not the technique per se).

Nonsense. There is >no< issue with negative feedback. The end. The people who claim there is are wrong. (Or worse.)

-k

 

[ken kantor]

None? Others measure (creates more complex spectra) and perceive differently.

Audio Distortion and Feedback

This "paper" is incorrect... in many ways. If you understood Putzys, you would know why. In fact, it inspired his recent work.

-k

 

[ken kantor]

None? Others measure (creates more complex spectra) and perceive differently.

Audio Distortion and Feedback

Like many things in audio, there are various subcultures that exist that are convinced of all sorts of ideas.

Out here in the real world, negative feedback is tried and true!

-k

 

[E-Stat]

This "paper" is incorrect... in many ways.

There you have it. Incontrivertible fact.

Mr Putz and you are most welcome to your opinions.

 

[E-Stat]

Out here in the real world, negative feedback is tried and true!

So what is the *real* world in your eyes?

 

[ken kantor]

I'm not going to argue with you. Believe what you want.

-k

 

[E-Stat]

I'm not going to argue with you. Believe what you want.

Just trying to establish your point of reference.

As for me, I go by what I hear, not what I believe.

Switching amps have measurably horrible square wave response (you just can't get the carrier fuzz out of the signal) and sound overly lean and electronic at the top - if that's the sound you prefer.

edit: for a cool $25k you can get Bruno's latest Mola Mola gear. Is that the *real* world?

 

[ken kantor]

There you have it. Incontrivertible fact.

Mr Putz and you are most welcome to your opinions.

Math is not an opinion. (At least at this level.)

-k

 

[bare]

Just trying to establish your point of reference.

As for me, I go by what I hear, not what I believe.

Switching amps have measurably horrible square wave response (you just can't get the carrier fuzz out of the signal) and sound overly lean and electronic at the top - if that's the sound you prefer.

Wellll This Fellow thinks he has.. And.. his resume supports his credibility .
http://www.diyaudio.com/forums/chip-amps/252436-lm3886-pcb-vs-point-point-data.html

But then there are those that believe that all amps sound the same :sigh:

 

[E-Stat]

Math is not an opinion.

Absolutely!

What part of increasing higher order distortion products via implementing NFB is counter to basic math principles? On the contrary, it is quite predictable. Feedback runs on the concept of fixing something that has already occurred!

If you want to mask inherently non-linear circuits with corrective feedback, go for it! I'd much rather listen to components that don't require such crutches (like my zero feedback Audio Research SP20) and have far simpler distortion spectra!

To each his own.

 

[E-Stat]

Wellll This Fellow thinks he has..

He has...exactly what? Improved the sound of the LM3886?

I should hope so!