How much damping factor do you need?

Athers-Aud

Athers-Aud

Active Member
Geeez ... this is the heaviest thing I've ever had on my bench. 144IIb (65Kg)
and a damping factor of 160 ... 250W (8 Ω) both channels driven wide band charactersistic of 5hz through to a stated 80khz

Which got me thinking ... with the efficiency of speakers today ... do you really need a damping factor at that power? ... enough to pull the moon out of orbit?

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Why would speaker efficiency have anything to do with damping factor?
160 is quite high for a damping factor but you can get higher. In practice the figures are a bit misleading if the impedance of the speaker cables are ignored. The speaker cable will bring the damping factor down to a less impressive figure than that quoted for the amplifier alone.
 
rothwellaudio said:
Why would speaker efficiency have anything to do with damping factor?
160 is quite high for a damping factor but you can get higher. In practice the figures are a bit misleading if the impedance of the speaker cables are ignored. The speaker cable will bring the damping factor down to a less impressive figure than that quoted for the amplifier alone.
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I guess where I am going with this question... is more to do with the load being todays speakers with their rare earth materials - tickle a speaker with a few watts and SPL is excellent and load not influencing amplifier like a set of old Apogee Scintillas (that's the efficiency bit) - from all that is I've seen in written papers and reviews, an impression that high efficiency speakers work best with a lower DF... but not sure that is true. ...but is DF really that important?

...Also compare load (spkr) design today to when these monsters were made. - do we need such gopping amounts of stored energy, and in this case, 24 output transistors per side each consuming 110mA a piece at idle, in an NFB amplifier (basically I can weld with it) ? I would have thought a DF of anything more than 100 is kind of a waste...unless flyback currents are so high. ....hmmmm...gives me an idea to stick an inductive load on this thing and do some measurements.
 
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My big amplifiers have a damping factor over 1,000 and an output impedance of 20 milliohms.

Yet most listeners prefer my Dyna ST-70 with a damping factor of 15, On the same speakers.

Although damping factor measures "Something" it's not an good indicator of speaker compatibility or performance.

It's important to remember that Audio electronics, acoustics and speakers are a "Resonant" system.

"Speakers are a pebble in a pond Not a fire hose" ... Buck.

Hard to keep that in mind when lots of speakers look like a Nozzle.

I stopped chasing that Dragon's tail a long time ago.

Yes, I was going to bring up Ribbon speakers.

Buck
 
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I'll admit to knowing nothing about electronics from an EE perspective, but I also must admit to always having been impressed by figures quoted as performance about which I also know nothing.

Case in point would be my favorite amplifier—a Crown Studio Reference-II—and it's quoted damping factor damping Factor:
Damping Factor: >20,000 from 10 Hz to 400Hz.
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Even my baby Crown, the PS-400, makes claims I don't fully understand:
Damping Factor: >400 from DC (0 Hz) to 40 Hz.
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yeah DF can get crazy high but even the small resistance in the cables shoots that in the foot if measured at the speaker end of things.

At one point I think that was one of the assorted "spec racing" numbers that people worried about but I don't know how much it really matters once it gets beyond a certain point. I don't know that anyone specifically designs for high DF anymore, but its sort of a consequence of high current, high feedback amplifiers that ends up with very low output impedance. High feedback is kinda needed if designing for DC to light sort of response with distortion below measurement thresholds.



damping factor is just speaker load divided by amplifier output impedance. Say its 400 and the speaker load is 4 ohms, that means output impedance of the amplifier is 0.01 ohms. What its supposed to represent is the amplifier's ability to control driver movement, basically if the signal pushes the cone out, the amp keeps it from over-extending or bouncing back. It follows the waveform accurately.
 
As I remember it's the same idea behind Four Quadrant Power Conversion Supplies.

We used these Teradyne testing computers and each one was filled with them.

Each probe can push:

Positive voltage/Negative Current.
Positive voltage/Positive Current.
Negative voltage/ Negative Current.
Negative voltage/Positive Current.

So each can supply power out or Absorb power acting like a Load.

Crazy stuff. Buck
 
It's important up to about 100 or so. Maybe not remembered correctly. More importantly cables and especially crossovers destroy that high number real freaking fast, evening the playing field quite some.
 
gadget73 said:
yeah DF can get crazy high but even the small resistance in the cables shoots that in the foot if measured at the speaker end of things.

At one point I think that was one of the assorted "spec racing" numbers that people worried about but I don't know how much it really matters once it gets beyond a certain point. I don't know that anyone specifically designs for high DF anymore, but its sort of a consequence of high current, high feedback amplifiers that ends up with very low output impedance. High feedback is kinda needed if designing for DC to light sort of response with distortion below measurement thresholds.



damping factor is just speaker load divided by amplifier output impedance. Say its 400 and the speaker load is 4 ohms, that means output impedance of the amplifier is 0.01 ohms. What its supposed to represent is the amplifier's ability to control driver movement, basically if the signal pushes the cone out, the amp keeps it from over-extending or bouncing back. It follows the waveform accurately.
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Agree; cable resistance and DCR of crossover coils in series with the woofer's voice coils will clobber the DF of an amplifier with barely milliohms of output impedance. High DF is pointless after a reasonable minimum is reached. High DF certainly won't hurt anything except maybe your wallet if you paid dearly just to get that.
 
As a tube amp guy I'm lucky to hit double digits with most of my stuff. Significantly less than 1 ohm with most amps isn't gonna happen just because of the DCR of the transformer secondary if nothing else. Not really a big deal, just don't run "floppy" speakers with a tube amp. I've had speakers that wanted some damping otherwise they were just boomy. Whatever Cerwin-Vegas I gave to a friend were really bad about it. Sounded OK on a solid state amp but on a tube amp it was like having your head inside the kick drum.
 
I think it's just a figure that allows people to bragging rights. In my book, the weight of (a class AB) amplifier tells more about the quality of sound to expect, than other figures may imply.
 
gadget73 said:
As a tube amp guy I'm lucky to hit double digits with most of my stuff. Significantly less than 1 ohm with most amps isn't gonna happen just because of the DCR of the transformer secondary if nothing else. Not really a big deal, just don't run "floppy" speakers with a tube amp. I've had speakers that wanted some damping otherwise they were just boomy. Whatever Cerwin-Vegas I gave to a friend were really bad about it. Sounded OK on a solid state amp but on a tube amp it was like having your head inside the kick drum.
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I measured my homebrew circlotrons, and they sit at a pinch under 1/4 ohm output impedance, everywhere from 18Hz to 18 or so kHz, where it rises a bit, but not too much, and I don't think that would be audible. I happy with that amount, and the amps don't sound flabby and out of shape at all.
 
egellings said:
I measured my homebrew circlotrons, and they sit at a pinch under 1/4 ohm output impedance, everywhere from 18Hz to 18 or so kHz, where it rises a bit, but not too much, and I don't think that would be audible. I happy with that amount, and the amps don't sound flabby and out of shape at all.
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Never fooled with a Circlotron but i find them interesting and would like to at some point
 
SaSi said:
I think it's just a figure that allows people to bragging rights. In my book, the weight of (a class AB) amplifier tells more about the quality of sound to expect, than other figures may imply.
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That says nothing about sound quality.
Thick steel plates and aluminium fascias don't add to sound.
The amplifier could also be having a SMPS that weighs 20% of the toroid or EI counterpart.
It could have a fan instead of large heat sinks.
 
gadget73 said:
Never fooled with a Circlotron but i find them interesting and would like to at some point
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Yamaha uses this design in their A-Sxxxx line. It is said to lower the noise floor but their amps with this design don't exhibit much better specs than the ones without.
 
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