Damping Factor - Interesting article

If there is benefit from going from 12awg to 11awg as Benchmark suggests, then why not go to 9awg?

djones512,195 posts06-06-2020 8:41am"What amplifer are you talking about turnbrown?...."

Marantz Integated Amps are a good example of DF specs with no load or frequency specified. Hegel, who prides themselves on very high DFs, list no load or frequency in their specifications.  

What amplifer are you talking about turnbrown? Some amps will have something like DF >400 at 20hz, I have seen some say DF > 300 20hz - 20khz @ 8Ohm. Use the Excel spreadsheet from Benchmark and input the numbers from your speakers. What Benchmark was showing is speakers that range from 2.6 Ohm to 18 Ohm DF of >200 was .1dB difference. Some like Pass use a low DF which produces higher dB in the Bass depending on speakers used.

I have paid very close attention to damping factor over the years starting with when I acquired my large Ohm Walsh speakers that use a single 12” driver operating Walsh style with wave bending.


I had read the large 12” driver benefitted from high damping and have found that to be very true.

I started off with a Carver m4.0t amp that is designed to emulate a tube amp with relatively high output impedance. This did very well with larger Maggie’s and modest tower design B&W P6 but I found I could do better with the Ohms.

I landed on the Class D Bel Canto amps which bring a higher level of control to the 12” Walsh style drivers. Everything is clearer and better especially bass which became clearly nuanced and articulate compared to prior.

I’ve used other smaller monitor speakers with these amps as well and find the benefits of the higher damping varies more there speaker to speaker.

Dynaudio contour monitors benefited but to a lesser degree. Small less extended Triangle Titus monitors even less. I run kef ls50s off the amps now and sound is very detailed and articulate. I heard these prior a few years back when someone brought a pair over to hear and found they sounded as described off my Class D amps but were actually quite bad, very flat and muddy, off a pair of tad hibachi amps I had at the time which were a zero feedback SS design. Huge difference with highly damped Class D versus zero feedback/high output impedance.


So the correlation between damping factor and sound quality seems to exist at least based on my experience.


Also I should note I tried a different more highly damped Class A SS amp prior to the Class D and yes brightness was an issue there possibly due to the bad harmonics associated with higher damping SS amps.
All this is a big reason I am a sold Class D fanboy these days. Especially if you have larger speakers that need a beefy high current SS amp to take vice-like control of the drivers

The problem I have is that even when Damping Factor is specified for an amp, the conditions are usually not indicated. Does it apply at 8 ohms or some other value? Also, the DF spec usually doesn't list the frequency. The DF at 20Hz may be significantly different at 20KHz.

I am copying Doug Schroeder's discussion on "Damping Factor" from his Dagogo Gold Note PA-1175 Mk II amplifier review.

Doug's findings with respect to this amp are, I believe, of significant importance and of critical value. For this reason, I am sharing it in it's entirety. The link to the review follows at the bottom of this post.

From Page 2 of @douglas_schroeder 's review:

"My enthusiasm for the amp was dampened slightly but became a white-hot flame of interest once I began to work with the unusual Damping Factor feature. I can put up with the quirks largely because of two things, the uncanny ability of Italians to get the Midrange perfect, and the “best of both worlds” experience the PA-1175 offers through use of the DF switch.

In the current amplifier market Gold Note may have the coolest feature available in the Damping Factor. This is no gimmick or marketing ploy, but a serious uncommon advantage conferred upon the owner. Anyone who has spent time with solid state versus tube amplifiers knows the variance in sound can be dramatic. Speakers react substantially differently when hooked up to a solid-state amp with high power versus a tube amp with lower power. For our objectivist friends reading this, I have no desire to debate my perspective with you.

Why am I discussing power when the Damping Factor is all about controlling the excursion of the drivers? For the simple reason that the DF feature alters the sound in such a way that one senses they have switched out the amp from a higher power SS design to a lower power tube design. That is how much the DF control changes the listening event. I have placed enough heavy monoblock class A or A/B amps with my speakers, and also enough heavy tube amps with those same speakers. to know the effect immediately. The DF operates in a fashion that gets similar adjustments to the sound as if had I physically moved two separate amps in and out of the system.

As an aside, on this topic we see the proclamations of specifications-driven audiophiles shown to be wrong by the reality of performance. I have seen dismissals of Damping Factor as irrelevant to amplifier operation, or at a minimum much less important than current delivery or wattage. It takes about ten seconds hearing the distinction to know that Damping Factor has a major effect upon a speaker, and while it is not typically treated as seriously by the hobbyist as those other design considerations, it should be. Once I heard the effect of switchable DF, I began paying very careful attention to that specification.

Gold note recommends “…use of the low DF (25) setting with high sensitivity speakers and mini-monitors as the amount of energy used to reproduce the lower range of frequencies usually suits these kind of speakers best… Bigger or mid/low sensitivity speakers perform better when driven by a higher power amp with a higher DF.” While I agree in general with that guidance, there are a couple of things to consider, one being the overall quality of the speaker. Some speakers are not terribly precise, regardless of the advertising that claims otherwise. I would tend to run such speakers with the higher DF in order to tighten them up, and I would turn to cabling to tune them in terms of tonality.

Conversely, a speaker with such beautiful expression as the just reviewed VanL Speakerworks Silhouette is a treat to hear with either of the DF settings. The Silhouette is a purist’s speaker, a refreshing departure from the crass offerings without the signs of a master craftsman’s touch. It is a minimalist speaker design, as is evidenced in the supreme quality of the 6/5” wooden cone dual motor mid/bass driver and minimal crossover, and as such lets the alternative settings of the PA-1175 be expressed readily with deftness. The Silhouette is not designed to be bone crunching, but soul caressing. See my article for a thorough introduction to this rare gem.

The other consideration is that there is no telling what the preference of the listener will be. Some people enjoy a fuller, less tight low end. Some people prefer a sharper, laser guided upper end. Others insist on a predominant midrange that draws attention away from both the upper and lower end, even to the point of suggesting anything lower than 40 Hz is unnecessary for acceptable recreation of the event. For that reason it is worth trying the DF setting in both positions regardless of the speakers you are running. As the PA-1175 is robust, and the power structure is not affected by it, you should not enter into a situation where a speaker will be underpowered by going to the low DF setting."

https://www.dagogo.com/gold-note-pa-1175-mkii-solid-state-stereo-amplifier-review/

This is an important discussion. Thank Yous to the the OP and all posters responses.

I was unaware of the importance of Damping Factor as a 'factor,' in maximizing synergies between speaker and amplifier, until I started considering Cube Audio's Nenuphar speaker.

Both major reviews of the Nenuphar speaker address Damping Factor, and confirm what Erik shared in his post.

In the case of the Nenuphar, both (reviewers) Srajan Ebaen and Dawid Grzyb find low / lower damping factor pairings to be ideal / preferred.

Specifically, @erik_squires points out:

For a counter point though, look at Nelson Pass. He wrote at least one article where he showed that with some speakers, low damping factor, not high, is ideal.

Many Nenuphar owners report the same THOUGH I'm sure other factors (in addition to damping factor) are also at play.

Kijanki, you are a respectful member of this forum, and I thank you for that politeness. Many would become obnoxious at such an exchange, and I would cease communicating with them at that point. 

It seemed to me that you questioned the result directly when you said, "Is it audible? Perhaps for trained ears, but it is not as dramatic as DF=20 vs DF=2000. There will be more sound change from less than perfect driving, than lower damping IMHO." 

My reaction to your comment is that you feel it is quite insignificant. I am telling you that you are wrong; the difference was more on the order of swapping an amp, or as you say, sound change from less than perfect driving (which is a good analogy). 

Regarding the Benchmark products, I am somewhat familiar with the culture of the Benchmark Audio mindset, and I also go against the grain when it comes to such things as the DAC being influenced by cables, or the amp by power cords. Read my reviews of these components also at Dagogo.com 

Some audiophiles, perhaps yourself, find it difficult to accept that there are significant sonic changes in situations where they calculate that there should not be. I'm in no position to argue with you about your prodigious specification assessment, but I am in a position to tell you that if you think Benchmark's sensitivity to cables, or Gold Note's PA-1175 Damping Factor function are insignificant, you would benefit from hearing such things.  :) 

@douglas_schroeder I don’t question what you heard at all. My experience is none compare to yours. I merely stated, that the sound difference you heard could likely be because of less stable output voltage while driving and not because of different damping.
As I said, the difference in damping between DF=200 and DF=2000 is only 0.6% but many people believe it is 10x more. The other question is how this high DF was obtained. The easiest way to lower output impedance is to increase feedback. Adding 20dB to feedback lowers output impedance 10 times, but there are consequences of that. One of them is TIM, that produces unpleasant higher order odd harmonics, that make sound bright and unpleasant. Even Benchmark in AHB2, that doesn’t have negative feedback in normal sense (feedback is non-recursive), settled only for DF=350@20Hz. Class D might have inherently low output impedance because output Mosfets always clamp output to low impedance (either GND or VCC), but for the other classes I would even avoid amps with very high DF (like 2000). Something has to give IMHO.

@douglas_schroeder  Yes, the difference between DF=20 and DF=2000 seems to be huge, but not for the purpose of damping.  Amplifier with DF=2000 has very low output impedance and will provide steady voltage (ideal voltage source) at all frequencies while speaker impedance vary greatly.   It will affect the sound because of that.  Damping is different story.  When we apply positive voltage speaker membrane moves forward.  When membrane moves forward on its own speaker generates also positive voltage, but now current flows from speaker to amplifier.  Opposite direction of this current produces opposite action on the membrane and membrane stops.  This current depends on back EMF produced by the speaker and impedance in the circuit/loop.  This loop contains speaker internal impedance, impedance of speaker wire and the output impedance of an amp.   Let's assume for a moment that wire is perfect.  Total resistance in the circuit will be resistive portion of the speaker impedance - most likely 6 ohm for 8 ohm speaker and resistance of the amps output.  At DF=20 total resistance in the circuit will be 6 ohm + 8/20 ohm = 6.4 ohm  while for DF=2000 it will be 6 ohm + 8/2000 ohm = 6.004 ohm.   Ratio of braking current in the circuit will be equal to ratio of total resistance - in this case difference of 6.6%.  Is it audible?  Perhaps for trained ears, but it is not as dramatic as DF=20 vs DF=2000.  There will be more sound change from less than perfect driving, than lower damping IMHO.  For DF=200 vs DF=2000 difference in damping will be 0.6%.

Read my review of the Gold Note PA-1175 MkII Amplifier  with switchable damping factor. It appears at Dagogo.com 

Today I received the Benchmark StarQuad XLR that is referenced in this article. They are replacing 2 Audience Au24 and Au24 SE cables that cost over $1000 combined some years back. The 2 StarQuad’s were $200. It should be an interesting comparison. I expect no difference with my Benchmark gear but audible difference with other gear.

@bifwynne  Benchmark selected 8 ohm speaker with 13 - 2.6 ohm impedance variation.  One ohm of output impedance would reduce signal to 13/14 and 2.6/3.6 respectively.  Ratio of reduced signals would be 1.286  (28.6% difference) = 2.18dB   It would be much less for my 6ohm speakers that have minimum impedance of 3.6ohm 

I just looked at the speaker load Stereophile uses:

https://www.stereophile.com/reference/60/index.html


That is a very easy to drive load compared to a lot of the speakers they review today, or are typical. I wrote to them in the hopes they update it. This speaker is a much more typical load:

https://www.stereophile.com/content/bowers-amp-wilkins-804-diamond-loudspeaker

I am 100% sure they will ignore me.

It's' my impression (with no formal data) that speakers have tended towards harder-to-drive as SS amplifiers got bigger, beefier and more expensive.  Even the DIY speakers I make have a tough time staying above 3 Ohms to get decent sensitivity out of them.

The Focal is an interesting speaker to chose, since I've analyzed at least one model in depth, and let me tell you, it deliberately dropped the impedance.  No doubt in my mind that having a low impedance was a crossover design goal. Since then I've seen they have a remarkably similar profile in many of their speakers, and it does make a difference.  It makes a speaker seem more "discerning" of amplifiers. "My Focal must be better because I can hear the difference in amps." is the message.


Still, people don't want to chat about that, there are many other high end speakers which brush with low impedance. From B&W to your average ESL. 


The Stereophile simulated speaker load is more forgiving than some, but you can still see the impedance dependent effects there if you look at a tube amp review. The principle is the same, if not as large.

Best,
E

Looking at the Sterephile simulated speaker load FR/Impedance diagram, you can see the lowest impedance is 6 ohm, vs the 2.6 ohm of the Focal. So their simulated speakers isn't as difficult to drive. WIth the Focal, the AR amp would have a higher variation, and you can figure out by how much using the equations from the Benchmark article.

I don't understand why they dont make an integrated amplifier...i'd be very interested.

kijanki ,... I am generally aware of the relationship between an amplifier's output impedance and a speaker's input impedance, the latter stat which varies as a function of frequency response.   What I found surprising is that Benchmark writes that if an amp has an output impedance of 1 ohm, the output level of the speaker could vary by as much as 2 db.  

I own an ARC Ref 150 SE. Some years back, John Atkinson (JA) reviewed an earlier version of my amp and reported his bench test findings here:  https://www.stereophile.com/content/audio-research-reference-150-power-amplifier-measurements

JA's bench test findings report that the FR changes of Stereophile's hypothetical test speaker varied by only .8 db off the 8 ohm tap.  Curiously, JA measured the Ref 150 as having an output impedance of 1 ohm.  FWIW, ARC reports that the Ref 150 has a DF of 14, which permits the inference that the amp's output impedance is .57 ohms (or 8 divided by 14).  

I know you are a  techie.  Can you please explain why there appears to be a difference between JA's findings and the Benchmark report.

Perhaps Atmasphere (Ralph) or Almarg (Al) can weigh in if they catch this thread. 

Thanks

BIF

Yep. This is why Stereophile tests with a simulated speaker load. Look at any amp review, and compare tube amps to SS in the measurements.

For a counter point though, look at Nelson Pass. He wrote at least one article where he showed that with some speakers, low damping factor, not high,  is ideal.


Best,E