... how important is Damping factor in determining what amp to buy


Hi there...

Just how important is damping factor in determining what amp to buy?

In literature and specs - I find this is an often left-out bit of info...


justvintagestuff
Here's my 2 cents.  I've had amps and avrs with damping factor specs from 50 to over 1100.  I can't say it's been a game changer for me or a crucial spec.  More and more I just want good synergy with the particular speakers I'm working with, and the best way to hear if an amp controls your speakers well is to hook it up, or audition it somehow. 

That said, if an amp manufacturer is paying attention to the damping factor performance of their products, they are probably really anal about how their products sound, and that is a good thing.  
That’s a good question. On the surface it looks like it should be very important.  The higher the DF the better the sounds would be a reasonable assumption.

Who wouldn’t want better control of the bass drivers? Wouldn’t that yield tight and accurate bass? While I’ve never purchased an amp based on dampening factor, I do have a couple Rotel amps which are listed as being 1000. Adcom is another brand that list high on the DF scale.

That being said, there are lots of very good amplifiers that have DF in the 100-200 range so maybe it’s a situation where anything over 100 is overkill?
Hegel H300 has a DF of 1,000. The new H360 is a DF of 4,000, Hegel advertises this hard in their literature and discussions, seems very important to them and I do love their top integrated units.
Listen to it.....don't even look at specs
From a post by Atmasphere in this thread on damping factor:
There is no speaker made that requires more than 20:1 for a damping factor, and there are speakers that prefer a damping factor of 1:10 (usually high efficiency full-range speakers).
From a post by me in that thread:
Damping factor and amplifier output impedance are inversely related. Damping factor, as usually defined based on an assumed 8 ohm speaker load, equals output impedance divided into 8 ohms. To the extent that the speaker’s impedance varies with frequency, that output impedance will affect tonal balance, by interacting with the speaker’s impedance vs. frequency variation.

Many electrostatic speakers, for instance, have high impedances at low frequencies, which descend to low values at high frequencies. A solid state amp, having a high damping factor and negligibly small output impedance, will produce LESS bass and MORE treble into that kind of speaker, relative to a tube amp. The tube amp, having a relatively low damping factor/high output impedance, will produce MORE bass and LESS treble into that kind of speaker.

Conversely, many dynamic (cone-type) speakers have low impedances in the bass and mid-bass regions, and higher impedances in the upper mid-range and treble. Driving that kind of load, a solid state amp will provide a stronger bass response than a tube amp, and the tube amp may sound excessively bright.

As was stated, synergy with the particular speaker is key.
From a post by Kijanki in this thread on damping factor:
Inductor in-series with the woofer has resistance approx. 0.08 ohm limiting DF to 100.
Adding to the above: Per Atmasphere’s comment, once damping factor gets significantly above 20 or so, further increases will make little if any difference. Although if one amplifier has a damping factor of 50 and another has a damping factor of 2000, it is almost certainly an indication that there are other major differences in the designs of the two amplifiers that will cause them to sound different. Also, once damping factor gets significantly below 20 or so, which is characteristic of most tube amps, and if speaker impedance varies significantly as a function of frequency, differences in damping factor within that range may significantly affect tonality, due to differences in impedance interactions. And, likewise, damping factor differences between those amplifiers and solid state amplifiers having higher damping factors will also result in differences in tonality, to a greater or lesser degree depending on how the impedance of the speaker varies as a function of frequency.

As I said above, synergy with the particular speaker is key.

Regards,
-- Al

... oh man! - was looking for abit more clarity about how important it is in the voicing and control of a speaker; I understand what it is and what it supposedly does and that all amps must have it to some degree... stringreen's approach ( which to me seems to be more financially-based) would have me all over town, listening to not in my space, or with my components...
MOre pointedly: I'm wondering if my vintage Onkyo A7 (65w/c) or Nikko DC Alpha 230 (120w/c) has enough DF to adequately control the woofer in a new-to-me pair of vintage Gershman Avant Garde RX-20s (before 2000) I've got on the way; I've been lead to believe that if a speaker is underpowered that you can damage a woofer, and I assumed this had to do with DF...
It appears that your Onkyo has a damping factor of 50, and the Nikko has a damping factor of 70. Both of those damping factors will be suitable in terms of sonics with any speaker that is suitable for use with a solid state amplifier.
I’ve been lead to believe that if a speaker is underpowered that you can damage a woofer, and I assumed this had to do with DF...
An amplifier that is underpowered relative to the application, and therefore may be frequently driven into clipping, can cause tweeters to be damaged. I am not aware of any means by which an underpowered amplifier can damage a woofer, or of any relation between damping factor and the likelihood of speaker damage.

Regards,
-- Al

Who wouldn’t want better control of the bass drivers? Wouldn’t that yield tight and accurate bass
Actually no. It **might**. Any loudspeaker can be overdamped- IOW, you can have too much damping. The result is 'punchy' bass without much in the way of definition (also called 'body' when low frequencies are being described). The correct bass will have punch and definition at the same time.

If you have too much damping, the speaker can't make the excursion it should to reproduce the waveform- which is why you loose definition. On top of that, the **amount** of 'punch' you get will not be correct (punchy, but not enough). A lower damping factor can allow for more bass excursion. Too much excursion of course and you have muddy bass, but IME that is actually pretty rare- most acoustic suspension speakers are internally damped already, while most bass reflex, horn and open baffle designs (which includes magnetic and electrostatic planars) really don't need that much.

If I knew absolutely nothing else about two amps, except that one has a damping factor of say 4 and the other had a damping factor of 1,000, I would take the amp rated 4 (it would most likely be a tube amp, and perhaps a single-ended triode with only one output tube).
As the owner of a pair of VTL MB 450 III with adjustable damping factor (4 settings) I can attest to the fact that damping factor matters. Obviously it's an interaction with the rest of your system but as I got my room resonances under control I could lower the DF on my Magico Q3s and now have it at the lowest setting. The effect of lowering DF is to lose some immediate "punch" in the bass but replace it with greater air, scale and overall body which is much more preferable. My suspicion would be that too many amps (especially solid state) are over damped but that's just my preference and I'm surprised more manufacturers don't offer adjustable DF

ps I can't find any specs on what the VTL damping factors actually are for the four settings, anyone know?
Actually no. It **might**. Any loudspeaker can be overdamped- IOW

Atmasphere is correct in this regard.

An example was the Linn Isobarics and the Sara which were voice to have great bass with Naim amps of the day, that had 20 damping factor. When a big Krell (>100 damping factor)was put on these speakers they had NO bass, too tight.

This was because Linn designed these speakers with a very over damped (low Q) bass, so they only sounded good in the bass with amps that had low damping factor. (just another marketing ploy by Linn, who were in semi partnership with Naim in those days.

Another similar case to (damping factor, but impedance matching) is poweramps that have very low 1kohm input impedance that could only be driven with preamps with very low (<10ohm) output impedances, usually of the same brand naturally.


Cheers George 

Folkfreak, I couldn’t find any indication of the specific damping factors for the four settings provided on your amp, as you couldn’t, but I did find this statement in the datasheet (which you’ve undoubtedly already seen):
Another new feature is a user adjustable Damping Factor feedback control that allows the user to adjust the amplifier’s output impedance by varying the amount of negative feedback. Impedance can now be precisely set to suit the listener’s taste, and to improve control of the loudspeaker loads to deliver best performance. The 4 possible settings are:
1. LOW -- Lowest damping factor, good loudspeaker control, most natural sound.
2. MED -- Better loudspeaker control, with some impact on sound quality.
3. HI -- Best loudspeaker control, with a little more impact on sound quality, but on speakers that need the control the sonic improvement is clear.
4. MAX -- Maximum damping factor, but sonic impact is noticeable
So since the amp’s damping factor is being adjusted via feedback, changing the setting can be expected to affect sonics in ways that are in addition to the change in damping factor itself. Most likely including changes that occur in the amp’s distortion characteristics. The "Low" damping factor setting, btw, is undoubtedly the one which utilizes the least amount of negative feedback.

Also, given that it is a tube amp I would expect that the damping factors corresponding to all of the settings would be at most not a great deal more than single digits, perhaps 20 or so at most. Which per my earlier comment would make it very expectable that sonics would change significantly among the various settings.

In any event, it certainly looks like a very impressive amp!

Regards,
-- Al

Almarg -- and it also affects the input sensitivity -- there's a nice discussion (extracted) in this review of these amps
http://www.theaudiobeat.com/equipment/vtl_mb450_iii_mb185_iii.htm

What’s the significance of adjustable damping factor? Far greater than you might imagine. The clue lies in the fact that it is derived from the degree of feedback, the higher the feedback level, the greater the damping factor. In this day and age it is easy to assume that all feedback is bad and that the less you have the better, but it isn’t actually quite that simple. There’s a world of difference between local or nested feedback (used within a circuit) and global feedback (that encloses it entirely). While feedback-free preamps are all the rage, feedback is critical to a power amplifier’s damping factor, just as Q is critical to a speaker’s voicing. Between the two, these factors have a huge influence over amp and speaker matching, and as Q is generally a fixed value (unless you happen to be using the large Focal Grande Utopias, with their adjustable-Q EM drivers) then being able to adjust damping factor to achieve superior matching is a major benefit, significantly broadening the type and number of speakers with which the amplifier can achieve really good results.

VTL offer four settings for damping factor: Low, Medium, High and Max. With any given speaker you will find that one setting is dramatically more musical, dynamic, involving and better integrated than the others. In my room and in most cases, I settle on either the Low or Medium setting. Those who crave a drier, more heavily damped sound might opt for the high setting, especially if the speakers are a little loose in the bass or the room is exaggerating the bottom end. I can’t really see anybody needing the Max setting, but it serves a useful purpose in establishing the continuum along which you are operating. Once you’ve heard what Max does to the music, you’ll treat the setting of the amplifiers’ damping factor with the appropriate caution and seriousness. It not only has a huge impact on performance, it offers a huge advantage in terms of choice and your amplifier’s longevity, should you (or should that be, when you) change your speakers at some point in the future. If the amp/speaker interface is the single most critical junction in your system, the Series III Signatures pull the neat trick of offering genuine adaptability, a serious benefit that’s not to be overlooked.


The VTL  data sheet states that the lowest DF setting is the most "natural" sounding. This seemingly implies that the less negative feedback the more natural it will sound. Larryi this correlates with your observation mentioned above. 
Charles, 
how important is Damping factor in determining what amp to buy
About as important as what color the amp is.
It's important enough to take into consideration along with everything else when trying to achieve a particular sound.  
Interesting discussion guys.
It is not important at all. It is just another way of expressing the amplifier’s output impedance.

Most SS amps have an output impedance of 0.04 ohms, which is a DF of 200 or 8 divided by 0.04. If you include speaker cable impedance of, say, 0.1 ohm that means the speaker is at 98.3% of the amplifier load and the amplifier’s output impedance is 0.5% of the load, an almost perfect voltage source that is immune from the speaker’s varying load.

If you substitute an amp with a 2000 DF, it has an output impedance of 0.004 ohms and that is 0.05% of the total load. That is only a change of 0.45% with respect to the amplifier’s contribution. The speaker is 98.7% of the load, despite the amplifier being a more perfect voltage source by a factor of 10.

I seriously doubt that 0.45% change is audible. However, a general rule of thumb is that an amp with a DF of 20 or below has sonic consequences. Doing the math, the speaker in this case is 95% of the load -- a considerable change that results in sonic degradation from dynamic load variation since the amplifer is no longer a perfect voltage source .

Almost all of today’s SS amps use global NFB and high quality output transistors. It is the norm to see output impedances ranging from 0.01 to 0.05 ohms. That’s why you don’t have to worry about it.
Another way to say it is it is practically most significant in distinguishing amps when damping factor is low as in <50 or so as is often but not limited to the case  of higher output impedance tube amps.   Speakers that are tube amp friendly will tend to sound more relaxed and perhaps more natural when amp damping is lower or correspondingly output impedance higher.  

Some SS amps designed to sound more like tube amps likely also have lower damping factor.  Two I have owned that attest to that are Carver M4.0t and TAD Hibachi both of which are SS designs made to sound more like a tube amp.  
Gs5556
It is not important at all....
... a general rule of thumb is that an amp with a DF of 20 or below has sonic consequences. Doing the math, the speaker in this case is 95% of the load -- a considerable change that results in sonic degradation from dynamic load variation since the amplifer is no longer a perfect voltage source .
Gs5556, I think you may have worded your post a little more broadly than you intended to.  In addition to these two statements being contradictory, you seem to be saying that any amplifier having DF<20 would cause "sonic degradation," and you seem to be saying that for good results all speakers should be driven by amplifiers that act as voltage sources (i.e., amplifiers whose output voltage is not sensitive to load impedance variations, as long as the amp is operated within its capabilities).

As I'm sure you realize, almost all tube amps have DF<20.  And as I indicated in my earlier comment, differences in damping factor and consequently output impedance within that range can certainly be sonically significant, if speaker impedance varies significantly over the frequency range (as it does with most speakers).  And certainly differences in damping factor/output impedance can contribute to sonic differences between tube amps and solid state amps.

And certainly some speakers are tube amp friendly (meaning they don't necessarily have to be driven by voltage source amps, and in some cases shouldn't be driven by voltage source amps), some speakers are solid state amp friendly, and some speakers (especially those having relatively flat impedance curves, highish impedance, and highish sensitivity) are friendly to both. 

As Mapman alluded to just above, at the low end of the range damping factor does matter.  Statements that it is of no importance are simply incorrect.

Regards,
-- Al 

I seriously doubt that 0.45% change is audible. However, a general rule of thumb is that an amp with a DF of 20 or below has sonic consequences. Doing the math, the speaker in this case is 95% of the load -- a considerable change that results in sonic degradation from dynamic load variation since the amplifer is no longer a perfect voltage source .
The 'traditional' thinking here is that frequency response is the last word on tonality.

It isn't.

It turns out that the human ear/brain system assigns a value to distortions; they are translated to tonality. In fact it now appears that there is a tipping point wherein colorations created by distortion can be favored over actual frequency response errors.

In addition, the use of global negative feedback is well-known to contribute to higher ordered harmonics (see Norman Crowhurst). The higher ordered harmonics are used by the ear/brain system to detect volume levels (rather than the fundamental tones). The result of trace amounts of higher ordered harmonics is called brightness and harshness because of human sensitivity to these harmonics.

This is why many designers don't use feedback and frequently favor tubes- to avoid that particularly annoying coloration. This often results in a high output impedance/low damping factor but this can be easily dealt with giving careful speaker selection. 

With most of the speakers in my house, including the OHMs and Dynaudios which are not inherently tube amp friendly speakers, moving from the lower Damping higher output impedance amps I mentioned to others with damping much grater than 50 produced perhaps the biggest sonic benefits of any change I recall in recent years.

Those same amps played very nice with my more tube amp friendly Triangle Titus XS speakers for which I would like to find a nice small easy to maintain tube amp. I use the Triangles also with my highly damped Bel Canto ref1000m Class D amps and the sound is quite good still in many ways (crystal clear especially at lower volumes) though somewhat sterile at higher volumes in comparison to the others that are a better match to that amp in regards to impedance and damping.

So I have found that damping/output impedance matters VERY VERY MUCH, perhaps as much or more than many other also important things. Understanding this has been a key for me to getting to a good place faster with fewer stumbles along the way.

Beats playing with fuse directions by a light year IMHE of course that is a much easier thing to do right being there are only two choices, more like answering a true false question that has no right answer other than what you think and/or hear.

@mapman, if I recall, your speakers are 4 ohms. Damping factor as a spec is usually stated with respect to 8 ohms. So in reality your speakers seem to need an amp with a damping factor of about 25, once you correct for the impedance. As I stated elsewhere, no speaker needs a damping factor of more than about 20:1 or so; your speakers seem to be within that ballpark.

Vibration of the speaker membrane, without signal, causes back EMF producing current that flows in opposite direction working against membrane motion, hence damping vibration. This current (damping effect) depends on the total resistance in the circuit including amp’s output, wires resistance, woofer’s choke resistance and speaker’s impedance (source impedance) itself, that is mostly resistive. All this will limit maximum possible "DF" to about 1. As long a amplifier doesn’t add to this limitation, there should be no difference in sound. AMP with DF =10 will affect overall damping only by 10%. Very high DF (my amp has 4000), come either from the output configuration or negative feedback used to reduce distortions, widen the bandwidth etc. Even shallow 20dB negative feedback will reduce output impedance ten times.

Damping Factor plays one very important role - it can be used to impress customers.

As for NGF - it is a wonderful tool when it is used wisely. It improves pretty much everything (bandwidth, distortions, output impedance etc). It might produce TIM distortions (higher odd harmonics, overshoot in time domain) for faster changing signals, because of increased amps gain caused by late summing of delayed output signal (phase shift). Reducing bandwidth at the input, perhaps to one that amp had without feedback, should prevent TIM. That would require designing a stable wide bandwidth amp with low distortions to start with. The main problem is that designers use cheap parts and poor circuits trying to fix it with deep feedback. For instance, very popular output transitors 2N3055 have very nonlinear h21e (Beta) - a current gain vs current. There are much better choices but they cost more money (2N3055 cost less than $1). NGF is pretty much free.

Atmasphere OHM generally indicates 6 OHM nominal impedance for their Walsh line speakers.

I have seen measurements and impedance curves on some models that show fairly high impedance >8 ohms over extended ranges with the greatest dip down to almost 4 ohm in the bass region possibly associated with the port.

Users over the years have indicated best results with higher damping amp ratings and I would agree. How high is needed is debatable but I always find the higher the better even if Justas an insurance policy and nothing concrete theoretically to support the need.

If I had to rate them based on what I know and what others report I would say they are moderately tube amp friendly, probably more so than many speakers in their class.


The Dynaudios most likely have lower impedances and are also generally known to not be very tube amp friendly and I would agree. In fact even with SS amps I find results can vary widely with Dynaudios whereas its very hard to find any good quality amp that sounds bad with the OHMs.

Remember also that the OHMs operate totally different than most dynamic speakers ie based on Lincoln Walsh’s transmission line principles. I suspect this may make them very unique in regards to impedance considerations but do not know enough about it technically to say for sure.


I have two OHM models, larger ones with 12" main drivers and smaller with 8".    The higher damping in the amps seem to make more difference with the larger models to me than the smaller although I'd say there are audible differences in general with both..

Hi Kijanki,

I pretty much agree with your post, as far as it goes. But your comments about damping factor just address ... damping. Keep in mind, as has been said, that damping factor is inversely proportional to output impedance, and once output impedance gets above negligible levels (as it will in the case of most tube amps, and at least a few solid state amps), it can certainly matter, as a result of impedance interactions between the amp and the speaker.

Best regards,
-- Al
OH MAN AGAIN...

Interesting to hear you Gurus going back and forth...

Need to reread this several times , list those for and against an effect, throw out the high and the low - and then consult the Russian Judge!

And in a some-what related question: I am presently using a Phillips High Fidelity Labratories Pre-Amplifier(1980?) - would the damping factor be affected if I switched to a Line-Level triode preamp (like the Wolze I have)? Does/can the preamp affect the damping factor of a amplifier?
... would the damping factor be affected if I switched to a Line-Level triode preamp (like the Wolze I have)? Does/can the preamp affect the damping factor of a amplifier?
No on both counts.  However in some cases bass can be weakened when a tube preamp is used in conjunction with a solid stage preamp (and, less frequently, with other combinations of gear), due to impedance interactions between the two components.  But although I don't have any information on the Wolze, that appears very unlikely to be a problem if it is used with your Nikko amp or with the power amp section of your Onkyo integrated amp, since they have high input impedances (50K and 100K respectively).

Regards,
-- Al
 
Al, I agree, but when people refer to DF (including this discussion), they mention control of the woofer.  The effects of complex load should diminish when source impedance is 10 times smaller than the load.  DF=20 should be a good choice.   At this point I would prefer output impedance that is constant with frequency over high DF.  My amp's output impedance varies from 0.002ohm@5Hz to about 1ohm@20kHz.  Tweeter's impedance is very high at 20kHz but there usually is some network of resistor in series with capacitor, parallel to the tweeter.  Can this affect the sound?

One more thing about control of the speaker at low frequencies - amplifier might be the one that is uncontrolled.  Audio amps are designed often with assumption that they will play 20-20kHz.  Because of that, they are often equipped with servo on DC that has bandwidth of few Hz.  Presence of very low frequencies coming form the source (movie, TT vibration, special effect etc) can make this servo to overcompensate and go crazy (unstable) affecting audible band.
Al, I agree, but when people refer to DF (including this discussion), they mention control of the woofer. The effects of complex load should diminish when source impedance is 10 times smaller than the load. DF=20 should be a good choice. At this point I would prefer output impedance that is constant with frequency over high DF. My amp’s output impedance varies from 0.002ohm@5Hz to about 1ohm@20kHz. Tweeter’s impedance is very high at 20kHz but there usually is some network of resistor in series with capacitor, parallel to the tweeter. Can this affect the sound?
sure! of course! The RLC network is frequency dependent. isn’t that the reason for Zobel networks? The Zobel is for the power amplifier (not the speaker) even tho’ some manuf recommend attaching the Zobel to the speaker’s terminals rather than the amp’s output terminals.

OH MAN AGAIN...

Interesting to hear you Gurus going back and forth...

Need to reread this several times , list those for and against an effect, throw out the high and the low - and then consult the Russian Judge!

And in a some-what related question: I am presently using a Phillips High Fidelity Labratories Pre-Amplifier(1980?) - would the damping factor be affected if I switched to a Line-Level triode preamp (like the Wolze I have)? Does/can the preamp affect the damping factor of a amplifier?
heh! heh! heh! ;-0
And, here you thought you asked an innocent question! ;-) 
Also search the archives for damping factor discussions. There is MUCH written on this topic....
And here's some more dope on the subject for you to read (seems to fall in-line with what Ralph/Atma-sphere was saying that DF of about 20 is sufficient):

http://www.butleraudio.com/damping1.php
Here's a further link:
http://www.dissident-audio.com/Loudspeakers/CriticalLSDamping.pdf


Correction to my previous post:  When I said "solid stage preamp" I meant "solid state power amp."  Not sure how that error occurred.

Regards,
-- Al
 
Important if it is off the rails in one direction or the other but, at normal values, somewhat less important, and....after a point, higher isn’t necessarily better, as others have pointed out.
It is simply a measure of the amplifier’s output impedance, which may be more important with speakers that have impedance variations with frequency, and/or large impedance dips. When you divide the amplifier’s output impedance into the speaker’s input impedance, that is your damping factor. Amp manufacturers often use "8" ohms for the speaker’s input impedance when they calculate their advertised damping factor. This may or may not be accurate, all or some of the time but they have no way of knowing what speakers will be used.
Damping factor is something to be aware of if you are changing out speakers or amps, but not usually a deal-breaker or deal maker.

As the VTL literature explains, achieving higher damping factor/lower output impedance, if done using negative feedback (as is often the case), can come at the cost of reduced sound quality above bass frequencies. A good reason to either bi-amp, or use a sub with a dedicated amp and a separate amp uncompromised by damping factor considerations for the main speakers. That, or chose a speaker not requiring a low output impedance amp to sound as good as it can at both low and higher frequencies.
... and in my on-going search for audio intelligence:
does the age or broken-in-ness of the speaker affect the amps ability to dampen it? (example: right now, my Phillips pre and Onkyo A7 Main-In is powering a vintage pair of JBL L25s...)
If the speakers are not broken in, they are most likely to be over-damped.
My experience has been that is is important, especially for certain speakers. For example, just before the original 801, B&W made a speaker called the DM 16, which had very sloppy bass with a lot of quality equipment, but very tight bass with highly damped amps.
     Consider this. A speaker is an electric motor and can be used as a microphone. On tube and Class A amps, speakers on each end of the circuit can reverse roles as mic or speaker, as on a PA system in my dorm in college. I sent a signal through this speaker into every room in the building, about 300 speakers, from my room speaker.
     BTW, I used the speaker output of a Magnavox suitcase portable stereo's removable speaker, and simply added a female RCA jack to the PA speaker.
       Students were not amused to hear William tell Overtures at 5 AM of the first day of finals.. After my RA told the powers that be that I sometimes played this, I was invited to take a term off, but when I returned, my EE prof seemed impressed that I figured this out.
      My family also built our house, and with some supervision, I had helped wire it, complete with phone taps and speakers for music in every room, speakers that also fed my reel to reel, the tapes of which were quite startling in divorce court.  
       When a signal is sent to a speaker to play a note, the cone vibrates. When the signal stops, the cone is still moving back and forth. and is an electric motor. This movement sends the electrical signal back to the amp, and a highly damped amp will stop the cone sooner.
     Having said that, there does not seem to be a great difference on MOST speakers until the damping factor is below about around 150-500, at least on the Dm 16's. A 150 versus 1000 from the same company, does make a difference, ad these amp use the same pre-drivers and outputs, but more outputs.    

I thought this was an interesting article relevant to the discussion and also clearly in the "it does not matter much" camp.


http://ohmspeaker.com/news/amplifier-damping-another-wet-blanket/