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

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

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

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

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 

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

... 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
 

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