Thoughts on Tube vs SS amplification for Sony SS AR1s

I am really surprised/stumped as to the results, as I had high expectations for the Accuphase and the SS AR1s. This Accuphase amp is highly regarded and in all the literature I read I would never have expected this outcome, but that's what my ears told me in the end. Obviously this is all down to individual taste and opinion, but the clarity of the Luxman was not bested by this entrant.

In a nutshell, high damping factors are overrated! Duke LeJeurne of Audiokinesis gave an excellent reason why (as a speaker designer):

" A high damping factor will provide very good control of the bass drivers."

Hmmmm.

For a quick summation of my thoughts, skip to the last two paragraphs. Apologies for getting fairly nerdy in between here and there.

In practice, any series resistance in between the amplifier and the woofer’s voice coil effectively ADDS TO the amplifier’s output impedance, and correspondingly reduces the damping factor.

Let’s run some numbers. Supposes our speaker has a nice 2.5 kHz second-order crossover, which calls for a 1 mH inductor in series with the woofer. Power handling requirements are easily met by an 18 gauge air-core inductor, which can handle 300 watts before saturation. The series resistance of this inductor is .51 ohms.

And let’s suppose we have an uber-amplifier with a damping factor of one zillion. Or one zillion zillion. Or one zillion to the zillionth power. It won’t matter.

After the signal passes through that inductor, our uber-amplfier’s amplifier’s effective damping factor is now about 17. And this is assuming only the one series inductor, and ignoring any other wiring.

So in most cases it really doesn’t matter how high the amplifier’s damping factor is. The series resistance in the crossover (and/or speaker wires) dominates.

Okay, but what about this "very good control of the bass drivers" that we’re apparently missing out on?

Well, turns out that it’s not nearly as dramatic as the wording implies. It all shows up as a change to the electrical damping of the woofer’s motor - the electrical system Q, or Qes.

Assuming a typical high-quality 8-ohm woofer in the example above, the series inductor effectively raises the woofer’s electrical Q by about 7%. So if the woofer’s electrical Q was .28, the series inductor effectively raises it to about .30. This could EASILY be an improvement! We'll get more bass with a higher Qes, but the designer should take it into account by sizing and tuning the box based on our modified Qes of .30. And if he hasn’t, this difference can still be largely compensated for with a few handfuls of stuffing material.

I think amplifier marketing departments may have oversold the benefits of having a high damping factor.

Or to put it another way, in my opinion, super-high damping factors are, in most cases, of academic interest only. I certainly would not trade off anything that really matters in order to get a high damping factor.

Duke

This post is fromhttps://forum.audiogon.com/discussions/how-to-accurately-gauge-speaker-sensitivity-to-match-with-tub...

Our most popular amps have a fairly low damping factor- if DF were that important, we'd have been out of business decades ago.

Hi,
Consider hearing them with a Pass amp. Sony at Shinagawa HQ test them with Pass power amps, Sony,s long discontinued N1, NR10, and lately demonstrate them with their own VFET, in an amp designed by Pass. Just food for thought. It’s a speaker that needs some push. You have an amazing speaker.

No doubt that damping factor (DF) is an important variable that affects and influences the performance of an amplifier and speaker pairing. I have to imagine there are other factors at play as well. By every reasonable and trusted test bench metric the Accuphase should ’clearly’ be a far more compatible  matching amplifier for these Sony speakers than the Luxman.

Assuming that the Accuphase isn’t defective in some manner, one has to ask what’s going on? How is it possible/explainable the tubed 14 watt (Into 4 ohms) Luxman so convincingly sounds better driving the current demanding difficult impedance Sony than the (Much) higher power/current Accuphase transistor amplifier?

Can it all be written off as merely subjective preference? If so it’s fascinating that this can occur in light of test bench measurements that would suggest a far different outcome. One has to ponder that there are things listeners can clearly hear that (At least for now) aren’t being measured or maybe can’t be measured.
Charles

Hi everyone
Thanks for the follow up comments~

@tomcy6 , I know exactly what you mean and I went looking for anything simple that would explain the lack of energy in the highs (like tone controls being engaged, etc).  There was nothing seemingly out of place, and if I didn't have the Luxman to compare it with, I would likely be extremely pleased, because the low end definitely had good authority and clarity. I know I'm not describing it well, but its like the Accuphase is putting all its attention into the low and low-mid end of the spectrum, and not bringing out a ton of character/clarity in the upper ranges - there is a track we were listening to with just male vocals and a guitar: with the Luxman he's in the room with you, with the Accuphase it sounds like he's trapped in the speakers.

@petg, thanks for the recommendations (those Sony amps would be amazing to come across)

@charles1dad yeah, I just wanted to update the group because I too found it really interesting. I'm by no means a bonefied expert in any of this, but just to provide some context for the other references I've had, I've spent time with really excellent amps from Luxman and Accuphase (obviously), Hegel, Sony, Yamaha, Vincent, Technics, JP-market Denon, and a few others. The Accuphase isn't in the top 3 for me - its also possible that I had such high expectations I set myself up for some disappointment, but it is interesting that you can't tell from just the numbers how things will sound. The Luxman has stayed at the top of the list for musicality (for me). One thing I wonder if if the LX380 is sounding so good on these SS AR1s, would a higher power tube amp from Luxman also perform well? If I get a chance to find out, I'll let you know~

Pass has sounded awesome on the AR1s when I’ve heard them at shows together. Now, you can’t get the VFET amps but I’m sure X series would work well. 

I like to use the Tron soundtrack by Daft Punk at 90dbs to see how much power amps really have. Most get flattened by it.