Thoughts on Tube vs SS amplification for Sony SS AR1s


Hi all~
Was hoping someone with more knowledge than me may be able to help clear up some confusion I’ve been having.
I recently was able to acquire my ‘unicorn’ speakers, the SS AR1s.  4 ohms, 88 dB, 28hz-60khz.
i have an integrated tube amp, the  Luxman LX-380, which on paper doesnt seem to deliver a lot of power for these speakers (14 w into 4 ohms), but i have been really surprised by how full/robust everything sounds with the Luxman in place. I had been advised that a more powerful SS amp (‘at least 200 w per channel!’)  would be needed to get the most out of the SS AR1s (and i have had a lot of SS amps in the past), but To be honest I’m pretty impressed with how it sounds already - So,  i was just hoping someone with more experience here could weigh in? Is it necessarily true that tubes just aren’t a good match for a speaker of this sensitivity? Would a more powerful amp like the luxman mQ-88uc (25 w into 4 ohms) be worth looking into? Would a powerful SS amp really make these speaker sing (and i just dont know what I’m missing)? I want to take advantage of the low-end of these new speakers (which is the main difference from my previous pair), so looking for some guidance re tube amps and exerting control over speakers like these.

thanks much!
sfmorris
Watts are highly overrated and misunderstood. Even listening at fairly high levels with relatively inefficient speakers the vast majority of the time is only some fraction of a watt. Its the peaks that call for power and its the ability to deliver during those peaks that determines our sense of power more than any measurement. The proof is in your experience, which is the same as mine, and matches a whole lot of others who have tried and compared. This is all boiled down in the adage that tube watts are greater than SS watts. 

In fact not even all tube watts are created equal, and its the transformer more so than the tubes that are responsible for this. Spend a little time researching Prima Luna or Raven tube integrated amps. Read the comments and reviews on my System. https://systems.audiogon.com/systems/8367 

That Melody is a 50 wpc tube amp. Before that was a 60 wpc Aronov tube amp. Both drove the same Talon speakers with more authority, volume, dynamics and bass than a 150 wpc SS McCormack DNA1, which is one very highly regarded SS amp. I had one, I know, as SS amps go it is truly great. As SS amps go. Tube amps are simply in another class. Its like CD, there are some really fine ones. Not ones you want to put up against a record, but good for what they are.

The plain fact of the matter is you get a really good tube integrated and how many watts it makes is just about the least relevant thing you could possibly measure. If you like what you're hearing what do you care what some other guy who you never met and will never hear your system thinks? 

Look at it this way- a beautiful 150 wpc MCCormack DNA1 amp. Does not sound as good as either of 2 tube amps 1/3 as powerful. Obviously power is not all its cracked up to be. Or as Robert Harley famously said, "If the first watt isn't any good, why would you want 200 more of them?"
sfmorris
Thoughts on Tube vs SS amplification for Sony SS AR1s

Forget tube, your going to need a "good solid state amp" that can deliver copious amounts of current in to 2ohms, if you want the bass of these to give their very best.
With the speakers being 90db you don’t need a huge amount of watts, 100-150w @ 8ohms will do, but they need to double those watts into 4ohms "and nearly double again into 2ohms", indicating good current delivery.

https://www.stereophile.com/images/711SS1fig1.jpg

Stereophile bench tests
The impedance drops below 4 ohms for much of the midrange, reaching a minimum value of 2.7 ohms between 350 and 400Hz and at 95Hz. The electrical phase angle (fig.1, dotted trace) is also quite severe at some frequencies; the combination of 3.4 ohms magnitude and –53° phase angle at 70Hz, a frequency where music can have a significant amount of energy, will require the Sony be used with an amplifier that is not fazed by 2 ohm loads.

Cheers George
That's a nice integrated you have and you say things sound good to you? Enjoy what you have don't worry about specs on paper or what others tell you. It's all about what sounds good to you.
The biggest issue, that I can see, is the dip in impedance between 100 Hz and about 700 Hz.

https://www.stereophile.com/content/sony-ss-ar1-loudspeaker-measurements

What I have found is that even with modest SS amps, this causes a noticeable depression in the output. So... what you may be enjoying is a very V shaped curve.  If you find yourself listening at low volumes, that's what's happening. You've set yourself up with an accidental loudness button. :)

Should you change it? Only if you are dissatisfied.  A beefy SS amp or just beefier amp in general, will flatten out the audible response.  Better for higher volume listening for sure.

I'm sure you'll hear a difference, pay attention to the ideal listening level when you try other amps, and the upper bass. Listen for a while and see if it's better or worse for long term listening.
Thanks everyone for the very helpful input - you’ve given me a few things to research, and of course reminded me to trust my ears (always a good reminder). @erik thats an interesting point you made about lower volume listening - I’ll spend some time listening a bit more carefully and see if can hear what you’re describing.

@jond thats exactly what i should be doing, you’re right~ I wish I had an SS amp on hand just to compare (I can’t imagine them sounding much better than they do)

@george accuphase seems to have some good integrated that double through to 2 ohms. Do you have any personal suggestions?

@miller thats exactly what i have been thinking as i listen to the luxman - forget what it says on paper, i cant see it sounding much better - one thing i dont get about the lx 380 is the power output for 4 ohms seems to be weakest? 20W + 20W (6Ω), 18W + 18W (8Ω), 14W + 14W (4Ω)
I’m not sure how to interpret that...
Luxman SS is also a very good candidate. Certainly I think more reasonably priced in the US.
sfmorris OP
@george accuphase seems to have some good integrated that double through to 2 ohms. Do you have any personal suggestions?


Yes, my order would be.  

Gryphon Diablo 120 or 300 if you have the funds
https://gryphon-audio.dk/shop/integrated-amplifiers/diablo-120/
https://gryphon-audio.dk/shop/integrated-amplifiers/gryphon-diablo-300-integrated-amplifier/

Parasound Halo Integrated. Hint-6
https://www.parasound.com/hint6.php

Hegel H190
Hegel integrated amps "maybe" but from tests the 160 couldn’t really do even close to doubling into 2ohms, they only managed a 20w increase from the 4ohm figure.

Same with the Pass Labs Integrated, on test they don’t increase too much both channels driven from 4 to 2 ohms

Cheers George
Almost without fail, tube amps will have greater low level detail, better linearity and a more organic presentation. Almost without fail, tube amps will react much more negatively than S.S. to low impedance speakers or impedance dips. 

One type of power is not better than the other and to say such a thing is foolish. Knowing Sony and also looking at the specs of your speakers, I would say that are grossly underpowering your speakers and would be best served by a more powerful S.S. amp.

This could be a situation in which you wont know what you are missing until you hear it for yourself. I think the speaker determines the amp in most cases.
sfmorris,
In your opening post you wondered if you don’t know what you’re missing regarding the sound quality (SQ) of your Sony speakers. According to George and jsautter the answer is a resounding yes! You don’t know what you’re missing. George provided legitimate technical test measurements to make a very strong case.

Based on the Stereophile Sony  measurements your Luxman tube amplifier is weakest ( decreased power of 14 watts/4  ohms i.e. lower speaker impedances) right in the range where the Sony speaker is most demanding of an amplifier.  . That’s quite the dichotomy it would seem. What’s fascinating is despite clear technical evidence that the Luxman should fail in miserable fashion, it sounds terrific according to you. I don’t doubt what you hear.

How is this apparent contradiction possible? How can what one hears be so contrary to what verified measurements would predict? sfmorris it would be undeniably interesting if you could get an amplifier (or very similar type ) suggested by George and compare directly to the 14 watt Luxman.

Would the technically corrdct/preferred powerful high current transistor amplifier expose shortcomings of the Luxman while effortlessly driving the Sony’s to new heights of sonic capability? Or would those 14 tube watts continue to impressively make beautiful music and possibly outshine the more powerful competitor? This listening comparison would be very insightful and informative.
Charles
sfmorris OP


The combination of 3ohms and -60 degree phase angle at around 70hz (right in the bass power region), makes it look more like 1-2ohm loading to an amp. Then a continual load from there of 2.7ohms out to 500hz. Very tube, and many weaker solid state amps unfriendly.
In fact looking at both graphs, this Sony speaker to me looks even worse at 70hz (because of it’s -phase angle) than the "king" of unfriendly speakers to drive, the Wilson Alexia!!!!.

https://www.stereophile.com/images/1213Walexfig01.jpg

These Sony’s seem to be just like the Wilson Alexia, a "real pig" of a speaker to drive, but once driven correctly the rewards are both are something to behold. I’ve heard the Alexia’s driven with Gryphon Antillion Evo, and it’s a sound that you will never forget and always strive to get yourself.

Cheers George

sfmorris


Nice score! Those Sony SS AR1 are killer speakers with not many fortunate owners. When Sony wants to make a state of the art product- it delivers!


Keep us posted on the system you choose to build.

Happy Listening!

When Sony wants to make a state of the art product- it delivers!


Yeah you got right, here’s their 3 way ESL’s they made way back 110kg each, I heard the Emperor of Japan had a pair.
http://www.thevintageknob.org/sony-SS-R10.html

Cheers George
George, 
Again from a pure technical analysis you are absolutely right in referring to the Sony speaker as a "pig of a speaker" given its extremely demanding need for current delivery.  How in the world does the low watt tube Luxman produce wonderful sound paired with this very difficult speaker load?  Can it be explained by the assumption that the Luxman has superb quality output transformers and power supply section or is it more complex than that? Really intriguing how this is pulled off.
Charles 
I think the OP is getting good advice from everyone.  If it sounds good to him, then why change anything.  At the same time, he really doesn't know what he has not heard.  If he tried the Sony with a high current solid state amp who's to say he wouldn't say his system is positively transformed?  Both of these lines of thought can be right at the same time.
Hi all - again, I cant tell everyone how much i appreciate the advice (extremely helpful).

As Charles pointed out, this is indeed a head scratcher - either the luxman has qualities that the spec sheet alone doesn’t account for, or I am in for a revelation if i can get my hands on a good SS amp (because this is already the best my setup has ever sounded, and the first thing my wife said was ‘everything sounds so balanced and full’ from the lows to the highs - this seems to go against what the measurements would predict when using the luxman). I’ll definitely keep people posted.

 I had had my eye on a few options (in keeping with the Japanese hi-fi theme of the speakers - i have a soft spot for these brands)
- accuphase e650
- marantz ma9s2
- Yamaha a s3000

Aesthetically, i have to admit I’m a fan of the Yamaha, but i know on paper it’s probably not the best of the three. The marantz monoblocks and preamp seem very highly regarded, but going from the single box LX380, those giant champagne boxes are going to look a bit ostentatious. I had a chance to pick up a rare sony TA-DR1a , but could find very little info on it. I’ll see if i can find someone local who perhaps has something that would fit and be willing to try it out here~

(if anyone has any strong opinion about the Yamaha, would be glad to hear your thoughts~)

thanks!

How in the world does the low watt tube Luxman produce wonderful sound paired with this very difficult speaker load?

It may sound good to him, I guarantee he has "not" yet heard these speakers at their best though.

If it sounds good to him, then why change anything.
He started this thread for a reason because he has doubts.

I had had my eye on a few options (in keeping with the Japanese hi-fi theme of the speakers - i have a soft spot for these brands)
- accuphase e650
- marantz ma9s2
- Yamaha a s3000
Don’t draw conclusions with these amps, they are good integrated amps for normal loading speakers, but not for the nasty loads the Sony’s present


Cheers George
Hey George
Thanks for the thoughts - even the mono block ma9s2 you think would be a poor fit?  I could go the route of separates if there are more options there that are likely to get the best out of these SS AR1s (I’ve only even had integrateds, so separates would be new for me)

Hey George
Thanks for the thoughts - even the mono block ma9s2 you think would be a poor fit?


No one has done bench tests on these, They "may" be ok, but they only have 6 outputs per channel, and they only spec them 8ohm to 4ohm wattage’s, no mention of what can be done into 2ohms or less.

So I would say no, as if they did well with even higher wattage’s into 2ohms, it’s in their best interest to say it.

You have a pair of iconic speakers, that yes are a pig to drive. That if were made today would be well over the $27k they were back then, more like $50k today. Give them the amp they deserve.

Cheers George
The Accuphase e650 specs 30 watt class A at 8 ohms
60 watts at 4 ohms
120 watts at 2 ohms.

The Marantz is (claims)  300 watts at 8 ohms
600 watts at 4 ohms
No specs given for 2 ohms.

But what can you surmise from these listed specs ? 
The Luxman could very well be single digit watts into 2 ohms yet it sounds very good to sfmorris.
The Parasound Halo amplifier George recommended earlier is readily available and reasonable cost ( And probably can be gotten with a return clause). 

Curious how the Parasound Halo with ample current (per George)  would fare against the Luxman head to head driving the Sony's. All that matters is which would sound better to sfmorris. Superior sound is the pertinent objective. 
Charles 

If you could find a used Adcom 535 you see how your speakers react and then sell this amp for nearly what you paid. This is the only amp that Adcom made that I liked. In fact this amp powers my garage system. I also owned the 555 and the 565s but could never warm to the sound.
Hi all
Per the advice everyone has provided I am looking into some separates that have reliable specs for power into 2 ohms (seems like there are a number of good options here) - will definitely report back as this is an interesting subject. 

Thanks!
Hi All,
I know it's been a while, but I thought I would report back as so many of you gave me helpful advice. I had a chance to try the SS AR1s with a very capable Accuphase integrated and the results were clear and surprising. 

Relative to the tube-based Luxman LX380, the solid state (and much more powerful class A/AB) Accuphase was muddy and muffled (and I say this as someone who was highly biased towards the Accuphase and was anticipating great things). As soon as I swapped them I could tell something had happened to the mid and high end of the spectrum - things were not nearly as clear or articulate - it was like there was a veil of something in between the music and me (really obvious on things like voices and acoustic guitar for example). I really can't think of any better word than 'muffled.'  I thought perhaps I was mis-hearing things so I had my wife do a few casual tests with her back to the equipment, and unprompted she made the same comments about "amp B" (the Accuphase).   With the Accuphase I certainly noticed a bit more definition in the lower registers and bass lines had a bit more clarity to them, but a) the difference wasn't like night and day relative to the Luxman (they were very close), and b) it seemed to involve a massive trade off for what I can only describe as 'transparency' in the high end. with the Accuphase in place vocals and acoustic instruments sound like a thin door has been closed between the music and my listening position (honestly)

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.

re next steps, I guess im looking at either something like very capable SS mono blocks (like the Marantz ma9s2) to see if that can overcome the acuphase's shortcomings, or a more powerful tube amp (which again, on paper, shouldn't play this well with the SS AR1s, but there you have it) - still not sure how the LX380's specs on paper should be working this well with these Sony's, but they sound far superior to the first SS contender~

Till next time!
@sfmorris,
There could be something wrong with the Accuphase.  It should not sound muddy and muffled.  You may want to check on that possibility before moving on.
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. 
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.
In this case I don't think so.  The Luxman is able to behave as a proper voltage source within certain limits, and the 8 ohm power they are getting out of it suggests that it might be set up so that it can put out a bit more power into lower impedances. This is done by simply 'light loading' the tubes in the output section by setting the primary winding of the output transformer to a bit higher impedance. On top of that I'm pretty sure that Luxman did their homework on the output transformer and has something that is spec'ed decently in there. This all does not seem that mysterious to me- I've seen it before.
atmasphere,
I understand your point and the significant importance of the output transformer. In threads discussing tube amplifiers I consistently advocate the undeniable need for high quality transformers if one is seeking excellent sound quality from tube powered amplifiers. 

My point is if you look at the Sony SS AR1 speaker measurements they are as George and others have rightly noted, a ’challenging ’ speaker load given its impedance curve and phase angle characteristics. Armed with this knowledge the last thing you’d recommend is a 14 watt tube amplifier.

The low watt tube Luxman is doing something obviously good that can’t be surmised from assessing its measurements or those of the Sony. So again, how is this gross mismatch (Via documented measurements for both products) able to produce such high quality sound? Something is occurring that isn’t accounted for with supporting test bench numbers.
Charles
If we weren’t in the middle of a pandemic and people lived nearby, I’d invite you all over for a listen!
I have seen this same phenomena play out with electrostats... Where most Solid State amps that double down/up on watts vs ohms just don’t sound very good while reasonably decent tubed amps, with much lower watts, sound wonderful... Excellent Transformers seem pretty rare in modern SS amps... I suspect there is a correlation between transistors and transformers and speaker impedance most SS amps just don’t play well with... Makes me wonder how bad a Class D amp would sound with these speakers...

ddude003,

Amplifiers that can double (or nearly double) their power as speaker  impedance is cut in half are touted as mandatory for difficult speaker loads such as this Sony. Although logical to the core, sonic results can be surprisingly poor sounding.. It is  just intriguing that there is no solid  explanation  for a good result such as the Sony speaker/Luxman amplifier or similar such  scenarios.

Charles

My point is if you look at the Sony SS AR1 speaker measurements they are as George and others have rightly noted, a ’challenging ’ speaker load given its impedance curve and phase angle characteristics. Armed with this knowledge the last thing you’d recommend is a 14 watt tube amplifier.
@charles1dad  In looking at this statement I think you might be conflating high power with the ability to drive difficult loads. But I suspect this load isn't as difficult as it appears, but regardless a small amplifier can easily deal with difficult loads if designed for it. Anyone making a tube amp these days has to deal with the simple fact that 4 ohm speakers and difficult loads are a lot more common than they were even 20 years ago! And I suspect that Luxman didn't go into that product design blind to this fact! 
hi all,
just a quick update but I did a few more casual tests with some other family members (brothers in law, etc) and was as careful as possible not to say anything that would bias them. Everyone so far,  unprompted, has said the same things about the two amps. 
I wanted some other opinions just to make sure I’m not crazy, and everyone has described the luxman’s output as more lifelike and vibrant (referring to the clarity of the mids and highs relative to the sound of the Accuphase) - one brother in law said amp A was like looking directly at the music , amp b was like looking at it through a window. 

@ddude interesting you’ve seen this before too. Maybe it’s a real phenomenon that just isn’t acknowledged much? 
@charles1dad @atmasphere I’ll let you know if I have a chance to test with any other kinds of amps. 

Atmasphere,

 In a follow up post I specifically mentioned amplifiers capable of doubling their power as the speaker impedance is halved. This would demonstrate high current output/delivery from the amplifier. This is what some have said the Sony speaker requires to drive it properly. There's no evidence to suggest that the Luxman has this high current ability as defined by this criteria..


 Nonetheless it is working in apparent marvelous fashion according to sfmorris. I have no reason to doubt his listening impressions nor those of his guests.

Charles

sfmorris,

I suspect the orthodox SS amp manufactures think the way to manage or handle "difficult loads" are to double the watts to drive the speakers into submission, when not all speakers have the same impedance curves, much to the chagrin of those manufactures... In my own experience, tubed amps and ss amps with autoformers seem to do better at managing those "difficult loads"... To be more clear, not all speakers present the same impedance loads/curves to amps as some manufactures would like or expect...  What happens when you double the watts at the wrong end of the curve?
 In a follow up post I specifically mentioned amplifiers capable of doubling their power as the speaker impedance is halved. This would demonstrate high current output/delivery from the amplifier. This is what some have said the Sony speaker requires to drive it properly. There's no evidence to suggest that the Luxman has this high current ability as defined by this criteria..
@charles1dad  What you are talking about is the amplifier behaving as a voltage source. Usually that means 'doubling power as impedance is halved' but it does not have to work that way; an amplifier can be a voltage source if it cuts power in half as impedance is doubled. The former is often how solid state amps behave if they have enough power supply current and the output section has the current handling capacity; the latter is how tube amps and smaller solid state amps do it (or somewhere in between, where there might be slightly more power into a lower impedance but definately half the power if the impedance is doubled).  So the Luxman wouldn't need all that 'high current' to be perfectly able to do the job.

The 'high current' thing tends to be overblown in audio to the point of being mythological- current can't exist without voltage and the two together make power, defined by the relationship of 1 watt = 1 volt/1 amp.
atmasphere,
You have more knowledge and experience in this realm than I. If you say that the need for high current is "overblown" I’m sure you have the evidence to substantiate that position. It’s just that the need for high current is nearly axiomatic by many posters on this forum when discussing driving speakers such as the ’challenging ’ Sony SS AR1. Purely out of curiosity and to gain further knowledge my question simply is how does the 14 watt (Tubed) Luxman accomplish this feat?

Earlier in this thread several posters said sfmorris didn't know what he's missing with his Sony's until heard driven by a powerful high current  solid state amplifier.  Ironically they were right but not as they would have  expected.. 
Charles 
Purely out of curiosity and to gain further knowledge my question simply is how does the 14 watt (Tubed) Luxman accomplish this feat?
If its output impedance is low enough, it will make its full power into the lowest impedance of the speaker (BTW its actually rated at 20 watts). At higher impedances its negative feedback will throttle back the power so as to keep the frequency response even. Since most of the power is in the bass, this really isn't a problem since the the higher frequencies need so much less power. But what is afoot here is really (as I'm sure you already know) that a watt, if nice and clean, is really a bit more power than you might expect.


I'm sure that the amp doesn't like the load all that much, and so its probably making more distortion as a result. But most tube amps are pretty well-behaved when it comes to distortion in that they tend to not make as much of the higher ordered harmonics as solid state amps. So I would expect it to sound smoother, even though it might be working hard, than a solid state amp. But if the load impedance were doubled, I bet it would sound even better if all other things were kept equal! About the closest was I know of to do that would be to use a set of ZEROs and see :)   www.zeroimpedance.com

atmasphere,
Thanks for your response. In light of the excellent sound quality sfmorris described with the Luxman and Sony pairing, your explanation makes considerable sense. One can’t help but notice the contrast to what George and erik_squires concluded per citing the Stereophile review test measurement results of the Sony speakers. I can understand their respective responses given the test bench numbers. 

Specifically the impedance behavior in the bass and lower midrange (Sub 3 ohm and steep phase angles) frequencies. You’d certainly predict the high current Accuphase to trounce the Luxman. This was far from the case. This has been a very insightful thread. Thank you sfmorris for sharing your very interesting listening experiences.

@atmosphere thank you for your informed comments as an experienced electrical engineer and manufacturer of highly regarded audio components.
Charles
BTW I know the Luxman is rated at 20 watts. However it is rated at  14 w at 4 ohm load. The Luxman produces its lowest power right in the rsgion where the Sony actually dips even lower to 2.7 ohm!!! So one would expect less than the 14 watts at this very low level. Fascinating outcome with this amplifier.
Charles
Hi all,
I’ve certainly learned a few things through this insightful exchange - thanks Charles and Atmosphere! I don’t know as much as I’d like to about amplifier topologies, but this has helped me a lot!

if I have any other listening takeaways, I’ll definitely let you know - I haven’t entirely thrown in the towel on high powered SS amps and may try another just to see. 
Take care
samuel 

sfmorris,

It would be very interesting if you could acquire another high current solid state amp as an additional  data point. I must say though that the Accuphase is considered to be an upper echelon solid state amplifier. They don't  get much better than that esteem Japanese brand.

Charles