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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
atmasphere's avatar
atmasphere
12,156 posts
 
 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.
charles1dad's avatar
charles1dad
10,250 posts
 
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 
atmasphere's avatar
atmasphere
12,156 posts
 
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

charles1dad's avatar
charles1dad
10,250 posts
 
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
charles1dad's avatar
charles1dad
10,250 posts
 
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
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