Is powerfull Amps only for low sensitivity speakes?

May I ask your comments also for the difference between single ended triode amps and push pull tube amps in terms of 2nd and 3rd harmonics capabilities.

Its not as simple as that might sound! SETs tend to make more of the 2nd harmonic than any other, with each successive harmonic at a much lower level than the one preceding it. The 2nd harmonic is where the 'richness' of single-ended operation comes from.

If an amplifier is push-pull, the harmonic structure varies depending on how the push-pull is accomplished. For example, if a single-ended input is employed, the 2nd will be canceled in the load, but there will be some present on account of the input, and you will also see a 3rd and a fairly prominent 5th. Many people that prefer SETs often point to the distortion of traditional push-pull tube amps as most are built this way, as being why SETs sound better.

But that is not the full story.

If the push-pull amp is entirely differential and balanced from input to output, the 3rd harmonic will be the primary distortion component but at levels about the same as the 3rd is seen in an SET. So this is considerably lower distortion and such an amp will tend to sound less romantic and more neutral, but will retain much of the musical character of an SET.

So topology plays a pretty big role and you really have to know what that is about. The 2nd, 3rd and 4th (the lower ordered harmonics) are musical to the human ear. The 5th and above tend to contribute to brightness and harshness, for example we've known since the 1930s that the 7th contributes to a metallic quality. Our ears are particularly sensitive to the higher orders and use them to sense sound pressure. All forms of distortion are perceived as some form of tonality.

"These statements are not accurate. If the amp makes too much power and the speaker has no need for it, the amp will be operating in a lower power region. With most higher power amps, this means it will have increased distortion. You can see this in their specs. The increased distortion is audible as brightness in most cases and will result in less detail as the distortion will mask lower level signals."

Not True! I wont even start here. I will ask you to think about percentages and hwo the FTC requires amps to be measured.

Actually the statement was quite true and simply looking at the distortion specs of the amp in question will bear this out. The FTC really doesn't have much to say about it. They are more concerned with distortion at full output.

Power is so so overrated. I have Magnepan 20.7, 86db and I’m currently driving them with a 90wpc tube amp without a problem and to be totally honest they have never sounded better. I use to drive them with ARC DS450M mono-blocks that put out a whopping 450wpc and 600wpc in a 4 ohm load. And to be frank they sounded like crap. I have never listened to music as long as I do with my current setup. Buy a well built amp that has bandwidth and high current and pay less attention with wattage. Just my humble opinion. Let your ears be your guide and not hyperbole. 

Someone wrote:
"These statements are not accurate. If the amp makes too much power and the speaker has no need for it, the amp will be operating in a lower power region. With most higher power amps, this means it will have increased distortion. You can see this in their specs. The increased distortion is audible as brightness in most cases and will result in less detail as the distortion will mask lower level signals."

Not True! I wont even start here. I will ask you to think about percentages and hwo the FTC requires amps to be measured.

Power is relative.  My wife has a Mini Audio system. Cheap,Cheap!  For what it is a $300.00 complete 10 CD changer, Radio, and 6" small bookshelf speakers.  It is rated at 100W RMS/ channel. the unit will get very loud, however it has no balls.  I have a 50W RMS / channel Crown PL-1 (22,000mf reserve capacitance) and in comparison at the same volume level the difference in the dynamics is astounding.  Playing on speakers of 89db /w 1W efficiency and driving about 20W the punch and low end off of the Crown amp is like night and day compared to a double the power rated amp in the cheap system.  It is like comparing a 50W crown to a 50W Mark Levenson amp.  Even though both are rated the same wattage the Levenson power supply would have I am guessing triple reserve in the power supply.  Not to mention the quality of the components from front to end.  So we can talk about watts but that also does not tell how it sounds. Generally you get what you pay for but I always recommend listening side by side on the same equipment.  The lesser wattage amp might sound better depending on what you like.  That is what matters - what you like. 

Dear Friends, thank you again for your comments.
May I ask your comments also for the difference between single ended triode amps and push pull tube amps in terms of 2nd and 3rd harmonics capabilities.
regards,
ozan

It's just a hunch but I would be surprised if 60W RMS pumped into 100db sensitivity sepakers doesn't at some point on bass heavy material run toward clipping. This is pretty much what I run and given my fondness of dynamic range and dislike of amp clipping I really wouldn't go below 60W.
For the more technically minded members here, given a 22' by 16.5' with 8'9" ceiling, well trapped room does 60 watts ever clip? I play it pretty loud but do the peaks require the full amp?

Are powerful amps only for low sensitivity speakers? No.

My 4-way hybrid-horn/dipole system is powered by eight identical Class D amplifiers. Each amp is rated 175W RMS, 325W peak power into 8 Ohms.

The compression driver mid horns and tweeters are very sensitive, about 110 dB/W/meter.

The four 15" woofers in four U-frames are each about 95 dB/W/M.

I don't know the overall system sensitivity - the horns had to be padded down by the active crossover to match the woofers - but it's pretty high. Total power is 1,400 W RMS/ 2,600 W, peak power.

I never push SPLs very high, I want to preserve what's left of my hearing, so usually power is under 1 watt, with brief peaks of 10, or 15 watts, maybe. Lots of head room. Sounds very good.

My 1.5 W/channel Type 45 SET amp, on the other hand, also sounds very good powering sensitive horns. And that little amp has pretty much no headroom.

 I have heard great sounding systems with both very efficient speakers and not so efficient speakers. But I do feel that with dynamic drivers if you go below around 90 DB you cannot get the really really great sound.  No matter how much power you add you cannot get the macro dynamics.   
 I believe the industry moved more towards less efficient speakers because they are much cheaper to manufacture as you don't need the tight tolerances.   And with the transistor it was easier to get big power so efficiency was not quite as important, or so they thought. 

+1 - Agree with Trelja and Noromance

From my 35+ years experience in this hobby, power corrupts, and have your ever really heard how loud 1 watt/channel can get?  We only have 1 set of ears and I like mine to last as long as possible.  A lesson I was taught many years ago by a stereo shop owner who was tone deaf but built the most amazing sounding speakers.

So I guess you started the equation with a lower power requirement for average level, by e.g. using more efficient speakers and/or a small listening room. And 4 Ohm is also pretty low.

This may be interesting: http://www.harbeth.co.uk/usergroup/forum/the-science-of-audio/amplifier-matching-mismatching-and-cli...
The point is that with significant dynamic range the peak power required is much higher than the average. In the quoted example, if you need 1 watt on average, you will need 160 watt to cope with a 22 dB peak above that average.

Interesting discussion.  I think at a certain point it just becomes about taste and experience.  Also what are our sources?  I'm a klipsch man myself, and am only interested in a pure analog system; mostly acoustic vinyl, tube pre, low watt tube amps, super high sensitivity horn speakers (Chorus).  I recently upgraded from 150 watt hybrid amp (moscode 300) to 20 watt monoblocks (quicksilver horn monoblocks).  I loved the moscode but there was always a little background hum, the lower watt amps are dead silent, and, in my very subjective opinion, show slightly more detail.  But my system certainly doesn't go as loud as it did, I tradeoff I can live with.  I've heard quad electrostatic speakers that are power hungry and sound incredible, but I decided not to pursue as I'd have to rebuild my whole system around them.  There is also the question of how much electricity you want to be burning.  To me the elegance of big, highly efficient speakers with super low watt amplification is very attractive (I'd love to try a really low watt single ended amp on my Klipsch), but I'm sure the right combination of small, inefficient speakers with mammoth solid state amp can also produce great sound.  In the end it's a matter of aesthetics, musical preferences, and $$.  

Kalali 1-20-2018
The OTLs are exceptions because they tend to have an un-tube like very low output impedance thus a higher than average damping factor.

Hi Kalali,

This is a rare instance in which I must correct an oversight in your usually sage commentary. OTL power amps do NOT have very low output impedance. A fundamental purpose of the output transformers that are incorporated into most tube amp designs is to transform the typically very high impedance of tube-based circuits to a much lower output impedance, which is accomplished by stepping down the signal voltage provided by those tubes while stepping up the current. OTLs typically compensate for the lack of the impedance conversion a transformer would provide by using a plurality of output tubes, and by choosing tubes suited to operation at relatively low voltages, but nevertheless the resulting output impedances and damping factors are usually in the same ballpark as those of many tube amps which have output transformers.

Atma-Sphere OTLs, for example, have damping factors ranging from a bit more than 1 to around 5 or so. An OTL that used to be made by Tenor had a higher damping factor, around 20, but even so the recommended load impedance for that amp was 8 ohms minimum.

Also, speaking of sage commentary, +1 to everything in the post by Charles which followed shortly after yours.

Best regards,
-- Al

Pairing of speakers with amp is really the key to any system. It's not just efficiency and power, it's clarity at desired volumes, voicing, damping, etc. I've always been of the opinion that you choose, in order: room, desired listening volumes, then speakers, then try different amps until you understand what the different amps are doing, then choose your amp. Bass in-room is the downfall of many an a'phile, most of whom cannot recognize standing waves when they hear the effect. Many audiophiles cannot hear when speakers are wired out of phase!

Some speakers require amplifiers with a higher damping factor (DF) and some speakers sound their best with lower DF amplifiers. The desirable level of DF is determined by the speaker design and the intentions of the speaker builder.

You can increase DF and inversely lower amplifier output impedance by utilizing more NFB. Some amplifiers tout DF level of 1000 or even higher. This ultra level of DF doen’t correlate with better sound quality.

There are speakers that sound superb driven by amplifiers with a DF of 2 or 3. It all depends on the speaker design mandate.
Charles

The answer is No for low sensitivity and don't be confuse with the motion that tube amps work only with 87 or 92 db range.  What you need is high efficiency speakers that will work properly in every amp category.

It should be no surprise that 15" drivers, regardless of their so called efficiency (or sensitivity), need higher voltages (or power) to operate at their best. You still need to move that large amount of air and that takes juice. In my opinion (hopefully a fact), the reason why a tube amplifier may sound a bit more "muddy" in the low octaves when compared to an SS amplifier is not (necessarily) due to the power rating, its mostly because of the typically much lower damping factor of the tube design. That usually translates to a "looser" bass. You'd have the same result even when you compare the amps - tube vs. SS, with identical power rating. The OTLs are exceptions because they tend to have an un-tube like very low output impedance thus a higher than average damping factor.

My experience is that inefficient speakers just never quite sound right to me, regardless of how much power the amp supposedly has. They always sound somewhat sluggish, effortful, leached-out, and, my horror-words in the audiophilic realm: "neutral" (means: bland) and "transparent" (means: thin). 87dB is the lower limit for me, 89dB is better, over 90dB is better. Then I'm free to use tube amps, EL34s, single-ended Alephs, sweet Creeks, integrateds, whatever I want. To low-sensitivity speakers I say "bah, humbug." I've yet to meet a high-wattage amp that honestly sounds really good, and I used to work in a high-end audio salon so I've heard amps that cost up to $25,000/pair. In my mind they just get you back to where you would have been in the first place if you'd gone with speakers of decent efficiency. Just my personal opinion according to the ears attached to my own head, YMMV.

I’ve heard it said many times that you cannot have too much power, but under-powering speakers and causing the high transients to clip the signal can do damage to any speaker; therefore, it is good to have headroom for the speakers in which to have room to function and breath properly. Using a water analogy . . . the fire department wouldn’t use a garden hose to put out a large fire. Even if there was plenty of water pressure, the hose could not handle it and would probably burst, and even if the hose was strong enough to handle that water pressure (power), it would not have the diameter to produce the VOLUME of water necessary to do the job.  Having all that water pressure . . . the firemen are always prepared in any given situation to do the job; however, if the water source does not have the pressure -- no matter the associated equipment and controls, the firemen can open up their hoses at full throttle . . . and they will only get so much volume coming out, and the building will burn.  Simply put, the right tools/sources to do the right job will produce the desired results and without disappointment -- if used with the proper knowledge, skills, and wisdom.

In the case of the power amp(s) being expensive, there are some class D amplifiers, that have capabilities of taking on various efficient to inefficient speakers like from 2 ohms up to 8 ohms or more with no sweat. In fact, some do so with great sound and not a high end price . . . i.e. a Crown XLS 1502 is rated at: watts/side @ 8 ohms: 330W; watts/side @4 ohms: 525W; and at watt/side @ 2 ohms: 775W. So you see, there is plenty of headroom, and this amp has level limiters so that you can set the highest limit of the amplifier’s volume to match the volume control of your preamp or input device so that you will not blow out your speakers or your ears. They have one model that has less power . . . and two models with higher power, I believe, in the XLS model.

In any case, it is always nice to have options and at reasonable prices. I have relatively inefficient speakers running at approximately 8 ohms and rated for up to 200 watts of power, and this amplifier, which can also be bridged into even higher power, has absolutely no problem running these speakers. In fact, I use a DBX to control my sound system to tune it to the room and have control over the way the speakers sound, and have thought about turning my speakers into active speakers with the DBX acting as an electronic crossover and using Crown amps for each frequency band. Right now I have the Crown operating the main speakers and my old monoblocks B&Ks (250 watts each) running the subwoofers, and the blend is seemless as the levels between the two. can easily be controlled. It is always nice to have options and versatility . . . and the Crowns do give you exactly those options.

All I can add is personal recent experience with a 500 watt Magtech amp compared to a my 70 watt cj tube amp. I was worried the 500 watts would be too much for my 90dB efficient Spendor SP100 speakers, maybe even blow them out. What I should have worried about was having to return the Magtech!  By comparison, The cj sounded so muddy and hazy, especially in the lows. For many years, I thought the Spendor’s were slow and had difficulty with a lot of more upbeat music. Now I know it was my under powered tube amp. The extra watts gave a much more overall relaxed, detailed, rhythmically assured presentation. I guess there is some midrange glow that the cj adds, but now it is very clear that this  effect is distortion. 

My home studio speakers are 15" Tannoys with 97db efficiency.  Out of the 4 good amps I own, the best match is my 300w/ch Bryston 4B-SST2.  That's way overkill on power, but the noise floor is inaudible when using the balanced inputs, and tonally it is just the right match for the Tannoys.  

Thanks for adding that. Some of the best recollections I have ever heard Wilson speakers has been with tubes. Brooks Berdan was a friend of mine and had me listen to the big X2 Wilsons on VTL monoblocks. The other system is OBGYN's system using all Lamm gear. To be honest I was close to buying your amps when I was running Martin Logan Odyssey electrostatic speakers. I was going to sell them and buy Soundlabs using your amps! I blame Brooks totally! ;)

Not a good impedance curve for tubes, this speakers needs current. but because it’s a very nice 90db efficient an amp around 150w or more will do, but as I say one that can deliver current!

In practice this comment does not bear out. John Giolas of Wilson Audio had our MA-1 amplifiers driving MAXXs and his system got some very nice comments from Soundstage!; so despite the apparent numbers, Wilsons have been traditionally fairly easy for tubes.

@sfroth  good point about inefficient speakers hiding noise. Another thing they hide along with that low noise is micro detail. 

Thanks George.

I am running Wilson Maxx 3 speakers (91db) using D’Agostino Progression.
The learning curve was quick as I found out that volume levels were not the same as when using a borrowed pair of ARC Ref 250 SE amps.
I am amazed when listening to classical discs. The dynamics at peaks are amazing. Every note is clean and in its proper space in the recording.

It’s not about the wattage ratings of both, that’s because the D’Ago’s have far better/more current delivery into low impedance’s than the ARC could give, which will give you the full dynamic impact of transients, also giving you more "space" between the notes, the ARC would sag a little and sound a little compressed with these transients compared to the Ago’s.

Not a good impedance curve for tubes, this speakers needs current. but because it’s a very nice 90db efficient an amp around 150w or more will do, but as I say one that can deliver current!
https://www.stereophile.com/images/archivesart/909WM3fig1.jpg

Cheers George

I am running Wilson Maxx 3 speakers (91db) using D'Agostino Progression monoblocks. Rated at 500 watts @ 8,1000 watts @4, and 2000 @ 2 ohms. I am very happy with the combo. I now understand what "headroom" actually is. The learning curve was quick as I found out that volume levels were not the same as when using a borrowed pair of ARC Ref 250 SE amps. I am amazed when listening to classical discs. The dynamics at peaks are amazing. Every note is clean and in its proper space in the recording.

One other thing to consider:
With many manufacturers, in a line of variably-priced items (in this case, amplifiers), as the designers have more money to work with, they often times put higher quality or performance in the higher priced items.  With power amps, the high powered ones, which command a higher price sometimes have better performance or features.
Back in the day (over 30 years ago), I'd say that many of the then high-powered amps did not sound that good at much lower power levels.  But I think that's a thing of the past.  I suspect that most "class a/b" amps today run in "class a" up to a watt or two; if you have efficient speakers, might be listening in "class a" much of the time.

Mine are low-mid 90’s I think as far as sensitivity. 
I run them with McCormack dna-750’s. 
Only rated at 250W. But boy oh boy do they sound sweeeeet, nary a hint of distortion anywhere with my CD player. 
Never a chance of clipping, and the peaks and crashes, double bass is flawless and tight. 

This is an interesting discussion.  My immediate query is why are there out there sensitive speakers and insensitive speakers?  I have no audio technical knowledge but I do know from reviews of speakers that apart from what they have in common in regard to most different brands, the approach to their design in some aspects are always slightly different in some way; its like the designer of each brand thinks he or she knows best how to create the perfect speaker.  However from my limited experience if one tested different speakers and amp with power (some oomph) in comparison with amp of lesser power, the amp with power will more likely show the individual 'talents' of each different speaker while the lesser power amp may not give the 'full sound' with some of the speakers.   

So, my opinion, in general is: High powered solid state amps can be a benefit to High Sensitivity speakers.

The generalization is the problem. I often run amps of 150 watts or more on my speakers, which are 98 db. I certainly don't mind the power!

I've heard 500 watt amps on that speaker and they can't make detail. They also sound bright for some reason. I've explained why.

So I think you have to define some limits, within which what you say is perfectly true.

A lot of interesting facts posted as well as a lot of interesting opinions.  Of course,  many times, Opinions turn out not to be facts, so,  I'm going to give one of each....
Fact:  Nothing says that sensitivity alone has Anything to do with the sheer sound quality of a speaker.  I've been building for near 40 years now.  This is a fact.  Well chosen high sensitivity parts can produce a high sensitivity speaker system.  Poor parts OR poor design will produce a lower quality regardless of Sensitivity. 
Opinion:  way back when,  We produced a particular speaker that was 97db sensitivity @ 8 ohms.  This particular speaker (15 inch 3 way) sounded great with Tubes and solid state,  but man,  when you put a really good big mama solid state amp on them with a great power supply,  these things reacted with dynamics like non other.  
So, my opinion, in general is:  High powered solid state amps can be a benefit to High Sensitivity speakers. 
Clear as Mud?  Tim 

Thank you again for all your comments. All are well noted.
kind regards,
ozan

But a powerful solid state amplifier allows you to use mostly far better inefficient speakers and avoid the distortion and non-flat frequency response of many tube amplifiers. Anyway, we are not going to persuade each other.

@willemj Actually I agree that a solid state amp with a lot of power is helpful with low efficiency speakers. If you do your matching homework, you can arrive at a pretty good solution.

Regarding the comment about tube amps- if the amp employs enough feedback, and many do, they will be just as flat as a solid state amp on a given speaker. All it has to do is act like a voltage source and tube amps have been doing that since the 1950s.

But there is a bigger issue- there is a lot more to high quality audio reproduction than just flat frequency response! The first problem of course is that such is just plain impossible because no speaker is actually flat. The next problem is understanding how the ear perceives sound and in particular how it perceives distortion.

Its that latter bit that is often where solid state and tube people part ways.

Distortion is heard by the ear as tonality. This is why tubes are often thought to be colored- because of the 2nd harmonic, which causes 'warmth'. People that don't understand that the warmth is caused by distortion often think that tubes just can't be flat; but that is not the issue!

But solid state amps have coloration too- and in their case as well, its not due to frequency response error- its due to distortion. Thinking that the small amount of distortion that solid state amps have as 'negligible' is a mistake.

The ear uses higher ordered harmonics to sense sound pressure (again, a fact that has been known for decades) so 'negligible' amounts are easily heard.

The ability to sense sound pressure is easily the most important aspect of hearing perception. The implication is its a Bad Idea to increase the harmonics used by the ear, unless high fidelity is not the goal.



 

I have DeVore O/93's and an ARC Ref6/Ref 150se combo. The GS 50 is identical to the Ref 150se but looks much nicer. First, it is a very good and very quiet amp. Second, you are going to need a very good pre, and preferably an ARC. Someone else posted this and he was 100% correct-the GS150 is balanced only and you are going to want/need a fully balanced preamp. After that, you will need really fine cabling, particularly from the preamp to amp, but I have learned that my speakers are extremely sensitive to speaker cable too. 

Kalali writes:

"An additional point against using high powered SS amps driving extra efficient speakers is most SS amplifiers produce higher levels of undesirable (higher odd order) distortion within their first watt or two just like but not quite as much as when they are pushed near their clipping limit."

This was - maybe sometimes still is - the problem with solid state amps and "lets drive the THD to zero" thinking. And yes, he is right withe the fundamental observation - tube amps naturally distort in a musical way; solid state tends to distort in a less musically way; but that is less a function of the devices than of how they are applied in a circuit. Honestly, that was all figured out and mostly mitigated decades ago. I even wrote papers on little pieces of how. So amps that behave that way are of the class of "bad amps designed by people who should have known better". A good solid state amp should have few nasty harmonics today. I’m frankly amazed at how far we have come in about 35 years. Heck, there are pretty decent sounding OPAMPS (!) today. really, again if you know how to use them (which most people don’t).

I'll also note that there is an implicit assumption that the amp is running in class-B mode, which, again, should never be the case for a serious high-end amp. It should run class-A for atlas a little bit (and after that don't bother me with subtleties, they are drowned out) :-)

Admittedly if you want bog power and low cost, it will sound like garbage, but that’s a COST issue, not a technical one. As I said above, the only problem with a big powerful amp is that you must spend money on that power and therefore didn’t spend it elsewhere.

Its easy to design "cost no object" pieces that are so impressive. Its much harder to make a great $1000 amp or whatever.

G

I reject the notion that inefficient speakers are inherently superior sounding. Not based on my listening experiences. In terms of sound quality there is much overlap between various categories of speakers . Low, moderate or high efficiency,  excellent sounding speakers exist. 

Now someone may prefer lower efficiency speakers and of course that’s fine. I just find that people who post very generalized blanket statements do reveal a lack of knowledge for a given topic. Ironically their blanket statements are presented as indisputable fact which they most clearly are not.
Charles

williemj"Clearthink would you please do something about your grammar? It might just add some clarity"

Well williemj I thought this was an audio group not a grammar group but since your raise dthis matter why don’t you issue me clear instructions on precisely how you would like my language to correspond to your considered ideal of how people here should communicate in the forum. Go ahead I’ll listen and take notes because obviously you have superior intellect on all things and not just audio but also now grammar. Of course it is patently clear that you are grossly mistaken about the inherent superiority of speakers of high efficiency and so I rather assume you now take issue with grammar and I suppose once this issue with grammar is resolved to your complete comfort and satisfaction you'll then raise another completley irrelevant issue such as the proper way I should brush my teeth or tie my shoes.

Clearthink would you please do something about your grammar? It might just add some clarity.

williemj"But a powerful solid state amplifier allows you to use mostly far better inefficient speakers and avoid the distortion and non-flat frequency response of many tube amplifier
I am very sorry you seem to be substantially misinformed on this basic principal there is no defined and verifiable factual correlation between speaker efficiency and speaker quality there are outstanding examples of each general type of speaker system of course you may prefer inefficient speakers in your Music Reproduction System to satisfy your own biases and that of course is completely fine but to claim that it is for inherent advantages of said inefficient speakers is mistaken, misleading, and a misrepresentation of clearly established fact. 

But a powerful solid state amplifier allows you to use mostly far better inefficient speakers and avoid the distortion and non-flat frequency response of many tube amplifiers. Anyway, we are not going to persuade each other.

It is true that distortion goes up a little bit at lower levels, but it is still very low and below the noise level: 0.05% at 100 mW. Look at graph 16 in particular, for the output range of 480mW to 7.7 W rms. In that range it never gets above 0.015% and rapidly descends to 0.01%. There is no way you can hear this.

Sure you can- if you have high sensitivity loudspeakers!

What you are not taking into account is the nature of the distortion (mostly higher ordered harmonics) and the fact that the human ear uses the higher ordered harmonics to sense sound pressure. We are more sensitive to them than almost anything else! So they manifest in amounts this small as brightness. This is what has fueled the tubes/transistor debate for decades.

Just look at the Audio Precison graphs at different power output levels of a 2x350 watt Yamaha p3500s pro audio amplifier: http://www.homecinema-fr.com/forum/amplificateurs-de-puissance-haute-fidelite/mesures-ampli-yamaha-p...
It is true that distortion goes up a little bit at lower levels, but it is still very low and below the noise level: 0.05% at 100 mW. Look at graph 16 in particular, for the output range of 480mW to 7.7 W rms. In that range it never gets above 0.015% and rapidly descends to 0.01%. There is no way you can hear this.

2. Is there any *disadvantage* to powerful amps with efficient or small speakers? No.

There is nothing about a powerful amp that is inherently a compromise of sound for power

These statements are not accurate. If the amp makes too much power and the speaker has no need for it, the amp will be operating in a lower power region. With most higher power amps, this means it will have increased distortion. You can see this in their specs. The increased distortion is audible as brightness in most cases and will result in less detail as the distortion will mask lower level signals.

@obatu Your speakers are only 92db; that is a moderate sensitivity- high sensitivity would be more like 98 or 99 db at a minimum. An amplifier of the power you mention will be no worries.

I can only give you my experience which is a reflection of what I believe Koost is saying. In short its about synergy. IME, my low powered systems have sounded better. IE, I had a Conrad Johnson MF2500A (250wpc) paired with a CJ PFR preamp.It sounded good with my Silverline Sonatas 93.5db. But I got an urge to try tubes. So I bought a fully modded Dynaco ST-70 just to dip my foot in to see what all the fuss was about for tubes. Its a mere 35wpc. Guess which amp kept?
Another amp which shined brightly in my system in the late ’70’s was a Harmon Kardon 45wpc Solid state. It was paired with large Advents and later Infinity RS series, both 89db (I believe)