Why do you need so much power?

I have a basic question.  I have a set of Tannoys with 93dB sensitivity. I’m told that a 25 Wpc amp like the First Watt J2 can power it just fine. (I don’t crank it to 11.). Someone also suggested an Emotiva amp with 500W RMS. 

So my question. Assuming you have a good set of speakers that are efficient (>90) and you don’t crank it till it’s clipping, then do you ever need such power as the Emotiva?  Thanks!
Depends what you are trying to do. If you are trying to get evicted, you'll need big power to make the windows rattle. After years of hi-power amps I make do with 25 and 50 watt amps now.  
(I don’t crank it).
Someone also suggested an Emotiva amp with 500W RMS.

I'd like to know who the fool was that said that.

Cheers George

Tannoys and Emotiva, just doesn't slide off my tongue.

The guy on the other thread didn't like Pass and Klipsch.


Pass and Tannoy, what could be better. A valve amp if that is your cup of tea. It would be mine. I like Tannoys, not suppose to blast..


Emotiva - NO. 
  And yes, even with high eff speakers, you will need the watts for headroom, and quiet to loud passages, the song ending slam of drums and guitar/bass.
    And with a good high quality/descent amp you will most likely not clip the amp. 
You don't need watts, just good power supplies for dynamic headroom.  I'm delighted with my 10 watts all day long.  My 100 watt monoblocks are gathering dust.
Robert Harley answered your question years ago:"If the first watt isn't any good, why would you want 200 more of them?"
Robert Harley answered your question years ago:"If the first watt isn't any good, why would you want 200 more of them?"
Yeah well, that's also a load of ****
The first couple of watts in any a/b amp are usually the better sounding Class-A biased ones, naturally the rest in Class-B are not as good, as they have a bit of crossover distortion in them

Cheers George
Raven CeLest towers with a Raven Blackhawk MK3 and I have 20W of musical heaven.

My 20 will smoke that Emotive 500.
Perhaps for the size of the room. When listening point is 2m away from the speakers your your speakers will deliver 93dB from just 1W. There will be 6dB drop for double the distance, but 3dB gain from room reflections and another 3dB from the presence of the second speaker resulting in unchanged 93dB at 1W. For the loudest forte of the orchestra (that your neighbors just adore, I’m sure) you don’t need more than 103dB resulting in 10W of required power. In larger room when you’re at 4m distance you will need 40W. My friends have very large room, open to the large kitchen with listening position likely around 8m - they would need at least 160W. Speakers that are 3dB less efficient, like mine, would require in that room 320W. Also, maximum amplifier power is specified usually at 4 ohm load and only half of that for 8 ohms.
1000W is overkill in any (other than ballroom) room, unless "When I listen to Black Sabbath, my neighbors listen with me". Sometimes people want more power for the amp to be universal (play with any speakers in the future) or to stay away from higher distortions at max power. I’ve seen 300W amp specification with small note: "at 10% THD".

PS: Watt is watt. There is no RMS watts or RMS power. Average power (sum of momentary powers) is the one that is equivalent in heat to one produced by DC. Pavg=Vrms*Irms
It depends on the speakers, how loud you want to go, how large the room is and how far back you sit.
Also the recording.

It’s like driving a car. more horsepower makes for a faster and more responsive ride on any road.

Clipping is hifi public enemy #1. Avoid at all costs. Extra power rather than not enough is your insurance policy against clipping at a minimum.
Thanks everyone. Since my room is of moderate size and I listen maybe 2m away, the 25w J2 is more than enough. To me, clarity, transparency and imaging is more important than volume. 
Volume and those things are not mutually exclusive but more power generally means more cost so need to know where to draw the line.  
No, for modest listening rooms with average efficiency speakers (90 dB or more) even 100 Watts seems overkill.

What will cause you a problem is speakers that dip to ~ 3 Ohms or lower, especially in the midbass, but sometimes in the treble (ESLs). 

It is very hard to find an amp ~ 100 W with great current drive.
I’ve hit clipping on 93 dB/Watt Tannoys (Kensington SE) with 25 tube Watts / ch, though only on certain material at higher volumes. And that’s hard clipping; soft clipping sets in well before that, so more overhead than you think you need is often a good thing for maximum clarity and dynamics. I heard that difference as I moved up in power amps.

I’ve even hit hard clipping once on those same Tannoys with a more powerful 65 - 70 Watts/ch tube amp, though that was a bit by accident - an extremely high dynamic range Sheffield Labs (direct to disc) record of Firebird Suite caught me well off guard! I ended up with 250 Watts/ch Rogue Apollo tube monoblocks and it was truly wonderful, and never ever clipped, even in "whoops" moments.

Now I run 96dB Tannoys (Canterbury GR) with 200 Watts/ch tube monos (VAC 200iQ) and there is really no possible way I will ever clip those lol. It sounds absolutely wonderful.

Of course, if you’re listening to rock/pop with almost no dynamic range (nothing against it, I enjoy a lot of it!) then yeah that 93 dB and 25 tube Watts will run you out of the room and you will never even reach clipping before your ears melt off.
A 25-watter for 93 db/watt speakers is not that different from my using 6-watt amps for my 99 db/watt speakers.  If you don't insist on extremely high volume output, the J2 will work.

I am a low-powered tube person.  I own a pair of  Audio Note Kageki (parallel single ended 2a3 tube amp) a custom built pushpull 45 amp, and a custom built 349 pushpull amp (my favorite).  I had the First Watt J2 in my system for about two weeks (on loan from a friend).  I liked it a lot.  While it did not sound quite like a low-powered tube amp, it acquitted itself quite well--it was lively and engaging in ways that I've not heard with most solid state amps.  It is a first rate amp at a quite reasonable price.
So much power? 

No, you don’t. 65 w/ch rms, clean, is plenty. Unless your amp doubles as a welding power supply.
the person suggesting the 500 wpc emotiva for your tannoy's is either self serving or he is an idiot

Complicated. Much depends on particular match, I guess. 500 seems excessive but 25 seems bare minimum. And what about current?
@mulveling, thanks for the response.  I listen almost exclusively to classical, opera and jazz; not so much orchestral recordings (so a lot of piano, violin, vocals).  What's most important to me is clarity, detail, transparency and imaging. 

The reason I'm partial to the First Watt is that those amps are designed to be musical--an ethereal and subjective characteristic but nonetheless, important.  I'm a violinist, so I value a system that communicates what the musician intended.

Let's see.  I'll try out the J2s and see what happens.  
Just get a sugden a21se, its class A and a good match to your Tammy's. 30 watts, all you will need. Mine is seldom turned past 10 am on the volume, plenty loud.
I used a Bedini 25/25 with the Quad 57's for years. Perfectly satisfying! But that speaker is severely limited by power handling and easily damaged.
2 watts, 20, 35 watts, etc etc. 

  there is no substitute for headroom, and having the reserves for those crescendos’ / peaks / quiet passages......and the full on massive orchestral frenzy of woodwinds, bass, as the fury of the full orchestra slams you like a ton of bricks,......... you will need the watts, to make the smooth transaction from the small flute, or simple cello, to the full orchestra smash which happens awesomely in classical music.
  Not having the reserve and power to deliver these peaks will result in unhappiness. 
 Speaking from experience. 

I have a 4 watt Decware tube amp with 92db Ref 3A de Capos.  Plenty loud in my 12x22 room, listen to rock, blues, folk and jazz
not concert loud
The same reason people drive 250+ horsepower cars - effortless performance. The Emotiva has WAY more power than you will need, so it will never strain. Another BIG factor is that Emotiva's are reasonably priced. I have an 8 wpc amp that costs more than the Emotiva! Your friend wanted you to get a bargain! It will certainly cost less than anything from PASS labs (I have two pass amps, not complaining). By the way 80 watts sounds only about 3X louder than 8 watts. To sound three-ish times louder than 80 watts, you'd need 800! Keep Smiling!

The same reason people drive 250+ horsepower cars - effortless performance. The Emotiva has WAY more power than you will need, so it will never strain. Another BIG factor is that Emotiva’s are reasonably priced.

while there is some truth to what you say, i would only add that there is a very important dimension of quality that matters, not just quantity of watts... if the objective is indeed to achieve great sound
Another point - you might look for actual measurements of your Tannoys if you can find them.  Many/most speakers are not nearly as efficient as the manufacturer's specs indicate.  Sometimes, the difference can be as much as 6db.
By the way 80 watts sounds only about 3X louder than 8 watts.
Should be only 2x louder. Perceived loudness is equal to
k^(1/3.5), where k is ratio of power. For 10x power it is equal to 1.93
10x power is equivalent to 10dB sound level increase equal to 2x loudness increase (3x will be sound pressure change).

@ssmaudio,  the Pass J2 is a great amp, do yourself a favor and pair it with your speakers.   I have never heard or owned an Emotiva amp.

The Tannoys are really quite efficient; the 89, 91, 93, and 96dB models I’ve heard of theirs all seem true to their rating when compared to other brands. You’ll especially notice this if you have a tube preamp without a dead-quiet noise floor. I know that some other brands have more "liberal" with their ratings, or do the 4 ohms / 2 Watts "trick" to add 3dB to the visible spec. Or sacrifice LF extension to goose the efficiency.
The old "only sounds 2x louder" thing is very subjective, and there are 2 versions of it: +6dB (8 Watts to 32 Watts) and +10dB (8 Watts to 80). All these rules of thumb, including 1dB being the smallest "perceptible" unit, are targeted for non-audiophiles, non-critical listeners. When I get in the sweet spot of my system and start listening, even 1dB is quite significant and readily noticed (or missed). 3dB is a lot, 6dB is a LOT, and 10dB is a HELL OF A LOT. So yes, personally I do appreciate these differences quite a bit.
It is always good to have a much more powerful amplifier than your speakers can handle for being able to handle highly dynamic music passages.  This will usually not happen with vinyl but will very likely happen with digital sources and home theater.

It is better to have it and not need it, than need it and not have it.