How Much Power Should You Really Need?

[walpurgis]

I've owned some powerful amplifiers, but despite trying just about every type of speaker around, I always seem to go back to fairly high sensitivity types and also using amplifiers of more moderate power. It just sounds more 'right' that way to me.

The only time I've heard speakers that craved power that I actually liked a lot, was a generation or two ago at a Hi-Fi show, listening to monstrous Apogee ribbon dipoles driven by huge Tandberg (of all things) monoblocks. This lot sounded incredible.

What is really best? Opinions?

[Firebottle]

'What is really best?'

Isn't that the question for everything?
It's often said the first watt is important, and typically normal listening levels use surprisingly little power.

It's the old clichè answer, but whatever sounds good to your ears.
My OTL amp clips at about 6 watts because I deliberately keep the supply voltages low to not overstress the valves.
I haven't wanted any more power

Alan

[Macca]

The trade off with high sensitive speeks is that you sacrifice low bass. Other wise it all makes a lot of sense, and most people are not too concerenced about reproducing the fundementals of low bass notes. Also they probably don't have the space for large enough speakers or WAF is an issue. Even so I think most amps are underpowered for what people ask/expect of them. Something I noticed with my XTZ amp is that with a dynamic recording there is a huge difference between loud and quiet passages, almost scary at times when things get going.

[Haselsh1]

I adore the sheer grip and thump of big powerful amplifiers and the effortless way they reproduce dynamics in the music so power will always be an issue I guess.

[jandl100]

It depends on the listener and the sound pressure levels you need/want to attain.

I generally go for music at moderate volume levels and I have had excellent results with small amps into quite insensitive speakers. For example, my 85dB/W or so MBL speakers sound really very good with a 8wpc Mini-T t-amp! Or at least, I think they do.

Personally, I usually find that high sensitivity speakers compromise too much in terms of colouration / frequency extension, although there are exceptions like the Avantgarde Uno horn hybrids I used to own - but they cost plenty and have active bass drivers.

[Ali Tait]

The trade off with high sensitive speeks is that you sacrifice low bass. Other wise it all makes a lot of sense, and most people are not too concerenced about reproducing the fundementals of low bass notes. Also they probably don't have the space for large enough speakers or WAF is an issue. Even so I think most amps are underpowered for what people ask/expect of them. Something I noticed with my XTZ amp is that with a dynamic recording there is a huge difference between loud and quiet passages, almost scary at times when things get going.

Depends on the speaker IMHO. I have twin 15" bass drivers per side at about 95db. No shortage of bass here.

[Reffc]

The more power the better, generally speaking. You can drive almost any speaker to make a noise with a handful of watts but you simply cannot drive insensitive/difficult loads to give a flat FR using flea powered amps, it doesn't work that way

As for sensitive speakers not doing bass...nonsense. It depends on the speaker. I had a pair of Horning Agathon Ultimates which had seismic bass response plus a 99dB/1w sensitivity. They could be driven hard with 20 watts. Of course, generating sufficient speaker control is quite another matter and the confusion most people have is that just because a speaker is sensitive, they think (again) flea powered amps will do the buisiness. The Agathons could be driven to 30Hz fairly flat with just 10watts on hand, so delivered the bass. However, the back emf (especially into valve amps) meant that there wasn't a lot of control and things could get wallowy. Hooked up to something more beefy with a better damping factor and they were transformed into scary stomach pumping bass monsters which started and stopped on a sixpence. Other speakers which do bass really well but are sensitive? Tannoy Prestige series and some of the HPD models.

Horses for courses. But there remains a lot of stereotyping about sensitive speakers not "doing bass" and also flea powered amps being able to properly drive insensitive loads. Both stand points are flawed.

[spendorman]

This illustrates effeciency of speakers quite well:

http://www.chuckhawks.com/speaker_spl_amp_power.htm


Incidentally, my friend's Dad had a Vitavox Klipshorn in his living room, was also the Technical Manager for Vitavox.

[Reffc]

This illustrates effeciency of speakers quite well:

http://www.chuckhawks.com/speaker_spl_amp_power.htm


Incidentally, my friend's Dad had a Vitavox Klipshorn in his living room, was also the Technical Manager for Vitavox.

Unless I have my maths wrong, that chart seems way out or at least I've mis-read it.

Noise damping in air at atmospheric pressure is about 6dB per doubling of distance so if we look at the 92dB sensitivity speakers:

1m, 1w produces 92dB so at 4.6m, 1w will produce approximately 71dB

To get 71dB back up to the 90dB at the listening position we would need to DOUBLE amplifier power for EVERY 3dB gain

so we have:

1w=71dB
2w = 74dB
4w = 77dB
8w = 81dB
16w = 84dB
32w = 87dB
64w = 90dB

So we would require an amplifier which delivered 64W into speakers of 92dB sensitivity to produce 90dB at 4.6m.

The chart states over 400 watts which would appear to be the requirement for 90 watts plus headroom (15dB) for transients.

[realysm42]

If my amp produces 85w into 8ohms and my speakers are 87db sensitivity and can handle 80w, is that a good match?

It sounds great to me but my hearing isn't exactly trained...