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 :)

:cool: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:spank:

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...

[Reffc]

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...

Should go plenty loud enough at a typical 3 to 4m but without much available headroom for transients. ie your amp could well be run into clipping for loud transients but it depends on how loud you listen. At 4m distance, to reproduce 90db you'd need 32 watts. To handle 105dB transients, you'd need closer to 1Kw!

[realysm42]

Should go plenty loud enough at a typical 3 to 4m but without much available headroom for transients. ie your amp could well be run into clipping for loud transients but it depends on how loud you listen. At 4m distance, to reproduce 90db you'd need 32 watts. To handle 105dB transients, you'd need closer to 1Kw!

Thanks man.

What's a transient?

[johnwhit]

Thanks man.

What's a transient?

A loud note of short duration

John

[realysm42]

Thanks again.

As I've got a ss amp, what should clipping sound like?

[Yomanze]

Thanks again.

As I've got a ss amp, what should clipping sound like?

A hardening up, harsh, brittle sound, loss of control.

[walpurgis]

Thanks again.

As I've got a ss amp, what should clipping sound like?

Nasty! You'll know if and when you're ever unfortunate enough to run into it.

It depends on amplifier type, but on the average transistor amp it's a ragged sounding break up of the signal.

[Macca]

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

Hi Ali

There's a difference between lots of bass, good bass and deep bass. IMO if a speaker cannot go flat down to 20hz then it cannot do deep bass. Your open baffles must cancel in the low bass due to the laws of physics so they cannot go that low although I appreciate in practice that with 2x15'' a side they will not sound bass light. Do you have measurements for them?

[walpurgis]

Speakers can do odd things when it comes to bass. If you hold a bare bass driver connected to an amplifier and playing music you'd expect the front to back cancellation to rule out any bass, but if you move round a room with it, depending on where you point it some deep bass fundementals will often be heard. Room acoustics of course, I remember those big Celestion subs with no cabinet, just a compact double baffle (can't remember the model No.), they were not short of deep bass.

[Sovereign]

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.

Not from where I'm sitting mate, I have never heard Marcus Miller sounding so deep and three dimensional :stalks:

[Ali Tait]

Hi Ali

There's a difference between lots of bass, good bass and deep bass. IMO if a speaker cannot go flat down to 20hz then it cannot do deep bass. Your open baffles must cancel in the low bass due to the laws of physics so they cannot go that low although I appreciate in practice that with 2x15'' a side they will not sound bass light. Do you have measurements for them?

Well all I'd say to that is, good luck getting a flat in room response to 20Hz!

Yes, correct about the OB's, you get a -6db drop in the bass due to the dipole nature of an OB, adding a second bass helper compensates for this. I have no measurements, but I'd say I get useful output down to around 30Hz.

IMHO it's not just how deep you can get, it's how accurate the bass is. OB's excel in this area to my ears, given there is no box to sing along. A box speaker may get lower, but a large proportion of the bass will be distortion. I'll trade a little depth for accuracy any day.

[Sovereign]

I tend to agree with you there Ali, I have always had deep'ish bass in my system. When I bought my OB's the bass, for the first time, sounded just like a bass guitar, not just bass. Very three dimensional imaging.

[Rare Bird]

13Watt, i can't even reach 9 o'clock on the volume control..

[Ali Tait]

I tend to agree with you there Ali, I have always had deep'ish bass in my system. When I bought my OB's the bass, for the first time, sounded just like a bass guitar, not just bass. Very three dimensional imaging.

Aye, that's a good thing with OB bass, it's very articulate. Box speakers all sound coloured in the bass to me now, they just don't sound quite right.

[Clive]

I contend that it's not so much about power, though you must have enough. What makes a big differnce to me is the number of output devices. An SE amp sounds better to me than PSE and for pushpull 1 pair of output devices sound better than multiple pairs. This is a generalisation of course but mostly I find it holds true.

[Haselsh1]

I guess in terms of what I really need, I need enough power and drive to overcome the inertia of the loudspeakers and really little more. I love to listen at that point where the loudspeakers just start to come alive and dance. Once I am there I am far enough.

[istari_knight]

Nowadays I use less than 10wpc at normal listening levels but used to listen relatively loud with low sensitivity speakers... Its amazing how quickly you run out of power when cranked !

I cant remember who said it but I do recall reading that its [relatively] easy to design/build a low output amplifier that sounds good but high output amplifiers require a lot more effort to avoid that cold/hard/sterile sound. That seems to bear true in the listening, there's loads of good sounding 30-40wpc amps out there but as you go up the ranges quite often they may be technically superior but the magic is lost.

I remember the 70's Marantz receivers, everybody lusted after the 2275 but the lowly 2215 & 2230 sounded far better, another [more modern] example is Rega amps from 10-15 years ago lots of people preferred the Brio to the Mira... I'm sure there's more [and better] examples but you get the picture.

Maybe our old enemy "synergy" is to blame for it all ? :)

[walpurgis]

There's a lot of truth there.

In the seventies, when transistor amplifiers were a relatively new thing, many of the smaller amps from Japanese companies used to sound better than their bigger brothers. The Trio KA 1000 and 1000A are a prime example, they are as clean and sweet as you could ask for, sounding rather like Class A amplifiers, but the larger models had a tendency towards brightness and sounded harder.

Rogers amplifiers were similar, the little Ravensbrook integrated sounding better than the bigger and dearer Ravensbourne.

[Rare Bird]

There's a lot of truth there.

In the seventies, when transistor amplifiers were a relatively new thing, many of the smaller amps from Japanese companies used to sound better than their bigger brothers. The Trio KA 1000 and 1000A are a prime example, they are as clean and sweet as you could ask for, sounding rather like Class A amplifiers, but the larger models had a tendency towards brightness and sounded harder.



I'm using a older Germanium version (TK150) of that amp, sounds brilliant, i prefer it to my 'KA1000'..

[StanleyB]

It was not easy for Japanese designers to design and build good sounding high powered transistors in the 70's. Most of the 2SA/2SB/2SC/2SD range were so so with high current applications. The European and US designers had a lot more success with the 2N range such as the 2N2955 and 2N3055.
The Japanese came up instead with high powered VFET (as used by Sony and Mitsubishi), and MOSFET (used by Hitachi).
Not withstanding the difficulties with designing a high powered VFET audio amp, it is still my favourite in terms of listening pleasure. My own power amp from that era has a VFET output stage. The Sony VFET amps are worth listening to as well.

[Ali Tait]

One of the lads that comes to Owston built a germanium amp, or gerainium as we call it. Sounded nice.

[walpurgis]

The Sony VFET amps are worth listening to as well.

I had a Sony TA-5650 integrated and the sound was exceptional. I hankered after an 8650, but never found one, although I have used one of the big V-FET Sony power amplifiers, can't recall the model. It wasn't as impressive as the 5650.

[StanleyB]

The Big VFET amps ( = high power output) had to use parallel wired VFETs. They were a pig to bias so that the different transistors did not interfere with each other signal wise. The MOSFET design from Hitachi (7500 and 8500 range) were the first FET designs to solve that problem. But they had different issues as well.