Valve amplifiers

[Ali Tait]

..and conversely, a 3db increase in speaker efficiency halves the power needed to achieve the same SPL's. John is quite correct though in that the impedance curve of the speaker will play a big part in this.

[Ali Tait]

Hi Marco,

Welcome to AoS, btw

Thing is, you're not the OP of this thread, Chris (Sarnies) is - which is why I was rather confused, as I indeed it appears Ali was!

Marco.

All this stemmed from post #13 in the thread mate.

[Macca]

..and conversely, a 3db increase in speaker efficiency halves the power needed to achieve the same SPL's. John is quite correct though in that the impedance curve of the speaker will play a big part in this.

Indeed and attempting to match amp and speakers just using power output and sensitivity figures is often a reciepe for disaster i.e buying the wrong amp. Been there, done that.

However most of these super-sensitive +100db speakers tend to be single driver efforts so the impedence curve/change won't be too drastic.

[Ali Tait]

These are the speakers in question-

[Welder]

Well chaps, if you’re going to start talking about power amp sonic signatures I’m going to have to do a bit of this

So far, once the measurable stuff has been sorted, I haven’t been able to tell the difference between one power amp and another.

This doesn’t mean that none exists and it doesn’t mean others can’t hear any.

What it may mean is for those of us with average hearing wishing to listen to music rather than analyse sonic characteristics of equipment, the measurable stuff is what is important.

[Ali Tait]

More info here-

http://www.avsforum.com/t/1412510/kl...i-measurements

Seems they are not as sensitive as advertised.

[Ali Tait]

Well chaps, if you’re going to start talking about power amp sonic signatures I’m going to have to do a bit of this

So far, once the measurable stuff has been sorted, I haven’t been able to tell the difference between one power amp and another.

This doesn’t mean that none exists and it doesn’t mean others can’t hear any.

What it may mean is for those of us with average hearing wishing to listen to music rather than analyses sonic characteristics of equipment, the measurable stuff is what is important.

I'd guess that how the amp deals with the impedance curve of the speaker it's connected to plays a big part in the resultant sound. IMHO.

[Macca]

I'd guess that how the amp deals with the impedance curve of the speaker it's connected to plays a big part in the resultant sound. IMHO.

Yes - and people mistake this for the 'sound' of the amplifier.

[Welder]

Just to put this in perspective a little.

I know someone who has a set of Harbeth Super HL5 speakers (86dB/1W/1m) and uses my old Exposure xx (55 Watts per channel) to power them. He listens in a reasonable sized room at approx 5.5 metres away from the baffle line.
When he bought the speakers a few of us suggested that it was time to move the Exposure on; basically it just didn’t have the grunt for loud (85dB to 95dB) listening with the HL5s.

Using the calculator above this gives around 92dB rounding the listening position to 15’.
I’m rather fond of the Hl5; nice tone and even response and I used to own the Exposure xx and I know it was starting to clip badly at around 51 Watts when I had it. I doubt it has got any better.
The HL5 when measured did approximately 84dB/1W/1m.
Putting in the new values gives 90dB; hardly earth shattering volume.
But, ideally we need another 20dB headroom before clipping and loud to me at least is 100dB +.
Erm, that’s about 450 Watts to produce around 100dB without clipping

For my speakers 93dB should I want to listen at concert level and not have the amp clip I need to be looking at 350 Watts, or more

Going by the above and assuming the math is correct it seems more than likely that some of us at least are listening to a system in clipping mode and apparently don’t even notice. It does make me wonder.

[Ali Tait]

Well I'd say that the vast majority of us do not listen at anything like concert levels, if we did we'd be getting a swift visit from the boys in blue. I mean c'mon, how many of us seriously listen to music in our living rooms at 120db?