Valve amplifiers

[Welder]

Sure Ali, concert level (120dB) is pretty extreme. However, 90db to 100dB isn't that loud in the right room when there is minimal distortion.
It might be interesting to measure just at what SPl one does listen at.

[Ali Tait]

Indeed. I do actually have an SPL meter from work. Must try it on the system.

I have noted in the past I tend to listen at lower volumes than some fellow nutters. S' me sensitive ears innit!

[Welder]

Bear in mind the ‘average’ vacuum cleaner is rated at 80dB.
Also, for those with the systems capable of erm, well, the scale people tend to talk about got from big drivers and realistic listening levels and how our perception of loudness doesn’t quite match SPL and of course, one musn’t forget than many partners can bend an ear at 85dB no problem and after all what’s a stereo for if not to drown out the missus and kids……….

I’m just sayin.

[lewis]

Something that has not been mentioned so far is the Damping Factor of amplifier and speaker. In fact it's hardly ever mentioned anywhere, considering it's importance, so could someone provide us with an explanation?

[Ali Tait]

Ok, just dug the meter out and tested it with some Led Zep. I deliberately drove to levels louder than I'd use even at a party, and the highest I got was 102db (C weighted)

[Ali Tait]

A normal decent listening level for me is 88-92db, having just checked.

[Welder]

Ah good man, got the right weighting as well.

More seriously, I'm looking at the 80dB to 90dB range and even at these relatively modest SPls I was trying to point out that a you may need rather more Watts than you might initially suppose when amp clipping and variations in loudspeaker impedance are properly considered.

If you want a system that is truly capable of trouser flapping bass and awesome "like live" reproduction you'll probably be needing a few more Watts than you might think.

I very rarely listen much above 80dB, mainly because the room self dismantles at much more. But, even at that kind of SPL, when clipping is taken into account and adequate headroom is allowed for enthusiastic transients, what initially seems an amp of adequate power output may fall to bits with just a teeny lil tweak of the volume control.

[Ali Tait]

Yes agreed, you need plenty of headroom for transients. One good thing about OB's to my ears is that they seem more immune to room effects than box speakers, so you can play to higher SPL's before the room becomes a problem.

[SPS]

my speakers are around 102 dbs , 2 watts (around half volume on the px25 amp) plays around 105 db peaks, with the average sound levels, dependant on the amount of compression in the recording...usually around 85-95 dbs ,
there very little in the way of distortion at those levels, i find 2-3 watts enough for the largest rooms, 96 db speakers would need around 8 watts to do the same.
but then you are getting out of the league of the the very best amplifiers.

[Ali Tait]

Yes, that's what prompted me to say that say 2 to 4 watts should be plenty for 102db speakers, having heard yours at Owston Steve.