I'm not sure if this is the right spot. But I'd like to know if anyone on here knows ratios on volume to wattage, etc. I know wattage measures power not volume, and I know a 60 watt amp would not be twice as loud as a 30 watt amp. I'd also like to know how much louder tube amps really are, and also how much speaker sensitivity affects volume. You probably don't the exact ratios, because it probably still varies on amps and settings, but this would be very helpful.
Quote by sticky
How loud are different amplifiers?

The power of an amplifier is a rough guide to how loud it is. This is measured in watts (W), for example 100W. There are two basic ways of measuring power. Peak output and RMS.

The actual voltage of the signal (input and amplified) varies over time. Think of this varience as a sine wave. Sometimes its high, sometimes its zero, half the time its negative.

One way of measuring the magnitude of this is just the height of the top of the wave. This is peak output. Anothr way is to estimate the average output over time taking into account the fact that half the wave is negative voltage and most of it is lower than the peak output, and is called RMS (root mean squared). Most amps output is given in watts RMS.

But this is important: the wattage of your amp (RMS or otherwise) is the electrical power of the amp. It doesn't translate straight to sound volume. Most of the power of your amp is used to make heat, electricity and the magnetic fields in the transformers. Very little is used to make actual sound energy. To put this into perspective a 100W amp is ten times more powerful, electrically, than a 10W amp, but only twice as loud (as a rule of thumb).

What the hells so good about high wattage, then?

Not all that much, after a certain point, but more powerful amps have more headroom. A 100W amp will sound far better than a 10W amp at the same volume because it can handle the power better, and produce a more musical output. It's kind of like a Ferrari and a Ford, both can do 70mph, but the Ferrari can do it better.

One of the differences between valve and SS amps is valves sound louder to the human ear (they aren't actually any louder they just sound it).

Yah.
Lets say your speaker has a sensitivity of 100 dB at 1watt/metre.
With one watt, you have 100dB.
ie. Go to 50 watts of power (intensity)
We are calculating for pressure ( dB spl)
Intensity = pressure squared, so the increase in pressure must be the root of 50, which is 7.07.
Then, a dBspl sum : - 20(log p2/p1)
= 20( log 7.07/1)
= 20( log 7.07)
= 20(0.84)
= +16.8 dB

So it'll be 116.8 dB at 1 metre.

It's mainly in speaker sensitivity though:
Compare two setups:
A) 50 watts powering 82 dB watt metre speakers.
B) 20 watts powering 88dB watt metre speakers.
A) dB SPL: 82dB + 20 (log 7.07) = 98.98 dB
B) dB SPL: 88dB + 20 (log 4.47) = 101 dB

Help much?