http://www.sengpielaudio.com/TableOfSoundPressureLevels.htm None of these numbers have any impact on the point we are debating (that is, whether two amp in series are better than one larger amp), but we can define them all if you like. It makes no difference to me what these numbers are so I'll pick some that are easy to work with.No, that is not the debate. Or, it confines the options to the exceptional.
At no time did I ever dispute that an all-powerful amp could not do complete justice to a (nominal) 2V signal.
a) All signal/range is present in a well-engineered recording. We can agree on that.
b) I will not accept your peak-to-average of 4. That would be a 40 dB spread - there is very little in source recording that even could encompass such a spread other than, perhaps an active Foundry. But, lets apply it to the full dynamic range of the recording. And, let's set the P/A at 30 dB. Still pretty rare, but not off the scale.
c) A speaker with a 100dB @ 1 watt at 1 meter will be a remarkable beast - but let's accept that. It kinda-sorta matches the flea-powered amp.
So, let's assume you listen at an average of 70dB. This is active conversation. And your peak would be, then, 100 dB. Your most quiet passage would be 60 dB.
Your flea-powered amp into those speakers would be 100% up to the job without the necessity of an active pre-amp. An exceptional condition, but within all the parameters given and accepted. BUT, if you were listening to that foundry, you would hear the loudest transients at 10 dB down. Under most conditions, that may be a blessing.
Now, let's take my example:
Speakers at 84 dB @ 1 watt @ 1 meter (Magnepan MG IIIa)
Average listening level of 80 dB
Same P/A as above
VTA 70 as the amp
So, 1 watt gives me 84 dB
10 watts gives me 94 dB
-line-level source cuts off at about 97 dB (35 watts).
100 watts gives me 104 dB
1,000 watts gives me 114 dB (rimshot) (down 17 dB from a line-level source - down 6 dB via an active pre-amp).
10,000 watts gives me 124 dB (foundry) (not gonna happen).
Go the other way - set line level at peak (104 dB)
Down 10 dB (3.5 watts) goes to 94 dB
Down 10 dB (0.35 watts) goes to 84 dB
Down 10 dB (0.035 watts) goes to 74 dB.
Down 10 dB (0.0035 watts) goes to 64 dB (Most quiet passages). Dubious - although the numbers work, few amps are capable of a cogent signal at that level, and fewer speakers will accept it as above the noise floor.
AND positing a X 10 transient capacity (350 watts), the rimshot will be ~ 5dB down. The foundry will be 15 dB down.
AND, still not very good. And that even with an active pre-amp.
Same example, with my brute-force 200 wpc/rms amp:
1 watt gives me 84 dB
10 watts gives me 94 dB
100 watts gives me 104 dB
-line-level source cuts out at about 107 dB
1,000 watts (rimshot) gives 114 dB, down 0 dB using an active pre.
At X 10, the foundry strike would be down only 7 dB - were not that I would do that to good speakers.
And that would be the point. In order to get a realistic differential, the full capacity of the amp must be realized. Or, the loudest passages are muted. Or, the softest passages go below the noise floor. A simple line-level input will not drive an amp to reproduce transients under typical real-world conditions.