Thursday, December 10, 2009
Ears and hearing: some Jean Hiraga's thoughts and the miracle of Western Electric 15A
Whether the amplifier is 20 Watts or 500 Watts, we always remain faced with an impossibility: that is to try to reproduce the real level of the signal. Table 1, which gives the lowest and highest levels of various instruments of an orchestra, indicates to us that a loudspeaker of 3 % output efficiency should be rated at 2200 Watts (the problem of the neighbours is not tackled) to reproduce the dynamics of an orchestra of 75 artists. We are thus far from the truth, in the maximum level as well as the minimum, by the great insufficiency of the signal-to-noise ratio. This same table shows the obvious loss of definition, if the scale of these levels is reduced to a level "in apartment", which is actually an effect of sound compression and limits in the signal-to-noise ratio of the recorded signal.
Table 1 : Acoustic level of various instruments and theoretical power of the amplifier required for a loudspeaker of 3 % output efficiency for the restitution of these levels. Notice that the acoustic level for an instrument can be as low as 0.005 microwatt, as the piano has the greatest dynamic ratio (80 dB) and that, for an orchestra of 120 musicians plus a choir of 200 people; the dynamics can exceed 120 dB.
N.o.B. (Note of Blogger;-)) - also come to mind this efficiency calculator
and the IMPRESSIVE efficiency ratio of, say, Western Electric 15A horn with WE 555 driver - i.e. about 70 %!!! Hey, I'm talking about the capability, the strenght to do not loose "energy" but for a (negligible) 30 %! Amazing!
P.S. - did you notice in "Table 1" about the "Cymbals" power?
Posted by twogoodears at 12/10/2009 09:32:00 AM