🚀 go-pugleaf

ljkong@napier.uwaterloo.ca (Lennard J. Kong) writes:

>From my experience I think the highest power you can get 
>from 12V without raising the
>voltage is about 33Wrms, which was a Clarion Eq/Amp.

You have to be cautious about accepting wattage ratings
from car amps. The manufacturers frequently exceed the laws of physics
with their ratings.

Using the equation P = V^2/R to estimate power is OK if
the correct V is used. 

I assume that the actual DC voltage is higher than 12, say 14.5
volts, but that the 2.5 volts is needed to boas the output transistors
of the amp, so I will use 12V to be consistant with Lennard.

A sine wave must be produced to measure RMS, so its max peak-to-peak
voltage is 12 volts. Its peak voltage is half that, 6V. The RMS voltage
is (SQRT 2)/2 times that, or about 4.2 VRMS. I will use 4VRMS for
simplicity. Then,

P = 16/R for a 12 volt DC supply. For an 8 ohm speaker, the max
output is only about 2 watts. Figure 4 watts for a 4 ohm speaker.

For Lennard's figure,
33 = 16/R means that the speaker resistance is about 0.5 ohms.
This would be sixteen 8-ohm speakers in parallel - not a likely
installation.

Perhaps the amp is a pair of amps bridged? Then the power quadruples
because the voltage is doubled. A bridged amp can put about 8 watts
into a 8 ohm speaker and 16 watts into a 4 ohm speaker. I would be
suspicious of claims of driving loads much below 4 ohms, except for
very expensive audiophile car amps, like Orion.
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