liborko wrote:
Forget 600W. Your stereo will never ever produce 600W. Average efficiency of speakers is around 95dB with one watt of power. That is a lot of noise. These things are notorious for overrating and there really is not any standard for rating. High quality home stereos are rated in RMS power usually into 8 Ohm load with stated level of distortion (THD). The only way to get any idea how much your stereo consumes is to measure DC current at 12 V at average volume and at high volume. My guess is it will be less than 3A. Multiply average DC current by hours of use to get rough estimate of ampere-hours(Ah) it will take from your batteries.
I mess around with all things audio. Your take is right on but there are two things that change the completely accurate measurement you state. Mobile speaker systems use 4 ohm speakers and the amplifiers are rated with that in mind. The amplifier will operate at a higher voltage than 12V. If only pushing two outdoor speakers, the amplifier will never output 600W (nor the 300W it is probably rated for into two channels).
FWIW, I operate two car audio amps in my truck, a 600W, four channel amp and a 1000W Class D amp. Neither sees the rated draw as I listen in moderate levels. IIRC, fusing I have is less than the highest rating of the amps. This system is powered by the single truck battery, the original I replaced at 10 yrs, 1 mon.
