DC Power supply question...duh...

<Boy does that sound like spec. inflation! 24 p-p is just 12 Volt peak in <either polarity with a bridge circuit. That gives 12/8 peak amps and 18 <peak watts (like with a +/-12 volt square wave). The RMS voltage and no that would be 24/4 (two speakers presuming they are parallel) or 6A. Assumes a 100% lossless bridge amp. at 24VPP and 6A you have 144W if it's a symetirc squarewave, less if sine(RMS). Now reality sets in, using the latest devices (VMOS/hexmos) there will be a few tenths of a volt loss arcoss the device. So let say the loss is 1V in that bridge amp of ours. Not allowing for resistance of wire and also assuming the PSU can easily supply in excess of the required current at 12V. 23Vpp/4 = 5.75A that times 23 is only 132.25... reality sets in some. also the difference 11.75W is heat!!! and thats the squarewave, it gets really bad for sincewaves (more like 25W as heat!). Can you imagine trying to get rid of say 40-50W (stereo case) of heat from one of those tiny boxes? Other assumptions, an 8ohm speaker is 8ohms. A non truth as it varies widely with frequency assuming a good encolsure. So at one frequency it may look like 6ohms and at another 15! Then we have copper losses from wiring and PC traces (resistance) and what if the 12V is really 11.95V? <amplifier. Don't tell me these "240 Watt" speakers are powered by 4 "AA" <batteries ;)... or use one of the many automobile ic amps that give about <4.5 watts with a 12 Volt supply and a 4 Ohm speaker. The other reality is it takes very few watts at a sustained level to cronk ones ears forever. 4AA cells can provide a remarkably large amount of power for and equally remarkably short period of time. (nominally 3WH) ;) A real 240W amplifier will cook a hotdog with two nails stuck in the ends in about 2 minutes at sustained full power! Real power = heating power. Allison