[quote author=3driverPA link=topic=136851.msg3240072#msg3240072 date=1248224762]
exactly what it says, the minimum amount of power required to power the speakers. If you have a sub that requires a minimum of say 600watts, but your amp only pushes a min of 100, you'll notice your headlights will dim like crazy. The amp pulls WAY more power from the battery to power the subs needs.
here the technical definition of min power or RMS.
The amount of continuous power, measured in watts, that an amplifier produces is called RMS power. The higher the RMS figure, the louder and cleaner your music sounds. When choosing an amplifier, the RMS rating is the power rating you should pay most attention to. Also, keep in mind that some manufacturers calculate the RMS power ratings of their amplifiers at different input voltages. For example, an amplifier rated at 100 watts RMS at 12 volts can produce considerably more power than an amp rated at 100 watts RMS at the more typical 14.4 volts.[/quote]
RMS power is actually the root mean square power. You could use it to describe any level of power. It's just the way you calculate the average output of any AC current. A proper amplifier rating will give RMS output power for a specified frequency range, with a specified distortion level, and at a specified input voltage. That rating is not the minimum, it is the maximum continuous clean power that an amp is capable of producing, with continuous referring to any time period longer than a small fraction of a second. I personally refer to any rating that doesn't provide all that information as an ILS - If Lightning Strikes - rating. Retard specs isn't a bad term for that either!
Unless you have everything at full volume, your amp isn't using anywhere near that much power. Like an electric motor, it only draws as much power as it needs, no matter what it's capable of. If you have an amp with a rating of 600W RMS at 20Hz to 20kHz with 1.0% THD at 14.4V powering four speakers, and the four speakers are at a volume where they're only using 5W each (maximum clean power for a typical head unit!), the amp is probably using somewhere between 20W and 40W, depending how efficient it is. It's capable of a lot more, but it isn't using it in that situation. The minimum power requirement for a speaker to function at very low volumes isn’t much – usually fractions of a watt - though I suppose speaker manufacturers may give recommendations for what level of clean power is necessary to take full advantage of a speaker's capabilities.
Whether your headlights flicker is determined by capacitance, not just how much power the amp can put out. A better amp will likely have more capacitance built in to reduce the effects of surges on the battery voltage, but if a smaller amp causes headlight flicker it’s not actually due to inadequate power, it’s due to inadequate capacitance. If two stereo systems have the same total capacitance (on the power input side), the one putting out more power will be the one that causes the most headlight flicker.
Of course, if your stereo can put out 1200W it would be drawing even more than that. So it does sound like our alternators put out plenty of electrical power for anything but the most extreme mods. I assume by "small cap" you're running a 0.5F cap?