Im new to this and need some help. I have 4 6x9's and am looking for an amp to power them. They have a max power of 260w each, but a nominal power of 60w. Am I supposed to get an amp that handles the 240w or one that handles the 1040w? Thanks
There are few things that are as misunderstood as power as it relates to speaker reliability.
It's not wattage that kills speakers, it's clipping. One way to look at it is to visualize a clipped signal as switched DC. Speakers are air-cooled devices. Dynamic drivers cool their voice coils by pumping air in and out through the spider (sometimes augmented by vented pole pieces). If a driver is fed a DC signal, it goes full transit and sits there. The voice coil is heating up, but there's no air moving so the voice coil doesn't cool. The speaker fries rather quickly.
Someone will jump in at this point and say that heat is conducted away via the magnet structure. A relatively small percentage is but, fancy "heatsinks" on the magnets not withstanding, ceramics just aren't that good at conducting heat. The heat that makes it up the pole piece is of some help, though.
You can run a speaker with more than its rated power forever...with a few caveats.
--The first and biggest is that the signal is flat. If you start jacking things around with tone controls, all bets are off. You can exceed Xmax and physically damage the driver. Don't bother asking how much power you can use if you use tone controls. There are approximately one googleplex of variables involved, and I ain't gonna start guessing how loud you play vs. how much boost vs. what frequencies are involved vs. the ambient temperature in a car (which effects cooling of the voice coil), etc. etc. etc.
--Without damaging the driver, you can still exceed the linear excursion. This increases distortion. How much this bothers you depends on how careful a listener you are.
--We're assuming that the drivers are made by reputable companies and are of at least average construction quality.
The upshot is that if you play fair and don't use tone controls you can exceeed the rated power by a considerable margin. I used to run 15W speakers with over 100W of amplification and never had a problem.
For people looking for a simplistic guideline: match RMS power on the amp to RMS ratings on the speaker.