power handling for resistors?

[tdemont]

a 12 watts RMS resistor used in an attenuator or zobel circuit in a passive crossover can handle how many watts from an amp before frying? don't tell me only 12! Thanks in advance

[tdemont]

What is the formula and info needed to decide on port size or port tuning?

[BobEllis]

How resistor power rating translates into system power rating depends on the application.

For the attenuator, it depends on the value of each resistor, your crossover frequency and the high frequency content of your signal. Rod Elliot's website has a chart showing music power distribution for "typical" music. There are many opinions as to the accuracy, but there is nowhere near as much energy at the high end as below 2000 Hz. For most typical crossover frequencies, tweeters and signals, your tweeters will fry long before a 12W resistor.

For the zoebel, it depends on the Resistor value, corner frequency crossover frequency and signal. The capacitor will limit the power dissipated in the resistor at low freqencies, the crossover will limit the dissipation at high frequencies. Again, you should be safe with normal signals and reasonable woofers.

[markp]

A wirewound power resistor will take peaks of about 10 times the rated power with no problem.