Max handling power for a 10w speaker resistor
There is no such thing as a 'speaker' resistor. A resistor is used for whatever purpose it serves. As a general rule resistors are not used at more than 50% to 75% of their maximum rating so there is some assurance of a long life.There are wire-wound high wattage (5W to 300W) resistors known as 'non-inductive' that are used mostly for RF and audio 'test' circuits, but could offer some benefits for tweeters, by not inducing inductance into the HPF circuit. A typical wire-wound resistor has some inductance, enough to be a problem with high frequency ultrasonic, RF and pulse circuits. Most any resistor can take a 50% overload for a second or so. A 10 watt resistor can handle 10 watts, but will last for many decades if run only at 5  to 7 watts. Running a resistor at its maximum rating can cause a 'slow-burn' over 1 or 3 years of continuous use. It may still work OK, but have a discolored look, with any markings burned off. For smd resistors, the overload margins are smaller and the 'slow-burn' chance is greater as they do not have enough surface area to dissipate extra heat. They are seldom used at more than 25% to 50% of their wattage rating.