Heat is an incredibly important parameter. It also plays a huge role in why HiFi speakers sound good at low levels, but PA speaker don't - and visa versa. When I designed custom passive crossovers for PA speakers, I tested and measured the performance ant 10 to 50 Watts input, while with home HiFi speakers I preferred 1 to 2 watts input power. This stuff makes a huge difference.
Think about it... the if you design a single pole passive crossover for 2,000 Hz based on a perfect 8 ohm impedance from the driver, it may work in the low power range of 0 to 1 watt, but if you get into the 5 to 10 watt range, the inductor will be too small while the capacitor will be too big. Meaning, the crossover frequency of the tweeter may have a crossover at 4,000 Hz and the woofer a crossover at 1,000Hz at high power input - or high SPLs. If you design a double pole or higher order crossover it gets even worse!!!
This is why since the 90s I've advocated for active crossovers with no passive components (other than resistors for ribbon or planar drivers) as it ensures the crossover parameters remain constant at all listening levels. It also allows for direct coupling of the amp to the driver which makes for the real benefits of damping factor which go away with a double order or higher crossover.
