I had a pair of HDH244t a long time ago, The passive crossovers really suck alot of power, If I remember correctly there's 4 20 watt ceramic resistors in there.
It all depends on what you mean by "sucking a lot of power".
Yes there maybe some resistors that get hot-but that does not mean you are losing any output.
Look at the typical horn/driver response. Look around 1-3Khz as compared to say 10Khz
Typically you will see a nice large "mound" or "hump" in the response. If you want the response to be flat-you have to get rid of the mound. You can do it electronically via an eq filter, or passively via a crossover filter.
Either way that "hump" needs to be brought down. You don't lose any "usable" power in the process.
Yes you can argue that the passive is "wasting" energy, and the electronic filter simlply does not allow the amp to reproduce those freq as loud.
BUt you still will not be able to get the horn any louder-because the limiting factor will the point at which the horn has the least amount of energy being radiated.
So it may be "wasting" energy-but you don't get anything extra (in terms of SPL) by not wasting it.