The amplifier in the headphones can be designed specifically for those headphones. It may well be that a transducer with a bizarre frequency response and an amp

The amplifier in the headphones can be designed specifically for those headphones. It may well be that a transducer with a bizarre frequency response and an amp/EQ that compensates is a better solution in the end. Where we are now, headphones need to have reasonably flat response (or be called Beats :-) in order to be acceptable. Or perhaps a wildly different impedance makes a better cost performance argument, can't go there now, but with active headphones you can. It may be a bit like the powered speaker market for PA gear. You can get light weight powered speakers for not a lot of money that perform quite well. The amplifiers do exactly what they need to for the exact speaker, they don't have to be able to handle whatever mystery load you plug into them. They can build in the crossovers and EQ compensation when the signal is small rather than in the speaker cabinets. Also, noise canceling ear buds become possible when you have power coming to them. Of course, the heap of Apple Earbuds I have whose clickers no longer work doesn't really inspire me about my new active headphone future.