Can someone explain to me why there are no drivers in a full size headphones?

Originally Posted by mrconfuse 

Why are there no high, mid , and low frequency drivers in a full size headphone. Won't the usage of multiple drivers give you all the frequency ranges that you can get from an actual speaker system? Won't that give you more realism since each driver/drivers can be dedicated to a part of a frequency instead of having 2 or 1 large dynamic driver handling all the frequency ranges

They do alright with one. Multiple drivers covering different ranges introduce their own issues -- phase, crossover, and coincidence distortions.

Some IEMs do have crossovers and multiple drivers though.

Headphones can achieve good enough frequency range with one driver, and using multiple ones is generally simply not worth the trouble of implementing it well and the added cost.

As was already mentioned here, crossovers add a whole new ball of wax.  In a purist sense, it's ideal to have one full range driver with a flat response across the frequency spectrum.  This is very hard to do in a full size speaker due to how the air must move to produce sound.  It is easier to do this in headphones because less air has to be moved to make the sound.  Simple is often better.

There are a few multi-driver headphones. They rarely are very good. You end up with a few problems - most noticeably 1. even tiny placement differences in the drivers can drastically change how your ears receive the sound when they are that close - for the most part, poorly. Stacking them can mitigate placement problems, but introduces wave overlaps, interferences and driver movement problems. 2. You have to use crossovers - those introduce some weirdness in the frequency response (the best crossover is no crossover). 

At the size and displacement headphone drivers are, there is no need for multiple drivers to address the frequency range. Unlike with speakers, where you are trying to move a much larger volume of air, and making a 12" stiff paper cone also produce good quality high notes, is an exercise in futility.

The soundstage realism in speakers doesn't derive as much from multiple drivers, as it does the interaction of soundwaves with the room.  

and because they are inserted into your ear canal - they don't have the head transfer function/outer ear to deal with, and distance offsets. 

I've never figured out how they deal with the crossover problem on multi-driver balanced armature iems... curious to know how those really work inside. But a great many very good IEMs use single drivers too... 

i remember around 25 or so years ago  AKG had some headphones with 2 or 3 drivers in each. They were expensive, and didn't seem to sell well.

There are a few gaming headphones now that use several as well. And the new Klipsch cans... they all are pretty terrible. 

Multi-driver headphones are a solution in search of a problem.

Quote:

Originally Posted by hodgjy 

Multi-driver headphones are a solution in search of a problem.

well said.