Multi-driver headphones have always been more experimental and novel in nature than anything else. Back in the 70s and early 80s there might have been slightly more of a practical reason as it was more difficult to make a single driver with true full range. The reasoning behind loudspeaker design was often just transferred over to headphones as that was simply the conventional wisdom of the time.
The diminishing practicality aside, there's also the space issue. Vintage multi-driver headphones often had the drivers overlapping each other, which presented as many challenges as it did solutions. More modern experiments had drivers side-by-side, but that greatly limits the size of the drivers and thus excursion force, but also presents potential problems with imaging.
It just makes more sense to apply that same development effort to make one driver that does it all, with some companies even going so far as taking what was traditionally just a tweeter driver and turning them into full-range drivers for headphones, such as HEDD Audio's Air Motion Transformer headphones. Those use a technology called Variable Velocity Transformation to produce different frequency ranges across the driver surface. Meze Audio's Rinaro drivers apply the same principle to planars.
Not that I don't absolutely love the experimentation.
The diminishing practicality aside, there's also the space issue. Vintage multi-driver headphones often had the drivers overlapping each other, which presented as many challenges as it did solutions. More modern experiments had drivers side-by-side, but that greatly limits the size of the drivers and thus excursion force, but also presents potential problems with imaging.
It just makes more sense to apply that same development effort to make one driver that does it all, with some companies even going so far as taking what was traditionally just a tweeter driver and turning them into full-range drivers for headphones, such as HEDD Audio's Air Motion Transformer headphones. Those use a technology called Variable Velocity Transformation to produce different frequency ranges across the driver surface. Meze Audio's Rinaro drivers apply the same principle to planars.
Not that I don't absolutely love the experimentation.
