T50 compared to YH-100
Does that mean if the T50 drivers go into the donuts, the end result will be super duper killer bass with nice everything else? Dangerous......
The difference between the YH-100 and T50 drivers is the difference between an acoustic-suspension woofer and one designed for a guitar amp cabinet. One only sounds right when it's in an enclosure that supplies resistances and compliances which, when added to the characteristics of the driver itself, yields (if all goes well) great results. Since every headphone has to contend with being pressed up against someone's ear with earpads that either form a sealed cavity or a leaky cavity or a damped cavity, and every headphone has to contend with reflections of the forewave and backwave off of ears, scalps, earcups, wires, grilles, etc, a designer has to account for the final form the headphone will take when he settles on the characteristics of the driver.
Like the open-back guitar amp cabinet speaker, the T50 is designed to operate more or less self-sufficiently in free air, with no help from the surrounding enclosure, with minimal damping and a low level of backwave reflections. It uses leaky but semisealing earpads that hold the diaphragm about a half inch away from the outer ear. All these things are accounted for in the design. Pull it away from your head even slightly and the bass disappears and the balance is lost. With a slight reduction in diaphragm tension, the T50 could play the part the YHD-1 failed at: operating entirely in free air in close proximity to the ear, for max soundstage-- sort of a nearer-nearfield K1000 that's much easier to drive. I like the compromise the T50's designers took, though. Whatever damping the fake fiberglass supplies, along with absorption of the backwave in the mids and highs, does the trick. Put anything denser than that near the diaphragm and you'd upset the balance with reflections and changes in effective diaphragm tension-- in other words, you'd kill the bass.
The YH-100 driver is like the acoustic suspension woofer, which only sounds good when acoustic resistance and backwave pressure act to acoustically support (ie, stiffen) the diaphragm. All this support comes from the enclosure, which becomes in our hands a rack for holding various means of adding or subtracting resistances, or trapping air pockets that act as springs and change the resonant frequency of the system, etc etc. We insert or remove discs of felt, chunks of foam, wads of cat hair, activated charcoal, anything we think will work. Yamaha left it up to us. This is what makes the YH-100 a good (not great, but good) candidate for a transplant, as swt61 has shown with his Strawberry Donut[phone]s. The T50 is already sounding as good as it ever will, and will frustrate and disappoint the heavy-duty tinkerer unless he has a way of retensioning the diaphragm.