Damping is simply about getting control of the diaphragm.
Even the largest of the vintage ortho diaphragms (the Fostex T50/30 and their OEM variants) can't catch enough air to be damped by the air load. Any springy thing that's vibrating with nothing to stop it will
keep vibrating, and it will vibrate over a predictable range of frequencies if the mass and springiness and losses are known. So it is with the vintage orthos-- they all had a slowly-falling treble and a broad resonant hump centered on the mid-to-upper bass. When given a step input, like the one produced when a phono stylus hits a groove boulder, this resonance would be excited, and it's in the nature of an excited resonance that the energy from the step input will be stored in the hump and released over several cycles so that a sharp tick or click would be smeared out into a distinctive
pwock. Describing it in words this way necessarily exaggerates the effect, but once heard, it's obvious, and obviously wrong. Wrong in the sense that the diaphragm is not following the input.
So whatever other benefits damping an ortho driver might have (and there are a few, including backwave control and a flatter frequency response), the primary reason is to make the diaphragm able to stop when the signal stops. Dynamic headphone drivers are almost always damped, so why not orthos?
This is
not to say that an undamped ortho driver can't be enjoyed; it certainly can. It's just going to have certain characteristics which will make it fail certain tests. If those tests don't reflect real-world use, and the known defects don't matter, then there's no argument. The droopy-treble and the bass-hump problems can indeed be solved in other ways, with earpad manipulation, for example. So there are many ways to make an ortho enjoyable, and the basic ortho virtues will shine through. But if you're after the ancient ideal of waveform fidelity, damping is necessary.
Has anyone revisited the old idea of using felt or fabric plugs in the magnet holes, taking the damping that little bit closer to the diaphragm? ..Like this:
Quote:
Originally posted by joelpearce:
I sometimes wonder if that would improve those vintage PMB-80s. ...those big drivers ought to be able to do something special...
My feeling too. I couldn't figure out what the heck was going on with the PMB drivers, and put them aside because there were other projects that promised easier results, but I still feel there's some unlocked potential there. What first leaps to mind is "TRANSPLANT!", but maybe that's not necessary. Maybe getting them out in free space will give you a clue.
