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Speaking of old orthos, do you use the old T50 you got a lot, or is some other can getting all the head-time?
The T50 or the now-aged Stage One Yama YH-100. If I'm just pfarting around, the Audio-Technica ATH-FC700. The modded Pro 30 gets a listen now and then too, since it's been with me for... well, longer than many of you have been alive. A frightening thought.
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Yamaha really left out dampening materials to save costs from materials? How much does felt cost, especially when purchased in bulk for a production run like that? Can't be more than a couple cents per phone. They probably already had the R&D done. I imagine the engineers were listening to their proto YH-100's damped to perfection
Yes. I'll bet a dozen good doughnuts that they could hear just as well as we can and that they were bothered by the underdamped resonance too. Somebody told them it sounded good the way it was and to leave it alone already and kick it out the door. More seriously, I imagine someone took a hard look at where American tastes were in 1976 (lotsa bass, who cares about the rest), figured they could save a manufacturing step (possibly a gluing-by-hand station; equals expensive) if they just tossed the driver in the cup and screwed the baffle on-- and of course on the cheap model they eliminated the screws. As always, it's the labor and setup costs that hurt, not the materials. Sometimes it doesn't take much to tip the balance and make the money guys say "whoa-- we can save some money if that doesn't happen". Remember the
Corvair.
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^^ not totally true.
They did use foam on the back of driver. Also the vents are damped with a thick felt like material.
The front of HP50A has a white fleece paper like material.
And the YH1k had the whole differential dampening scheme.
I believe that while they realized that the best way to dampen the drivers was differentially with multiple layers of accoustically different materials, but the costs involved with the process were probably too high to be transferred to anything but their flagship headphone.
And felt was hardly the material used in any of premium vintage planars. The choice seemed to be a yellow fibreglass like biscuit & that stuff is actually a bit costly.
Well, we're leaving the YH-1K out for the moment because it's an outlier, but although a lot of people just love it, to my ears the YH-1k is a typical 'phone of its time, very midrange-centric. It's as if they tuned the diaphragm higher (by making it lighter or decreasing the compliance somehow), necessitating absorptive material rather than acoustic-resistance material, the same as we find in the '70s stats. Stats' natural resonant frequencies, due to their lighter diaphragms, are in the midrange, sometimes the upper midrange, sometimes even higher.
The reason we use felt on our lesser vintage orthos is because their resonant frequency is in the bass, and the bass is where the diaphragm has to really move. That's lucky for us, because we can just add an acoustic series resistance and preferentially (though some might say differentially) suck the energy out of the resonant peak. But when the diaphragm isn't displacing much air, as in the upper midrange, that kind of damping won't help. That's why with the Staxen and A-Ts and in the single case of the YH-1k, the designers resorted to absorptive pads, and often this wasn't enough, as anyone who's listened to an un-EQ'd TK-33 knows.
The orange/yellow foam disk in the first-gen Yama Orthos is simply there to prevent rattles. It's just about useless for damping.
You do bring up a good point about the damped vents, though in their case it's backwave management rather than the overall sound Yamaha was concerned with. All I can think of is that the felt inserts that cover the vents were necessary to keep the bass up, and that must've been the overriding concern, because they stayed and the felt on the back of the driver didn't. Again, the hand of A-T seems to be at work here-- the ATH-5 and ATH-8 (aka the TK-22 and the TK-33) have similar venting, though, oddly, their vents aren't damped. The rest is a shrug. Again one wishes for the ghost of a Yamaha designer to come have a cup of tea with us and tell us the story.
As for the paper (or whatever it is) in the HP-50, I haven't disassembled mine so I can't be sure what effect it has, but I suspect it's there to shave off some treble.
