[wualta]

Quote:

Originally Posted by AudioCats /img/forum/go_quote.gif 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......

It's my opinion (and only that) that the technical improvements wouldn't be worth the bother, because the enclosure the T50 driver is in is already near-optimum for that driver. Besides, the T50's not a basshead phone, though it takes bass boost nicely. Note how thin the T50 earpads are.

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.

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[facelvega]

Yeah, no offense, cats, it's not your fault that the gospel has spread on the goodness of those suckers. I wonder what a pair of donuts would go for on that site! Luckily I don't think Steve is going to go to the dark side anytime soon. And hey, how many of us would even know what a Fostex T50 was if it wasn't for this forum?

I also have to say, Spritzer's idea of an SR-X donut is intriguing, and would make for a fantastic level playing field for a vintage planar shootout.

 

[swt61]

LOL! You are correct Sir. I don't have any plans to deal with the eBay riff raff anytime soon.
The Stax Donuts would be a whole different animal, it might turn out great, but it's an unknown entity at this point. I'd certainly be willing to tinker with someone's, I just couldn't make any guaranties.

 

[wualta]

Quote:

Originally Posted by facelvega /img/forum/go_quote.gif Yeah, no offense, cats, it's not your fault that the gospel has spread on the goodness of those suckers.

Yes, and besides, with every little tweak we get better and better at improving our Orthos and Pro 30s and T20s, to the point where today they nip at the heels of the T50. There's no need to go hog wild for them anymore. Where they show they're still special is a certain liquid smoothness to the treble. It's like the difference in treble between, say, a Stax SR-5 and an SR-X. Or, more to the point, we can get at least as close to the T50 as the T50 is close to the SR-X, which it resembles.

The YH-100 has more bass (sometimes too much, depending) and can have a treble that's just as extended. In an optimized enclosure, I have no doubt that it could pull right alongside the T50.

And thanks to the efforts of FooTemps, swt61 and others, pretty soon we'll have Orthos that surpass the T50 in headstage. So don't become overly fixated on the T50. It's useful as a guide, something to shoot for in our experiments; its rarity shouldn't concern us overmuch.

For now, I'm going to concentrate on these inexpensive and most importantly readily available 38mm Sawafuji copies of the Audio-Technica driver and see just how much good stuff they've got in them. I don't foresee a shortage of these drivers in the near future. All we need is a good host 'phone, and by good I mean cheap, easy to take apart, enough room for damping materials, open back, thin earpads. Kind of like the Pro 30 but with an open back. Any suggestions?




In news of irritation, just got a Panasonic XR55 digital receiver (ostensibly to replace the iffy XR25 my son is using, which crackles as it wakes up), and found to my mild horror in testing it that the top end on it is different from my XR10, which is to say the whole top octave and a half or so is noticeably stronger on the XR55 even after two solid days of burn-in. Another rubber yardstick! How do they expect me to tune headphones properly if they can't keep digital amps sounding the same? Of course this receiver has to drive Heil-tweeter speakers too, so this extra brightness will shine right through. Great. I wish there was a way to determine which of the digital amps (well, the headphone outputs, anyway) is closer to flat.. sigh..

MAIOR ADDENDUM:
To recap: In 1980 Fostex changed the T50. In the catalog of that year there's a photo of a T50 with a single rather than double headband [below left; 1978-80 T50 on the right]:

This wouldn't be remarkable except that all the OEM T50s we've seen (Maior, NAD) also have this single headband. When ericj first sent me his Maior (which I could tell he wasn't thrilled with), I could tell immediately that they were different from the T50-- they weren't as flat. I blamed this on Maior (whoever they are) specifying a different "voicing" for a different market. A mere matter of marketing, though an expensive disappointment for ericj.

At first I thought the Maior had weak bass and an elevated upper midrange. Actually, what it has is normal bass and an even more elevated upper midrange. The response curve reminds me of the T20v1: nice and flat until you hit about 2.5kHz, where it zooms up, then plateaus until roughly 8kHz, then starts to drop off rapidly. In other words, a 'phone trying to sound like a pro audio monitor of the day. Aaarrrghhh! I'm beginning to suspect that when Fostex changed the headband in 1980 they also changed the 'phone and that the Maior may be (this is still just a hunch) nothing more than a faithful copy of the 1980-and-later ("Mk 2"?) T50. What a horrible thought.

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[AudioCats]

Quote:

Originally Posted by swt61 /img/forum/go_quote.gif I'd cast my vote for supporting someone here to win the T50's. We could decide who to support, and all agree to stay out of the bidding. That won't guaranty anything, but at least he or she wouldn't have to be dodging Head-Fiers too. These are a rare phone, and maybe should belong to a devout Ortho fan.

Yeah, a set of T50 in that condition and with a carry case (didn't say whether Fostex or not though), will likely go to a collector. They should not come to me (and my bid is low), I am too much of a tinkerer.

 

[ericj]

Quote:

Originally Posted by wualta /img/forum/go_quote.gif That won't happen anytime soon, because the T50's case is the driver. To extract the driver's guts would involve cutting away the plastic of the existing housing without disturbing the parallelism and alignment of the magnet grids. It could be done, but it'd be a nightmare, and the technical improvements wouldn't be worth the pain.

I've had the Maiors open more times than i care to rememer, and i can kinda second this: The best you could do is put a different cup on the back.

All the fostexen have that issue, though.

I'd have to measure (and they're at the lab, so i can't) but iirc the baffle diameter of the T50 is larger than the beyerdynamic struts can span. Trimming it down to fit into a wooden cup could get . . . . interesting.

 

[AudioCats]

Quote:

by good I mean cheap, easy to take apart, enough room for damping materials, open back. Kind of like the Pro 30 but with an open back. Any suggestions?

Koss TD60, small superaural pleather pads, solid baffle, room for damping, pops open by pulling the baffle forward (connects to the back housing with two ball-socket posts), driver size 40mm. They are closed back, but open sided (3/16" gap all the way around, with a foam seal), so they are still semi-open.
Comfort is good, though nowhere close to the 45x level.

 

[AudioCats]

What is the OD of a T50 driver?

 

[wualta]

Quote:

Originally Posted by AudioCats /img/forum/go_quote.gif What is the OD of a T50 driver?

Outer case is 100mm. Driver assembly is 85mm. Magnet grid diameter is 62mm.

Photos tomorrow. Turns out some of the screws holding my T50's case together are rusted, and I can only disassemble the left side.

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[wualta]

I was incorrect in saying the T50 case is the driver (and I've edited the earlier post), but the driver assembly is only slightly smaller than the case. And as I said earlier, the case is a good one.

Quote:

Originally Posted by ericj /img/forum/go_quote.gif All the fostexen have that issue, though.

The T30 driver is also still intact when you open its case, but you would still have to cut it down a little if you wanted all driver no baffle. The T20 and T40 driver clamps could be jigsawed out of their baffles. You could make your own clamp (see the photos of the PMB and Audio-Technica drivers) or glue the driver together as Yamaha did. But.

It isn't something you'd want to do.

And except for the T30, you really wouldn't feel the need to.

Well, the T20v2/T40v1 could use a true open back rather than a vented closed back, but the rest is pretty okay as it is. In my opinion.

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[AudioCats]

100mm!
wow, even bigger than the SFI midrange..... So the driver itself is somewhere around 80-90mm I supposed? Now I see why they are so expensive, collector value aside, a set of phones with such huge exotic drivers definitly won't be cheap.

Somebody should put them into a wood enclosure and tune them into super phones to rival the K1000

 

[ericj]

Quote:

Originally Posted by AudioCats /img/forum/go_quote.gif 100mm! wow, even bigger than the SFI midrange..... So the driver itself is somewhere around 80-90mm I supposed? Now I see why they are so expensive, collector value aside, a set of phones with such huge exotic drivers definitly won't be cheap.

The whole driver is in the 80-90mm range, yeah.

That vent on the back is essentially the effective size of the membrane.

And, yes, the T50 is the hardest anybody ever worked for isodynamic headphone bliss.

Instead of a single shaped ferrite on each side, they used the best magnetic material they had, in the form of little stick magnets, and glued them to vented steel plates.

It would be interesting to attempt to reinvent the T50 with modern magnets and membrane, but there are so many patents involved that pretty much Foster or Matsu****a/Panasonic/Technics would have to do it.

And they don't appear to be interested.

As for repotting them in wood, you have to understand that the original is just two layers of the "I don't know what this is but it isn't fiberglass" damping pads that only Stax, Foster, and Audio-Technica ever used, followed by an open vent.

Cavity resonances? There aint none. There's a tiny halo of open air around the driver, two fiber damping pads (that completely cover the back of the driver), and a vent the same size as the driver.

If the outer rim of the baffle is 100mm, that's the same size as a Beyerdynamic earpad flange. You could theoretically make a wood earcup that you could bolt the baffle to (iirc beyer earcups are about 90mm?), but what are you gonna do with it? Make the design less open?

I guess you could just make it prettier and more comfortable. I am Not A Fan of the fit and finish of the foster headband. It's basically comfortable once you get it adjusted but i spent 10-20 minutes getting them adjusted. There's just too much range of motion for something that big and that heavy.

The earpads on the Pre-1980 T50 wualta posted a picture of look fluffier than the pads on the Maior and the 1980 version of the T50 (which is a bit like a huge version of the Pro 30 earpad, but not as soft). That's less than a quarter inch of earpad. You might be able to devise some sort of bowl earpad but it has to sit close to the ear.

Wualta: Can you compare the Maior earpads to your T50 earpads?

 

[wualta]

[staggers over to chair after mind-numbing listening sessions on two different Panasonics] I'm awake!

I think. Anyway, yes, the driver is 85mm. I've edited the earlier post to reflect this.

I believe the pads on the T50 and Maior were at one time similar, but ericj is correct, the Maior pads are thinner, the material slicker and more like the PVC it is. The foam inside the T50's pads is intact, so they're still fluffed up, but I'll bet if we cut the Maior pads open, we'd find YH-2 foam. As Bones would say, "That foam's perished, Jim." The T50's pads are more leatherlike. I don't feel a big difference when they're on my head, but I do agree about the single headband. It's less secure, given the gimbaling the earpieces are capable of. It takes practice (and large hands) to pick up a T50 and put it on straight. It would make an excellent sobriety test.

Could Fostex have sabotaged their own landmark headphone? or was it Maior? Time to let Miss Marple in to solve this bafflin' case..

Anyway, for the last three hours I've been going back and forth with the Maior, the T50 and the Pro 30 on the XR10 and XR55, and it's true: with its dots in place, the Pro 30's treble sails on past the T50's. Of course, on some amps and to some ears, it would be considered too bright, but like the modded T40v1 it's so clean and smooth that it's hard to dislike, and on the XR55 it's downright amazing. To me. The midbass has a hump in it-- congested is a good word for this-- and it must be got rid of (I have a strategy in mind) [UPDATE: This turned out to be caused by insufficient pressure holding the damping felt against the driver, an easy fix], but even with that the bass extends as low as the T50's and is stronger. That's saying a lot for a cheap little sucker like the Pro 30, but ericj will soon have a chance to judge for himself.

Does the modded Pro 30 put far more spendy 'phones to shame? Shame is such an ugly word, and we're not finished with the modding process yet. Let's just say you'll want to get out your Lambdas to calibrate your ears. Does it have the same sense of effortlessness, the sense that there are reserves that would allow it to play at concert-hall levels and remain composed? No. The little diaphragm does have its limits. But the limits are benign and come on gradually. Once I get the midrange flattened down I'll give it a proper crescendo test.

Oh yes-- an odd thing about the front of the T50 driver: there's a brown nonwoven fabric ring glued to the front of the magnets that could be an attempt at symmetrical damping or else showing a need to cut down the exit aperture of the driver to the size hole you see in the earpad, or both.

.

 

[spritzer]

Quote:

Originally Posted by swt61 /img/forum/go_quote.gif LOL! You are correct Sir. I don't have any plans to deal with the eBay riff raff anytime soon. The Stax Donuts would be a whole different animal, it might turn out great, but it's an unknown entity at this point. I'd certainly be willing to tinker with someone's, I just couldn't make any guaranties.

Any of the vintage Stax would benefit from a better enclosure but it should be relatively open and not too long to minimize any tunneling effects. The SR-X would benefit a lot but the SR-Lambda would be totally transformed.

Now I need to buy a SR-X to send to you...

 

[Psiga]

Quote:

Originally Posted by ericj /img/forum/go_quote.gif It would be interesting to attempt to reinvent the T50 with modern magnets and membrane, but there are so many patents involved that pretty much Foster or Matsu****a/Panasonic/Technics would have to do it. And they don't appear to be interested.

I do wonder about that. If the T50's good model was born in 1980, then its patents are over 25 years old. They should be public domain at this point.