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Fostex T30 isodynamics (what, again?)

post #1 of 24
Thread Starter 

Many of you are probably tired of hearing me rant about this type of headphone and make wild unsubstantiated claims for them (sample: "This type of headphone has merit! YMMV! IMHO! DBM!"), but I have to say, they really do merit more attention than they've gotten, which is just about zero.

And thanks to the miracle of eBay, they're ridiculously cheap. Would you believe $22.50 for two? Only 2 people bid for them. Sad.

This was pro-audio specialist Fostex's second-best headphone from late '77 to who knows, probably '87 when the new line was introduced. They listed for well over $100.



For those who don't know what an isodynamic 'phone is, it's simple (in principle): draw a spiral of aluminum ink on a thin sheet of Mylar, stretch it just enough to make it flat, and sandwich it between two grids of powerful magnets. It's the magnetic analog of an electrostatic, with the simplicity of a dynamic but a sound more like an electrostat. This type of 'phone was popular in the consumer market for about fifteen years, from '76 to about '91, then dropped off the map, though Fostex still makes isodynamics for the pro market (there's a catch-- see below).

What we have in the picture is a 'phone with a very smooth-sounding response curve that is fairly flat in the midrange but tilts downward toward the treble and rolls off smoothly and gradually at both ends. Apply some EQ and... well, you won't believe what I'm about to say next, so just consider it mad hyperbole: they have more bass detail, and much more bass smack, than my Sennheiser HD-600s do, with or without added EQ. In my system, of course-- Your Mileage May Vary In My Humble Opinion Don't Blame Me and all that. All I'll say is that it's very interesting what kind of sound was being produced nearly thirty years ago. How good would they be if someone was making them now?

SPECS (from original September 1977 brochure):

Impedance: 50 ohms @ 1 KHz.
Sensitivity: 96dB @ 1 mW input.
Maximum Power Input: 200mW (3.2 Vac}
Frequency Response: 20Hz -35k Hz
Cord Length: 2.8m with 1/4" stereo plug.
Weight: 330g (without cord)


Edited by wualta - 8/29/11 at 8:53am
post #2 of 24
I would love to check these out. They look very interesting. I don't know anything about the technology of the driver, but it sounds interesting as well. On my way to see if I can find a pair of these somplace. Anyone else have any experience with these or similar headphones?
post #3 of 24
I think they look like Grado with dual headband and more comfy pads.

Nice find.
post #4 of 24
Damnit Wualta, look here: I'm done buying headphones. At least for the next month. Two weeks. Week. Days? Ok, you have no right to make me want to get more!

But... $20... that's not much... Hmmm, maybe ebay...

AARRRGGGHHHH!!!

P.S. I will check these out in a few weeks or so. I have a lot of interest in the sound other types of transducers create, as well as some quality vintage phones. What are the specs on these, in terms of impedance and sensitivity, and what do you drive them with? Also, you said this was Fostex' second best model, around the time. What was their best?
post #5 of 24
Thread Starter 
Quote:
Originally Posted by catscratch
But... $20... that's not much... Hmmm, maybe ebay...

Definitely eBay. I don't know of any other place where you could get old pro audio gear at such ridiculous prices.
 

Quote:
AARRRGGGHHHH!!!

There, there. I know. It'll be all right. Besides, these come up on eBay so rarely that even if your tramp of a wallet wanted to throw itself shamelessly at every Fostex isodynamic that came along, you'd still have most of your money left after 6 months.

 

Quote:
I have a lot of interest in the sound other types of transducers create, as well as some quality vintage phones. What are the specs on these, in terms of impedance and sensitivity, and what do you drive them with? Also, you said this was Fostex' second best model, around the time. What was their best?

There's little information on the web about the original '70s line of Fostex 'phones, even on Fostex's site. They've gone the way of all flesh, to coin a phrase. The T30 plays louder (ie, has higher sensitivity) than the average Yamaha Orthodynamic for a given input. Impedance 50 ohms, nearly purely resistive. That means the T30s are an easy load for any competent amp/preamp. They're less exotic than dynamics in this respect. They're not as sensitive/efficient as modern 'phones, though. They need an amp with some oomph (= current reserves).

Right now I'm simply running them out of the headphone jack of my vintage Hafler DH-110 preamp. The testing CD was Bela Fleck's greatest hits, by the way.

I tried them with my little MiniDisc portable recorder with its bass boost on and got up to some very respectable levels without hearing the crunch of chip amps in distress. 

Fostex's top model in the '70s and '80s was the T50 (not the current T50RP), a very nice 'phone indeed. The T50's sensitivity is more like the Yamahas', a few dB lower than the T30's. Interestingly, while the T30 is rather dark and has real bass capabilities (especially when some deep-bass EQ is dialed in), with a response that tilts downward toward the treble, the larger T50 is more flat overall, and has an extended high end. Very different-sounding 'phones in terms of frequency response though very similar in "signature". For example, you can hear the telltale isodynamic articulated treble on both 'phones, despite the T30's dark character. Based on experience with other tilted-respone 'phones, I fully expect that with a change of damping material the T30 can really come into its own, though it will remain a shockingly uncomfortable 'phone to wear.


Take a peek at this post for a look at the T50, then maybe slog through at least the first few pages of this thread to get an idea of the tradeoffs and compromises involved in this kind of driver and what you can do should you bump up against a headphone containing one.


Edited by wualta - 8/29/11 at 9:12am
post #6 of 24
Sweet. I guess that I'll now be one of 3 or 4 people worldwide on the lookout for these phones!
post #7 of 24
Thread Starter 

A LOOK AT THE T20

Quote:
Originally Posted by catscratch
Sweet. I guess that I'll now be one of 3 or 4 people worldwide on the lookout for these phones!
Good luck, and welcome to Lost Cause Fi. Sorry about your reputation.


Aside from the now-rare T50, there was one more model-- actually two more-- in the original Fostex T series, introduced in late 1977. One was world famous: the first-version T20 (pictured below). You see it being worn by studio musicians on a lot of old LP jackets. Big circular Mickey Mouse deep-dish supra-aural earpads that formed a kind of tent over your ears but with a fairly conventional isodynamic driver inside, which is to say, more like the Yamaha Orthodynamic consumer line-- no fancy magnetic materials, perforated disc magnets instead of a grid of bars, spiral voice coil rather than serpentine. Then there was the T10, but I only remember it from the Fostex handouts twenty-five years ago. Looked vaguely like a T20, with a similar but less efficient driver. I've never actually seen one. And I've never heard a T20.

UPDATE: I now own an old T20, thanks to member Tyre. Very comfortable, much more so than the T30. Disassembly shows a small (45mm) driver looking very much like the ones in the Yamaha's much later YHD series. The sound is... well, there's an upper-midrange plateau and then the treble slopes off steeply. Listenable, certainly. Smooth. Like an old Sennheiser but with better bass. No high treble, so it's a little like listening to current-day FM radio. The damping pad is a wad of closed-cell foam.. hmm.. this could be improved. [UPDATED UPDATE: It can. See later posts to see the results of damping] Still haven't heard or seen a T10, but Tyre is holding on to his, which tells you something.

Studio 'phones lead a rough life. T20s in varying states of disintegration show up on eBay fairly frequently, but prices vary all over the lot. A pair went recently for $25 and included a meter bridge/headphone amp for an old Fostex reel-reel machine!

ca.1978 Fostex T20....photo by TYRE

.
post #8 of 24
Quote:
Originally Posted by wualta
There was also a T10, which as I vaguely recall looked like a T20, but I only remember it from the Fostex handouts twenty years ago; I've never actually seen one.
I have a pair of minto condition T10s...any idea if they're any good? I really don' know what to compare them to. My UM2s are so much more efficient it's hard to compare. The iPod will barely drive them, although with it all the way up, they sound pretty nice. Haven't really listened to them analytically yet - just re-discovered them in a box of old stuff I had in storage....

Andrew
post #9 of 24
Thread Starter 

A LOOK AT THE T10

Quote:
Originally Posted by hook
I have a pair of minto condition T10s...any idea if they're any good?
Sure they're good. UPDATE: Since doing this thread I've been able to collar a T10 on eBay-- they're basically the old T20 minus the big Mickey Mouse earpads. . but the driver is very different (see below) and they have mineral-wool damping like the top Fostex models of the day. They actually sound better in stock form than the old T20 and should have good/easy modification potential.

Quote:
Originally Posted by hook
I really don't know what to compare them to. My UM2s are so much more efficient it's hard to compare. The iPod will barely drive them...
Yeah, they were never designed for portables. These are pro or semipro 'phones designed for testosterone-crazed pro electronics capable of putting out some serious juice. You need a good stereo amp from the '80s or '90s with a really good preamp or else a dedicated headphone amp.

Try to find something solid to plug them in to and let us know what you think.


FOSTEX T10


FOSTEX T10 DRIVER-- photo by TYRE
post #10 of 24
I have a pair of T40s that I really don't use anymore. Nice sounding cans but they don't work for my usage. Anyone interested?
post #11 of 24
Wow 20 bucks for two of them? I was actually trying to hunt down some Fostex 'phones on ebay a few months ago. But for like 3 weeks straight, even the T20's got bid up to over $60 - which for me personally is too much for a relatively unknown pair of cans. I might try looking for them again if they're down this low -- but this thread probably will push it back up
post #12 of 24
Thread Starter 

As I've posted elsewhere, I was wrong in my original post to give the impression that no one was still making 'phones like the T30. Strictly speaking, it is true-- no one, including Fostex at the time this is being written, is still making the big 60mm elaborate bar-magnet / serpentine-voicecoil type drivers like the ones found in the T30 or the old T50. But unbeknownst to me, Fostex was making the simpler 45mm spiral-coil / perforated-disc-magnet variant until very recently. This is the type of driver used in the original T20; RedLeader first showed me that Fostex had been producing a version of it with photos of his T40. Big thanks to RL for that.

Fostex uprated the original T20 driver to use in the first-version T40 (1996?-2006), aka the T40v1, and the second-version (1986--2006) T20, aka the T20v2-- both now, in 2006, sadly being phased out.

So the good news is that you can still buy some of the old-style Fostexen new-in-box if you look hard enough, and they're not that expensive, and weren't even when new. The bad news is that these models (T20v2 and T40v1) are being replaced by Mk II versions which externally look almost the same, will be confused with the earlier models by eBay sellers and even b&m stores, but don't sound anywhere near as good, at least in stock form.

This post will help you tell them apart. Good luck.


Edited by wualta - 6/13/11 at 6:36am
post #13 of 24
post #14 of 24
Thread Starter 
Sixty bucks including shipping isn't bad-- it's not great but not bad. If they don't go much higher than that, grab 'em.
post #15 of 24
Quote:
Originally Posted by wualta
Many of you are probably tired of hearing me rant about this type of headphone and make wild unsubstantiated claims for them (sample: "This type of headphone has merit! YMMV! IMHO! DBM!"), but I have to say, they really do merit more attention than they've gotten, which is just about zero.

And thanks to the miracle of eBay, they're ridiculously cheap. Would you believe $22.50 for two? Only 2 people bid for them. Sad.

This was Fostex's second-best headphone back in the mid-late '80s. They listed for well over $100.



For those who don't know what an isodynamic 'phone is, it's simple: draw a spiral of aluminum ink on a thin sheet of Mylar, stretch it just enough to make it flat, and sandwich it between two grids of powerful magnets. It's the magnetic analog of an electrostatic, with the simplicity of a dynamic but a sound more like an electrostat. This type of 'phone was popular for about fifteen years, from '76 to about '91, then it dropped off the map.

What we have in the picture is a 'phone with a very smooth-sounding response curve that is fairly flat in the midrange but rolls off smoothly at both ends. Apply some EQ and... well, you won't believe what I'm about to say next, so just consider it mad hyperbole: they have more bass detail, and much more bass smack, than my Sennheiser HD-600s do, with or without added EQ. In my system, of course-- Your Mileage May Vary In My Humble Opinion Don't Blame Me and all that. All I'll say is that it's very interesting what kind of sound was being produced nearly twenty years ago. How good would they be if someone was making them now?

so if these were their second best phones, which were their best ones? and do they operate via the same principle?
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