Finally found some photos of these oldsters on the 'net.

I'd read about these as a Toshiba product back in the late '70s and discovered that they used electrets in a unique way that wouldn't compromise the classic "true" electrostatic sound, plus allowing fully portable operation with standard 1/4" headphone outputs, so I said "This is for me!", sat down, folded my hands and patiently awaited their arrival in stores, whilst humming to myself a happy song.

Decades passed.

They never arrived.

Maybe some of you in the EU and Asia have seen them or even own them with the Aurex name. Aurex was Toshiba's luxury brand. The HR-910 was the top of the line:


Toshiba Aurex HR-910

This is the accompanying transformer box, which you would presumably plug into a standard 1/4" headphone jack. Note the selections: DIRECT; IMP[EDANCE] HIGH (1kohm)-- FOR AMPLIFIER; IMP. LOW (8 ohms) -- FOR TAPE DECK; and SPEAKERS.


HR-910 adaptor box

There were also a 610, 710 and 810, all of which had the stepup transformers built into a fat 1/4" phone plug.

The Toshiba is interesting both for its engineering and the fact that cosmetically it's very reminiscent of the Pioneer SE-700, a headphone different in almost every possible way but equally weird/unique/ingenious:

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Pioneer SE-700 piezoelectric-film headphone, late '70s....................Beyer ET 1000 electrostatic, ca. 1976

The Japanese website that holds photos of many early electrostats, including the Sony electrets and the Beyer ET1000, is

http://earsp.web.fc2.com/comp/comp.htm

-all photos stolen from webpages and eBay auctions-

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Sounds interesting. The 1/4 plug is unusual for electrostatics right? How did they design the electret? Is it similar to the sony electrets? Thanks for the link, btw and its good to see another uga alumni on board

Edit - It seems like every single company made an electrostatic headphone back in the day. I wonder why they quit making them? They sure sound whole lot better imo than dynamic headphones.

The Pioneers look like Beyers.

There is some resemblance to the Beyer ET 1000-- must've been the Scandinavian styling influence (furniture, flatware, tennis players, etc.) left over from the '60s.

The quarter-inch plug isn't that unusual among electret 'stats; the stepup transformers don't have to be huge (but it helps). They could be built into an inline "pod" in the cord like the Philips N6325, or into an enlarged (shall we say scrotal? we shall) plug like the one on the Toshiba HR-810. And of course they can be built into the earcups, as in the AKG 2-ways (eg, the K340), the Audio-Technica AT-707, and the Maruni ES-801. All of these 'phones plug straight into a standard headphone jack with no problems. Mostly.

Stax, as always, was the exception. They used big transformers in their SRD-4 transformer box, and the stepup ratio wasn't high enough to drive Stax's electret 'phones from a headphone jack (but I'll bet it could be made to work with a little tinkering). The closest Stax came to a portable setup that would plug into a 1/4" jack was the SRD-X amp.

The Toshiba is a "back-electret" type; the electret material is coated on the stators and the varying voltage is applied to a normal Mylar diaphragm-- the socalled inside-out style of electrostat. That way you could make the electret material out of anything you liked and make it as thick as you liked, since it didn't have to move.
 
[The only other electret headphone that used this design that I know of was the Audio-Technica ATH-8 (sold in the US as the Signet TK33), and the Toshiba realization is superior-- the response is flatter. See below.]

By the way, it's worth noting that electret-condenser microphones are all of the "back-electret" type now, since it has been shown over the decades to give superior results.

So if anyone sees or owns or knows anything about one of these, either as Aurexes or Toshibas, especially the HR-910, scream real loud, okay?

Thanks to Carl Of The Zealands, an alert reader whose excellent eyesight spotted a pair all the way over in England, a pair of HR-910s will wing their way across the Big Pond here to The Lab, where they will be lovingly dissected (sonically) and described. [turns suddenly evil:] At length! Ha ha!

Good job, mate. Now we'll see if they're as good in real life as they were on paper.

Interestingly, the seller claims that there are magnets in the earpieces. Hm. We'll see.

Good job.

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Could they be the electrets?

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Not on my part, certainly. If I wrote posts that compelled belief and dredged up mighty ancient headphone lusts and stirred the masses to throw over their German and Brooklyn masters, somebody might have bid on the HR-910 besides me!

As writer Cullers McCarson so memorably aphorized, the ear (or some other organ) has a lonely hunger. Or mangled words to that effect.

[hangs head] Obviously, like the demagogues and bloggeristas before me, I shall have to practice endless hours in chat rooms, the better to hone my pitiful rhetorical skillz. I will practice trying to convince little children to get their parents to buy them SportaPros. [slinks off with a pronounced slink, gripping greasy carpetbag full of greasy headphones]


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I'm not sure what the seller had in mind. We'll have to see what written matter, if any, accompanies the headphones-- this might give us a clue.

The bigger question is, why aren't these headphones better known? Why did they (apparently) fail in the marketplace? Unlike the Koss A/250, we can't blame the packaging.


Toshiba HR-910 in carrying case with spare earpads visible

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They've arrived, with that lightning Royal Mail speediness heretofore reserved for bringing me my weasel coffee, Lyle's Golden Syrup, Penguin bars, and anamorphic Region 2 DVDs.

The transformer box is small, about the size and shape of one of the smaller multiband portable radios. It's heavy, though, and all metal, with sharp corners, absolutely unsuited to pocket use. The back is covered with a felt pad so as not to cause furniture laceration.

The outer insulation for the headphone cord really is cloth, just like the cords on the other old 'stats like the SR-X Mk 3 and ECR-500 and on the ancient 'cans' used by old ham radio operators.

The headphones play at a very low but listenable level when plugged directly into a headphone jack.

When used with the transformer box, the setting that sounds best so far is the high-impedance one.

They are, as expected, very "flat" (which is to say "neutral", "accurate", "wysiwyg"), with a smooth, extended, utterly limpid high end, and we're talking about smoothness and flatness on the level of the Stax SR-X Mk3... but no deep bass. No surprise there, really, since many 'phones of the period, including the Mk 3, needed some help down there. Attempts to boost the bass on the HR-910 have so far resulted in the little transformer box gagging and taking the left channel hostage. Obviously there are some 30 year old spiderwebs in there that need to be DeoxiTed and/or parts that need to be pumped back up or updated.

The 'phones themselves are in great condition, with near-perfect channel balance and good "mono image", which indicates good channel matching up and down the frequency range.

The headset is very comfortable, which is very fortunate, since there are few adjustments. Oddly, the "spare" pads are not only spares, they're alternatives: the ear-opening is smaller, for folk with tiny ears, perhaps. Hard to say.

By the way, the low-impedance setting is louder, but it's tubby and bloaty. Still, this leads me to hold out hope for real bass some day, given some tinkering. I'm pretty sure one of the options is to power the 'phones from an amp's speaker outputs, and that might give some extra bottom-end oomph. Haven't tried that yet.

Not a whole lot of out-of-earpiece imaging, as shown by the Reflecting Hand (aka Open Palm) test: while listening to widerange program, you slowly bring your flattened hands, held parallel to the plane of the diaphragms, closer and closer to the back surface of the earcups, listening for the whooshy comb-filter effect caused by backwave reflections from your palms. Lack of the effect indicates the use of acoustic-resistance material (felt, porous nonwoven plastic fiber, etc.)-- bad for flat-out binaural, good for waveform fidelity.


In sum, an extremely tantalizing headphone. Extraordinary performance from a design that showed great promise, yet as far as I know these were the first and last of their kind, except for the Signet TK33, which isn't in the same league. A real pity.


PS: For the curious, a history of Toshiba (Tokyo Shibaura Denki) is here.







UPDATE: A poor-quality but readable scan of the owner's manual for the HR-910 has turned up:






And it turns out Toshiba did some OEMing. Here's the Rotel version of the HR-810:






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I am very interesting in this headphone, and I found many files about this headphone. But many people say electrets is short-lifed, after about 5 years, you must change the electrets. Is it ture? I have some pictures about Aurex headphones (from net), anyone interesting?

and, Would you mind tell me, how much did you buy it? I wanna buy one , but first, I worried about the life problem; 2nd, I thought it is a little expensive.

The style reminds me of my Echo electret headphones, which had their transformers inside the earcups.



A very clean sound to those but incapable of high volume and the pads were awful. I modded them with some NAD16 pads and sold them on for a few pennies. Those toshibas though are clearly the shiznitz on which these were based as some sort of cheap alternative.

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The myth of the short-lifetime electret dies hard. All I can tell you is that I've never seen a documented case of an electret that just died from old age without being exposed to fire, flood, ionizing radiation or scissors. I have seven pairs of electret headphones, most more than 30 years old, and all work fine. I did get stuck with one pair of partially-blown Stax SR-80 from That Auction Site, but they still made noise, indicating the electret properties were intact. I know that's not a scientific study, but I can say that my experience in no way supports the myth.

I paid the equivalent of US$50 plus shipping, if memory serves.

Where did you find "many files" about the Toshiba electret headphones?

oh, Thank you very much for your answer. My English is very poor, I found here:http://earsp.web.fc2.com/comp/comp.htm there are some hr serial headphones.

I'm pretty sure the stories of electrets giving up the ghost can be pinpointed back to the Sennheiser Unipolar 2000, which actually does have a rather bad reputation (deserved or otherwise) for just dying on people. Stax and Audio Technica electrets are generally still going strong today.