Orthodynamic Roundup - Page 2

I have a pair of flat-pad SR-80s. I've only compared the Grados directly to the modded (that is, damped) YH-100s.

The first thing you notice is the big difference in efficiency, about 10dB, in favor of the Grados. Aside from that, the overall sound is surprisingly similar, but in my setup at least, I found the YH-100 to reach lower and play cleaner in the bass and stay smooth and transparent in the treble while the Grado clouded up a bit. These differences weren't huge, but they were obvious. You could listen farther into the music with the Yamahas. The Grados airbrushed the music. Both were pleasing. They cost about the same (I bought both used). I wouldn't want to give up either one.

I hope that answers some of your questions.

UPDATE, LATE 2007: By sheer cussed persistence and good Team Ortho work in coming up with simple, cheap reversible mods that tackled the problems of response extension, headstage and damping as they arose, it's my humble opinion that we've brought the sound of the best Orthodynamics and isodynamics to a point that far surpasses the sound of my Grado SR-80 and moves it up (with some reservations) into competition with the sound of all but the best electrostatics. Others may disagree, of course. Read on to find how we did it and what we learned along the way.

Before I start in on the YH-1 and YH-100, it would be good to point out that the isodynamic headphone driver (and this includes all the Orthodynamics) is inherently a dipole-- it radiates sound equally out the back and front, which means that if, when the headphone comes to be designed, the backwave isn't absorbed, deflected, baffled, delayed or otherwise prevented from mixing directly with the frontwave, the bass will completely disappear, since the front and back waves are equally strong and have a kind of matter-antimatter relationship, especially for bass frequencies-- we say that the two are 180 degrees out of phase. They must be kept apart. This is both easier and more complex than it sounds.

Moving-coil drivers can have a strong backwave too, but often this is attenuated, sometimes to zero, by the construction of the individual driver or the cups they're mounted in. Sennheisers have long been a notable exception.

The point is that the backwave must be dealt with. Since letting it leak past the driver's baffle (that is, the surface the driver is mounted to, the one inside the earcup that almost touches your ears) and into the space where your ears are would cause a severe lack of bass, the designer of good open-back 'phones first makes sure the driver is sealed airtight to its baffle, then sends the backwave directly out the back of the cup through something like the "tunnels" on the back of the more expensive Grados, and doesn't put anything in the way that would reflect any of the escaping soundwave back toward the interior of the headphone. This delays the backwave enough so that any bass cancellation that happens due to incomplete earpad sealing is much reduced. The out-of-phase information can even serve to enhance the stereo effect, but consideration of this sends us off to the black art of headphone design, a topic best left for another day.

There's another consideration for Orthodynamic owners, though: If the treble backwave bounces around the inside of a hard, reflective, closed cup, some of it will bounce right back into and through the diaphragm and into the listener's ears. This is tantamount to putting a wastebasket over the listener's head, since the brain interprets the resultant sound as "big flat surface close to my ears". This isn't hugely oppressive in practice, but the collapsed soundstage of the closed-back Orthodynamics is noticeable when compared to other, more open, headphones. Installation of damping pads alleviates the claustrophobic feeling a bit, but the soundstage is still "closed".

The radical YHD-1 was both open-back and open-front. That ought to've solved the problem, right? Yes and no. We'll get to that in the next installment.

* * * * * * * * *

YH-1




Since owners of the HP-1 have often spoken of it as THE Orthodynamic, I was surprised to see and hear how similar the YH-1 is, especially in view of the price difference ($200 vs. ~$95). As I said, both were top of the line for their respective model years. In any case, the YH-1 doesn't represent an advance over the HP-1's design in any respect, nor does it seem to be a backward step (in the direction of cheaper construction, &c). What audible difference there is between the two seems to give a little more bass to the YH-1 at the expense of treble extension, once the 'phone has had the damping treatment, but the difference is very minor and could be explained by any number of things.

I'm not certain of the chronology of the YH-1; that is, I don't know when it hit the US/NA market, and I have only basic specs for it. So far, they're identical to the HP-1's:

Impedance: 150 ohms

frequency response: 20-20,000Hz

Rated input: 3w

max input: 10w

Harmonic distortion: < 0.3% at 90dB SPL

Since the YH-100 of 1981 shows both stylistic and electromechanical differences, and the YH-1 and HP-1 are virtually the same, I'm going to assume the YH-1 was an attempt to make a more affordable HP-1 some time between 1976 and 1981.

I can only speculate on the HP-1a, which has only shown up in a single Yamaha brochure [see above] that also shows a square-holed driver. The only mention of it in a magazine was Hans Fantel's test back in September 1975, right around the time the Orthodynamic line was about to be introduced to the US market. It's just possible it was a marketing name for pre-production HP-1s, the ones sent out to reviewers.


* * * * * * * * * * *

YH-100




In any case, the YH-100 shown above is the only top-of-the-line Orthodynamic other than the rare YH-1000 not styled by Mario Bellini. In fact, in this case there is no line in the usual sense. The YH-100 was alone; there is no YH-200 or 300.

It's heavier than the HP-1 and appears to be more substantial except that it has those same @#$! plastic struts. The earcups are bigger, 80mm in diameter versus 72mm. The center opening of the earpads has grown proportionately, making the pads rest partially on and off the ear. Inside, the driver has changed: despite the larger earpieces, it's the same 55mm as the HP-1, but there are thin perforated metal plates covering the front and back of the ferrite "sandwich", presumably to give a boost to the flux gap's field strength and thus to the 'phone's efficiency (about +4dB).

Most importantly, the diaphragm's natural resonant frequency has been lowered, either by increasing the compliance (different pleat shape?) or by thinning the diaphragm material. However it was accomplished, it has the effect of moving the diaphragm's resonant frequency and bass cutoff down an octave or so. Keep in mind that this is speculation based on how the YH-100 sounds compared to its brothers and how it responds to added damping-- taking the magnet sandwich apart for observation or measurements, tempting as the prospect is, would almost certainly destroy it. If someone would like to donate a burnt-out YH-100 (or any other Orthodynamic) so that photos and measurements can be made, PM me.

A more compliant diaphragm should be more capable of "real" bass. Unfortunately, no extra mechanical damping was added to control the expected greater excursion of the diaphragm. The result: a smooth but dull, bass-heavy and hollow sound that was at first very discouraging.

* Frequency Response: 20 - 20,000Hz (no tolerance given, sigh)
* Magnet: anisotropic ferrite, 55mm
* Impedance: 150 ohms
* Sensitivity: 98dB/mW
* Rated Input: 3W
* Maximum Input: 10W
* Weight (with cord): 390g

Note that the power handling specs are up to HP-1 levels.

Once damping is added, the YH-100s become the most entertaining, if not the flattest, of the Orthodynamic line so far. This is the one whose sound changes most after damping treatment. Especially with a little goosing in the low bass, the sound of the YH-100 could be soberly described as powerful. This, understand, was a great step forward for isodynamic phones, since until the YH-100 their deep bass output had always been referred to, when referred to at all, as polite -- but this one rocks. Sounds good on classical too.

Some lumpiness in the upper bass remains after my primitive damping treatments, but overall the sound resembles what one would expect from a good modern phone, except of course for the low efficiency and the partially-collapsed soundstage. Yes, I've compared them to the Stax Lambda Nova and the Sennheiser HD 600, and no, I don't hear any transient "crippling". In fact, in some respects (a quality of dry liveliness, snap, alertness, the ability to leap instantly out of silence and then return to silence just as quickly), they are moderately superior.

Unfortunately, the YH-100 appears on eBay less frequently, roughly every 2-3 months. Otherwise, of the Yamaha Orthodynamics I've heard, it's the recommended buy-- if you're willing to intervene and install damping material. Out of the box, the HP-1/YH-1 sounds much better. Don't buy a YH-100 unless you're willing to take it apart.

Next, the lovably weird (but fatal) YHD series and the end of the line.

* * *

Late addition to the menagerie:


a Bang & Olufsen U70-- Styled by B&O's Jacob Jensen and made for B&O by what was a merger of Peerless and MB Quart known as PMB, with specs a notch below the HP-1's but with interesting driver differences: the 55mm ferrite discs have tiny holes, perhaps to add acoustic resistance (ie, damping)..? My sample came without earpads, so there's no bass... yet. Very odd (but of course very stylish) construction-- note that there is again no direct venting of the backwave, giving us the same problems as the Yamaha design: dipole driver firing straight at a blank wall. PMB did add damping in the form of two thick felt pucks that are wedged between the back of the enclosure and the back of the magnet. This, it turns out, is standard damping for PMB-built 'phones, but doesn't guarantee there will be any bass or even that the treble will be flat. See for comparison later in this thread for info on the Telefunken TH 700 and Peerless PMB 100. The B&O's driver looks just like the Telefunken's and the PMB 100's (second version). Also search for other posts by HF member torrid ear, in real life MB Quart's Willi Presutti, for photos of the 55mm PMB driver used in the PMB 100 and some interesting history and commentary.

U70 Headphones

UPDATE: Adding earpads to the U70 gives a surprising, disappointing result: the pads keep the backwave away and increase effective bass output, but the whole upper octave seems missing! It goes out flat, then seems, subjectively, to drop like a rock. For a panicky moment I though I'd gone partially deaf, as little twiddles on tambourines and other tinkly details were wiped out of certain test songs, but it turns out to be due to some failing of the U70's drivers. So for now the ultrastylish U70 remains a looked-at rather than listened-to headphone, at least for me.

Interestingly, B & O's next headphone used a conventional dynamic driver and was more or less properly vented. So why couldn't they have done the same for the U70?

More to come...

YHD Series

If you've read this far in the survey of Orthodynamics, you probably won't accuse me of overpraising Yamaha's design efforts up to this point. The drivers had great potential, yet a goodly chunk of that potential was tossed aside for the lack of a 10-cent damping pad. The rest was partially spoiled by the strange location of the earcups' vents, as if the headphone contained a standard dynamic element rather than something a little more special.

This wasn't a case of a design being bad; rather, it seemed to have been left unfinished.

Yet the headphones still sounded pretty good to many buyers, enough to encourage Yamaha to carry on.

And the HP and YH headphones sound good enough today, given laughably minimal tinkering, to make you stop and wonder.




YAMAHA YHD-1 / YHD-2


Around 1985, someone at Yamaha stopped and wondered how good their Orthodynamics could sound if the drivers were liberated from those bad-news earcups, as Xanadu777 did in this thread. By now the headphone market had decidedly shifted to small, lightweight, efficient 'phones for portable tape players, so Yamaha and Mario Bellini took advantage of this change and started from scratch. First they came up with (or bought from an OEM) a tiny but powerful driver which let them shrink the whole headset. At some point in the simplifying process they were inspired to do away with cups entirely. Then, while they were at it, why not, they dumped the earpads too. The result was a wonderfully elegant, simple, compact, functional design stripped to the essentials.

In the YHD-1/2 the virtually naked driver was held lightly right up against the ear in a spring-loaded frame, letting the driver operate as a proper dipole for the first time in Orthodynamic history. As far as I know, this was the only cupless/padless design ever marketed by a mainstream manufacturer, at least until AKG's K1000.

Here's what the 38mm YHD-2 driver looks like:

The holes look much smaller than the holes in the 55mm drivers, and it's not just an illusion-- they're about half the diameter. Interestingly, a very similar driver but with thicker magnets and fewer, much larger holes had shown up in the Audio-Technica ATH-1 and ATH-2 and the Realistic PRO-30 about 5 years earlier. Obviously those three are from the same OEM-- or I am very much mistaken. Could they have built the YHD drivers too?

A major change was made in driver design, aside from the obvious reduction in size. Note that there is no wire coming out of the middle of the driver, as before; both lead-ins are available right at the driver's edge, as the photo above shows. This means that the center of the diaphragm in this type of driver is free to move, since it doesn't have to carry an electrical connection. Another difference is the diaphragm is tensioned and smooth rather than pleated or corrugated. This is the type of driver that was used from the start by Fostex, and is directly analogous to the clamped, tensioned diaphragms found in all electrostatic headphones.

Could the greater diaphragm excursion possible with the tensioned design be responsible for the higher efficiency and healthy bass output of these much smaller drivers? I suspect so. At any rate, in terms of diaphragm construction, the entire isodynamic headphone community, what was left of it, was now finally on the same page with the introduction of the YHD series.

The only problem was that again there was no mechanical damping, so the bass, while certainly present in sufficient quantity, lacks clarity and punch, and the treble rolls off gradually after about 1kHz, making the 'phones sound dull.



DIFFERENCES IN THE YHD-1
UPDATE 8-1-06: Finally obtained a YHD-1. My sample sounds a little bassier than the YHD-2 and is more efficient but is otherwise similar. I have not yet heard the YHD-3-- with the cups offering some delay and attenuation of the backwave, it could be a sleeper, though the drivers aren't as efficient as the YHD-1's.


INTRODUCING THE YHE-50S



UPDATE 10-25-07: I still haven't heard a YHD-3, but I have tested a rare variant, the YHE-50S, specially built to accompany Yamaha's Electone line of electronic organs. It's tiny and cute-- the earpads you see are only 53mm O.D. I don't know how its internals differ, if at all, from the YHD-3's, but though it sounds dull due to the typical lack of damping, it does have both decent bass and decent headstage. If the YHD-3 is at all similar (it has flat foam pads instead of the little donut supra-aural earpads of the YHE-50S), it really is the sleeper of the Ortho line. Who'da thunk? The specifications for the YHE-50S are the same as for the YHD-3, below.




SPECIFICATIONS FOR THE YHD SERIES (YHD-1 / 2 / 3):

Diaphragm Thickness: 6 microns. Note the halving of diaphragm thickness compared to the original series. This driver has been miniaturized in more ways than one-- it's been properly scaled down. The thinner diaphragm is [probably] lighter, giving us a little more efficiency.

Impedance: 125 / 125 / 125

Magnet: 38mm / 38mm / 38mm
anisotropic ferrite / isotropic ferrite / isotropic ferrite

Sensitivity: 100dB/mW / 97dB/mW / 98dB/mw The YHD-1 is more efficient than the earlier Orthodynamics, but not as efficient as the YH-1000 (see next post). Note the odd jump in sensitivity for the YHD-3.

Rated Input: 1W / 0.7W / 0.5W

Weight: 167g / 155g / 142g.



END IN SIGHT
Earlier, Frank W asked why, if these isodynamic type headphones are so darned good, they're not made any more. If they shelled out for the YHD-1, they may have wondered where the treble went. Beyond that, even the trimmed-down YHDs are still much heavier than the typical miniature dynamics just then flooding the market.

So how did YHD owners react? Mostly, by now they figured that if Yamaha couldn't deliver the Orthodynamic Promise with light weight and tiny size, it just couldn't be done, and therefore they'd already seen the best an isodynamic 'phone could do. Add to this that most portable tape players already came with headphones that were good enough for most folks. For the audiophiles, the promise of a rugged dynamic with some of the virtues of an electrostatic just wasn't coming true.

It was a bum rap, of course, but the market was moving on. The YHDs were the last signpost before the dead end for all isodynamics in the US consumer market around 1990.




WHY OH WHY
The question keeps coming back: why did Yamaha never try simple mechanical damping of the driver? It would've saved not only a line of headphones but an entire type of headphone. The interesting, puzzling answer is that Yamaha did see the need, and did use damping, but only once, and that was in the expensive and hyper-rare HP/YH-1000 (see next post).



MEANWHILE, BACK AT FOSTEX


PHOTO: TYRE

One company was making an audiophile-grade isodynamic headphone with a reasonably well-damped diaphragm and properly designed open-back earcups, but that company was Fostex, and the only dealers selling their very expensive T50 headphone (above; introduced to the NA market in 1977) were pro audio dealers. Fostex's original NA-market T50 [hereafter called the T50v1, though there was also a T50v0] sounded better straight out of the box than any of the unmodified Yamahas simply because more attention was paid to the details. Its only fatal flaw was, and is, rarity. It's discouraging that the newest of Fostex's current production isn't of audiophile quality and requires the driver to be cut out and remounted to achieve audiophile quality. [EDIT: This has changed somewhat with the introduction of a different earpad design. Do a search for the T50RPn] Other Fostex 'phones require modding in a manner similar to the Yamahas, with a similar, and sometimes better, result.


PROSPECTS
So the audiophile isodynamic/planar-magnetic/magnetostatic/orthodynamic headphone quietly awaits a manufacturer that will develop the type along the lines already described and bring its strengths to the audiophile market. How long do you suppose we'll have to wait? [Four years.]

Meanwhile, we have the damped YH-100 as a useful preview of what should come. And the short-lived Monsoon multimedia speakers, as a kind of tease.

Yes, I have a pair of those too.


EPILOGUE
Hope this series of windy essays has been of some use. I invite corrections, specs, scans of brochures and descriptions of other Orthodynamic models by Yamaha. I'd also like to hear descriptions of the models marketed in Europe by companies like Wharfedale, Leak, Peerless/MB Quart (aka PMB), PWB (Peter W. Belt), Grundig, Dual, and Eagle.

There were isodynamic headphones made all over the old Soviet Union with brand names like Amfiton, Echo and Elektronika. Some were copies of Yamahas, some were influenced by Fostex, many were downright original. In this thread you'll see several of these models depicted and dissected. I've heard one of these, an Elektronika TDS-5M, and it's every bit as good as the headphone it copied, probably better. A great resource is still largely closed to us here in the US, but I hope to see that situation change soon.

I'd really like to get my hands on the two Wharfedale Isodynamic Models. Wharfedale built the first commercial isodynamic headphone in 1972 . I'd also like to get hold of a YHD-3.



DISCLAIMER: NO FANBOY
I should point out that there have been, and are, great headphones made using each of the four main drive principles; that is, I don't play favorites. I own at least one of each type, including piezoelectric. But only two of the four, moving-coil (aka "dynamic") and electrostatic, own a visible piece of today's marketplace, so I felt it was no sin to bang the table a bit for what today seems a long-gone lost cause, or know the reason why.
.

ADDENDA, APPENDA and EXTRA MISCELLANEA

Over the years this thread's been in operation, some of the information, including some distillations of the good bits that some may find useful, has gotten scattered over other HF threads. As I come across them, I'll link to them here.

Quickie rundown, updated, of the top moddable isodynamics currently available, and how hard/easy it is to mod them.

Separate Fostex T50 thread, also updated.

Separate Fostex T30 thread, ditto.

How to tell the good Fostex from the bad (well, non-audiophile).




* * * * * * * * * * *

The HP-3 (the later analogous model, YH-3, has identical specs and appearance) was the least expensive of the first wave of Orthodynamics. No Mario Bellini styling, just a simple plastic headband with the smaller (HP/YH-2 size) drivers. When Yamaha took away the elaborate arch-and-strap, they gave back some durability: the HP/YH-3 have a much more rugged cup pivot which is user-repairable.




Impedance: 150 ohms

Magnet: Isotropic Ferrite, 46mm

Sensitivity: 93dB/mW 101dB/V
Rated Input: 1W

Max Input: 3W

Weight (with cord): 210g



What's interesting is that the HP/YH-3 have a HP/YH-2-sized driver which seems to've been tuned low, like the YH-100, thus giving them bass (excessive bass in stock form) and modding capability far beyond that of its stablemates. As of this writing (late Jan 2008), damping experiments are proceeding.

* * * * * * * *


The YH-1000 finally surfaced on eBay in March 2006. It doesn't look quite like any other Orthodynamic, and inside it's different as well, with very interesting specs. German Wikipedia says the dates of production are '78-'80, which puts the YH-1000 before the YH-100, which looks more and more like the replacement. UPDATE: The HP/YH-1000 service manual is dated March 1978.



IMPEDANCE: 100 OHMS

DIAPHRAGM DIAMETER: 50mm

VOICE COIL: copper foil, 9 microns thick

DIAPHRAGM THICKNESS: 12 micron polyester

MAGNETIC MATERIAL: cerium cobalt

SENSITIVITY: 103dB/mW

RATED INPUT: 3W

MAX INSTANTANEOUS INPUT: 10W

Note well the 10 watts peak power handling spec coupled with the leap in sensitivity afforded by the stronger rare-earth magnets. Note also the use of copper rather than aluminum and the resulting lower impedance. Note further that the cups are aluminum instead of plastic, and the driver is slightly smaller than the standard 55mm. Don't know if the drivers were finally given some mechanical damping (UPDATE: Yes, they were, the only Orthodynamics to get any real mechanical damping). As of this writing (June 2008), still haven't seen or heard one.

Here's Yamaha's frequency response graph (upper trace) from a Japanese-market HP-1000 brochure (The HP-1000-- not to be confused with the famous Grado model-- and YH-1000 were entirely identical; the service manual applies to both and shows identical specs and parts except for the adjustment slider blocks where the model number is printed). This was Yamaha's best Orthodynamic, yet note the treble droop after 1kHz. It's not as bad as it looks, but it isn't flat.




This pair has a broken earpiece strut. Didn't I warn you? Ah, but it turns out that on the YH-1000, this part is (or was, when parts could be had) replaceable!

A YH-1000 owner in Poland showed up in post # 1443, p.145, with wonderful closeup photos plus detailed listening impressions. Tomek is a member of pl.rec.audio, a group that's hip to isodynamic headphones.


* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *


Thanks to HF member Steve Vujovic, we can take a peek at a 1978 Yamaha brochure showing an HP-1A alongside an HP-2, which supposedly was available in black as well as the maroony color we've all seen. I'd been hoping the HP-1A was a sort of missing link between the HP-1 and the YH-100, but oddly the specs are exactly the same as the HP-1's, so I still don't know how the 1A differs from the 1. Here's the specs chart:



Note the close similarity between the HP-2 and HP-1A specs despite the smaller size of the HP-2 driver.


* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

Attention DIYers! Not confident of taking apart your vintage Yamaha headphones to do the mods described herein? Here's a site that shows you what's involved in disassembling an HP/YH earcup: Refurbish Yamaha HP-1 headphone

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *


Back to England for a moment. Anyone ever hear, or hear of, the Leak 3000 Isodynamic? Visually it's identical to the second Wharfedale isodynamic, the ID2.



Is it related in any way to the original Wharfedale (see post #42)? Is it an in-house design, and if so, who designed it, Wharfedale or Leak?


Another British isodynamic is Peter Belt's PWB Dyna-X. It needs some work to make it sing, but member JadeEast says it's got the right stuff. It uses a driver similar to that used by Audio-Technica in the ATH-2. Photos courtesy JadeEast and, of course, those crazy online auction sellers.

Have your Ergo AMTs arrived yet? It would be interesting to see Sennheiser acquire the rights to the AMT and finally make something of it for headphone use.

Believe it or not, even AMTs need mechanical damping. Be sure to let us know if Precide added any.

 

Good point. It's a real word and can be used generically, but it's probably safer to use the less-heavily-trademarked term isodynamic when talking generally about this type of driver. Then of course the question arises: does orthodynamic mean ortho in the sense of perpendicular or ortho in the sense of correct? or both?

And has anyone tried any of the Fostex line, current or vintage?

 

I hesitated to revive this dead thread but I couldn't think of a graceful way to bring the discussion of future 'phones around to the subject without context, so I did it the awkward way.