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CD3000 gone Planar... pics

post #1 of 14
Thread Starter 
In 1978, Yamaha teamed up with Mario Bellini to produce the HP-1, Orthodynamic headphones which used a planar magnetic driver. With a Isotropic ferrite magnet on either side, the voice coil is sandwiched in the middle on a thin polyester diaphram. Shown below is a 50mm CD3000 driver with a top and bottom view of the HP-1 55mm drivers. Side view of sandwich...



These sold new for $200 in '78, I picked them up recently after reading a few good things about them. Once I heard them, I knew they would benefit from a recable but I noticed they needed something beyond what a cable could do, a new enclosure. Since I had a driverless pair of CD3000's handy, I decided to give them a try since the drivers are of similar size. A little dissasembly on the HP-1's and I was ready for testing. Wow, I liked what I heard much better than the Yamaha enclosures so then it was seeing if it was feasible to do. Trying the drivers at different distances from the ear was eye opening, maybe even worth looking at CD3000 driver placement adjustments. Once I found what I thought was the sweet spot, I mounted them with success. Pretty easy actually using a wooden pressure mount. Proceeded to recable with the usual one I use.



They are nice and tight and aren't going anywhere. After putting the pads back on, I've tried a number of woody's and think the R10 Zebra may be the ticket for these or a combination of Paduak and Zebra.

I'll have to say that these are really sounding good to me. Something about the planar sound is real satisfying. Fatigue factor is 0, so darn smooth it seems. Plenty of bass and I get a feeling of quickness that I'm assuming is inherant when there is no cone movement. Soundstage is wonderful. I believe the HP-1's were the only HP or YP series that had the 55mm driver. Rated input is 3w, I can max my PPA's volume without it being too loud, max input is 10w. I need to hear these with a more powerful amp that can drive these 150 ohm planars a little better.

Since I need sleep now, I'll leave it at that
post #2 of 14
I am a bit Planar driver fan myself
I have never laid eyes on a pair of HP1's but do possess a pair of HP2's.
I think the Bellini styling is fab, very clean tight looks without the overdone
flashiness that some modern phones possess.
As for the sound, I like that too, kind of retro sonics with that laid back sound, but sill very pleasant...
Another oldie I possess is a pair of Wharfdale isodynamics from the 70s, again
these sound pretty nice, but cosmetically they have suffered the ravages of
time less well.

It does seem a bit of shame that you have disassembled the classic Yams
with the intention of using them in the Sony shells [Grrrr ] do you intend to
reassemble them at some point?
It would be a shame to see yet another classic piece of audio kit go by way
of the trash can when the novelty wears off...


HP2:

http://www6.head-fi.org/forums/attac...tachmentid=330


http://www6.head-fi.org/forums/attac...tachmentid=331

The Wharfdale phones:

http://www6.head-fi.org/forums/attac...tachmentid=333





Cheers

Setmenu
post #3 of 14
EDIT: Since the photos of Xanadu's Sony CD3000 project mentioned in post #1 went away because of a server change, here are two of them:



I've also gone back through my posts in this thread and corrected many woolly-headed errors having to do with the effect of magnet strength on the damping of isodynamic and ribbon drivers. You can see what's changed by comparing with setmenu's quotes.

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


Guys, sorry I'm late on this, but the Yamaha YH-100 did have a driver the same size as the HP-1's [EDIT: and so did the YH-1]. Great little driver. Now-- the interesting thing is that the YH-100 has a thin layer of soft iron (or steel?) covering each ferrite disc, presumably to focus more of the flux onto the diaphragm and gain a little efficiency. I don't see that in the photos, so I'm assuming it was added with the introduction of the YH-100.

Efficiency is nice, but none of the manufacturers of this type of 'phone (except Fostex) ever added enough mechanical damping, and after all, that Mylar diaphragm is lightweight, but not nearly as lightweight as the diaphragm in, say, a Stax electrostatic, because it has to carry the considerable mass of the aluminum voice coil. The upshot is that nearly all the 'phones of this type suffered from the uncontrolled but low-Q characteristic resonance of their diaphragms (the center frequency of which depended on diaphragm size, thickness, and tension if any, with the majority of them in the low midrange/upper bass), and no matter which model you bought, you ended up with a smoothly humped response with rolled off treble and a more or less hollow sound.

So I'm suggesting that you try putting a thin, dense layer of felt or other nonwoven porous material (I've used felt plus a layer of construction paper with some success) on the backside of each driver and see if you don't like the sound much better.

The payoff is the promise of any diaphragm driven isodynamically: cleaner, more detailed sound from top to bottom. The potential performance built into these little flat drivers is startling. If you get the damping just right, you can have contests with owners of electrostats.

Anyone willing to give it a try?

.
post #4 of 14
Woah. Interesting experiment.

Have you tried a speaker output adapter (K1000 style) with it?

Maybe drive them balanced that way?


-Ed
post #5 of 14
Quote:
Originally Posted by wualta
Guys, sorry I'm late on this, but I think the Yamaha YH-100 had a driver *about* the same size as the HP-1's. I measure about 52mm. Got the same number of holes, anyway. Great little driver. Now-- the interesting thing is that the YH-100 has a thin layer of soft iron (or steel?) covering each ferrite disc, presumably to focus more of the flux onto the diaphragm and gain a little efficiency. I don't see that in the photos, so I'm assuming it was added with the introduction of the YH-100.

More magnetic flux would also increase the inherent damping of the driver and help get rid of what I call "the isodynamic thunk" (the sound any of these headphones makes when trying to reproduce a transient). But it isn't enough. And without the "keeper" layer, it could only be worse. Magnets of the era (ca. 1980) just weren't strong enough for the job, so all the 'phones of this type suffered from the uncontrolled characteristic resonance of their diaphragms, the center frequency of which depended on diaphragm size and tension, and no matter which model you bought, you ended up with a smoothly humped response and a more or less hollow sound.

So I'm suggesting that you try putting a thin, dense layer of felt or other nonwoven porous material (I've used felt plus a layer of construction paper with some success) on the backside of each driver and see if you don't like the sound *much* better.

I've owned Audio-Technica, Realistic (!) (made by Audio-Technica) and Yamaha isodynamic phones and they all needed much more damping than their makers gave 'em. The payoff is the promise of any diaphragm driven isodynamically: cleaner, more detailed sound from top to bottom. The potential performance built into these little flat drivers is startling. If you get the damping just right, you can have contests with owners of electrostats.

Anyone willing to give it a try?

Walt Brand
Nice to see another planar fan here..
Are the transducers used in your phones rectangular or circular?
I love my own HP2's for their design as much as anything else, I have
never seen a picture of any of the other yam planar phones, but I do
seem to recollect one model having rectangular drivers?


Setmenu
post #6 of 14
Aside from your own Wharfedales, setmenu, the only rectangular-diaphragm isodynamics I've ever seen are the current-production Fostexes (ie, the T50RP and the mk II versons of the T20RP and T40RP). I'm pretty sure everyone else has been using the usual etched-aluminum-on-polyester spiral voice coil arrangement. [EDIT: Fostex used both spiral and serpentine voice coils on tensioned, round diaphragms in their original 1978 line. Technics used a square serpentine diaphragm between square magnets in the EAH-830. The Russian isodynamics TDS-7 and TDS-15 used rectangular drivers, and in the case of the TDS-15, a round diaphragm with a square magnet structure and aperture! Yamaha used a spiral copper voice coil in its YH-1000.] Yamaha used 5 different sizes of driver, 55mm, 50mm (with a copper voice coil), 46mm, 38mm and 20mm (only in the ultrarare YH-5M intra-aural) but they're all round with spiral voice coils.

I've only now discovered what you've been up to with your DIY isodynamics, setmenu. Well fabbed! I haven't got to the point where you explain why the diaphragm is held in a kind of sine-wave trough, but I expect I'll find it. If you haven't visited the Fostex site, you might want to, just to get a look at the fuzzy picture of the T50RP's diaphragm-- yours is reminiscent. Theirs is over-tensioned [EDIT: may be, but with the improved earpads Fostex supplied after 2007, it does, finally, have bass].

Sounds like you're trying to make a true ribbon element, yes? Clamped only at the ends and free to move alarming distances in the middle? Nifty idea.


.
post #7 of 14
Quote:
Originally Posted by wualta
Aside from your own Wharfedales, setmenu, the only rectangular-diaphragm isodynamics I've ever seen are the modern Fostexes. I'm pretty sure everyone else has been using the usual etched-aluminum-on-polyester spiral voice coil arrangement. Yama seems to have used at least 3 different sizes of driver: the ~52mm, the ~46mm and the ~39mm, but they're all round.

I've only now discovered what you've been up to with your DIY isodynamics, setmenu. Well fabbed! I haven't got to the point where you explain why the diaphragm is held in a kind of sine-wave trough, but I expect I'll find it. If you haven't visited the Fostex site, you might want to, just to get a look at the fuzzy picture of the T50-RP's diaphragm-- yours is reminiscent. Theirs is over-tensioned.

Sounds like you're trying to make a true ribbon element, yes? Clamped only at the ends and free to move alarming distances in the middle? Nifty idea.
So the yams are all round , interesting as I have seen a picture of a rectangular diaphragm in a book I have but they made no mention of it's source.
I assumed it might be yamaha, seems there are more planar phones
out there to be discovered....

Regarding my own phones, the ribbon is formed into such a 'sine wave' to
relieve tension on the ribbon and prevent radical changes in tension as
the ribbon moves too and fro.
The type and number of folds plays a large part in the resonant behavior
of the ribbon itself.
The ribbons have as little preload as is possible to achieve when installing them.
And you are quite correct stating it is free to move alarming distances,
this sort of design has very very little mechanical damping [mesh screens that cover and protect the ribbons also play apart here too] and relies
on the above mentioned folding coupled with material choice and electrical
damping.

Setmenu
post #8 of 14

Driver Distance

"Trying the drivers at different distances from the ear was eye opening, maybe even worth looking at CD3000 driver placement adjustments"

I totally agree! The fact most headphones don't allow this normallly is a shame.
If you saw significant difference adjusting driver distance that little, imagine the truly HUGE difference in sound I experienced when I moved the AKG K1000 drivers to literally sit on my earlobes!
post #9 of 14
Setmenu: The US-market Yamaha drivers were all round, but in this world of crazy international markets, who knows what was served up elsewhere.

Can you think of any audible advantages to a rectangular diaphragm?


I should correct myself on one point: Fostex's range of isodynamic 'phones has always been properly damped (well, more or less-- the original 1978 T50 was the only truly properly-damped Fostex), which is why I'd like to get my hands on a T50. It never 'thunked'; it could actually reproduce a 'tic'. [UPDATE: I did get hold of a T50 and started a big thread on iso/orthodynamics and, well, caused a LOT of trouble for many wallets... for which I apologize..]


Still, there's no shame in giving a given diaphragm an external damper (shock absorber), so to speak. Well, maybe a little shame, but not much.

I wonder what could be done with a twin ribbon using a kind of Heil-tweeter arrangement-- they'd move toward each other in a kind of hand-clapping maneuver... wouldn't need to excurse (or excur, although you'll also see the neologism excurt) so much... Hm.

Anyway, get those Yamas out of the closet, get some bonded-polyester batting, felt, chamois, B&K measurement mics, whatever it takes.

Team Critical Damping!
.
post #10 of 14
Quote:
Originally Posted by wualta
Setmenu: The US-market Yamaha drivers were all round, but in this world of crazy international markets, who knows what was served up elsewhere. B&O sold some isodynamics, and the frames were rectangular.. reminiscent of the AKG K1000. Audio-Technica I suspect did lots of OEM work for others.

Can you think of any audible advantages to a rectangular diaphragm?


I should correct myself on one point: Fostex's range of isodynamic 'phones has always been properly damped, which is why I'd like to get my hands on a pair of old T30s (ca. 1986). They never 'thunked'; they could actually reproduce a 'tic'.


As for ribbons, if there's enough mechanical restoring force in the ribbon itself, the magnets, if they're strong enough and if the flux is flung into a large enough volume to accommodate max ribbon excursion without losing uniformity, the magnets, I say, should provide sufficient damping. Still, there's no shame in giving a given diaphragm an external damper (shock absorber), so to speak. Well, maybe a little shame, but not much.

I wonder what could be done with a twin ribbon using a kind of Heil-tweeter arrangement-- they'd move toward each other in a kind of hand-clapping maneuver... wouldn't need to excurse so much... Hm.

Anyway, get those Yamas out of the closet, get some bonded-polyester batting, felt, chamois, B&K measurement mics, whatever it takes. Team Critical Damping!
Rather than modify the yams , I prefer to spend time on my own phones as
I can change more.
When I first got the inspiration to make some ribbon phones I new very little
about ribbons or transducer design other than the basics, it was more about
having some educational diy fun than anything else.
After building some single transducers with hand drawn ribbons :

http://www5.head-fi.org/forums/attac...tachmentid=205

I was sufficiently pleased with the performance to have ago at making my first pair of complete phones:

http://www5.head-fi.org/forums/attac...tachmentid=218

These also have hand drawn ribbon traces.
The later phones use ribbons that are commercially etched based on drawing produced with CAD program.
They also have a superior magnetic circuit.

As for their sound , they do suffer from peaky bass due to a fundamental
issue with the coil design,with my lack of basic knowledge at the time
of designing the coils I failed to allow for the fact that part of the coil is
not doing active work and there fore behaves as a source resistance ,
effectively the transducer sees an equal resistance to it's own.
this produces an enormous bass hump and lack of damping.[if my understanding is now correct]
The only way round this has been to roll off the bass with a filter.
[It does prove that these ribbons are capable of producing one
hell of a bass kick though!]
On the plus side the midrange and treble are pretty nice, voices
can sound delicious with a smooth naturally grained feel that I may even
prefer to the stax at times.
Instruments such as cymbals have a nice clean full bodied sound that could
possibly need just a tad more at the very highest frequencies.

But of course all the above aside there is still a good deal of work to do!
These phones have been on the project back burner for some time now
and it was seeing a couple of threads on the planar /ribbon subject that
has perked my interest again.....dam![$$$]
So hopefully at some point I will be building another pair of these incorporating
many revisions to solve outstanding issues, [and no doubt revealing fresh challenges] one such revision is likely to be a substantially lighter ribbon produced from a different material and process.....



Setmenu
post #11 of 14
Quote:
Originally Posted by setmenu
Rather than modify the yams, I prefer to spend time on my own phones as I can change more.
I understand. Just keep in mind that the difference in the Yamas is the difference between a frequency response shaped like a rainbow and one that's more or less flat, the net effect of which is that the deep bass and the high treble suddenly come out because all the excess midrange has been carved away. There's actually more deep bass because the diaphragm is producing it without doubling and smear.

The mod will cost you 25 cents and max 20 minutes of your time. You don't have to glue anything, which means you can always go back. Plus you get to see how Yamaha (or perhaps Audio-Technica) made the drivers.

I feel like Darth Vader: "Come, join me on the Damp Side, little Yamaha headphone. It issss.... your desssstiny."

Just slap me if I become egregiously messianic.

Anyway, I'm curious to see an HP-1 owner's results since so many people liked these just as they were, back in the day.
post #12 of 14
I modded my old Yamaha HP-1's earlier tonight as per Wualta's recommendations. The result is exactly what Wualta predicted: the addition of extra damping materials in the transducer housing (in this case a piece of round felt directly behind the driver across it's entire diameter) flattens the freq response by smoothing a low frequency resonance hump. This results in better perceived high frequencies and a better differentiation of lower bass extension from, say, the mid-bass area. Sonic characteristics (the amazingly smooth, non-fatiguing presentation, etc) remain intact. I never fully perceived the so-called "orthodynamic thunk" so it's hard to say whether or not this has been lessened... but thanks for the tip Wualta. I must say, as a recording engineer, I've listened to many different types of headphones and monitor speakers. These Yamaha's now remind me very msuc of the vaunted Yamaha NS-1000's whose freq response was amazingly flat and accurate. I can now do final mixing and mastering on these headphones with this improvement. But who wants to do that...i'd rather just listen to great music all night long with these incredible cans. Team Ortho-fantastic!
post #13 of 14
Very gratifying to have Bias' results.

The reason the mod works so well is that the resonance modes of isodynamic diaphragms are simple-- they're dominated by the one main resonance formed by the diaphragm's compliance/tension and its mass. Get that under control and you're pretty much home.

By contrast, in a normal dynamic driver's diaphragm, which is driven directly only at the voice coil attachment, the diaphragm tends to lose firm mechanical coupling to the voice coil as the frequency goes up and "breaks up" (ie, begins to vibrate in chaotic ways), like a cone or dome in a loudspeaker: bell modes, radial modes, rocking modes, funny little random modes caused by sections of the diaphragm coupling and decoupling with one another (see the old Celestion laser interferometry images of tweeters in distress-- what a revelation that was!). It takes a lot of work and computer time to keep these all under reasonable control, and the truth is that they're never completely under control, but the payoff of the design is greater excursion (for strong bass) and high efficiency.

As for the infamous "thunk", all you have to do is be old enough to have worked with vinyl records and their unending supply of obnoxious little tics and pops (especially in radio with its stacks of cue-burned LPs). The tics, crackle and pop give a headphone (or speaker, preamp, phono cartridge) a very nice informal impulse-response test: if you listen with any unmodded isodynamic 'phones (original Fostex T50 excepted), you'll hear the sound of an underdamped diaphragm trying to cope: the nice sharp Tic becomes a lifeless, hollow thokkh.

With critical damping added, the Yamahas' transient response goes from being worse than that of any conventional dynamic 'phone of comparable price to being, in my 'umble opinion, better than most, if not all, dynamic 'phones, and very close indeed to electrostatics, for the reasons mentioned above.

As has been pointed out elsewhere, excellent transient response translates into smooth, flat frequency response. Unless something goes wrong.

The next project will be to get the properly-damped Yamaha diaphragms out of the semi-closed earcups of the HP and YH series (they're vented around the circumference, a bad idea borrowed from the old Audio-Technica / Signet TK22) and into something with an open back-- which brings us back to the start of this thread!

.
post #14 of 14
~-~ <-------------------------- This thread.













<------------My head.

When I got dizzy, I stopped reading. Good work guys, I hope you offer to sell some of these to us less ambitious types...
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