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Orthodynamic Roundup - Page 4

post #46 of 23695
I've spent this evening with my modded Yamaha HP-50A (recabled to stereo jack, extra dense foam backings in earcups) and they are just Brillo pads. The bass on them is just wonderful. For a pair of headphones which look kind of like a nicotine stained children's toy and originally shipped with Yamaha electric organs and which go on eBay for only a couple of quid a pop, they really are superb. Best value buy since the KSC75. You've got to feed them tonnes of juice to get them going though. An iPod just wont cut it.

Here are some pictures originally posted in the AMT thread.






So yeah, I'll be joining team Ortho. ;D
post #47 of 23695
Thread Starter 

A Quid-Poppin' Daddy

Quote:
Originally Posted by Duggeh
...headphones which look kind of like a nicotine stained children's toy...

Heh heh. Back when cigarettes were all the rage, there was a factory color you could order for the Cord 812 called Cigarette Cream.


 

Quote:
Originally Posted by Duggeh
...go on eBay for only a couple of quid a pop, they really are superb.

Yaaass. I enjoy popping the odd quid myself. Pop! There goes one now! I'm glad your opinion of the Yamahas has risen.

 

Quote:
Originally Posted by Duggeh
So yeah, I'll be joining team Ortho.

Welcome to the team. We really must get you some felt, though.
 

Quote:
Originally Posted by Duggeh
Regarding damping and the backwave and such, wouldnt the best solution be to have a completely open backed design so that the backwave isnt an issue? Or is the damping actually nessessary in order to obtain low frequency response?

Damping will help the quality of the bass (by reducing overshoot and boinging) and, because the midrangey bloat is reduced, the apparent bass quantity increases.

Yamaha seemed to make two different kinds of diaphragm for the early Orthos-- tight and loose. The loose ones sound worse out of the box but firm up nicely with help. They're also the ones with real bass. But how to keep that bass from leaking away?

Actually, opening the back of a headphone increases the danger of bass backwave comin' sneakin' 'round yo' door. Luckily, since the drivers are sealed to their baffles (you did seal your drivers to their baffles, didn't you?), and there are earpads to block out any bass backwave that might come sneaking by, bass cancellation isn't a problem with any of the non-YHD Orthos and wouldn't be even if the back of the driver were open, as we see with the Fostex T50 (of course the T50 has a damping pad, so technically it's not fully open. It also has the biggest dang earpads you ever saw, just to make sure).

In a classic dipole, treble doesn't have a backwave cancellation problem because the wavelengths are short enough that they just beam straight out the back. Treble doesn't bend and wriggle around things to come back to bite you the way bass does (it can be diffracted around solids, but that's another discussion)

Bass, on the other hand, is tricky but stupid. It would kill you and give your family a hard time if it could only figure out how. It acts like water-- it bends around obstacles and goes everywhere. Control it with earpads and vent damping and it won't hurt you.

True, treble acts more like light and is mostly harmless, but like light it can be reflected-- and this property can, if left uncontrolled in a headphone cup with no absorptive material inside, roughen up the top end (the old comb filter effect), and that cuts down on the sparklies. This is true no matter the operating principle of the driver, but it's especially true for dipoles-- all planar headphones qualify. [UPDATE: However, we can use this quality of treble wavelengths to our advantage with something called the "reflex dot", mentioned further along in this thread, here.]

Mostly the problem with the bass in most iso/orthodynamics is, it's just underdamped-- there's no impact or focus, and pitches of bass notes aren't easily heard. The underdamping creates a big smooth very broad lower-midrange hump in the response curve that makes the 'phones sound "dark" or "heavy" or "ultra mellow". By adding an acoustic resistance, we deflate this hump by sucking the energy out of it (and converting it to heat) and thereby let the mids and treble emerge and do their thing. The effect is akin to opening the blinds in a room.

And yes, damping does limit the headstage or spaciness you get with completely open 'phones. It's the same as the difference between the Lambda and the SR-X. It's a tradeoff. This is why I have both.




From that Ergo AMT thread is my famously longwinded Essay On The Need For Damping:


THE PROBLEM IS LAID BEFORE MISTER DUGGEH

Mr. Duggeh, I won't make you read my famously obsessive-compulsive post "Orthodynamic Roundup" (Yeee haw! git along thar, ya mangey varmint headphones! haakkkk ptui!). If you look at Tyre's Driver Pics thread, you'll notice that all the dynamic drivers have dense damping pads discreetly glued to their backsides. This is because with current tech and affordable pricepoints, just about any diaphragm except the most diaphanous of electrostat films needs something to act as a damper-- they're just too heavy not to.

It's just like on your car or mountain bike-- if all you had was springs, you'd go boinging down the road. You need mechanical resistance (analogous to an electronic resistance) to damp down the natural oscillations of the car's suspension. Get the damping right and the wheels stay firmly planted. The amount of damping which is just sufficient to keep the wheels planted in the maximum number of situations is called critical damping (close enough for our purposes).


OUR WORK AND WHY WE DO IT

Same thing applies to any sprung moving mass, including the ones inside all our headphones. A good rule of thumb is that as you approach the point of critical damping, something magical happens to the headphone's sound-- it starts to faithfully follow all the little bumps and twitches of the input audio signal without overshoot or boing. In other words, the headphone stops making sound of its own. What does a good headphone that falls just short of critical damping sound like? Just about all of them, because having just a teensy bit of underdamping acts like a soft-focus lens-- it makes everything look smooth and happy. All the zits are airbrushed away. Plus it cranks the bass and midbass up a little, which always impresses the rubes.


SEEKERS OF VERITAS

So, because we are seekers of truth, we put an acoustic resistance (ie, a disc of dense felt) on the back side of the Ortho drivers. This acts as an air damper-- as the diaphragm bulges out, it has to blow out air through the felt; likewise as it unbulges and has to suck air through the felt. Get the picture? All dynamic 'phones have a similar air damper system of some kind-- even your Ergo AMTs. Why Yama (and some others) thought they didn't need this, I really don't know. So we need to finish their headphones for them, that's all.

GRADUS AD PARNASSUM, BABY

When we do, we find that isodynamic 'phones have some unique virtues, just like the ad copy said they were supposed to have. One step closer to the source, that's Team Ortho Critical Damping, aka Team OCD.


Edited by wualta - 7/3/11 at 9:28pm
post #48 of 23695
Dammit, now I'm getting all nostalgic for some Ortho action again. Where can I get some?
post #49 of 23695
Quote:
Originally Posted by smeggy
Dammit, now I'm getting all nostalgic for some Ortho action again. Where can I get some?
http://page.auctions.yahoo.co.jp/jp/auction/93598077

I'd go for some Ortho action myself but my wallet is already hurting too much right now.
post #50 of 23695
Thread Starter 

That auction's for another HP-50A and anyone who buys it will have to go through what Mr. Duggeh did. Allow me to suggest a consistently cheap alternative, Radio Shack's Audio-Technica-built Realistic Pro-30:

 

Realistic PRO 30 box.JPG

When it appears on That Auction Site (every couple of months or so), it generally goes for $15 or less, shipped. I just walked away with a NIB example for that much. It's a real sleeper that's pleasant-sounding (but bland) right out of the box, responds very well to damping, and is easy to work on and modify, since the earcups detach from the headband, Koss A/250 style.

My first successful damping mod, circa 1986. I used to use a modded Pro30 to do video production back in the '80s.


Edited by wualta - 1/28/11 at 4:00pm
post #51 of 23695
I have no idea how I would even start on the Japan sites. I don't even use ebay, I get my wife to do it. How do non-Japanese speakers work with Yahoo auctionsJapan? I tries google translations but they are sketchy at best.
post #52 of 23695
Quote:
Originally Posted by smeggy
I have no idea how I would even start on the Japan sites. I don't even use ebay, I get my wife to do it. How do non-Japanese speakers work with Yahoo auctionsJapan? I tries google translations but they are sketchy at best.
Well, if you don't know anyone in the country, the easiest way is probably to use a deputy service. Examples are...
http://www.rinkya.com/
http://www.crescent-shop.com/
There's others around too.

They can ask questions on your behalf and via their websites you can bid using their YJ accounts. Shipping of course will not be cheap and you'd want to take costs like that into account before deciding how much you're willing to bid.
post #53 of 23695
Thanks for the help all.
post #54 of 23695
Quote:
Originally Posted by wualta
They'd been loved and loved until they became real, just like the Velveteen Rabbit.


I think setmenu feels the same way about his, since he's kept them running all these years. I've heard other people express the same fondness for them.

Yes, I still give then the occasional listen but they are rather fragile these
days.
They were my father fathers ,he died shortly after purchasing them, so they
have a value to me beyond mere headphones.
I guess it was my father who passed on the audiophile gene, he ran a hi-fi
shop that was founded and owned by his father.
I have many childhood recollections of all manner of equipment arriving and
leaving the house.
So those Whafdales were my first headphone experience, the planar sound
has influenced my tastes ever since.
Even when I had the desire to get new ones I could not find anything that I
preferred, so I kept using them.
I got through numerous ear pads and head bands.
Years after the demise of the product I managed to track down the
warehouse where all the remaining parts were stored and got myself parts to
make up two more pairs!
These were loaned/given two a couple of Friends who also loved the sound.
Unfortunately my Friends did not cherish theirs as much and they went
missing over the passing of the years.

Mine no longer have the grill that covered the transducer, I removed this
years ago and preferred the sound without them.
I used to drive the phones directly from the speaker terminals of an
integrated amp rather than the headphone jack.
I finally stopped regularly using then in the late 80,s when I discovered Stax
Lambdas.

It was the wharfdale that inspired me to have ago at doing my own phones.
The wharfdale transducer whilst being described as planar magnetic etc,
could also be described as a ribbon.[al be it a wide one]
Because unlike others [as far as I know] it only fixes its diaphragm at two
end points.

Good to see this great thread still nicely chugging along.






.
post #55 of 23695
I thought this was a discussion about braces o.O
Completely new to me.. might watch out for some
post #56 of 23695
It was fun to read through this thread. My first audiophile headphones were Yamaha YH-1000's. I had them for a few years before the stem holding the driver housing on broke. I replaced them with my AKG K340's in 1985. I can remember that the 2 phones were night and day. Memory plays tricks, but I remember the Yamahas having deeper bass, but being darker and more veiled than the AKG's. I held on to them for quite some time hoping to repair them, but we got seperated somewhere in my moves. If memory serves me it seems like I paid in the $100-$150.00 range for them new in 1983.
post #57 of 23695
I had a curious-- troubling?-- experience yesterday in the great tradition of orthodynamic tweaking. After a remedial lesson from Wualta on the difference between the virtues of damping and the need to control bass backwave, I thought I had an answer for my beloved PMB100 earspeakers, which sound phenomenal but lack deep bass. Let me explain.

Originally, I'd been under the impression that damping would solve my problems, but that seemed inadvisable considering that a team of designers advised by Joerg Jecklin himself had gone to great pains to make sure that there would be no damping whatsoever on these orthos. (apologies for the lack of pics, my camera broke two months ago, and every time I have some spare electronics cash, I blow it on headphones, of course) Moreover, MB's Willi Pressuti personally advised me not to damp: "keep him completely open as he was born", he said.

But then when I better understood the symptoms of a bass-canceling backwave, I realize that this was my real problem, and not the damping after all. (The highs are quite crisp and what bass there is clear, so damping should be unnecessary.) So, I took another look at those headphones, and what did I see but what had been staring me in the face all along: 51 2mm holes, 6 mounting bracket gaps, and 8 long slits all venting each earcup all around the business side of the driver. About as much backwave as you could get without closing the backs of the earcups as well. It seemed I had sleuthed out the bass-stealing culprit.

So I set to work with a pair of scissors and some electrical tape. (n.b., mustard-yellow electrical tape, to go with the olive green of the PMBs) I covered everything but the 8 slits, which were well above the rest and pointed upward. I gave it a listen: plenty of bass, as expected. However, somehow the sparkle had been diminished, the open airiness compromised. Vocals and acoustical music, previously the strong point of these headphones, were reduced to the level of my DT990-- i.e., still good, but not magical. So I started removing bits of tape, trying to reach a balance. Slowly, I removed ALL of the tape before I was satisfied again.

So how can this be? It seems Willi's warning was right, but how do we explain it technically? What besides allowing in a bass backwave are these holes doing to make the headphones sound so good?
post #58 of 23695
Thread Starter 
Quote:
Originally Posted by swt61
...My first audiophile headphones were Yamaha YH-1000's. I had them for a few years before the stem holding the driver housing on broke.
That could be your YH-1000 on the preceding page! I'd love to get hold of a YH-1000. Sounds like Yamaha pulled out all the stops on their original design before ditching it for the YHD series.

Facelvega, yours is the dilemma (actually trilemma) of ambitious headphone designers everywhere: how to have sound that's spacious and free and yet have the full frequency spectrum, smooth and billiard-table flat, with whipcrack transient response. It seems that if you get one right, it kills one of the other two.

In a good design, as with good cuisine, balance is everything.

If we prevented the bass from getting around but allowed unrestricted access to the midrange and treble we'd have the best of all worlds. We can approach this by delaying the backwave long enough to keep its troughs from reaching their corresponding crests in time to cancel them, and we can do that by forcing the backwave through a labyrinth (with the problems of reflections within the labyrinth), or we can use a largish baffle board which looks hilariously funny when worn, or we can send the backwave out away from the head through a waveguide (eg, a short tube) a la Grado, .... or we can try combining aspects of a labyrinth and a damped transmission line and force the backwave through a damping medium covering the back grille or the back vents of a headphone, the labyrinth in this case being the tiny over-under-around-and-through paths the air pressure has to take to get through the tangle of fibers in a layer of felt. There's some damping (ie, resistive loss) due to friction, so it's a lossy labyrinth, a good name for a rock band. Damping the back of a driver begins this process, but it can be aided significantly by damping any exit the backwave might take.

Without the headphones in front of me I can't be sure of the construction or the results, but I'd try the damping pad first simply because it's easiest and makes an attempt to arrest the problem at the source. The problem will be to press the pad tightly against the driver without resorting to glue. Opencell foam pads do the job in the semiclosed Yamaha 'phones, but I don't know how (or if) this would work in the PMB 100. Sorry, I just need a picture or a sketch. UPDATE: See next page for photos from facelvega.

And it's entirely possible that MB and Jecklin designed all the elements of the PMB 100 to work in an optimum way as Jecklin envisioned it, and changing anything will upset the balance of the design. Using a YH-100 driver might be necessary, or Gott knows what else. Sometimes, as with the SVT Contour, the best policy is to let the thing be itself. But I would at least try the damping pad. If it doesn't work on a Jecklin design, I wouldn't feel bad; in fact, it would show us a bit about how Jecklin arrived at the final form of the PMB 100.

.
post #59 of 23695
Thread Starter 
Quote:
Originally Posted by setmenu
The wharfdale transducer whilst being described as planar magnetic etc, could also be described as a ribbon [albeit a wide one]
because unlike others [as far as I know] it only fixes its diaphragm at two
end points.
First, thanks for your story about the Wharfedales. No design exists in a vacuum-- someone has to buy it and appreciate it.

The little bombshell you dropped with this ribbon business makes me go whaaaaa? They only fixed it at two ends, as far as you know?? Omigod, here we go again with yet another diaphragm design. When you get a chance, we need closeups of that driver, stat. I gotta go sit down.
post #60 of 23695
Quote:
Originally Posted by wualta
First, thanks for your story about the Wharfedales. No design exists in a vacuum-- someone has to buy it and appreciate it.

The little bombshell you dropped with this ribbon business makes me go whaaaaa? They only fixed it at two ends, as far as you know?? Omigod, here we go again with yet another diaphragm design. When you get a chance, we need closeups of that driver, stat. I gotta go sit down.
Yeah, that sounds right from when I pulled mine to bits. The Wharfedale was a square driver, no center contact on those puppies. If you look at the pictures of them dismantled you see the 'coil' is really stripes and the magnets were shallow arcs to let the film flap about between the end anchors.
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