Head-Fi.org › Forums › Equipment Forums › Headphones (full-size) › Ripping Apart An ATH-2: a continuant saga
New Posts  All Forums:Forum Nav:

Ripping Apart An ATH-2: a continuant saga

post #1 of 36
Thread Starter 
Those of you who are Audio-Technica fans may be interested to know that the company started in the headphone biz with a full line of different types of 'phones (no buds, though-- they were yet to come). There were several decent electret electrostatics beginning in the mid-70s, along with some nicely styled but boring-sounding dynamics, and then in the late '70s came the ATH-1 and ATH-2. These were isodynamics with a miniaturized driver. A few of you have the ATH-2-- it's favored by folks who really dig the colors of the '70s: olive green, chocolate brown, pumpkin orange [shudders]. Oh, and chrome. Ya gotta have chrome. Chrome plated plastic, that is. The ATH-2 has these in spades.



Yes, it's another early arch-and-strap headband. In this case the strap is a rather stiff piece of plastic, but the ATH-2 isn't that heavy anyway, though on my head it's a little clampy. Why would we want to rip it apart? To add extra damping. Why'd we wanna do that? To suppress the midranginess and tighten up the bass and bring up the treble. All good reasons. Turns out, most consumer headphones using this type of driver were criminally underdamped, which left them, instead of better than any dynamic of their day, worse, maybe intentionally so-- but if you want the whole sad design-engineering-marketing saga behind the marketplace failure of the isodynamic headphone as a type, you'll have to read the amazing, interminable Orthodynamic Roundup thread, at least the first three pages. The upshot is, we have to finish the job the manufacturers started but left half-done at best, if we want to bring out these headphones' true potential, which is considerable.

So first we pop the left and right cups off the headband pop-bead style. Clever construction. Then we peel off the earpads. All seventies supra-aural 'phones have earpads stuck on with the famous Japanese doublesided extra-thin tape. I think much of Japan is still held together with this tape. It lasts forever and never loses its ability to stick. You can peel off the earpads many times and still stick them back on if you go slowly and keep fingerprints and dust away from them.

Peeling the pads usually reveals several phillips-type self-tapping screw heads. In the case of the ATH-2, there are only two screws. Wonder why?



Right now we just want to look around and take note of what we see.

The baffle plate is a thick chunk of chrome-plated plastic with perforations (visible at far left in photo) to let the sound reach your ears, even though those perforations don't in any way line up with the perforations in the disc magnets of the drivers (shame!). Will that affect the treble? Yes, though not as much as we might think. Tiny holes don't present that much of an obstacle, though we wish the obstacle wasn't there.

The back cup (photos at top of page) is open and properly vented-- very unusual among isodynamics of this vintage!. And look, the driver already has a thin nonwoven damping pad glued to it-- looks like A-T is trying to make this driver work the way it's supposed to. By the way, the driver is stuck to the baffle with a gooey tape or glue, so at least we know there's an airtight seal there. Don't want that backwave getting loose in the earcup, despite what your AKG K501 is whispering in your ear.


It turns out that the ATH-2's driver is about 3dB more efficient, but visually, it's the same as the one in the Realistic Pro 30:



Compare the holes in the driver to those holes in the chrome baffle. Mmmm, not optimal.

Impedance freaks should note that the impedance of both the ATH-2 and Pro 30 is about 32 ohms.


But there's more stuff to find.
The baffle is thick, which means even if we drill some bigger holes to expose more of the driver, there'd be a short tunnel between the driver and our ears, which means a minor cavity resonance. Not a huge problem.. We could saw out the perforated part of the baffle completely and bring the driver forward until it was flush with the rest of the baffle... though I'm not going to do that because it would spoil the stock '70s vibe that so many love. I intentionally make all my suggested mods completely reversible, because what sounds right to me may not be to everyone's liking, plus there's the resale value of a vintage 'phone to consider.

We know from a brisk listening session that the bass is not great and the treble is droopy, even with A-T's damping measures in place. Looking for the source of the trouble, we look some more and.. whuzzat? Holes in the baffle? Yes, there are two good-sized holes, one of which can be seen in the photo above, on the right of the baffle. What're they for? They're not screw holes. They don't seem to serve any useful function. The lip of the back cup covers them, but why do manufacturers risk the bass response of their headphones by doing these things? Why assume that the cup will seal perfectly to the baffle all the way around?

Then just to the left and right of the passageway for the headphone cord at the bottom of the baffle you can barely see two slots; two tabs from the back cup engage these, and that's why there are only two screws. Hmm. What happens when you let backwave from the back of the driver into the earcup area? That's right, the evil bass cancellation. So those slots will be filled with yellow-tak, even though the earpads cover them-- I don't trust earpads or loose-fitting tabs to block bass frequencies. So maybe by doing some stealthy yellow-takking we'll have rockin' bass out of these things. That's good, because if we need to add a lot of damping, the phones will tend to pick up a lot more treble, and we want the two to balance.

Finally, note that the vented back cup uses only a thin donut of opencell foam to damp the vents, and we know from working on the Realistic Pro 30 that we can gain quite a bit of low bass by damping vents with felt. Open-cell foam always makes a lousy damping material.

Hey, it's not perfect, but being one of the very few open-back isodynamics, this thing has possibilities. More to come.

.
post #2 of 36
I like the colors! It's frustrating, all of these portable-sized orthos that cannot be driven by any portable equipment. We need to get one of the amp makers to do a short run of absurdly-overpowered portables. Something like 3x9V with seriously high gain settings. Or has anyone found that one of the existing portable amps is up to the task? My Go-Vibe V5 can handle orthos if it's amping a proper source, but amping my mp3 player it's out of the game.
post #3 of 36
This looks interesting. I absolutely hate "pumpkin orange" though.
By the way, what are the pads made of? They look pretty substantial in that closeup picture.
post #4 of 36
Thread Starter 
Quote:
Originally Posted by facelvega
I like the colors!
Are you a Child Of The Seventies?

Quote:
It's frustrating, all of these portable-sized orthos that cannot be driven by any portable equipment.
The higher-efficiency ones can (YHD-1, YHD-1000), but your selection is very limited. The lower-impedance 'phones fare pretty well. The old Fostexen are 50-60 ohms; the impedance of the ATH-2 is given, puzzlingly, as 4-60 ohms (both they and the Realistic PRO 30 measure about 30 ohms DC, which is close to the actual impedance); the non-YHD Yamahas are about 150. So give the ATH-2 a try, if you can find one, after we get the mods straightened away. I had pretty good results with a MiniDisc portable and the T30, even with bass boost on. An amp sees an iso 'phone as pretty much a resistor, which makes amps happy.


Quote:
We need to get one of the amp makers to do a short run of absurdly-overpowered portables. Or has anyone found that one of the existing portable amps is up to the task?
Even the old Yamas can blow your ears off (mine, anyway) powered by a simple CMoy amp. I have one called The Little Black Amp that doesn't even have a gain control. Works great. Is that what you meant?
post #5 of 36
Thread Starter 
Quote:
Originally Posted by Esidarap
By the way, what are the pads made of? They look pretty substantial in that closeup picture.
The usual vinyl plastic filled with foam. Nothing special.
post #6 of 36
Quote:
Originally Posted by wualta
Are you a Child Of The Seventies?
...
Is that what you meant?
A. I was born in the seventies, so yes if only in the technical sense. Also, believe it or not I'm a professional design historian (mainly architecture, but a little of everything), so I've had a normal sense of contemporary styling beaten out of me. 1910, 1970, 2006-- it all looks new to me. Or old.

B.I guess mainly what I meant about the portable amps is that my HOK80, though a bit smaller than an HD25, are harder to drive than my PMB's or my K240M, even though they're listed at 2x60 ohm. I had this idea of going ortho at home and on the road, but I guess I'll need another pair to handle that. It's okay, I guess, I'd hate to drop my HOK80's and bust an earcup.
post #7 of 36
Thread Starter 
Quote:
Originally Posted by facelvega
A. I was born in the seventies, so yes if only in the technical sense.
Doesn't Jung say we ineluctably recapitulate our childhoods? The ATH-2 must remind you of a pumpkin-orange model car or a stuffed toy orangutan. Or.. a pumpkin.


Quote:
Also, believe it or not I'm a professional design historian (mainly architecture, but a little of everything), so I've had a normal sense of contemporary styling beaten out of me. 1910, 1970, 2006-- it all looks new to me. Or old.
Yes, and I'm still waiting to buy your book. The "industrial" design of everyday objects interests me too-- it's almost as if examples of a given era tell stories about the times they come from. You like the Facel Vega, I like the '54 Panhard Dyna.

As a design, the ATH-2 is actually very well optimized, just not from an audio quality standpoint. But that's not unusual for this type of 'phone back then. The thick, drilled baffle is probably the worst feature, and it's not a dealbreaker. Well, that, and the underdamped drivers. But at least they tried!

I do really like the pop-off cups.

Quote:
...my HOK 80, though a bit smaller than an HD25, are harder to drive than my PMB's or my K240M, even though they're listed at 2x60 ohm.
Ah, now I see what you meant. A lot of importance is placed on impedance, but what people mostly are talking about is sensitivity. Impedance places an upper limit on the output voltage the amp produces. Sensitivity is a measure of how loud the 'phones are at that limit. Apparently the DDR didn't have strong ferrite magnets.


Quote:
I had this idea of going ortho at home and on the road, but I guess I'll need another pair to handle that. It's okay, I guess, I'd hate to drop my HOK 80's and bust an earcup.
Yep, they're too rare for playful on the go use. Too bulky too, I'd guess. A Yamaha HP-1 just went for $19 shipped on That Auction Site. Try one of those with a CMoy. Or the more compact and cheaper Realistic Pro 30. One of those just went for $9.50 shipped. The wide, flat coiled cord might have to be swapped out, though.


.
post #8 of 36
Thread Starter 
Anyway, to start the disassembly of the ATH-2, first pop the two drivers off the headband. Just pull 'em straight off. Then carefully peel the earpad off one driver and put it in a plastic bag or someplace where it will not come in contact with any household surface. Dust and grease and cat hairs are your enemy now.


See the two phillips screw heads on the left side of the damn-hard-to-photograph chrome baffle? Unscrew 'em, carefully-- the screws have ludicrously, outrageously fine threads-- and slowly take off the vented back cup with a peeling motion. I put some of the yellow fluffy stuff you'll find lying gently against the diaphragm of the Stax SR-30/80 in the photo to show that this same weird stuff was also used in these Audio-Technicas... and... nowhere else that I know of. Suspicious, eh? EDIT: Stax used these mineral wool "biscuits" in the SR-X Mk 2/3, the original SR-Lambda and Lambda Pro, and others, and Fostex used them in the T30 and T50. But it's true that there's suspicious commonality of parts/styling/design that all these headphones share.





There's that fluffy stuff, just like I said, except it's not resting gently on the diaphragm but rather acting to mop up any "extra" sound aimed in its direction and sort-of seal the hole in the back of the cup. It looks like fiberglass but it isn't.

Pretend fiberglass?

Below there's the back of the driver on its baffle, and the inside of the back cup is shown at left. You can see both the thin donut of opencell foam that covers the vents and a little poof of that fey yellow fake fiberglass damping fluff-- sufficient neither together nor separately to have any effect on damping whatsoever. But they won't hurt, either, so don't throw them away.



The above photo is similar to the one at the start of the thread, but it gives a much better picture of the strange holes and slots in the baffle that I mentioned earlier. We must plug any and all pathways, no matter how small, that might let bass backwave into the earcup, but first let's set about damping the driver.

Not that A-T is going to make it easy for us. They've bent the driver's leads tightly over its back, so we'll have to carefully bend them out of the way to slip a disc of felt or nonwoven polyester door-sill weatherstripping material (see photo in post #9) between them and the driver. They'll also unavoidably interfere with getting nice even pressure on whatever damping material we use. Maybe we can figure out how to get them out of our way without breaking them off. If not, I'm sure we can still get a noticeable improvement in the sound.

Okay so far? Inkmo has volunteered to look on and maybe follow along with his own screwdriver as time permits. I'm hoping we can get his opinion of the sound of the ATH-2 as we make various adjustments and modifications. Thanks, by the way to HF members ericj, facelvega and of course Inkmo, both cartoon and human, for much-needed moral support.


Oh-- just for thrills'n'chills, here's the driver from an HP-1 sitting next to the ATH-2 for a size-does-count comparison. Guess which one has more bass potential.



.
post #9 of 36
Thread Starter 

The next step-- find some porous density



Okay, now we've tucked some of that white door-sill sealer tape under the driver leads. Notice how well cut out it is. Happily, precision isn't called for at this point. Even more happily, you don't need door-sill tape either. Use some lightweight acrylic craft felt if that's what you have.

Now we need two things: One, a felt donut that will tightly cover the vents in the back cup. That foam donut presented close to zero acoustic resistance, being of the open-cell type and only about 2mm thick. Two, a roughly hemispherical chunk of stiffish opencell foam to act as a spring to press this damping pad tightly against the back of the driver. Gonna rummage now...

.
post #10 of 36
Thread Starter 

Finally--

Okay, a few little felt bits to make, then we put it all together.

(1) Damping pad: You don't have to use this nonwoven polyester stuff I used. A felt disc from the fabric or craft store will do just fine. A 40mm disc.


(2) Backwave damping: We're going to let the backwave out of the cup, but we're going to make it give up some of its energy by putting a real acoustic resistance-- not just foam-- behind both the cup's vents and the hole in the middle. Using the foam donut as a template...



cut out a felt donut of the same size, but don't throw away the hole.


(3) To act as a spring to press the damping pad tightly against the driver, we need a chunk of stiff opencell foam. You could take a cube of it and laboriously shape it with scissors to fit the earcup back, but I just cut out one "egg" of that eggcarton shaped foam that's used to transport motherboards and suchlike-- curved side facing away from, flat side facing toward the damping pad. Here's the stuff I'm talking about. Extra points if you get the pink stuff:







Here's the final sandwich. We'll fill the cup first:


a) driver cup or back cup, aka the cup. See the hole? It's bisected by a plastic bridge that holds the snap that pops into the headband. We have to damp the hole too.




b) felt donut. Press it down into the cup. Make sure the vents are covered.

c) gray foam donut (above) covers ring of felt, holds it in place

d) felt "donut hole", smack in the middle of the donuts, covering hole in center of cup

e) shaped foam "spring". --This should pretty much fill the cup.






Okay, now we move over to the driver:


a) damping disc - slipped under the lead-ins as depicted in the previous post.

b) the fake fiberglass disc goes on top of the wires, covering the back of the driver.


The cup halves will not want to go together easily if you've made your shaped foam "spring" correctly. Squeeze the cup halves tightly as you screw them together.

Fill the holes in the baffle with silicone or yellow-tak. The driver cup covers them but ideally you want to be sure of an airtight seal. When you're completely satisfied with the sound of your 'phones, you could lay down a bead of hot glue or silicone around the back cup's perimeter. Making the seal airtight forces the backwave to take the long way 'round, through the damped vents, but don't get obsessive about this. If this step sounds like too much trouble, just ignore it.

Done! Voyla, much-reduced bass-heaviness (I still hear a lower-midrange hump); tight bass with good extension, plenty of treble. Able to take EQ gracefully but sounds pretty good as-is. Keep in mind how much these 'phones cost.

Is it as good as the Pro 30? the YH-100? Very close. I still prefer the YH-100's treble, but the ATH-2 turned out better than I expected. It sounds more open than either the Pro 30 or the YH-100, as we'd expect. It's a good-sounding, usable headphone with isodynamic clarity, very good bass, and better sensitivity than most isodynamics. Give the mod a try, ring whatever changes you like, and report back.

.
post #11 of 36
egad! No images!
post #12 of 36
Thread Starter 
My thousand-and-one words should make up for any lack. I had to peel the damping pad you see in post #9 in half thicknesswise to get the sound I was after, but they finally do sound crispish on top with a nice tight bass and better headstage than just about any other isodynamic except the Fostex T30 and T50. A-T was trying to do something special with the ATH-2-- it was only their damping materials that were inadequate.

.
post #13 of 36
My ATH-3 is trembling in fear, sir.
post #14 of 36
Thread Starter 
Quote:
Originally Posted by configure
My ATH-3 is trembling in fear, sir.
Hee hee. The ATH-3 was (and still is!) a dynamic, and has nothing to fear from the likes o' me, guvna.
post #15 of 36
Man, I need to hurry up and do this mod. Next weekend maybe.
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Headphones (full-size)
Head-Fi.org › Forums › Equipment Forums › Headphones (full-size) › Ripping Apart An ATH-2: a continuant saga