Orthodynamic Roundup

[lcsaszar]

I am also a proud owner of a pair of Peerless PMB 100. I purhased them from Germany, and of course I disassembled and inspected them inside. I also recabled them internally, painted the internal felt black and repainted the rear metal grille. I replaced the ear foam with thin perlon wool covered with loudspeaker silk. Its sound is great, but its comfort is not the best. It tends to fall down from one's head if not sitting straight (e.g. in laying position). Also they are lacking bass.

I played around a bit with an audio signal generator. The falling of bass is noticeable below 100 Hz, and no sound can be heard at 20 Hz. I am very interested how could be the bass boosted with the holes covering or internal felt trick.

I have (had ) another set of ortos, the Technics EAH-820. It has rectangular diaphragm. Unfortunately one side is broken. Could someone give me some advice how can I replace/repair it? I removed the good diphragm, and it could be used as a template for photograhic duplicating. I even purchased some thin aluminium-covered plastic foil, that seems to be similar in thickness. Now I have to transfer the pattern from the good diphragm to the foil with some photoresist method, then etching it. Here is a photograph of the diaphragm:

http://tube.fw.hu/Technics_diaphragm.jpg

 

[ericj]

Wow, that technics serpentine diaphragm is beautiful!

What is wrong with it? It looks like the membrane is intact.

If it is an open circuit, if you can find the point where the circuit is broken, you could carefully mask the area and use conductive ink to repair the break. You can get this either in the form of a "Circuit Worx" pen or a window de-froster repair kit from an auto-parts store.

 

[ericj]

And speaking of orthos, my Realistic Pro-30's just arrived.

I like the construction. the capsules have a quick release from the headband that allowed me to hose down the headband with formula 409 and rinse it in hot water, so that's good. headphones this old are always dirty.

The vinyl of the earpads is the least offensive I've known to date, which is to say that i still prefer velour. Clamping force is significant, but they are essentially comfortable.

They sound . . . good . . . but I'm not immediately falling in love with them the way i did with my yamahas. So far I've only listened to A Silver Mt Zion's "Horses in the Sky" and Belle & Sebastian's "Lazy Line-Painter Jane" with them.

Any recommended damping tactics?

 

[lcsaszar]

This is the intact diaphragm indeed. The other is broken. I tried repairing it with "liquid silver", a PCB repairing fluid, but no avail. I contacted a company who scanned it and probably it is possible to transfer the pattern to the foil, but I have no idea how to do it. Someone suggested that I should try with a photoresis lacquer, the type used for home printed circuit boards. BTW, here is the scanned pattern:

http://tube.fw.hu/fejhpoz.tif

I looked for some data from the Technics EAH-820 on the web, but I could not find any word on it. I searched about the original operating instructions that is in front of me. I will make photos from it and from the parts.

 

[facelvega]

Quote:

Originally Posted by lcsaszar /img/forum/go_quote.gif I am also a proud owner of a pair of Peerless PMB 100. I purhased them from Germany, and of course I disassembled and inspected them inside. I also recabled them internally, painted the internal felt black and repainted the rear metal grille. I replaced the ear foam with thin perlon wool covered with loudspeaker silk. Its sound is great, but its comfort is not the best. It tends to fall down from one's head if not sitting straight (e.g. in laying position). Also they are lacking bass. I played around a bit with an audio signal generator. The falling of bass is noticeable below 100 Hz, and no sound can be heard at 20 Hz. I am very interested how could be the bass boosted with the holes covering or internal felt trick.

Hey lcsaszar, welcome to head-fi! Wow, you did an internal recable? You're way ahead of me. Are you still using the stock removable external cable? I fully agree with you about the way they can slide off if you're not standing or sitting upright-- but as long as I'm upright, I find them pretty comfortable actually.

On your bass issue: as I found with the tape experiment, the driver is producing more bass than is reaching the ear, and it can be recovered by cutting the backwave. I haven't yet started experimenting with felt to see if I can find a happy medium between soundstage and bass, but in principle it should work.

FV

 

[wualta]

This upsurge of isodynamic brotherhood is amazing. Where to begin?

First, here's a photo of an EAH-830's diaphragm, still in its frame.

As you can see, it will probably be more trouble to repair such diaphragms than to simply buy another set of headphones via online auction. You could probe along the aluminum trace with an ohmmeter and a low-power microscope and try to aim a tiny dab of silver paint when and if you find the break (which could be a microscopic hairline crack), but it's not the method I'd recommend if you aspire to sanity. This is especially true of the original Orthodynamic and PMB100 diaphragms, which are corrugated and thus harder to inspect.

Having said that, some of us are artists. We don't think in practical terms. If we see something that strikes us as elegant and beautiful (in both Apollonian and Dionysian senses), we must have it in its pristine state, no matter the cost. So don't let me talk you out of trying to make the diaphragm from scratch using the photolithography techniques originally used by Matsush'ta/Technics. Just don't expect it to be easy, cheap or successful at the first or even third go.

The EAH-830 thread is here, by the way. I took the liberty of PhotoShopping Icsaszar's scan of the 820 diaphragm and posting it to that thread.



Damping the Pro 30 is just like what we might call Stage One damping of the Yamahas: stick one or two discs of cheap fabric-store felt behind the driver and cut rings of felt to damp the circumferential vents (the Yamahas already have felt for the vents). The stiff foam pad in the Pro 30 presses the felt against the drivers very nicely, or at least it did when the headphone was new— you might want to add some fresh foam. The Yamahas could use something like that. I'll try to take apart my Pro 30s this weekend and shoot some photos. And you're right, they'll sound kinda sorta okay, not bad for 1984, right out of the box. Audio-Technica, who made them for R.Shack, did try to damp them, but left the job only half done. Sneak over to JoAnn Fabrics (a national chain with an online presence), get a 25-cent 12" square of felt, borrow your mom's scissors, practice good scissors safety, and practice cutting until your felt discs are perfect circles-- doesn't help the damping but does wonders for the feng shui-- and report back.

To answer an earlier and very important question put forward by brewdog, the way to tell if a headphone (or speaker or any transducer) needs damping is to see if it has difficulty handling transients-- sharp clicks and tics. With a headphone, the easiest test would be to quickly brush the heaphone's connector across a voltage source, like a small battery. Some inexpensive clip leads from, yes, Radio Shack come in handy for many things, and this is one of them. You should hear perfectly sharp little tik-tik sounds, almost like the ripping of a fine fabric where you can hear individual tiny filaments breaking. If you hear anything else, there's a problem. Yamaha proved with the Orthodynamics that a headphone could have an absolutely lousy transient response and still sound halfway decent. I've always maintained that the reason the Orthos could get away with this was that their natural resonance was fairly smooth and linear and distributed evenly over a large area of the audio spectrum rather than concentrated in one spot, but that's another story. Try the DC-flick test on the YH-1000 and report back.

To all of you embarking on this "finishing the job the manufacturers started" adventure, welcome. These things are as rewarding to work on as bicycles.

 

[ericj]

Quote:

Originally Posted by wualta /img/forum/go_quote.gif Damping the Pro 30 is just like what we might call Stage One damping of the Yamahas: stick one or two discs of cheap fabric-store felt behind the driver and cut rings of felt to damp the circumferential vents (the Yamahas already have felt for the vents). The stiff foam pad in the Pro 30 presses the felt against the drivers very nicely. The Yamahas could use something like that. I'll try to take apart my Pro 30s this weekend and shoot some photos. And you're right, they'll sound kinda sorta okay, not bad for 1984, right out of the box. Audio-Technica, who made them for R.Shack, did try to damp them, but left the job only half done. Sneak over to Field's Fabrics, get a 25-cent 12" square of felt, borrow your mom's scissors, practice good scissors safety, and practice until your felt discs are perfect circles-- doesn't help the damping but does wonders for the feng shui-- and report back.

I've actually got a good sized scrap of an impressively dense wool/rayon blend felt that I've been cutting discs out of in my YH-2 experiments. I need to take some pictures of that and report my results here . . . . some time this weekend.

As for the Pro 30, yeah, in 1984 I doubt anyone was disappointed for the $50 these cost. It's really not bad at all. I'm just not feeling the *beauty yet, yaknow?

I almost wonder if that disc of white material clamped to the back of the Pro 30 driver is too agressive, but I can't convince myself that it's a problem. Or that i can safely remove it without screwing up the driver.

 

[wualta]

Quote:

Originally Posted by ericj I almost wonder if that disc of white material clamped to the back of the Pro 30 driver is too agressive, but I can't convince myself that it's a problem. Or that i can safely remove it without screwing up the driver.

It's glued on, and you're quite correct-- it's not a problem; in fact it's a help, and though it may look "aggressive", in practice it's not aggressive enough, but you'd still be setting yourself back if you removed it (simple enough to do with a blowtorch, but why bother with headphones when there are cats to frighten?).

The rule with damping these things is that if it looks like too much, it's probably only half of what's needed. Having said that, too much damping is, well, too much. It gives you fantastic transient response but a bloodless trebly sound that only certain people will like. If you do a damping mod and all the bass goes away and won't come back even with a bass EQ boost of seismic proportions, you've overdamped.

It's also worth noting that two layers of insufficiently-dense damping material doesn't double the amount of damping, at least not in my experience. Sounds weird, I know. I have no good explanation for this. Damp properly in one layer (and/or tweak this one layer with a reflex disc), but if that doesn't do it, find a denser material for your damping disc.

 

[brewdog52]

Hey all,

I don't have my digi camera handy right now but I'll post some pics tomorrow along with the damping results. I think I will check into those Koss KSC-75 headphones, these yamaha's are for more at home and not the best for portable use. The player i'm using is a Cowon A2 with a 1/4" to 1/8" adapter, for most of my pcm wav tracks I have the volume set between 34 and 38 out of a 40 max and it's pretty loud(Some songs I have maxed but it's still plenty loud). Would I still benifit from having an amp? If so any recomedation on what to look into? I also have a sony 650w receiver but haven't tried that yet because I need to retrieve some cd's out of my dvd changer ( I tipped it upside down like an idiot while moving it around, and now the doors stuck open). - Thanks again for all the replies, I'm getting pretty excited over these old headphones. Take care all.

 

[wualta]

Quote:

Originally Posted by brewdog52 I don't have my digi camera handy right now but I'll post some pics tomorrow along with the damping results.

I strongly suspect you'll find that Yamaha placed no more damping in the YH-1000 than it did in any of the other Orthodynamics. I'd be pleased to be proven wrong. Eagerly awaiting the photos.

UPDATE: Not that I want to break the suspense, but the photos never arrived. However, Yamaha DID use damping of a sort (the fake fiberglass cookies used in Stax electret and Audio-Technica and Fostex 'phones) in the YH-1000. 

 
Quote:

Originally Posted by brewdog52 I think I will check into those Koss KSC-75 headphones, these yamaha's are for more at home and not the best for portable use.

Yes, don't take them outside. There's a structural weak point, the short plastic strut that connects the headband to the earcup and ends in a ball joint. If that breaks, you're done for. You'll like the KSC-75. Watch HF for excited postings indicating they're on sale somewhere.

 
Quote:

Originally Posted by brewdog52 Would I still benifit from having an amp? If so any recomedation on what to look into?

Yes, definitely, or even deafanatley. Start with a simple inexpensive CMoy amp. Tons of 'em available on eBay.
 
Quote:

Originally Posted by brewdog52 I also have a sony 650w receiver..

Be aware that the amps (and thus the headphone output) in midrange Sony home theater receivers tend to sound terrible.

 

[ericj]

Quote:

Originally Posted by wualta /img/forum/go_quote.gif Yes, don't take them outside. There's a structural weak point, the short plastic strut that connects the headband to the earcup and ends in a ball joint. If that breaks, you're done for. You'll like the KSC-75. Watch HF for excited postings indicating they're on sale somewhere.

I suspect that the metal cup that the joint terminates to is held into the earcup with the same double-sided sticky tape as most of the stuff in these are held together with.

If that's true, an extended soak in alcohol will make it possible to disassemble the earcup and retrieve pieces of the joint.

What to do then? Heck, I don't know. Maybe solvent weld with methyl-ethyl ketone.

I also wonder if removing the "L" or "R" label from the headband will reveal a screw.

 

[brewdog52]

well I just tried the damping test with a 4AA clip and aligator clips. I did get what very much resembles a tearing sound when quickly running the clip acrossed the surface and more of a click when I just tapped the clip on the surface. Pictures are not up yet, I need to find my usb cable ( I haven't used my digi for months). If I don't find it soon I'll run into town and grab a cheap card reader later today. I also ran across some DIY CMoy amp plans that looked interesting ( made from a altoid tin and another made out of a cig pack), or it might be easier to buy one. Anyway I should have some pics up soon.

Edit: I just tried the damping test with the headphones that came with my player and it somewhat sounded the same but alot more static sounding and not as distinct tearing sound, more like a static tick.

 

[brewdog52]

I just recorded the damping test with my A2, so I can let you guys judge it. I just need to find a place to upload it( never uploaded mp3's before).

 

[brewdog52]

http://www.fileden.com/files/2007/3/...ing%20Test.mp3 I'm trying to download this myself and it's super slow.

 

[wualta]

Quote:

Originally Posted by ericj I suspect that the metal cup that the joint terminates to is held into the earcup with the same double-sided sticky tape as most of the stuff in these are held together with.

I wish. Turns out the metal cup has a flange that sits in a cutaway just the right size with keyways to make sure it's oriented correctly, then a ring of plastic is sonic-welded (looks too neat to be solvent) down on top of it, locking it in place. You basically have to destroy the cup to get the thing apart.


Quote:

Originally Posted by ericj What to do then? Heck, I don't know. Maybe solvent weld with methyl-ethyl ketone.

Hee hee. I was thinking epoxy the heck out of the broken strut, then a steel ferrule (like a butt connector) clamped gently over the still-curing joint for reinforcement. The strut's hollow, as it turns out. Thick walls but still hollow. Couldn't believe it. The whole assembly seems needlessly complex for something that ends up being so vulnerable. Want to see a photo?

You can see the chewed-up fixing ring that holds down the metal cup. The front half of the ring has been broken off. ...Does this seem needlessly complex to you?

Quote:

Originally Posted by ericj I also wonder if removing the "L" or "R" label from the headband will reveal a screw.

Good idea, but nah. Checked it both with a NdFeB magnet and by near-total destruction.

Brewdog, the difference in efficiency between the two 'phones will make it difficult to compare. But if the YH-1000 really does go tic instead of chickhhh (and I'm exaggerating here for clarity), no hollowness, no rubbery echo, just a quick start and stop, then it may have some damping goin' on. That I'd like to see. Do see if you can get hold of a KSC-75, though. It'll give you something known-good (not great, but good) to compare to.

UPDATE: Listening to the mp3 and accounting for compression artifacts and microphone quality, it doesn't sound too bad. Thanks for doing the test and recording it! That was going above the call of orthodynamic duty. Loaded quickly for me, by the way.

.