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hello im sean 9th May 2012 06:13 PM

DIY Orthodynamic drivers? (for headphones!)
Hi I'm new here from HeadFi. I figured this was the best place to ask because i've seen a lot of full sized speaker builds using planar tech but has anybody made maybe a 80mm orthodynamic driver for a custom set of headphones? It seems that tiny rectangular neodymium are actually pretty inexpensive to obtain in the US which is where i am. To me the tricky part seems like making a diaphragm that tiny. Could it be done with an ESL approach to the diaphragm by using a conductive coating? or does it absolutely have to be a conductive wire? I've only just gotten into Ortho's and ESL but it really interests me and i'm a pretty handy DIY'er. Any advice would be greatly appreciated. thank you


khbaur330162 10th May 2012 01:48 AM

I'm probably not the best to answer your questions, but certain areas of this forum seem pretty, well, impatient with guys like us (limited knowledge). Being in a similar boat as you I figured I'd respond and hope to be of some help. Maybe we can draw some attention and get the older, more experienced members to whip our mindsets into shape, who knows?

The magnetic field is created per the direction of current in your conductor. If you wanted to use a "coating" I'm imagining some sort of conductive ink that you'd be printing onto the substrate which then leaves me questioning the power handling of said conductive ink/coating, heat dissipation, reliability, etc. An expensive route requiring job specific equipment with pretty up in the air results for a one-off, imo.

Those tiny cube magnets would be hell to check the polarity, orient directionally, and then somehow glue or clamp in place. You'd basically be making standard bar magnets with hundreds of tiny 5mm^3 pieces which seems like a lot of hassle for what it'd save you in cost. That said this patent could maybe put good use to those tiny cubes if you took the time to measure everything out perfectly, although that's an extremely ambitious design for a first-time DIY planar magnetic project. It sure drives me away.

Capacitor foil could be etched into the desired circuit design. It's very close to what I'd consider near optimum for a diaphragm material. ER Audio also sells Aluminized tweeter foil that might be right up your alley with a similar idea in mind. If you didn't want to etch it yourself RFID's are scary close to what you'd be trying to create so if you can find a place that's in both the foil and RFID business that can create a polymer film per your spec and "print" the desired artwork >>in small runs and for cheap<< you'll have to tell me who they are because I'd really like to know. I'd imagine most places are looking at 10k+ feet and thousands of dollars as a minimum order, and that's if you can find a place that's even willing to humor something that specific and short of a run.

Head-Fi member Setmenu made his own ribbon drivers. Have you seen that? Most of the pictures are dead and information is strewn between multiple threads, but other people saved/hosted a few snap shots of the second gen carbon fiber prototypes that he got running and it was all very interesting to read about and see.

hello im sean 10th May 2012 03:49 AM

Thank you so much I really appreciate your response. I came to this forum to try and learn as much as I can as fast as I can. There's a great culmination of knowledge here too. Hopefully ill be able to contribute back some day thank you.

lcsaszar 11th May 2012 01:56 PM

I have a pair of Technics EAH-820 and a pair of Peerless PMB-100 orthydynamic headphones. The Technics can be taken apart (I did). The diaphragm has an aluminium layer etched, which is difficult to reproduce. You can see it in this other thread:

Technics EAH-830

Also the magnets are flat ferrites with holes, and an alternating pole magnetism. There are paper spacers, and the plastic frame holds all together. The magnets are mounted in a repelling fashion against each other, so that the flux lines are parallel to the diaphragm, perpendicular to the wires.

You can buy such and other old headphones cheap on eBay, there is no sense to build one IMHO.

hello im sean 11th May 2012 03:18 PM

i suppose any production driver would be better than one i can make. the more i research the more finicky i realize it is unfortunately. thank you though, i was curious to see if it had been done before.

JAMESBOS 13th May 2012 09:58 AM

10 Attachment(s)
I did start a planar headphone using an old headphone I had,using 2 different magnet layouts, but got sidetracked with something else. Never finished them. See photos!

JAMESBOS 13th May 2012 10:22 AM

10 Attachment(s)
They are very fiddly to stick the foil to the thin diaphragm, especially at my age(73)!! It's easier with the full size diaphragms, although it does get harder when you use 6 um mylar!!!

khbaur330162 14th May 2012 06:35 AM

Henry: That looks awesome. Got a couple questions, though. What's up with your circuit layout? I'm trying to follow it and it looks like you've got current running opposite directions in very near proximity. Also, you planned on only having magnets on the rear, correct?

Anyway, really cool and I hope you finish the project. Ear speakers like a Stax Sigma could be interesting taking this route, imo.

JAMESBOS 14th May 2012 07:47 AM

This layout is the epsilon layout, which uses the whole area of the magnets to improve control and sensitivity, the foil direction goes in groups of 3 i.e.3 up 3 down, 3 up on 1 magnet and 3 down on the next. Yes magnets on the rear only.

hello im sean 14th May 2012 01:39 PM

very interesting design, so you were going to have magnets on only 1 side of the headphones as well? also what is the foil in the diaphragm made of? and one more question, please excuse my ignorance for i'm trying to learn, but why push all of the magnets together so close? on most planar headphones i've seen the magnets are much more spaced out

Back to my idea on drivers i was thinking i could cnc an imprint of a very thin serpentine groove into a round block of aluminum then mirror it over to an identical block. Then i'd have the fun time of finding a sturdy conductive and thin wire i can lay in between the sandwiched blocks. after i get a good fit and the wire bent into shape i could find a polyester sheet maybe 3 microns thick that can be thermally bound. place the polyester on the face of each aluminum block and press the wire between them. after that all i'd have to do is heat the aluminum hot enough to bond the sheets of ployester and there you have it. does this sound logical? or am i missing something crucial.

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