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DIY Planar/orthodynamic/isodynamic drivers

Discussion in 'd.i.y.' started by Sposhal, Nov 28, 2019.

  1. Sposhal

    Sposhal Member

    I have fixed all the resonance issues I was having, was all to do with the way the diaphragm was glued. Going to work on finding or producing a thinner film to make this driver as detailed as I can get it to sound although I admit it sounds pretty nice right now. I also need to work on increasing its impedance as it is currently measuring at 3.1 ohms which is rather low.

    Edit: resistance not impedance
     
  2. sq225917

    sq225917 situation engineer

    Are you measuring impedance, or resistance?
     
    Sposhal likes this.
  3. Sposhal

    Sposhal Member

    Typo, meant resistance.
     
  4. Sposhal

    Sposhal Member

    Small update whilst I wait for new materials to arrive. I decided to test mount the drivers on a spare headband I had lying around for some easy listening. After adding felt strips to the magnets and some thicker natural felt over the back of the driver it sounds pretty good, but I think with a thinner diaphragm I could get a bit more detail out of them.

    [​IMG]
    [​IMG]
    [​IMG]
     
    Marra likes this.
  5. sq225917

    sq225917 situation engineer

    They look awesome
     
    Sposhal likes this.
  6. Sposhal

    Sposhal Member

    Glad you think so :)
     
  7. davidsrsb

    davidsrsb pfm Member

    The tracks could be made much thinner, allowing far more "turns" and get the impedance up to a nominal 32 Ohms.
    This would also improve the efficiency.
     
  8. Sposhal

    Sposhal Member

    I intend to do this once I get the new material as aluminium will increase that too, that way I can work out how many more turns to add.
     
  9. Sposhal

    Sposhal Member

    I changed my mind, I decided to experiment with the turns on the trace, I'm so glad I did. With the current material I am able to get very fine traces with my set up so I wanted to see how far I could push it, although I think I could probably have gotten a bit smaller if I tried. Here are some photos to show the difference, had to break out the dslr as my phone wasn't able to focus where I wanted.

    Original - 4 turns - 1mm per line - 3.2 ohms
    [​IMG]
    V2 - 7 turns - 0.5mm per line - 7.1 ohms
    [​IMG]
    V3 - 14 turns - 0.5mm per line - 31 ohms
    [​IMG]

    V2 sounded significantly more detailed and the midrange wasn't muffled any longer, V3 improved on that further. Not sure if I will be able to get these tolerances with future thinner and lighter materials but I'm not going to go for less turns than on V2 any more :)
     
    Mike P and Marra like this.
  10. a.palfreyman

    a.palfreyman pfm Member

    Looks an excellent project. You might need to consider coating the copper to avoid long-term oxidation, e.g. a brush-on silver plating solution?
     
    Sposhal likes this.
  11. Sposhal

    Sposhal Member

    Don't worry, I'm not sticking with the copper, I will be using aluminium in the final product, just sourcing a different material at the moment.
     
  12. Mike P

    Mike P pfm Member

    Great work :)
     
    Sposhal likes this.
  13. davidsrsb

    davidsrsb pfm Member

    V3 is nice as that is spot on a standard impedance for headphones. Impedance and resistance will be the same thing up to at least 1kHz.
    Actually measuring the impedance against frequency is easy to do with a PC soundcard and highlights any resonances in the driver
     
    Sposhal likes this.
  14. Sposhal

    Sposhal Member

    I'm definitely interested in finding out what resonances I have as I found that depending on how well the diaphragm is glued it resonates more or less, still working out which glue works best/ most consistently. I have tried measuring past prototypes using rew with a rough setup using the umik-1 mic that I had lying around but I haven't used rew much so I wasn't able to gather much info from it other than frequency response and distortion. Going to wait until I try the new material before I measure again as I think it's natural resonance will be out of the playing range.
     
  15. davidsrsb

    davidsrsb pfm Member

  16. Sposhal

    Sposhal Member

  17. awkwardbydesign

    awkwardbydesign Officially Awesome

    I would if I could understand it! Both inputs of the soundcard? What? :confused:
     
  18. davidsrsb

    davidsrsb pfm Member

    It is a measuring bridge. I suggest 100 Ohms for the sense resistor. Two inputs allow you to measure the voltage across this resistor and hence the current. Given the voltage across the load and the current through it, you can plot impedance and phase.
    Resonances in the diaphragm and magnet frame will show up as wrinkles in the trace
     
  19. awkwardbydesign

    awkwardbydesign Officially Awesome

    Two inputs to the soundcard is where you lost me. I understand a measuring bridge, in fact I have a funky diy manual version.
     
  20. Sposhal

    Sposhal Member

    Well I hope to put in an order for a roll of 6 micron aluminium + 12 micron mylar, shame you have to order so much of the stuff but I definitely wouldn't be running out for a long while. In the mean time I have some 10 micron aluminium arriving in the next 4 days to experiment with attaching to some 3 micron mylar I already have, should be interesting.

    Oh and for a laugh I decided to make a diaphragm out of regular kitchen aluminium foil and the mylar I already have, sounds not bad considering how thick it is

    [​IMG]
    [​IMG]
     
    Last edited: Dec 6, 2019 at 5:53 PM

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