Oh shit! SINAD can suck my ****s

Discussion in 'Measurement Techniques Discussion' started by Marvey, Jul 2, 2021.

  1. Hartono

    Hartono Rando

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    Does these later test done with only one driver connected ? or both L&R channel driver connected to the amp ?
     
  2. Marvey

    Marvey Super Friend

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    Both. L and R signals and measurements are run separately to avoid effects of crosstalk.
     
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  3. Marvey

    Marvey Super Friend

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    This is mounted on my head (not free-air). Fs is around 73Hz. Even if free-air, Fs doesn't change much, although bump goes down a bit. Chalk it up to production variances and silent revisions. It's all close enough. 6H choke - haha.
    upload_2021-7-14_9-18-23.png
     
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  4. atomicbob

    atomicbob dScope Yoda

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    Version 3, will implement this one.
    HD650 simulator v3.png

    Correlation between HD650 LCR Z measurement and the circuit simulation:
    HD650 LCR Z vs Sim Z v3.png

    I have two HD650 headphones and the LCR Z measurement is very close between them.
     
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  5. Hartono

    Hartono Rando

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    if both driver are connected to the amp during the whole procedure, I think the situation I described in post #116 is still happening here, albeit at much reduced level because the shared (L&R) return ground wire from the Y splitter is much shorter.

    Not to derail or not respect the original intent of these tests, just trying to get to the real cause here. Really appreciate all the effort for the testing.

    Maybe it is not back EMF but rather the second channel amp is interacting and cause this distortion, if that so then all 3 pin non transformer/balanced stereo headphone are affected.

    The only way to be sure is to have only one driver channel connected during the testing.
     
  6. Marvey

    Marvey Super Friend

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    Now that I feel I can get consistent results:
    1. I'll give it shot with only one driver connected and driven.
    2. Will try other Y connectors to see if there is any difference.
     
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  7. NekoAudio

    NekoAudio Acquaintance

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    I guess you'd need to have the other channel's wiring completely removed from the equation, meaning a custom-made cable?
     
  8. nobodyNoot

    nobodyNoot Rando

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    For anyone who wants to quickly double-check their math on these filters, here's a website I found a while ago with a whole bunch of useful tools:
    http://sim.okawa-denshi.jp/en/

    Good luck!
     
  9. Marvey

    Marvey Super Friend

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    Thanks for link!

    I don't know if you saw @atomicbob's post but he already validated and tweaked the RLC-RL-R circuit in SPICE.

    LTSPICE does circuit sims. The only downside is a crappy UI which hasn't changed since the days of MS-DOS.
     
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  10. atomicbob

    atomicbob dScope Yoda

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    breadboard proto validation

    HD650 impedance measurement with Dayton Audio Test System v3
    01 20210702 HD650 impedance DATS L.png

    LT Spice simulation for HD650 impedance simulator
    02 HD650 simulator v3a.png

    HD650 impedance simulator breadboard proto measurement with Dayton Audio Test System v3
    03 HD650 simulator proto.png

    measurement setup
    04 IMG_2907_small.jpg

    Closeup of HD650 impedance simulator breadboard proto
    05 IMG_2909_small.jpg

    Next step is to create a two channel hard proto.
     
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  11. wormcycle

    wormcycle Friend

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    I wonder what people way more knowledgeable think about this video. I do not know if he gets everything right but it is well made, and I definitely learnt from it
     
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  12. Ox Cart

    Ox Cart Facebook Friend

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    I didn't find the argument convincing. As i understand it, the idea is that not all distortion is created equal, so boiling it all down to one number misses details about the distortion profile. The video then gives the example of -50dB distortion at higher order harmonics. The problem is, with super high SINAD, none of the higher order harmonics is anywhere near -50db, so it's not necessarily audible.
     
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