HD600 raw driver measurements

Discussion in 'Audio Science' started by Serious, Sep 21, 2016.

  1. Serious

    Serious Inquisitive Frequency Response Plot

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    Hinted at it here and just realized I never posted them:
    [​IMG]
    As you can see, the driver is resting on my coupler. For this measurement the material sat on plastic box, so there's a hard plate behind it. Might be interesting to repeat these measurements, but with only air or a very soft foam behind the material. I would also like to measure the driver from some distance like you would measure speaker drivers. Ultrabike posted such a measurement a few days ago, but of the whole headphone and not the driver itself.

    I think we should get more "raw driver" measurements of headphones. Maybe we should start measuring the headphones themselves in free space like the old stereophile measurements? But I'm not sure how well that would work. It seemed pretty difficult to get good results with the HD800 this way, but the HD800 driver seemed to be more linear than the HD600 driver (which seemed bumped up around 3-4kHz). BTW (if I wasn't clear enough on that before) the HD800 driver has extremely awesome CSD measurements with no hint of ringing at 6kHz (or any other frequency in the audioband for that matter).

    I mainly did these measurements to confirm that the HD600 driver has a resonance at 5kHz. It also has a resonance at 12kHz and at 24kHz.
    Raw Driver FR.png
    The green line is the driver resting directly on the material (as pictured). The red line is the driver on its back, resting on the black plastic cage. The blue line is the driver resting on a 2cm thick foam. I used a very thin foam that doesn't absorb a lot of HF energy.

    Here's what the CSD looked like for the driver resting directly on the coupler:
    Front CSD.png
    I know the 12kHz resonance looks horrible, but it's actually pretty benign with more distance to the driver. It's not very bad with the actual headphone on a coupler or on a head. The slow decay on the left is simply how the bass rolloff affects the CSD visualization. That doesn't mean shit. Apart from the resonances at 5 and 12kHz the decay is very clean.

    I think the HD600 driver itself actually has more treble energy from 5-7kHz than the HD800 driver which just goes to show that there's much more a headphone than its drivers. The HD600 driver also has a rising response from 12kHz on up to its 24kHz resonance. When I put the headphones at some distance from the coupler, the HD600 CSDs never look as clean as the HD800. I will probably post those measurements soon.

    I wouldn't try to use headphone drivers as tweeters for speakers, even if the HD800 driver is very special. I'm sure its sensitivity is crap for speakers and its resonant frequency is very high for a driver of its size. You can't use it below 2kHz. Tak measured the HE-6 driver at 50cm distance and I think that also seemed pretty flat (like many other good headphone drivers). From a pure material coloration and distortion performance point of view I'd be interested in using the HD800 drivers as tweeters, if just for a comparison against other exotic tweeters. Anyway, enough rambling. I thought this would be interesting.
     
    Last edited: Sep 21, 2016
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  2. New Reformation

    New Reformation Almost "Made"

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    This is such an awesome service to the community! Most drivers I have seen being sold from china are measured without an enclosure. By having measurements like what you have provided, those who want to experiment with building headphones from scratch or performing driver substitutions can be better informed on what to look for.



    John Grado says, "Hi".
    [​IMG]
     
    Last edited: Sep 21, 2016
  3. Armaegis

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  4. Serious

    Serious Inquisitive Frequency Response Plot

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    Getting back to this now.

    I'm not sure how useful one measurement on my particular coupler is, but thanks! Generally I would look for drivers with smooth responses.

    Those two speakers with headphone drivers look insane. Doubt they sound good though, especially the Grado one.

    Tried some more of those measurements. Settled on an extra 3cm coupler foam behind my 1" thick coupler plate. I might go for such a thick coupler for all of my measurements, but it usually makes the measurements look very bassy. The plus side is that it gets rid of the small wiggles between 50-300Hz that I get with the HD800 on the thinner material, so I think it's a more realistic, less resonant coupling. Anyway, here's what happens when I put both headphones on a 4cm thick, very open sponge, on top of the regular coupler. I tried it with and without pads for both headphones and preferred the results with pads. This is supposed to isolate the driver more from the cups.
    HD600+HD800 on baffle2.png
    The HD800 driver has a very smooth response. I'm not sure where the tiny bump around 9kHz is coming from.

    What's more interesting are the CSDs for these measurements. Look at the scale, these go up to 42kHz. I tried to compensate my microphone for the results to make more sense but I might have overdone it a little. I'm not sure how high the HD800 driver extends. They're probably inaccurate above 20kHz.
    HD6004cmDistCSD4.png
    This is really just another confirmation that the HD600 driver rings at 5, 12 and 24kHz.
    HD8004cmDistCSD4.png
    As you can see, huge resonance at about 38.2kHz. I wouldn't worry about the weird response around 30kHz. That's just my wonky compensation curve trying to compensate for microphone resonances.
    We knew that the Elear would ring like mad, but the HD800 driver is a softer material. It still has a very sharp resonance. 38kHz is impressive for a driver this size. The 1" ceramic tweeters ring at a lower frequency. In this measurement the 9kHz bump looks like it could be a driver feature, but I think it's something else. With the coupler we don't see a bump around here. There also doesn't seem to be a bump here with more distance.

    Finally, here are both drivers measured at about 1ft distance, to get closer to a speaker driver measurement. This is in my room and I gated it after 5ms to avoid most reflections, but there are still some early reflections. Would be much better to just repeat this measurement in anechoic conditions. This measurement seems to confirm that the 9kHz bump in the HD800 measurement is not the driver.
    HD600+HD800 1ft free air 5msGate3.png
    I'm not sure what's up with the steep notch in the HD800 plot at about 13.3kHz, or the 5.4kHz notch with the HD600. The 4kHz dip in the HD800 plot is probably related to the enclosure. The driver itself seems smooth in this region. In this case the HD800 driver seems to be about 5db more efficient. With the headphones on the head it's not as much.

    Anyway, these measurements were mostly just to reiterate that the HD800 driver is pretty fantastic with no resonances in the audioband. The stock HD800s issues can actually be corrected with mods, whereas I'm sure that no mods can fix something like the Beyer Teslas.


    EDIT: Tweaked compensation a little for the ultrasonic results. Should be more accurate now.
    Also fixed level for the free air measurement and applied the new compensation to the other FR plots.
    I think all plots are sorted now. Pretty tired now.
     
    Last edited: Sep 30, 2016

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