MEASUREMENT FAQ

Discussion in 'Measurement Setups, Systems, and Standards' started by purr1n, Sep 28, 2015.

  1. purr1n

    purr1n Finding his inner redneck

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    MEASUREMENT FAQ

    Q: Can't measurements bias one's perception of a headphone?
    A:
    Of course! However, lots of other things can influence how a headphone is going to sound like. Comfort, fit, construction, build quality, marketing, advertising, Jude's YouTube videos, hype (deserved or undeserved), price, et. al. will also influence how a headphone is going to sound like. The good thing about measurements is we don't have to look at them. Longtime readers of this site will know that I always listen to a headphone first to jot down subjective impressions before taking measurements.

    We can also make a counter argument: measurements might help us become better (more critical) listeners.


    Q: Can measurements "lie"?
    A:
    Absolutely. Measurements don't tell the whole story, the information they provide is too limited. This is why I like to post as many different kinds of measurements as easily obtainable: frequency response, cumulative spectral decay, and distortion plots. I like to think of measurements as a tool. Measurements can more easily tell us if something is wrong with a headphone than if a headphone is awesome.

    The frequency response measurements have perhaps the strongest correlation to what we hear as tonal balance. CSDs seem to be most effective at discerning any issues (peaks) from the midrange on up; and have some limited correlation to articulation and resolution. Distortion measurements tend to relate to overall clarity, "blackness", "fidelity" of sound; and appear to be the most difficult for measurement newbies to correlate to subjective sound quality.


    Q: Should I use measurements to determine whether I should buy a headphone or not.
    A:
    Best to get the headphone and try it out for yourself. Otherwise use numerous sources. Talk to friends who have heard it. Talk to people you trust. Use measurements. Consider all sources of information for proper due diligence. Use measurements here. Use Tyll's measurements. Most of all, consider negative information, whether they be measurements or subjective impressions. It's impossible to get transducers to do everything right.


    Q: Your measurements say bad things about headphones like the Grado, therefore I don't agree with your measurements.
    A:
    That's fine. I respect John Grado for tuning his headphones according to a vision. He had a vision for a certain sound, and he's certainly hit the target right on the mark. I'd be more worried if Grado headphones sounded all over the place.

    While you may not "agree" with the measurements, the measurements do tell us that Grados (RS-1 and below) have a consistent house sound that is very different from that of Audezes headphones. I'd argue that measurements tell us more about the differences between a Grado and an Audeze and than two fanboys arguing over which one is better.

    Finally, measurements have nothing to do with personal preference.


    Q: Your measurements look different from manufacturer provided measurements.
    A:
    Measurements can be used as marketing tools or inadvertently improperly presented. One "trick" I've seen recently with measurements is to present distortion graphs using a linear instead of logarithmic scale on the Y-axis. We hear on the logarithm scale. The use of linear scale can hide "problems". Also, SPL is a huge factor in distortion measurements. One way to lower distortion is to run at softer volume levels.

    Other methods can involve setting the floor too high on CSD plots, using excessive smoothing, visually compressing the Y-axis while expanding the Y-axis range on frequency response graphs, etc.

    I tend to measure at high SPL and present measurement visualizations in a manner which I feel slightly exaggerates issues so we can "see" what is going on. Changstar is not trying to sell headphones or get sponsorships. We want to know all possible issues with a headphone - with the understanding that nothing is perfect.


    Q: Can I compare measurements using one method with measurements using another?
    A:
    In general no, unless you are really familiar with the methods and how they tend to deviate from each other. However, this does not mean you cannot look at a measurement here, and then check InnerFidelity to see if there are certain consistent patterns.


    Q: I don't understand the measurements here.
    A:
    If you own several headphones and we have measurements of them here, a good way to start out is to listen to the headphones and study the measurements. The more we do this, the better we get at understanding measurements. There are various ear training resources on the Internet which might give you a head start in understanding the frequency response measurement. Finally, you can always ask. Asking how measurements work is not a stupid question. Please ask questions.

    This site started a few years ago with only a few headphone measurements. It has definitely been a learning experience even for me to see how measurements correlated to qualities of sound.

    Like all technical things, it does make a little bit of effort and intelligence to grasp.


    Q:
    What is the ideal frequency response for your graphs?
    A:
    This is a tough question to answer. My current V2 measurement rig is set up to be most comparable to a measurement taken at the listening position with a wand microphone for a pair of speakers. The ideal response for me personally is a flat response up to several hundred Hz with a gentle downward slope where by 20kHz it's 6db down more or less. This is pretty standard for how things are setup in a quality mastering studio.

    Your ideal frequency response may be different from mine.


    Q: Wait, are you saying a flat line on your current measurement rig will sound a little bright?
    A:
    Yes.


    Q: I don't hear this "high" distortion I see on your graphs.
    A:
    Distortion is probably the trickiest to hear or describe. Distortion in most cases here (which is usually dominated by 2nd order), does not sound like an amplifier clipping. Distorted bass tends to sound muddy and blurred. Distorted midrange tends to sound dirty or unclear. Distorted treble often coincides with peaks an octave higher.

    Based on discussions with people here, there seems to be high variability on people's ability to discern certain kinds of distortion. The other factor is what headphones are you comparing against? If you don't hear distortion on a headphone with high levels of measured distortion, perhaps it's likely that the other headphones you've owned have had similar distortion characteristics.

    Finally, it's possible that you are not sensitive to distortion. That could be a blessing.
     
    Last edited: Oct 11, 2015
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  2. Koloth

    Koloth Klingon SBAF Ambassador - Friend

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    Q: Are any of the measurement pirates located in Europa and willing to measure headphones sent to them by mail?
     
  3. Thujone

    Thujone Friend

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    Q: I'm looking to build a new measuring setup to avoid using my in-ear mic setup. I need something more consistent. I'm following the suggestions back @changstar for the build but the software side of things is hazy for me. What softwares are typically used other than REW? I've seen a lot of talk about sine sweeps vs. pink noise but which is better and why? Lastly, how do I go about making a compensation curve, or is this not commonly done?

    I swear I'll have content to give back to the community. o_O
     
    Last edited: Oct 1, 2015

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