Headphone FIR equalization using Foobar

Discussion in 'Headphones' started by ultrabike, Sep 10, 2016.

  1. ultrabike

    ultrabike Measurbator - Admin

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    It would be rceps in Matlab...
     
  2. Gatucho

    Gatucho New

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    Got it, thanks! I also found this function "mps.m" in some university repository.

    In addition to try to minimumphasezise everything I will try to separate both parts and make a MP filter for the MP part and a NMP filter for the NMP part.

    Maybe this is all non-sense :rolleyes:, but it's kind of fun.
     
  3. ultrabike

    ultrabike Measurbator - Admin

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    The rceps function gives the minimum phase equivalent filter. It's just one set of coefficients.

    Make sure the magnitude of the FR makes sense. It's not 100% always.
     
  4. ultrabike

    ultrabike Measurbator - Admin

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    @Gatucho, the LS approach does seem to work fine. It takes a bit of memory though, and in my laptop/Octave setup I had to reduce the number of taps. Also, for the B&K use the .' operator (Transpose), not the ' operator (Hermitian).

    Congratz!
     
  5. Gatucho

    Gatucho New

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    Thanks. Yes, it can be computationally intensive, a 4000x4000 matrix inversion!
    Sometimes Im lazy with the transpose, I should know better.
    I'm playing with the minimum non minimum thing. Although making the whole thing minimum phase seems easy enough, separating both parts looks a bit more difficult. I'm still digesting a little bit of the theory in this regard (https://ccrma.stanford.edu/~jos/fp/Poles_Zeros_Cepstrum.html) will get it, eventually :rolleyes:

    Ultimately will need to make some tests by ear to see if this actually makes an audible difference, for me at least. I don't have such a fine hearing anyway :p
     
  6. Psalmanazar

    Psalmanazar Most improved member; A+

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    @ultrabike quick question about your HD 600. That's a pretty flat measurement for it that looks more like the HD 580 than those of newer HD 600s where the upper mids and low treble are actually louder than the bass hump in my experience. Is yours a black driver unit, just have older, broken-in pads, a golden new unit, or just your measurement rig? I'm just thinking to myself, "I want an HD 600 that sounds like that."
     
  7. ultrabike

    ultrabike Measurbator - Admin

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    Mine are actually from the newer batch. Bought them from Massdrop.

    I actually measured some original HD580s and they measure almost the same as my HD600s.
     
  8. Serious

    Serious Inquisitive Frequency Response Plot

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    @Psalmanazar I think that's just mostly his measurement rig and how you'd interpret his measurements. They do need a target curve, which may not look similar to the B&K target. His measurements do show too much upper mid energy around 3-4kHz. His coupler is more open which I think gives it less bass hump and possibly makes the 3-4kHz bump look less nasty and the treble smoother. My HD600s measure with a 5db bass hump on my rig. They do have too much midbass for my tastes. HD650s probably have slightly more.
     
  9. ultrabike

    ultrabike Measurbator - Admin

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    The measurement rig is not perfect IMO. However a few comments are in order:

    1) The new HD600 and the HD580 measured effectively the same, in the same rig. Go figure. I can post that later tonite (I did that before @ CS)
    2) The coupler is not more open. I measure closed and open cans the same these days. Including measurements in this thread.
    3) The 3-4 kHz bump is there (not that nasty), but possible the lower treble is higher than it should be an is masking it. This is possibly due to the coupler. See these observations:
    http://www.superbestaudiofriends.or...alization-using-foobar.2772/page-2#post-79113
    4) Bass hump is about 5 dB in these measurements as well. Be mindful of the y-axis. HD650 IME does not have much more or much less bass hump. EDIT: Seems more like 2.5 dB in my rig. Proly depends on how much pressure one exerts against the baffle. I wouldn't over-do-it as we don't press cups hard against our head either.

    Further note: Sorry for mixing up "this" with "these". It's a common Spanish native language speaker mistake. I do this and other things often sometimes and it's hard for me to catch them as I write, unless I proof read very thoroughly.

    Hope this clarifies some of my observations and measurement conditions.
     
    Last edited: Oct 31, 2016
  10. Gatucho

    Gatucho New

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    Well I have been testing this thing on my hd600s. I still have not been able to "separate" the minimum phase thingy from the non-minimum. It seems it is a little bit more complicated that it appeared at the beginning. The thing is that the non-causal parts of the impulse response correspond to the unstable zeros, BUT the whole linear phase filter also has a minimum phase symmetric causal part.This instead of separating minimum phase from non-minimum phase it would be more correct to separate linear phase and the remaining minimum phase. But i digress...
    Right now I was testing linear phase vs minimum phase filters and sincererly I just cannot hear the difference. The difference of using no eq vs eq is huge, however I dont know if like the eq version better. My measuring rig is still too crappy so my target may be too skewed. I really believe that this can be a very useful tool. Currently using the filter the hd600s kind of sound like the T90s without the impact of those jajaja.

    This is the measured gain response without eq and using a linear phase and minimum phase filter. Both filters look very similar. (original purple, lp green, mp blue)
    [​IMG]

    This is the measured phase after removing the effect of the measured delay. The linear phase is almost constant and the minimum phase does have a low frequency roll as the uneq response. I dont know if this is supposed to be this way.. Maybe I got the linear phase and minimum phase thing screwed :confused:
    [​IMG]

    By the way I also made an eq filter for the onkyo fc300 and they did improve more than the hd600ss, maybe the hd600s are just too good already.
     
    Last edited: Nov 6, 2016
  11. ultrabike

    ultrabike Measurbator - Admin

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    The HE600s are hard to fine eq indeed. I have some other ideas that might improve measurement rig accuracy as well. But haven't tried those ideas yet.
     

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