Equalizing HE400i – Take Two (v7.28)

November 2017 Update: I made a revised version here.

TLDR

Use the files in the Download section below to give your HE400i a neutral frequency response. It sounds good.

Introduction

My first attempt at developing an equalizer setting to flatten the HiFiMan HE400i‘s frequency response yielded excessively elevated 8KHz and 10KHz regions. This is because I used InnerFidelity‘s measurements. They are consistent among themselves, but the Hammershøi and Møller HRTF curve that I used for frequency response compensation is inappropriate for Tyll Hertsens’s Head Acoustics HMS II.3 head simulator, so the compensated frequency response was a off in the treble.

This time, I asked Solderdude (administrator of DIY Audio Heaven) for his measurements of the HE400i made with his home-made measurement rig. Although Solderdude’s device is not a calibrated HATS, I find his measurements to be very accurate.

Measurements and Correction

(The corrected graphs are predicted/calculated results instead of real measurements, because I don’t have access to Solderdude’s measuring equipment, and Solderdude no longer has access to an HE400i.)

Darker blue = original frequency response; lighter blue = frequency response after EQ

Darker blue = original frequency response; lighter blue = frequency response after EQ

Solderdude’s measurement shows the very audible 8KHz peak that InnerFidelity’s graph didn’t show. According to the graph above, the corrected frequency response is ±1dB from 20Hz to 13KHz, but the actual effect will be different for each person using this correction due to individual HRTF differences. However, an approximately neutral frequency response is assured.

Darker red = original impulse response; lighter red = impulse response after EQ

Darker red = original impulse response; lighter red = impulse response after EQ

Since frequency response and impulse response are interrelated counterparts of each other, modifying the frequency response using an equalizer inevitably changes the impulse response. The corrected impulse response has less reverb and is more ideal.

HE400i Filters 7.28 Inverted

This is a graphic representation of the parametric filters. Extremely sharp boosts and cuts are avoided.

Listening Impressions

  • Bass extends better.
  • The 8KHz sibilance edge is gone.
  • Soundstage has expanded and imaging is more precise.
  • Voices are less muffled.

On Equalization Methods

Impulse response convolution appears to be the highest-quality, most versatile and most customizable method of frequency and impulse response correction. I tried DRC (Digital Room Correction) by Denis Sbragion on the HE400i, but I chose to use Room EQ Wizard instead for the following reasons:

  • DRC cannot avoid automatically correcting the >13KHz region of unreliable measurement data. This could make the sound worse than it originally was.
  • DRC tries to extend the bass way down below 10Hz, causing unnecessary subsonic rumble.
  • DRC shows no significant quality advantage over REW in this case of headphone measurement.

Downloads

15 comments

  1. Thanks for all the work! I’m a bit confused though. Is the equalizer set to Parametric EQ or Graphic EQ? After ABing the two, I found the Graphic EQ to be less veiled are more engaging to listen to.

  2. using amarra for tidal and used your post to approximate the eq curve – albeit visually. Very impressed with the results. I never knew what frequencies were killing me sibilance-wise. helpful indeed. my sincere thanks, man!

      1. Brad, do you think it’s possible that certain frequencies (especially the highs) resonate louder than others because of the ear inside the cups? Every sound test dummy I’ve seen (and home made rig) just has holes in the side of its head (or yoga block) and no ears! Also the way the frequencies are channeled into the ear canal by way of the ear contours/folds itself may cause a resonate frequency to develop for someone at 6K and another person at 8K.

        The reason I ask this is because I ended up tuning mine by ear using a controllable sine sweep plugin and HOURS of computer time behind Fab Filter ProQ2 (trial). What I found was that there were nasty peaks at 6.2 and 7.2K for my ears which I cut hard and a complete null at 8.3 which I had to boost with a high Q value surgically. My hearing is good and I can hear all the way to 17K almost, so that’s not the issue.

        After my initial post, I ended up modeling your exact settings in FFPQ2, and compared it to my manual attempt. Suffice it to say, the results of my manual tuning were subjectively better sounding to my ears than this guide’s settings. I’m thinking it’s either ear shape, unique anatomical sensitivities to certain frequencies, or poor QC on the cans by Hifiman. What thoughts have you?

        1. your specific ear shape and ear canal will make the ideal curve rather personal. If you want a lot of technical information on those head dummmies (many are based on averages from the 1960s or ignore ears altogether) as it applies to HRTFs see here: https://core.ac.uk/download/pdf/36418235.pdf.

          Your personal ear shape can cause frequency responses of more than +-5dB all over the frequency spectrum. Some of that you may normalize so it doesn’t really matter, some you may not. But it is personal for sure.

      2. I get very good result with your files. Thanks for sharing. Now I no longer feel that Hifiman HE-400i is very bright on certain songs.

  3. Hi Brad, thanks for the config. Can you confirm that I remove everything in the Equalizer APO and then add the Convolver wave file? Or don’t i need to removethe standard pre-amp and config.txt?

    1. It doesn’t really matter. You can remove them or simply turn them off, or you can even use them if you want. Play around with the Configurator! You might find something that you want to add. But for my configuration, you don’t need anything else.

  4. I’m pretty sure I have this working with JRiver and a text file created with Equilizer APO. In any event, Norah Jones sounds a whole lot less shouty now with the HE-400i’s. Many thanks…

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