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

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[…] HE400i EQ […]

Terracon
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Terracon

Thanks for your work) Sadly I can’t check how it works on my phone cuz txt file link is broken

RadDad
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RadDad

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.

Vince Buonassi
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Vince Buonassi

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!

Pierre Ye
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Pierre Ye

Is your Hifiman HE-400i the newer version with 2.5mm connector and without the backplate?

Stefaan M
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Stefaan M

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?

Gary
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Gary

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…

Dai
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Dai

How to use the file ? can i have any guide?