Big Sound 2015 Bob Katz EQing Headphones with the Harman Target Response
Today I performed a long awaited experiment of creating an EQ for two pairs of headphones from my understanding of the raw frequency response measurements and the Harman target response curve. The acid test was whether or not Bob Katz felt the EQ good while listening to tracks he's intimately familiar with.
I will write a more detailed explanation in future, but the basic process was this:
First I looked at the Harmen target response curve, which is the black curve on the plot below.
I then printed out a large version of the frequency response plots for the headphone we were trying to EQ. In the case below, it's the Sennheiser HD 800.
Because the Harman response curve is measured at the ear drum, we compare it to the Raw frequency response plots, which are the plots at the bottom of the graph. You can ignore the compensated plot at the top of the graph.
I then superimpose the Harman plot (by hand) over the HD 800 raw plots, aligning the two graphs at about 150Hz. Once the plot is drawn satisfactorily, I then measure the difference between the two plots at numerous points along the plot. It is these differences that make up the compensating EQ for the headphone.
Bob used the parametric equalizer in the J-River software suite. Using a parametric EQ is a bit of a trick, and it took us about an hour to develop the basic compensation curve for the two headphones we adjustedan Audeze LCD-X and Sennheiser HD 800. After the initial stab at EQ using the Harman curve, Bob would spend about 15-20 minutes gently tweaking the curve using various pieces of music with which he was very, very familiar. In general, his tweaks were on the order of 2dB or less, and were generally reducing the offset suggested by the Harman curve. However, the general shape and overall Harman correction was retained.
One particular area of interest to me was the gentle rise from 200Hz to 1kHz. This rise is rarely found on headphones. It exists due to the acoustic gain of the head, neck, and torso when in a sound field.
The plot above shows the ear drum response when in a flat sound field. The total response is the black curve (somewhat miss-) labeled, "Ear Resonance." If you look carefully, you can mentally sum the head gain (Plot 1), torso and neck gain (Plot 2), and a bit of the first ear canal resonance (Plot 5), and you will see that it results in this rise from 200Hz to 1kHz.
When I have heard this rise on a pair of headphones (NAD VISO HP50, and Focal Spirit Pro) I felt it did a much better job of presenting the human voice with all its overtones, and chest, throat, and nasal resonances and sounds. This better balance of the voice causes it to be very stable in image depth (not smeared in depth) and removes any sense of veil or excess distance to the voice.
Well, I simply couldn't be more pleased that Bob Katz agreed. He found the EQ a truly excellent starting point for further tweaking by ear, and he had never even thought of including this rise and felt it did, indeed, improve the tonal balance.
More, of course, of Bob's feelings can be heard in the video.
AURALiC Vega DAC ($3499) and Taurus MkII headphone amp ($1899)
Simaudio MOON Neo 430 HA ($4300 w/DAC).
HeadAmp GS-X Mk2 ($2800)
Schiit Ragnarok ($1699) and Yggdrasil ($2299)
Burson Audio Conductor Virtuoso ($1495 w/PCM1793; $1995 w/ESS1908)
Woo Audio WA-234 ($15,900)
Antelope Audio Zodiac Platinum DSD DAC, Voltikus Power Supply, and 10M Rubidium Atomic Clock. ($13,045)
Apex High Fi Audio (TTVJ) Teton ($5000)
Eddie Current Black Widow ($1248)
Violectric V281 ($2299)
Bakoon HPA-21 ($2995) current output headphone amplifier.
KGSSSRE (Kevin Gilmore Solid State Special Reviewer's Edition E-Stat Amp ($Unobtanium)
Sennheiser HD 800 ($1599)
Audeze LCD-3 ($1945) and LCD-X ($1699)
JPS Labs Abyss AB-1266 ($5495)
Stax SR-009 ($4450) and SR-007 ($2350)
HIFIMAN HE-1000 ($3000)
Mr. Speakers Ether ($1499)
Enigmacoustics Dharma (~$1200)
Audio Zenith PMx2 ($1398)
Headphone stands by Klutz Designs