## MathAudio Headphone EQ Help

# How to detect and compensate for the unwanted resonances of your headphones

It is known that the frequency response of headphones substantially depends on the shape and size of the listeners' pinna (outer ear) and inner ear canal. Consequently, it is impossible to make ideal headphones that will fit all people. In particular, the acoustic mismatch between headphones and ear canal creates one or a few unwanted acoustic resonances. These resonances decrease the quality of the sound because they overload your ears on certain frequencies and mask all other frequencies. Additionally, these resonances create a specific ringing which worsen the time-domain response of headphones.

MathAudio Headphone EQ allows you to check your headphones in order to find the unwanted resonances. It also helps you to compensate for the unwanted resonances.

MathAudio Headphone EQ can be used with all types of high-quality headphones and earphones. The correction of the unwanted resonances improves the neutrality of the sound which is important for professional musicians.

Another known problem of headphones lies in the complete separation between channels. The complete separation between channels creates an unnatural super-stereo effect which leads to listener's fatigue and even headaches. MathAudio Headphone EQ includes a crossfeed algorithm which allows you to reduce the channel separation to a natural level.

The following step-by-step instruction will help you to improve the sound of your headphones. Before starting the work, try to find recommended numerical values of filter parameters for your headphones at Oratory1990’s list of headphone EQ presets or Jaakko Pasanen's resource. The recommended values can substantially simplify your work because fine-tuning the ready parameters is a much simpler process than correcting your headphones "from scratch". The "Preamp gain" coefficient which is often included into the recommended parameters can be safely ignored because Headphone EQ automatically calculates and applies it.

1. Install one of the following packages:
- Install Headphone EQ VST plug-in if you want to use it with a VST compatible host software. If you work on Windows, the version of your VST plug-in (x32 or x64) must correspond to the version of your host software.
- Install Headphone EQ AU plug-in if you want to use it with an AU compatible host software.
- Install Headphone EQ for Foobar2000 if you want to use it with Foobar2000 media player.

2. Open and adjust your VST/AU host program (Reaper, Cubase, Nuendo, Foobar2000, etc)

3. Set minimum buffer length
Set minimum buffer size in the audio driver settings. A buffer size that is too large can slow down the responsiveness of the plug-in to the movement of its sliders.

4. Include the Headphone EQ plug-in as the last plug-in to the stereo signal path
Open the editor of the plug-in. You will get the window shown in Fig.1. Play music and make sure that the audio signal comes through the plug-in.
Fig.1. Screenshot of the MathAudio Headphone EQ plug-in.

5. Click the "Sweep" radio button
The "Sweep" radio button activates the test signal generator. Please note that some hosts don't activate VST/AU effect plug-ins when the input signal is absent. If you don't hear the sound of the test signal generator, activate the playback of any music in your VST/AU host program. You will hear the sound of the test signal generator instead of the music. If you use the Foobar2000 version of the plug-in, you can change the output device by means of the additional "Sweep Out" button which is shown below.
Fig.2. The "Sweep Out" button (Foobar2000 version of the plug-in).

6. Find the first resonance frequency
Make sure that your headphones are in their usual comfortable position on your head. Slowly move the "Sweep" slider and listen to the intensity (loudness) of the test sound. The unwanted resonances (areas of increased loudness) are most frequently located in the frequency interval from 5 to 10 kHz. Usually the resonance peaks are not wide. Your ability to hear the unwanted resonances depends on the volume of the test sound. Use the "Sweep signal volume" slider to find the optimum volume. Usually the test sound should be loud enough, but still comfortable for your ears. The green line indicates the current frequency of the test signal generator. You can click the green line and move it instead of using the sweep slider. Find the central frequency of the first resonance peak and leave the green line in that position as it is shown in Fig.3.
Fig.3. The green line shows the first found resonance frequency (the resonance frequency of your headphones can be different).

7. Tune the first filter to the frequency of the first resonance
This program supports up to 99 filters. Each filter can be assigned to left channel, right channel or both of them (radio buttons L, R and LR correspondingly). The radio buttons L and R can be used for individual correction of the left and right channels if necessary. The number of the current filter is shown in the edit control in the left bottom corner of the plug-in window. You can use the buttons '<' and '>' to change the number of the current filter. You can also click the edit control and type the required number on your keyboard.
Make sure that the filter 1 is selected. The frequency of that filter is shown by the white vertical line on the plot. Click the "Set filter frequency" button or right-click the plot area. The white line will move to the location of the green line.
Fig.4. The white line shows the frequency of the chosen filter.

8. Compensate for the first resonance
Move the "Gain" slider left. You will see a notch in the frequency response of the filter as it is shown in Fig.5. Move the "Sweep" slider and listen to the intensity of the test signal sound near the frequency of the resonance. Adjust the positions of the "Gain" and "Q" sliders until you no longer hear the resonance. If you need to change the frequency of the filter, move the green line to the desired position and click the "Set filter frequency" button or right-click the plot area.
Alternatively, you can use "Frequency", "Gain" and "Q" fields to enter numeric values of the corresponding filter parameters. Don’t forget to press the "Enter" key on your keyboard after typing in the numeric values to the corresponding fields.
Fig.5. The first filter is activated.

9. Find and compensate for other unwanted resonances, if any
If your headphones or earphones create more than one unwanted resonance, you can find and compensate for them in the same way as you compensated for the first unwanted resonance. Select the second filter in the left bottom corner of the plug-in window and adjust the positions of the "Gain" and "Q" sliders to make the second resonance disappear. Repeat this procedure for all found unwanted resonances.
Fig.6. The second filter is activated.
Sometimes the unwanted resonances are located close to each other and the compensation curve looks as it is shown in Fig.7.
Fig.7. The case of close location of the unwanted resonances.
Please note that the sensitivity of human ears is small on the edges of the audio-frequency band (frequencies that are closer to the left and right edges of the plot). It is not necessary to compensate for this natural phenomenon. The loudness of the test sound must smoothly fade out when you move the green line to the edges of the plot. If you hear any narrow-band spikes of the loudness, compensate for them.
Sometimes manufacturers add some extra boost to the low-frequency portion of the headphones frequency response to give you some impression of the physical punch that is felt by your body when you listen to powerful loudspeakers. You can leave it as is if you like it. However, we believe that such boost is not a natural replacement to the physical punch. If such a boost is present in your headphones, the loudness of the test sound does not smoothly fade out when you move the green line to the left edge of the plot (low frequencies). You can compensate for this boost in the same way as you compensated for conventional unwanted resonances. The only distinction is that such boost is usually much wider than a conventional unwanted resonance as it is shown in Fig.8. Change the positions of the "Gain" and "Q" sliders until you will hear that the loudness of the test sound fades out smoothly when you move the green line to the left edge of the plot.
Fig.8. Low-frequency compensation.

10. Switch the plug-in to the "EQ" mode.
Click the "EQ" radio button. The "EQ" radio button switches Headphone EQ to its normal operation. The "Bypass" button allows you to compare the corrected sound of your headphones with the uncorrected sound. The "Bypass signal volume" slider allows you to decrease the volume of the unprocessed sound to make it similar to the volume of the processed sound for the correct comparison.
Please take into consideration that Headphone EQ does not allow you to increase the volume above 0 dB to prevent the clipping of the audio signal in your sound card.

11. Activate and adjust the crossfeed
Stereo recordings are meant to be heard through loudspeakers. The important distinction between loudspeakers and headphones lies in the fact that the sound of every loudspeaker reaches both ears of the listener (though the amplitudes and delays are different), while the sound of each headphone speaker reaches only one ear of the listener. This distinction results in an unnatural super-stereo effect. The super-stereo effect is especially unpleasant when the sound recording contains intensive low-frequency stereo effects. The super-stereo effect causes the listener's fatigue. This effect can be compensated for by the crossfeed algorithm. Play a music recording with intensive low-frequency stereo effects. Click the "On" radio button in the "Crossfeed" group box to activate the crossfeed algorithm. Change the position of the crossfeed slider if you feel that the amount of the crossfeed is too large or too small. The "Restore default" button allows you to restore the initial position of the crossfeed slider. The crossfeed algorithm is not dependent on the EQ algorithm. You can use these two effects independently on each other.

12. Adjust the position of the "Headphone EQ gain" slider
Headphone EQ doesn't clip the sound. However, the amplitude of its output signal can exceed 0 dB. If you use the volume control and the clip indicator of your host program, set the "Headphone EQ gain" slider to 0 dB and don't use it any more. Otherwise, play an audio file and look at the indicator which is shown in Fig.9. The red color of this indicator means that the amplitude of the Headphone EQ output signal exceeds 0 dB. Click the indicator to move the "Headphone EQ gain" slider to the position corresponding to 0 dB output. Repeat this process with a few other audio files.
Fig.9. Indicator.

13. Save preset
Click the "Save preset" button and save the accurate state of the plug-in as an .hdp file. This file will help you to restore the state of the plug-in if necessary. You can use the "Load preset" button to load the necessary .hdp file.

14. Give yourself some time to get used to the neutral sound
If you use your headphones for a long time, your ears have adapted to their resonances. Give yourself some time to get accustomed to the neutral timbre of your equalized headphones.

## Contents

Welcome to the MathAudio Headphone EQ Help

### How to detect and compensate for the unwanted resonances of your headphones

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