MathAudio Microphone EQ VST/AU

• Linearizes the frequency response of microphones (removes peaks and dips) with the help of a measurement microphone.
• Compares two vocal microphones and converts the sound of the first microphone to the sound of the second microphone.
• Transforms a pair of identical (same model) microphones to a matched pair of microphones for stereo recording.
• Supports microphone calibration files.
• Transforms the sound of a measurement microphone to the sound of an ideal measurement microphone by means of utilizing the microphone calibration file.
• Suitable for real-time applications.
• Applies 64-bit signal path throughout.
• Supports full range of sample rates from 44,056 kHz up to 384 kHz. All sample rates are supported without resampling to avoid any possible loss in quality.

Microphone EQ Help

It is known that the sound quality of a microphone mainly depends upon its frequency response. High quality microphones have better frequency responses than low quality mics. MathAudio Microphone EQ compares the frequency response of your microphone with the frequency response of a measurement microphone to remove peaks (resonances) and dips (antiresonances) in the frequency response of your microphone. You can also transform your microphone into an acoustic replica of another microphone.

There are two important restrictions: (1) MathAudio Microphone EQ doesn't reduce the self-noise of microphones. If you buy a microphone for using it with MathAudio Microphone EQ, make sure that the microphone is not noisy. Usually condenser microphones have a smaller self-noise than dynamic ones. (2) MathAudio Microphone EQ doesn't change the directional pattern of your microphone. The directional pattern has a large influence on the sound of the microphone.

MathAudio Microphone EQ is also able to transform a pair of identical (same model) microphones into a matched pair of microphones for stereo recording. Such matching can increase the quality of stereo recordings. If the microphones acted differently, your left and right channels would not sound exactly the same, which could result in timbre anomalies between them and a smearing of the stereo image. MathAudio Microphone EQ can match your microphones much better than they were matched at the factory. Use MathAudio Microphone EQ to transform you right microphone into the replica of the left one. It is also possible to transform both left and right microphones into replicas of a third microphone.

MathAudio Microphone EQ is a sort of a self-learning system: it first compares the signal of your target microphone with the signal of your reference microphone. Then it creates a mathematical algorithm which changes the spectrum of the signal of your target microphone to make it similar to the spectrum of the signal of your reference microphone. Please note that the microphone which will be corrected is referred to below as the target microphone.

There are two methods of generation of the correction files: direct method and postponed method. The postponed method includes recording of the microphones in one place (e.g. in recording studio) and analysis of the sound file in another place (e.g. on your home computer). The postponed method will be discussed near the bottom of this page.

The direct method includes the following steps:

1. Install one of the following packages:
- Install Microphone 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 Microphone EQ AU plug-in if you want to use it with an AU compatible host software.

2. Connect your target microphone to the sound card of your PC

3. Connect the reference microphone to another input of the sound card
Both target microphone and reference microphone must be connected to your sound card simultaneously. They must be connected to the different inputs of your sound card. For example, connect your target microphone to the right input of your sound card and connect the reference microphone to the left input.

4. Place the microphones at the preferable distance
Both microphones must be placed at the same distance from the source of the sound. If you correct a vocal microphone - place both microphones at a preferred distance from your mouth.

5. Switch off your speakers
Your speakers must be switched off to avoid the acoustic feedback. Use headphones to monitor the sound of the microphones.

6. Open and adjust your VST/AU host program (Reaper, Cubase, Nuendo, Logic, etc)
Your VST/AU host program must work in stereo mode. Adjust the direct monitoring of the microphones. Make sure that you hear the sound of both microphones in your headphones. Touch the microphones with your finger to make sure that the stereo mode is activated and you hear the sounds of microphones in different ear cups.

7. Include the Microphone EQ plug-in to the stereo signal path
Open the editor of the plug-in. You will get the window shown in Fig.1.

Fig.1. Screenshot of the MathAudio Microphone EQ plug-in.

Check the state of the radio buttons in the Inputs tab of the plug-in. The selected inputs must correspond to the inputs of your sound card that were used for connecting your microphones. Switch the Reference Mic and Target Mic radio buttons if necessary.

9. Add a calibration file if you have one
If you have a calibration file for your reference microphone, you can use it. Just rename the calibration file to calibration.frd, calibration.cal or calibration.txt and copy it to the Documents -> MathAudio Microphone EQ folder. Then exit your DAW and start it once again. The name of the calibration file will be shown at the top right corner of the graphical area and the frequency response of the microphone will be shown on the graphical area as it is shown in Fig.2. Please don't copy more than one frd/cal/txt file to the Documents -> MathAudio Microphone EQ folder!
If you set the "Output" radio buttons to the "Reference Mic" position and use a calibration file, the Micophone EQ plug-in corrects the sound of your reference microphone to make the frequency response ideally flat. In other words Microphone EQ converts the sound of your reference microphone to the sound of an ideal reference microphone (please note that conventional measurement microphones are usually too noisy for high-quality recording purposes).

Fig.2. Screenshot of the MathAudio Microphone EQ plug-in with a calibration file.

10. Adjust for comfortable sound volume
Use headphones to monitor the microphone signals. Select the "Reference Mic" radio button. Use the volume control of your VST/AU host program to adjust for comfortable sound volume. Then select the "Target Mic" radio button and use the Microphone EQ's slider to adjust for comfortable sound volume.

11. Start the measurement
Click the "Start" button. You have 10 seconds to speak or sing to the microphones. Don't bother about the quality of your speaking or singing. The progress bar in the MathAudio Microphone EQ window will show you your progress. Fill the full 10 seconds with the sound of your voice. The signal correction algorithm will be generated automatically in a second after the end of the measurement process. You will get the plot of difference of frequency responses of your microphones as it is shown in Fig.3 (your plot will be different). The white line shows the result of the DSP correction. Please note that the result of your measurement depends on both distnace and direction. Use your habitual distance between you and your microphones to get the best result.

Fig.3. The plot of difference of frequecy responses.

12. Listen to the processed sound of your microphone
Click the "Corrected Target Mic" radio button. Speak or sing to your target microphone. You will hear the processed sound. Then click the "Reference Mic" radio button to compare the processed sound of your target microphone with the original sound of your reference microphone. The sounds must be similar. Please take into consideration that both left and right output signals of the plug-in are absolutely identical. Use two instances of the plug-in if you want to process the signals of two microphones. You can pan the output signal by means of your DAW's pan control.

13. Manually correct the sound of your microphone if you still wish to change something in the sound
Click the "Corrected Target Mic" radio button. Move the cursor of your mouse to the graphical window, press the left button of the mouse and draw your own frequency response. You can also use the right button of the mouse to draw straight lines. Speak or sing to your target microphone to hear the processed sound. For example, you can reduce bass as it is shown in Fig.4. Use the "Reset" button to reset the reference curve if necessary.

Fig.4. A manually corrected frequency response.

14. Choose the resolution
Switch "High resolution" and "Normal resolution" radio buttons and compare the sound. Leave the resolution which corresponds to a better sound. If you hear no difference, leave the switch in the "Normal resolution" position because it puts less load on the CPU.

15. Save preset
Click the "Save preset" button and save the accurate state of the plug-in as an .alg file. This file will help you to restore the state of the plug-in if necessary. The .alg file includes all the information about the correction algorithm. You can use the "Load" button to load the necessary .alg file.

16. Postponed method of generation of the correction file
Sometimes it is more convenient to record the sound of the microphones in one place (e.g. in recording studio) and generate the correction file in another place (e.g. on your home computer). In that case you can make a short (20-25 seconds) stereo recording of your voice (right channel - your target mic, left channel - the reference mic) and save it as a WAV file. Then open that file by means of your VST/AU host software and include the Microphone EQ plug-in to the stereo signal path. Start the playback of the recorded sound, then click the "Start" button in the plug-in window and save the resultant correction file. Of course, you don't need to use microphones and speak to them because the recorded sound replaces the sound of microphones. The postponed method allows you to get exactly the same result as the direct method.