This tutorial will help you modify the sound of your microphone in order to transform the sound of your microphone into the accurate copy of the sound of a better microphone. You can also transform a pair of identical (same model) microphones into a matched pair of microphones for stereo recording. The proposed digital mod is simpler than an electrical or mechanical mod, and in the same time it ensures incomparably higher accuracy.
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 is a VST effect plug-in which corrects the frequency responses of microphones. In fact, you can take your medium quality microphone and transform it into an acoustic replica of a high quality microphone.
There is an important restriction: 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.
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 VST 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 the Microphone EQ plug-in set to you computer
Choose the right installer. If you use the x32 version of your VST host, use the x32 version of the Microphone EQ installer. If you use the x64 version of your VST host, use the x64 version of the Microphone EQ installer.
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. If you correct an instrumental microphone - place it at the preferable distance from your musical instrument.
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 host program (Reaper, Cubase, Nuendo, etc)
Your VST 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 VST 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 VST 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. Then switch the Reference Mic and Target Mic radio buttons and touch the microphones to make sure that you hear the corresponding microphone.
9. 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 host program to adjust for comfortable sound volume. Then select the "Target Mic" radio button and listen to the sound of your target microphone. A volume control knob will appear as it is shown in Fig.2. Use the knob to adjust for comfortable sound volume.
Fig.2. Screenshot of the MathAudio Microphone EQ VST plug-in with the volume knob.
10. Start the measurement
Click the "Start" button. You will get the window shown in Fig.3. You have 10 seconds to speak to the microphones (if you replicate a vocal microphone) or play all the notes of your musical instrument (if you replicate an instrumental microphone). Don't bother about the quality of your speaking or playing. 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 or the sound of your musical instrument. The signal correction algorithm will be generated automatically in a second after the end of the measurement process.
Fig.3. Screenshot of the MathAudio Microphone EQ VST program with the progress bar.
11. Listen to the processed sound of your microphone
Click the "Corrected Target Mic" radio button. Speak to your target microphone or play your musical instrument. 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 very similar. Please take into consideration that both left and right output signals of the plug-in are absolutely identical. You can pan the output signal by means of your DAW's pan control. Use two instances of the plug-in if you want to process the signals of two microphones.
12. 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.
13. 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 host software and include the Microphone EQ VST 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.