How to Mix Multiple Microphones for a Clean Broadcast Audio Feed

Overview

Clean and professional sounding audio can be very important to the success of your livestream, but it can become a bit tricky to get right when you introduce several microphones and even more complex when all of those are different types of microphones like lavaliers, or podium mics and handheld mics etc. In this guide, we'll touch on the basics of how to set your gain, apply some basic EQ, fix feedback issues and generally get you squared away for a professional broadcast.

Step-by-Step Instructions

1. Set Proper Gain Levels

First, you’ll want to start with the mixer controls. Specifically, the audio gain. You’ll want to have the speaker talk at a normal volume and as they’re talking check the audio levels. Our goal here is to get to around -12db. Increase the gain on the microphone until the voice consistently peaks at that volume level and make sure that it isn’t distorted. If the higher gain is causing distortion then you might need to look into a pre-amp. Repeat this process for each microphone so that you get a nice balanced signal across all of them and there aren’t wild swings in microphone volume level. 

2. Apply Basic EQ to Improve Clarity

Next we’ll tackle the EQ, this is where we can dial in the characteristics of the audio.

When it comes to this there is a decent amount of playing around with the settings to be done but in general high pass filters can be somewhat helpful and you will want to use them to allow for higher frequencies to come through while blocking some unwanted lower frequencies. If you boost the upper midrange of audio, it can help to increase the clarity of the speaker. And finally if the microphone sounds “boomy” it could be worth looking at the low end frequencies and reducing them to help prevent that. Each microphone and speaker is a little bit different so you will need to experiment. 

3. Prevent Feedback

Here are some simple tips to prevent feedback:

1. Try to keep microphones behind speakers, speakers will be picked up by the microphone and can cause a feedback loop.
2. If certain microphones are not being used, you can just turn their audio channel off or reduce their gain.
3. Try not to go wild on the EQ!
4. Finally, using directional microphones will help reduce the amount of sound being reflected back towards the microphone. 

4. Build a Dedicated Broadcast Mix

Creating a broadcast mix is essential if you’re running an in person event that is also being broadcast. This mix should not be the same as the in-person mix, you can create an auxiliary send or mix bus specifically for the stream. In this mix you want to keep the room microphones lower and your goal is shifted towards clarity and the main presenters or the talent. 

5. Apply Compression

Compression is helpful in that it helps to smooth out the audio level difference that a speaker might have. For example it helps so that they can be loud and emphasize points without peaking the microphone. When applying compression, start with something conservative and then adjust as needed until you reach a point where the levels are consistent but does not have an overly processed characteristic to it. If you have ambient microphones for the room sound, don’t apply compression to these, this is mostly just for talent. 

6. Send the Mix to Your Switcher or Encoder

Now is the simplest part! Just send that mix out through the output cable on your mixer to your production switcher, encoder or computer. Double check that everything is looking good and sounding good and you should have a fantastic sounding broadcast! Just make sure to ensure that the output level matches the input requirements (line level versus microphone level) to avoid distortion or low volume.

Troubleshooting Tips

• If voices sound distant, increase the level of direct microphones and lower the room microphones.
  
  
• If distortion occurs, reduce gain and check compression settings.
  
  
• If background hiss is present, lower the preamp gain and increase the fader level.
  
  
• If the audio sounds echoey, move microphones closer to the source and use tighter pickup patterns.