Most new PA system owners aren’t aware of the fundamentals of equalization. They don’t understand how frequencies interact with a room. They certainly don’t know how to use pink noise to auto EQ a room with a Midas MR12 or any other device! If you are new to owning a PA system, you’re probably becoming aware of audio feedback and how it can negatively impact both the sound of your PA and your performance.
There’s nothing worse than a massive low end honk of feedback when trying to increase the volume of an acoustic guitar in front of a crowd! I recently purchased a Midas MR12 wifi mixer for my PA system and learned an easy way to use pink noise to EQ any Output Bus using an ipad and a cheap reference mic. Let’s learn about feedback and room equalization. We can then learn just how easy it is to use pink noise to auto EQ a room with a Midas MR12! This process will also work with a Midas MR18, Behringer XR12, XR16 or XR18.
What Is Feedback?
Feedback is one or more frequencies on the audio spectrum that begin to squeal, honk or rumble out of control when the sound from the PA speaker is picked up by a microphone on the system. It forms a continuous loop that increases in loudness until the offending frequency is removed from the source. These frequency loops can be caused by placing a microphone or source too close to a speaker. They are also caused by the natural reverberation of the room itself. Most experienced sound technicians will “ring out” their PA system before sound check. This is done either by ear, by use of a spectrum analyzer, or both.
Auto EQ Using Rack Equipment
Some sound technicians will use a DBX Driverack or similar device, which uses pink noise to both determine the appropriate EQ settings for a PA system (or portion of a system) and adjust the EQ to accommodate those settings. Ringing out a PA system by ear requires lots of experience. You must be able to hear the offending frequencies and know “by ear” which frequency to adjust on a 31 band EQ. I’m no where near that capable! The process becomes easier when using a frequency analyzer that will show which frequency is peaking during feedback. You can then manually adjust the offending frequency on a 31 band EQ to compensate. Both of these techniques require more expertise to adjust the EQ to compensate for room reverberation and speaker / mic placement. An automated system is needed for most inexperienced PA users. This will help users like us get the most out of our PA and minimize feedback.
For several years I used a small rack mounted Driverack PA to automatically adjust the EQ for my system. The process was pretty simple and somewhat easy to do. The Driverack is essentially the EQ, Compressor and Crossover for the entire system. A reference mic is connected to the Driverack. Pink noise is generated by the Driverack and played through the speakers. The reference mic captures the pink noise playback and the Driverack adjusts the EQ to “flatten” the EQ of the room. The downside of the Driverack is the added cost and the added equipment to lug around from show to show!
The Result of Using Auto EQ
The result of Auto EQ-ing a PA system to the room is a cleaner sound that is less prone to feedback issues. I recently began using a Midas MR12 wireless mixer. This mixer includes a 31 band EQ built-in for every output bus. You can either ring out the system and manually using the built-in frequency analyzer as a guide, or you can use an app to automate the process!
Skip the Rack and Auto EQ with a Wireless Mixer!
To automatically use pink noise to EQ your PA system using either a Midas MR12, MR18, Behringer XR12, XR16 or XR18 wireless mixer you will need a few additional items: a reference microphone, a pink noise generator or WAV file of pink noise, and a specific IOS app. The IOS app is called “M AIR iEQ” and costs only $8.99! I use a 3rd Generation Ipad Air with a Dayton Audio iMM-6 Calibrated Measurement Microphone. The microphone is very affordable ($20 – $25) and is provided with access to a calibration file if needed.
My auto-EQ PA system is made up of the following equipment:
Ipad Air – 3rd Generation
Dayton Audio iMM-6 Calibrated Measurement Mic
3.5mm Extension Cable
Pink Noise WAV file
M Air iEQ – IOS app
Begin the Auto EQ Process
To begin the auto EQ process simply setup your PA system as you normally would. I typically use powered PA speakers, but passive speakers with a power amp (or multiple power amps, depending on the complexity of your system) are also compatible. Open the M Air iEQ app and provide the IP address of the Midas MR12. The app will remember this setting for future use. Make sure the MR12 and the Ipad Air are on the same wireless network (this is very important). Once the app recognizes the mixer, you can then select the mix for Auto EQ (L/R, Bus #, Rack #, etc…).
The next step is to connect the measurement mic to the Ipad. An extension cable can also be used to place the mic at ear level, but this isn’t necessary. You then select the iPad mic within the M Air iEQ app under “Settings”, “Inputs” – “Headset Microphone”. Place the measurement microphone at the sweet spot of the PA system (or monitor listening location). The next step is to either generate Pink Noise or play a WAV file of pink noise through the PA system. This can be done with the iPad via bluetooth, but I typically use another tablet or my cell phone to minimize confusion. Once the pink noise begins playing, increase the volume to performance level and the pink noise waves will be visible on the main screen of the M Air iEP app.
Select the “RTA/GEQ” button at the bottom of the app screen, then select the “AUTO EQ” button. The app will then analyze the pink noise and adjust the EQ. This adjustment will also be visible on the iPad screen. The EQ adjustment will be sent via WIFI to the wireless mixer and the results will be immediately noticeable!
More Auto EQ Options:
It is possible to adjust the EQ curve in real time via the app. The scale of the adjustment can be changed to make the curve more or less dramatic. I typically use a setting of .8 for this value. It’s also possible to increase all EQ values equally to provide more total system output. This same adjustment can decrease all EQ values for less system output if needed. To Auto EQ a monitor bus, simply change the mix to the correct bus number and run the process again. You will need to move the measurement mic to the position of the musician hearing the mix in order to get the correct EQ adjustment. These EQ curves can be saved for different venues, PA setups, etc… The clarity improvement is awesome once your PA is adjusted!
This process may seem complicated, but it’s actually very easy once you’ve learned how to do it! It’s much faster than the older Driverack’s I used in the past. It’s also much more flexible. If you are plagued with feedback, or are not happy with your live mixes, this is definitely worth using. Feedback is much easier to control if the natural room reverberation is already accounted for. Check out my video below outlining the process and give it a try yourself!