Question: How do I coordinate frequencies when using both wireless microphone and IEM systems?

Answer: We often get asked about the best method for selecting frequencies when using both wireless microphone and IEM systems. With this article we hope to provide some insight, as well as solutions, on using your systems simultaneously.

Previously we took a quick look at intermodulation and the negative effects that arise when transmitters get too close to other transmitters or receivers. A good way to help minimize or avoid intermod is by using wireless coordination software, such as Audio-Technica’s Wireless Manager. Programs such as this can help ensure that assigned frequencies are at least 250 kHz away from any third-order harmonic without having to perform any intensive calculations.

When setting up a system that utilizes multiple wireless microphone and IEM systems, one may be tempted to just find the best usable frequencies and have both types of wireless systems’ frequencies intertwined. This means you may have microphone frequencies tuned between ear frequencies, and vice versa. While sometimes this is impossible to avoid, as you may have a mix of wireless systems operating in different frequency bands, you will find that this setup is more prone to interference. The best strategy is to separate wireless microphones and IEM systems into tight groupings on each end of the band. We would then want to separate these groupings from each other with a gap of at least 4 MHz (or more if possible).

Along with grouping and separating the wireless microphone and IEM systems, we can also look to add band-pass filters to the A & B antennas of the wireless mic system. These filters will only allow frequencies within their assigned range to pass, while frequencies outside the range will be blocked/attenuated. This will make the IEM systems invisible to the wireless microphone system, which will help reduce any interference from out-of-band signals. RF Venue makes a handful of these band-pass filters that can be purchased through the Audio-Technica website. Ideal filters for A-T wireless systems are the 470 – 530 MHz (DE2 band) and 530 – 590 (EE1 band) models.

While it is possible to use these band-pass filters with the IEM systems, it would require adding a filter to each IEM body-pack receiver. This would not be practical as it would add a significant amount of bulk to each body-pack and come at a high monetary cost. And, in any event, IEM systems are less negatively affected by wireless microphone systems. This is due to the transmitting power from wireless microphones usually being much lower than the IEMs, which makes wireless microphones more prone to out-of-band interference than in-ear systems.

If you have additional questions regarding frequency coordination when using wireless microphone and IEM systems together, please contact the Audio Solutions Team for further assistance.