The true worth of a wireless system is determined by its overall sound quality, dynamic range, freedom from dropouts and interference, and its operating range. Essentially, you want a wireless system to sound like a wired system. You also want a system that has easy-to-use controls and easy-to-read displays. There are a number of other common features that are true for all wireless mic, instrument, and in-ear monitoring systems that are not so immediately obvious.
Automatic Frequency Selection
With this feature, a frequency-agile system selects the frequency automatically. It's a nice feature to have if you need a system with frequency agility as described in the previous paragraphs, because you’ll be resetting your system fairly often. Some high-end systems offer automatic setup of your entire wireless system.
When purchasing a system (especially one that is not frequency agile), you will be asked to select from several frequency options. These choices are designated by a combination of a letter and a number, but these designations are not standardized from one manufacturer to the next. Each manufacturer has its own system, but the letter usually designates a particular band range for the unit. The second part, the number, refers to a specific frequency within the range specified by the letter. You should choose the letter that works best for your location, and a number that is different from other systems being used alongside yours. For the most part, the frequencies offered will work anywhere in the country.
As with any piece of electronic music gear, how well a wireless system keeps you informed of its status is an important consideration. Having a display that's highly legible and well-lit is a big help during setup and performance. It should indicate signal strength, identify the channel being used, and have low-battery level warning indicators or battery-level meters. Battery-status displays are usually located on the transmitter, but some high-end systems have them on the receiver too.