The difference between high- and low-Z microphone cables with XLR connectors can be confusing to the beginner, but it is easily determined. Most new microphones use female XLR connectors on the microphone connection end, but must be used with the proper cable and mixer-end connector.
Microphone and audio equipment impedance, also called "Z", is either high or low. Simply put, impedance is the resistance of AC voltage going through the system. All professional audio components are low impedance, as it offers increased resistance to outside radio frequency (RF) interference. High impedance is sometimes called "unbalanced" and low impedance is "balanced."
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The real difference between high- and low-Z microphone cable types is the number of wires inside the cable. High-Z cables use two-conductor cables (positive and ground), and low-Z cables use three-conductor cables (positive, neutral and ground).
Standard low-Z microphone cables use XLR connectors on both ends, with a female XLR at the microphone end and a male XLR at the mixer end. Standard high-Z microphone cables use a female XLR on the microphone end with a standard quarter-inch phone plug at the mixer end.
While standard high- and low-z microphone cables can be identified by the connectors, there are exceptions. Before XLR connectors became the industry standard, some manufacturers used different connectors for the microphone end but still used the standard quarter-inch plugs for high-Z and XLR male plugs for low-Z cables on the mixer end.
In practical use, low-Z microphones are the professional industry standard not only for their resistance from outside frequency interference, but for the ability to run very long cables without frequency loss. High-Z microphones have limited useful cable lengths and are made primarily for home users and beginners. As high-Z cable length increases, frequency loss and the likelihood of outside interference is increased.
Although XLR connectors on the microphone cable will fit both high- and low-Z microphones, impedance is set by the microphone, not the cable. While no damage to equipment will occur, a loss of volume will be noticed. For best results, low-Z microphones must be matched with low-Z cables and equipment and high-Z equipment must also match in mic, cable and equipment type. Most modern equipment accepts both low- and high-Z microphones and cables.