Better headphones have tighter tolerances in the variation of their drivers' frequency responses. To reproduce a faithful stereo image, the left and the right drivers must respond equally to every frequency in the audible spectrum. When this condition is fulfilled, the drivers are said to be "matched."

Our driver matching test sweeps all these frequencies (up to 10 kHz) and sends exactly the same levels to both earpieces. Play the test tone at a moderate level and listen: the sweeping tone should keep a perfect central position across all frequencies, playing right in the middle of your head, without any deviation.

A panning that departs from its central position for a particular frequency will highlight poorly matched drivers... or mismatched ears.

To ensure that your headphone’s drivers cause the problem, not your ears, perform the test again, with the earpieces swapped: the left channel now feeding your right ear and vice versa. The panning should now deviate in the opposite direction.