Keep low-frequency content centered in the stereo field for mono compatibility and equal speaker loading

Low-frequency sounds — kick drums, bass instruments — should sit in the center of the stereo field rather than panned or widened. Two reasons: these are high-energy sounds that need to be shared equally by both speakers, so panning off-center loads one speaker more than the other; and low frequencies carry little directional information, so centering costs nothing spatially. Off-center or artificially widened low end introduces L/R differences that partially cancel when summed to mono, losing low-end energy and thinning the sound on club, phone, or TV systems, and can create phase artifacts. The nuance: the upper harmonics of a bass sound do carry directional cues, so those can be spread even while the fundamental stays centered. When widening is desired, a multiband stereo imager widens only above a crossover (typically ~200–500 Hz) and leaves the low band mono.

Examples

A bass synth or kick: keep the fundamental centered regardless of arrangement. A Rhodes: low notes center, upper harmonics spread wider. Multiband imager with a 400 Hz crossover: widen the high band (guitars, cymbals), keep the low band at 0% extra width, then mono-check that the low end stays full.

Assessment

Explain why panning or widening a kick drum causes problems on a mono system, and describe the standard professional approach. A student widens a full master and it sounds wide on headphones but thin in mono — diagnose the cause and explain how multiband imaging fixes it.