MSV, MOL, and VSA are the formal metrics for evaluating multi-subwoofer bass.

Evidence

The most important by far is Mean Spatial Variance (MSV). Other similar metrics have been used by other researchers. Lower values for MSV indicate less variation of frequency response from seat to seat, which is the goal. Low-frequency efficiency is expressed by Mean Output Level (MOL), quantifying a mean output level from 20 to 40 Hz, including correction factor for the number of subwoofers (“bass-per-sub”, if you will). Finally, we have variation of spatial average (VSA), which describes how flat the response at each seat is on average. — Toole, Floyd E, Sound reproduction- the acoustics and…, 1588

Categorization

• DEFINE: Defines the three key objective metrics (MSV, MOL, VSA) for evaluating low-frequency spatial performance.