Multiple identical subwoofers reduce seat-to-seat bass variation

Evidence

Not long after the preceding events took place, I moved to California to work for Harman International as corporate vice president of acoustical engineering. I carried with me the notion of having substantial control of room resonances without the visual and real estate commitments to large bass traps. A room could be an ordinary room, visually and acoustically, with ordinary acoustical properties and problems, until the “play” button was pressed—then it could become extraordinary. … He first tackled the case of simple rectangular rooms, and after substantial analysis, involving simulations using from one to 5,000 subwoofers (acoustic wallpaper?), concluded that two or four subwoofers—identical, and identically driven—created a central zone in which seat-to-seat variations were usefully reduced (Welti, 2002a, 2002b). This means that equalization can benefit several listeners. — , Toole, Floyd E - Sound reproduction-…, 958

A suggested rough guideline, based on experience of the authors, is that a 25% decrease in the MSV or VSA values would be noticeable while a 50% or more decrease of the value would be a game changer. … Finally, remember that seat-to-seat variation (MSV) is the only metric that cannot be improved with larger subwoofers or equalization. — Toole, Floyd E, Sound reproduction- the acoustics and…, 1603

Not long after the authors started working together, we thought that mode manipulation should be able to work in a more generalized sense, not just for one mode in a specific custom room installation. Todd first tackled the case of simple rectangular rooms, and after substantial analysis, involving simulations using from one to 5000 subwoofers (acoustic wallpaper?) concluded that two or four subwoofers—identical, and identically driven—created a central zone in which seat-to-seat variations were usefully reduced (Welti, 2002a, 2002b). This means that equalization can benefit several listeners. — Toole, Floyd E, Sound reproduction- the acoustics and…, 1586

Categorization

• XREF: Connects to the reader’s interest in institutional/systems thinking about built environments and engineering tradeoffs. — connects to: Seating that avoids low-order null lines reduces seat-to-seat variation — Toole, Floyd E, Sound reproduction- the acoustics and…, 1595; Optimized multi-sub systems can use much smaller subs at some locations; Brute-force parameter search minimizes seat-to-seat bass variation (+3 more)
• DEFINE: Defines MSV (mean spatial variance) and VSA as the two key metrics, and gives calibration values for what counts as noticeable (25%) vs. game-changing (50%) improvement.
• corroborated: 3 independent passages support this claim — , Toole, Floyd E - Sound reproduction-…, 958; Toole, Floyd E, Sound reproduction- the acoustics and…, 1603; Toole, Floyd E, Sound reproduction- the acoustics and…, 1586

Broader Connections

• Adding extra subwoofers rarely improves bass without controlled placement #qualifies (0.85) — , Toole, Floyd E - Sound reproduction-…, 1044
• Equalizing subwoofers individually yields unpredictable combined in-room response #qualifies (0.80) — , Toole, Floyd E - Sound reproduction-…, 1045
• Room differences dominate loudspeaker differences when listeners cannot adapt #expands (0.75) — Toole, Floyd E, Sound reproduction- the acoustics and…, 547