Adding extra subwoofers rarely improves bass without controlled placement

Evidence

Most often they are not identical subwoofers, and they are not located where they need to be, and they may or may not be driven with the same bass-managed signal. Unpredictable results and debates are almost inevitable. — , Toole, Floyd E - Sound reproduction-…, 1044

One of the most common misconceptions is that simply adding another subwoofer or two will automatically improve things. Most often they are not identical subwoofers, they are not located where they need to be, and they may or may not be driven with the same bass-managed signal. Unpredictable results and debates are almost inevitable. — Toole, Floyd E, Sound reproduction- the acoustics and…, 1662

Categorization

• QUESTION: Would be useful to know what quantitative listening tests show for same-signal, well-placed multiple subs versus naive ‘just add another sub.’
• corroborated: 2 independent passages support this claim — , Toole, Floyd E - Sound reproduction-…, 1044; Toole, Floyd E, Sound reproduction- the acoustics and…, 1662
• XREF: connects to: Subwoofer placement itself can be optimized alongside DSP settings; Multiple identical subwoofers reduce seat-to-seat bass variation — , Toole, Floyd E - Sound reproduction-…, 958; Optimal woofer placement makes boundary distances as different and non-multiple as possible — , Toole, Floyd E - Sound reproduction-…, 1068 (+1 more)

Broader Connections

• Optimal woofer placement makes boundary distances as different and non-multiple as possible #expands (0.85) — , Toole, Floyd E - Sound reproduction-…, 1068
• Equalizing subwoofers individually yields unpredictable combined in-room response #corroborates (0.80) — , Toole, Floyd E - Sound reproduction-…, 1045