Equalizing subwoofers individually yields unpredictable combined in-room response

Evidence

When measurements are done, it is common for some individuals to try equalizing each subwoofer separately and then to combine them. Again, disappointment is almost guaranteed because when the system is in “play” mode all subwoofers are operating simultaneously, and the result of the acoustical summation is unpredictable. The measurement that matters is the one done with all subwoofers operating simultaneously. For individually measured subwoofer outputs to sum in a predictable manner, the measurements must be of the transfer function—amplitude and phase—not the steady-state amplitude response. — , Toole, Floyd E - Sound reproduction-…, 1045

Categorization

• DEFINE: Explains why simultaneous, transfer-function (amplitude and phase) measurements, not per-unit amplitude sweeps, are the only valid basis for multi-sub optimization.
• XREF: connects to: Opposite-polarity subwoofers can null a specific room mode’s coupling; Subwoofer placement itself can be optimized alongside DSP settings; Subwoofers must be equalized together, not individually, to sound right (+5 more)

Broader Connections

• Room reverberant fields typically rise in bass, necessitating bandwidth-matched equalizer cuts for distant miking #expands (0.75)
• Flat-response speakers unavoidably produce a bass-heavy steady-state room sound #corroborates (0.72) — , Toole, Floyd E - Sound reproduction-…, 1216