Room pressurization creates a compliant bass boost below the first axial mode

Evidence

Whatever the shape of the spectrum of the direct sound from musical instruments, or loudspeakers reproducing recordings of those musical instruments, the steady-state sound in a normal room will exhibit a version of that spectrum that rises at lower frequencies. Highly reflective concert halls attempt to preserve the limited sound output of musical instruments and voices in reflections, delivering as much of it as possible to listeners, while not masking temporal details in the music, and still creating a pleasant sense of envelopment. It is a difficult acoustical balancing act. Sound reproduction spaces are much less reflective: the principal cues to space and envelopment are in the multichannel recordings, and a volume control changes loudness at will. Loudspeakers designed with flat on-axis frequency responses, so as to accurately reproduce the initial timbral signature of the recorded sounds, will therefore exhibit a rising sound power output at lower frequencies. — , Toole, Floyd E - Sound reproduction-…, 1216 (#expands, via linked claim)

2. By placing the speaker carefully, with respect to the boundaries, one can eliminate some of the variation in the response. However, one still has a 9 dB rise in response at low frequencies. This is well known and the 9 dB rise at low frequencies is inherent in operating in an environment with three boundaries. In general, the lowfrequency responses of loudspeakers designed to be placed close to boundaries is tailored to compensate for it. — David Howard, Jamie Angus, coustics and Psychoacoustics, 2193 (#corroborates, via linked claim)

Categorization

• XREF: connects to: Every stage of the audio chain high-pass filters bass, accumulating phase shift.; Flat on-axis speakers naturally produce rising bass power and downward-tilted room curves.; Bass rises in reflected room sound for all forward-firing loudspeakers (+6 more)

Related

• Flat on-axis speakers naturally produce rising bass power and downward-tilted room curves. (similarity 0.92)
• Bass rises in reflected room sound for all forward-firing loudspeakers (similarity 0.91)
• Room reverberant fields typically rise in bass, necessitating bandwidth-matched equalizer cuts for distant miking (similarity 0.91)
• Room resonance excess masks loudspeaker bass deficiency to listeners (similarity 0.89)
• Flat-response speakers unavoidably produce a bass-heavy steady-state room sound (similarity 0.88)
• Operating a loudspeaker near three room boundaries imposes a 9 dB low-frequency rise (similarity 0.86)
• Resonances are the primary problem in loudspeakers (similarity 0.84)
• Recorded room ambience may distract listeners from evaluating raw loudspeaker quality (similarity 0.84)
• The listening room, not the loudspeaker, determines perceived bass quality. (similarity 0.84)
• Room acoustics dominate perceived bass response below roughly 250 Hz (similarity 0.84)
• Room reflectivity at low frequencies determines bass elevation in measured steady-state curves (similarity 0.84)
• Equalizing only the low-Q resonance substantially improves subjective loudspeaker ratings. (similarity 0.84)
• Even anechoic rooms have a low-frequency operational limit (similarity 0.83)
• Most loudspeakers need equalization to correct low-frequency room resonances (similarity 0.82)
• Bass accounts for roughly 30 percent of perceived sound quality (similarity 0.82)

Broader Connections

• Flat-response speakers unavoidably produce a bass-heavy steady-state room sound #expands (0.95) — , Toole, Floyd E - Sound reproduction-…, 1216
• Bass rises in reflected room sound for all forward-firing loudspeakers #corroborates (0.92)
• Operating a loudspeaker near three room boundaries imposes a 9 dB low-frequency rise #corroborates (0.88) — David Howard, Jamie Angus, coustics and Psychoacoustics, 2193
• Room resonance excess masks loudspeaker bass deficiency to listeners #corroborates (0.78) — Toole, Floyd E, Sound reproduction- the acoustics and…, 549
• Room reverberant fields typically rise in bass, necessitating bandwidth-matched equalizer cuts for distant miking #corroborates (0.75)
• Comb-filtering undulations from room reflections move to bass and become inaudible #corroborates (0.72)