Greater loudspeaker-wall separation shifts the adjacent-boundary dip to lower frequencies

Evidence

If the loudspeaker were positioned at a distance from the wall, as when using a mounting bracket, the dip would begin at a lower frequency. The greater the separation, the lower the frequency at which the depression begins. The more directional the loudspeaker, the narrower the frequency range over which it exists. This is the mechanism of the classic adjacentboundary effect. — Toole, Floyd E, Sound reproduction- the acoustics and…, 1488

Categorization

• DEFINE: Defines the adjacent-boundary effect mechanism: distance from wall determines the dip frequency, directivity determines its bandwidth.