Wall boundaries alter loudspeaker output by modifying acoustic impedance seen by the driver

Evidence

When a speaker is placed near a reflecting boundary, an image source is formed due to that reflecting boundary, as shown in Figure 1.28 in Chapter 1. Thus when a speaker is placed near three reflecting boundaries, three image sources are formed, as shown in Figure 6.59. The effect of these image sources, which represent reflections from the boundary, is to modify the local acoustic impedance seen by the loudspeaker. Because a dynamic speaker is mass controlled in its normal working region, it forms a high impedance source, and therefore the radiated power is affected by the local impedance variations. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2133

Categorization

• DEFINE: Clarifies the image-source mechanism by which reflecting boundaries change the acoustic load a loudspeaker sees.

Related

• Boundaries alter bass output by changing the loudspeaker’s acoustical radiation resistance (similarity 0.84)
• Room boundaries alter loudspeaker output through reflected image sources (similarity 0.84)
• Room boundaries alter a sound source’s radiated power, not just its perceived sound (similarity 0.83)
• A single sound source near a reflecting surface creates interference via an image source (similarity 0.83)
• Greater loudspeaker-wall separation shifts the adjacent-boundary dip to lower frequencies (similarity 0.83)
• Loudspeaker directivity and early reflections affect sound quality and imaging (similarity 0.82)
• Sound waves diffracting at speaker cabinet edges distort the frequency response (similarity 0.82)
• A single sound source near a reflective boundary creates a virtual second source (similarity 0.81)
• Nearby reflective surfaces can load a source and boost its output (similarity 0.81)
• Walls and corners near a sound source increase its power output (similarity 0.80)
• Reflections from a nearby hard wall can double the sound amplitude toward the listener (similarity 0.80)
• A reflecting wall doubles total sound power output from any source (similarity 0.80)
• Toe-in aiming of front loudspeakers minimizes problematic side-wall reflections (similarity 0.80)
• Adjacent boundaries alter radiated sound power via acoustical radiation resistance (similarity 0.80)
• Room acoustics requires modeling direct sound then early reflections (similarity 0.80)