Loudspeaker enclosure shape and size alter frequency response via diffraction

Evidence

In 1950, Olson (1969) demonstrated, experimentally, that the enclo­ sure shape and size significantly affect the frequency response of a loud­ speaker, due to diffraction effects. These diffraction effects can occur at any frequency where the wavelength is of similar size, or smaller than the box. This means that they can occur in any small enclosure, such as a top mounted tweeter. They can also occur in the main cabinets if there are drivers whose frequency ranges produce wavelengths of appropriate dimen­ sions relative to the box sizes. — David Howard, Jamie Angus, coustics and Psychoacoustics, 2198

In 1950, Olson (1969) demonstrated experimentally that the enclosure shape and size significantly affect the frequency response of a loudspeaker due to diffraction effects. These diffraction effects can occur at any frequency where the wavelength is of similar size or smaller than the box. This means that they can occur in any small enclosure, such as a top-mounted tweeter. They can also occur in the main cabinets if there are drivers whose frequency ranges produce wavelengths of appropriate dimensions relative to the box sizes. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2146

Categorization

• QUESTION: Olson 1969 — worth chasing the original experiment for the exact diffraction curves and how enclosure edge geometry was varied.
• XREF: Connects to the book’s earlier treatment of diffraction and baffle effects, and to wavelength-versus-object-size reasoning that recurs in room acoustics. — connects to: Resonator pitch scales with gas speed, volume, neck geometry; Real loudspeakers show flat magnitude response only below 800 Hz with a midrange dip — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 505; Reflection and diffraction of sound both depend on object size relative to wavelength (+8 more)
• corroborated: 4 independent passages support this claim — David Howard, Jamie Angus, coustics and Psychoacoustics, 2198; David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2146

Broader Connections

• Sound waves diffracting at speaker cabinet edges distort the frequency response #corroborates (0.95) — David Howard, Jamie Angus, coustics and Psychoacoustics, 2199
• Loudspeaker enclosures should curve near drive units to reduce diffraction #expands (0.90)
• Spherical enclosures give the smoothest loudspeaker frequency response #expands (0.85)