Extending the Low Frequency Acoustic Centre Concept to Directional Loudspeakers

Hargreaves, Jonathan

Abstract

The Acoustic Centre of a loudspeaker is defined as being the point from which spherical waves appear to radiate. This is useful to know when performing phase, level, or time alignment, for example. For a single driver in a sealed box, it is typically on-axis a few centimetres in front of the diaphragm. Standard methods involve measuring level and/or phase at two or more points, and then fitting a monopole model to it. This works satisfactorily if the loudspeaker is omnidirectional, but it is not appropriate for ones that are not - modern cardioid subwoofers for example. This paper therefore explores an alternative definition based on a spherical harmonic representation of its directivity. This is still valid for omnidirectional sources but supports directional ones too. Its properties are investigated through simulation and used to optimise cardioid radiation from a loudspeaker.

• Presentation Conference Type: Conference Paper (published)
• Conference Name: Reproduced Sound 2023
• Start Date: Nov 14, 2023
• End Date: Nov 16, 2023
• Acceptance Date: Oct 13, 2023
• Online Publication Date: Nov 15, 2023
• Publication Date: Nov 15, 2023
• Deposit Date: Jan 23, 2024
• Publicly Available Date: Jan 26, 2024
• Publisher: Institute of Acoustics
• Volume: 45
• Series Title: Proceedings of Reproduced Sound
• ISBN: 9781906913472
• Publisher URL: https://www.ioa.org.uk/catalogue/paper/extending-low-frequency-acoustic-centre-concept-directional-loudspeakers