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PA Loudspeaker System Design Using Multiphysics SimulationR. Balistreri

QSC Audio Products LLC, Research and Development, Costa Mesa, CA, USA

Introduction: Public Address Loudspeakersneed extra design considerations ifcompared with normal speakers. Coverageover a certain frequency range it is importantand COMSOL has the capabilities to do awhole system design simulation keepingprototype times at a minimum.

Computational Methods: The simulationuses lumped circuit equivalents for theelectrical to mechanical domain, (AC/DCmodule) and then applies the relativeacceleration to the diaphragm boundary,where solves the Helmholtz equation(Acoustics module).

The circuit below is one side involving thewoofer side including a second order lowpass filter.

Results: The whole system can then besimulated and optimized with the abilityto display graphs that are otherwisemeasured at great cost in term ofresources and time.

Conclusions: Beside being an excellent investigative tool, results of the simulations are close to the measurement cutting prototype work and resource investment.

References:1. L. L. Beranek, Acoustics, the Acoustical Society of America

(1993)2. A. N. Thiele, Loudspeaker in Vented Boxes Part I, part II,

Journal of the Audio Engineering Society, (May-June 1971)3. COMSOL, Lumped Loudspeaker Driver, Application

Library (2014)4. M. Kleiner, Electroacoustics, CRC Press (2013)

Figure 2. Circuit Equivalent

Figure 4. Polar@6.2kHz and mapped response duringdesign before (left) and after optimization (right)

Figure 5. Frequency response comparison

Figure 1. The model

∇ ∙ −1

𝜌𝑐∇𝑝𝑡 − q𝑑 −

𝑘eq2 𝑝𝑡

𝜌𝑐= Q𝑚

Figure 3. Simulated response for two different woofers and filters

10k

120

100

80

60

4 Meiloon Luix TW 4V 1m 2pi MLS 00deg.m ls(dB) Level, Cl io MLS SPL

Frequency ( Hz)2k 3k 4k 5k 6k 7k 8k 9k 20k

110

90

70

10k

120

100

80

60

4 Meiloon Luix TW 4V 1m 2pi MLS 00deg.m ls( dB) Level, Clio MLS SPL

Frequency ( Hz)2k 3k 4k 5k 6k 7k 8k 9k 20k

110

90

70

curve at60 degrees

on axismeasurement

Excerpt from the Proceedings of the 2015 COMSOL Conference in Boston