Acoustic metamaterial absorbers can realise previously unattainable absorption spectra with sub-wavelength dimensions approaching the theoretical minimum. Such an optimal metastructure is presented in this work and implemented in a loudspeaker drive unit. The strategy is discussed and the engineering challenges are highlighted. Special attention has been paid to optimise the driver-absorber coupling and preserve the unique properties of the metamaterial absorber by using a one-parameter horn and an exact impedance match at the interfaces. The results are finally compared to exponentially tapered tubes, demonstrating the superiority of the metamaterial approach, not only in terms of performance but also versatility, size and cost.
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