PASSIVE TUNED LOUDSPEAKERS AS ABSORBERS FOR ROOM ACOUSTICS

This paper presents a novel approach to improving the performance, tunability and efficiency of low frequency membrane absorbers. It is shown that a passive loudspeaker within a cabinet can be used as an efficient and adaptable membrane absorber, with variable passive electronic components connected across the terminals to alter its mechanical resonance properties. This allows the system to be tuned/re-tuned and installed in different rooms without the impractical geometrical re-design and manufacture needed for standard membrane absorbers. Impedance tube data is presented for an absorber with different electronic loads connected. Varying the value of a single capacitor across the loudspeaker terminals is shown to reduce the resonant frequency of the system by up to 30%, whilst varying solely resistive loads is shown to alter the effective bandwidth of absorption. A lumped element model is derived, allowing the system to be optimised for different resistive and reactive component combinations for a specific driver. Absorber systems of this type could find a place in small critical listening environments, where the damping of room modes is vital for good acoustic conditions