Electroacoustic absorbers represent an interesting solution for low-frequency sound absorption in rooms. These systems simply consist of closed-box electrodynamic loudspeakers, whose acoustic impedance at the diaphragm is judiciously adjusted by connecting a passive or active electrical control circuit. This paper presents a method for designing different electroacoustic absorber systems constituted of simple electrical and mechanical components that are coupled to a primary loudspeaker, resulting in multi-degree-of-freedom resonators. Each system is optimised to maximise the absorption performance with respect to different metrics. Experimental evaluations in an impedance tube confirm the model accuracy and method efficiency for achieving low-frequency absorption.