An apparatus acoustic loading of a diaphragm is disclosed. The apparatus comprises a rear face having a shape corresponding to a shape of a compression side of the diaphragm, a front face opposite to the rear face along an axis of symmetry, and a plurality of voids formed between the rear face and the front face. The plurality of voids are arranged so that their intersection with rear face forms a plurality of inlets, the plurality of inlets defining a higher compression ratio in the proximity of a voice coil compared to a compression ratio defined in at least a portion of the remaining area of the diaphragm.