for a good and efficient sound reproduction from a loudspeaker unit it is prescribed that two woofers are arranged back to back , one on a front plate of the unit and the other on an internal partion plate , whereby a front compartment of the unit operates as an effective bass reflection system , while a closed rear compartment contributes , via the rear loudspeaker , to improve the quality of the reproduced sound . the back to back arrangement of the two loudspeakers results in a non - vibrating unit .