34 pieces of abs the placement of the smaller box inside the larger one creates a resonant cavity that provides improved low frequency performance the boxes are left open on the bottom and can be placed on stand offs to allow air flow in and out of the boxes the height of one box relative to the other can be adjusted to change the acoustics of the system the piezoelectric elements 91 92 95 and 96 are connected in parallel and driven by an audio amplifier 97 similar to the one in fig2 again a cd player or tape deck 98 is used to provide the audio signal fig1 illustrates the application of a dual channel speaker box that uses the walls of a room near a comer to achieve stereo separation the triangular shaped box 99 has piezoelectric elements 100 101 on two sides the third side is used to support a dual channel amplifier 102 which is essentially two audio circuits as in fig2 the difference being that the two audio inputs are not summed but are instead fed into separate audio amplifiers the sides 103 104 radiate a pressure wave toward the walls 105 106 this radiation is then spread out as it is reflected from the walls 105 106 because the sides 103 104 of the box are at a 90 degree angle and the vibration from the piezoelectric elements is predominantly tangential to the sides of the box little couplings exist between the two sides 103 104 the unit should be placed close to the corner.