A planar electro-acoustic transducer has an adjustable back cap option that provides a dipole/monopole radiation that has different roll-off characteristics. The planar electro-acoustic transducer includes a diaphragm and a plurality of front and rear magnetic bars. Each magnetic bar has a side facing the diaphragm and disposed adjacent thereto. The thickness of each rear magnetic bar is larger than the thickness of each front magnetic bar. The thickness of each front magnetic bar is less than a quarter-wavelength of a cavity resonance at 10 kilohertz. The planar electro-acoustic transducer also includes a non-magnetic acoustically transparent metallic mesh that is disposed coplanarly with the sides of the front and rear magnetic bars that face the diaphragm.