The APE40RS, a Ø40 mm sphere, offers a more noticeable on-axis boost between 2 kHz and 8 kHz. It also offers stronger off-axis attenuation than the Ø30 mm version. This gives a marked increase in the directivity of your recordings (at 4 kHz, the front-to-back sensitivity ratio is 8 dB). It also decreases the effects of reverberation and off-axis sources.

When using Acoustic Pressure Equalizer, 40 mm Ball, you can modify the spectral characteristic of a source by simply altering the angle of incidence to give a frequency boost, a flat response or attenuation.