The APE30 is a Ø30 mm sphere shaped Acoustic Pressure Equalizer, designed for use with the Reference Standard Microphone 4006A or the ST4006A stereo kit. For use with the compact 4006C, the microphone must be either hung or placed in the clip with an XLR connector plugged in.
It gives a mild modification of your microphone's on-axis and off-axis frequency responses, and a slight change in the direction-to-reverberation ratio.
This will give your recordings greater presence, nearness and clarity on-axis (especially around 4 kHz).
An on-axis boost, between 2 and 8 kHz, and high-frequency roll-off off-axis, will sometimes help you capture the subtle audible details of both musical instruments and voices.
This accessory substitutes the former L30B, suitable for 4003, 4006, 4006-TL and their stereo kits. The L30B cannot be used with the modular series 4006A or 4006C and vice versa.