More on acoustic modification
The Acoustic Pressure Equalizers ? APEs ? are passive acoustic processors functioning as both spatial and spectral modifiers. They use diffractions on the surface to modify the sound field near the microphone diaphragm. This technique is only possible on omnidirectional pressure microphones.

Two primary changes occur:
1. An upper-midrange/high frequency boost (without changing the low end) due to the pressure build-up at certain frequencies depending on the element’s size.
2. More directionality at higher frequencies (focus).

A presence (upper-midrange) lift is often desirable in rhythmical genres, to make a voice or an instrument cut through a mix or simply to make it more intelligible or well defined. For symphonic music, the frequency response of certain legendary vintage types of microphones can be obtained using one of the APEs. However, you will achieve a much higher degree of naturalness and detail when using a precision handcrafted 4006A.