Equalization (or EQ) refers to the adjustment of audio frequencies produced by kick drums, which can either be cut or boosted to reduce or increase the presence of a specific frequency or frequency band. This is usually done to improve the audio aesthetics of kick drum sounds.
EQ may also be used to eliminate or reduce unwanted sounds and transients, and altering EQ is a good way to adjust the timbre of the kick drum by modifying the substance of its frequencies. This can furthermore assist in fitting the kick drum track within the sonic spectrum and overall context of the mix.
Depending on the application, different EQ units can be more suitable than others
i.e. frequency fine tuning, removing bad or error frequencies, boosting highlighting tones
Some popular choices include:
API 560 and 550A for tweaking problem frequencies and boosting highlighting tones
Classic Neve EQs such as 1073 and 1084 for smooth, gentle frequency nudging
SSL E Series for more drastic and creative shaping
Pultecs with Plus/Minus on 100Hz or 60Hz with 5Hz for the click