The electric bass is the foundation that a song is built on, but even the best players sometimes struggle with keeping the levels consistent. Erratic levels are normally tamed by inserting a compressor. But due to the nature of how compression works, the end result can lack the harmonics and attack needed to allow the bass to fully realize its role in the song. However, using a little EQ can tame the consistency problems without damaging the fundamental sound of the bass.
A cut in the low-frequency, around 6-8dB at 30-50Hz, keeps the excess bass energy at bay. This can help the entire mix, since unnecessary low-frequency tones can add mud to the mix, and make the bass “boomy.” A cut in this range also keeps the bass from masking the kick drum. A boost around 100-400Hz will help beef up the low end that was removed by cutting the lows. A boost between 1 and 3kHz will bring out attack and harmonics. Be careful not to boost these high-mids too much — it can counteract the compression-like effect of applying EQ in this manner by accentuating the attack.