If your bass doesn't cut through the mix without muddying up the low-end, the solution might not be in the bass frequencies at all.

Here's a quick tip to solve the problem, taken from EQ Strategies - Your Ultimate Guide to EQ

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It's a common problem for the bass guitar to get lost on smaller speakers. If you mix on great monitors with a nice bass response you don't realize how your EQ decisions are affecting the mix on other playback systems.

Boost Harmonics

For instance, if your bass is really grooving and thick due to a nice boost at 100 Hz, try boosting the harmonic multiples of that frequency. If the fundamental frequency is 100 Hz, adding broad boosts to 200 Hz, 300 Hz and higher in the right multiples enhances the natural sound of the bass without excessively boosting one big frequency.

Also, if your bass guitar is sounding muddy, skip the low-end boosts and just concentrate on adding the harmonics. It gives you a well-rounded bass guitar sound without cluttering up the low-end.

Middle of the Road

Don't neglect the importance of the middle frequencies. Just because it's a bass guitar doesn't mean you should forget about everything above the low-mids. Here's where you add clarity and punch to your bass guitar.

Boosting around 600 - 900 Hz (I'm being broad here because it depends on so many factors) makes the actual tones of the bass guitar shine through. You won't just hear the low-end rumbling beneath all the other instruments, you'll actually hear some definition from the bass notes.

Presence

Some engineers like their bass guitar a little brighter. If you need to have the bass 'pop' just a little bit more, boosting the frequency areas around 1 - 4 kHz gives you even more clarity and presence to the bass strings.

It can bring out the plucky sound of the bass guitar, especially if the bass player is using a pick.

I wouldn't venture much further up the frequency spectrum. Most of the higher frequencies just add hiss and high frequency noise that's not particularly flattering to the bass guitar. You could even filter out the highest frequencies with a low-pass filter to focus your sound solely around the frequency areas you want.

EQ Bass With the Best of Them

It's hard to hear how these tips work without using them in a session, so go open up your DAW of choice and go play around with your bass guitar.

If you're still confused and struggling, or just need more info on EQ in general, check out the rest of EQ Strategies - Your Ultimate Guide to EQ here.