[Darkjedi]

I used audacity and applied a high pass filter (play around with the Hz level, could be anywhere from 100-400Hz, it depends on your specific song) on my ringtones so they don't sound distorted when my phone rings. This does the opposite of what you want as it decreases the bass, but the output is much more clean with the filter in place because the speakers on our phones aren't meant for full frequency reproduction of sounds. This is the supposed preferred method of creating cell-phone friendly ringtones.

If your ringtone has high frequency range, you can compress it down so that you don't lose the lowend frequencies. If your ringtone relies espeically on low end frequencies, apply the filter and amplify the ringtone or normalize it to like -3dB.