This may sound like a simply trick to some of you, but when I first discovered this it felt like the world had fundamentally changed in a split second.
This technique is primarily useful when trying to add distortion to a bass, but multiband processing itself can be applied in a myriad of ways, and multiband distortion can be used on any source, so by all means experiment and realize that affecting specific bands of the frequency range isn’t just for distortion.
In electronic music many times you want to give your bass a nasty growl. Running it through a metal zone petal can make it scream, but more often than not adding distortion doesn’t help out with your sub bass, or your “low lows” as some say. I’m not sure why, but for some reason the same grimy distorted sound many of us love doesn’t work out so well on low frequencies. For the most part sub bass is something you feel, more than something you hear. It’s not as much about tone as it is about making the earth shake, or bones rattle. Distortion doesn’t usually help this.
So, how to do it… if you have a plugin like Izotope Trash it’s much easier as they have already built in the multiband function. If you don’t already have a distortion plugin that offers a multiband approach it’s not to hard to set up yourself. Just route your bass to two sends, buses, etc. You’ll have two sources for the bass now, so route the main output of your bass track to nowhere when using this approach. Now, simply add a high pass filter (HPF) on one send/bus and a low pass filter (LPF) on the other (together the two sends/buses will sound like the original bass). Set them so that one is just the low lows, say 150hz. and under, and the other is everything above 150hz. Of course this value may need to be adjusted depending on the bass, and you could of course use more than two bands.
If using something like Izotope trash you don’t need the sends/buses, just create two or more bands in the plugin and set the sub band so that it’s not getting any distortion. From here simply dial in the distortion any way you like it. Try something subtle or completely muck things up, it’s your call. Using this technique you can add some nastiness to your bass without losing the presence of your subs.
You could also just run distortion over the whole bass and roll off the lows or filter them out. Then just add another layer of bass for sub, usually a sine wave with most of the mids/highs rolled off.
Again, this trick is old hat for some, but to others, this may really open some creative doors. Best of luck to all and most importantly, have fun!