Ok, this sounds like a crazy idea but... The standard sub-bass is a pure sine wave at around 40-80hz. (E1 - E2, that octave) Lots of people have asked in the past: how to I make my subs sound bigger and deeper? Usually, the answer is to add distortion/ saturation (or use a square wave). This makes the sub sound bigger by adding harmonics, which interfere with the main bass sound, (The lowest harmonic of the sub (not the fundamental) is at twice the frequency of the fundamental, or 80 hz - 160 hz, which is really where a lot of the main bass usually sits.) So why not instead of adding harmonics, add another pure sine wave a fifth up, or +7 semitones. This is 1.5 times higher than the sub itself, or 60 - 120hz which is between your main bass and the sub, so it adds weight without interfering. That was the theory, but I have really shit speakers and only moderately good headphones so I'm not sure how much difference it makes. I can hear some difference, it does sound better, but I don't really trust my crappy set up... Someone check it out for me and see if I'm talking bollocks or not.