Hi Dave, i'm not too sure about that in all honesty, the added (sub) harmonics thing i mean Not sure i'd need anything like that in all honesty as i have quite a bit of music with heavy sub 25Hz content & a lot of that is sub 20Hz, so in certain respects i don't need to make what isn't there as it already is

Besides which if you are going to try this thing out you'll need to use a speaker that can actually reproduce whatever frequency it is producing. If you are going to run some kind of reflex speaker then make sure it's tuned really low (like an LLT) or you may find that you are just moving the cone & cancelling via the port.

More on LLTs (large low tune) in the future

More on the 8033 as well once i feel up to pulling a load of kit out of my rack & fitting them in...