There's only so much one can do with baffles and expansion chanbers and there is a limited amount of space. But I have experimented with different types.
My latest uses a two stage multi chamber approach and seems to chop off some highs. The facts remains is that these are powered by an engine running
at 8000 to 12,000rpm which will never sound like a Maybach. That's just one of those things you buy off on when you run these. I have a separate page on my
site that details some of my sound experiments.
My website is
http://tanks.linte.com
Jerry