In my experience many basic PA type bass speakers are not designed to handle really low bass. Electro Voice doesn't strike me as a company name either which excels in bass speakers either but I am not familiar with them. It sounds like if you want really deep saturated bass you probably do need a sub woofer as has already been mentioned a few times. Or really well designed bass enclosures with kick ass speakers.
Also I don't recall any mention of what your Sub 37 is plugged into. The output signal is very hot and may need to attenuated or fed into a line input. Just something else you may want to double check.
In a Moog Mood? Here's a forum for discussion of general Moog topics.