I have a carton of NSBs - inexpensive 4" fullrange drivers good for about 90dB/1W and 10-15W of power handling. I'd like to build two line arrays of 16 per side, and use these for some inexpensive PA speakers. I've also got a carton of 200 Onkyo tweeters, though I'm not sure I'll use them - comb filtering is bad, but no tweeters greatly reduces the potential for clipping damage.

How low can I get away with using these before I really need a sub? Any thoughts on their use?