under pink noise, Delta 10A's dustcap seems to have some pronounced resonances. Removing it and going to a smaller & softer dustcap might help - but its a gamble - -hopefully the crossover will prevent those resonances from being excited. "BSC" = "baffle step compensation" and is often done to get a reasonably good bass to treble balance as low frequency waves will wrap around a free standing cabinet. It can be done with a larger inductor in the lowpass section or a resistor in parallel with an inductor. Re: "screw-on" - IIRC, (?) Erich mentioned one of the big compression drivers manufactured as a regular 1 3/8" thread which will screw on to standard threaded horns/waveguides and coaxial woofers. What crossover are you using?