I make a point to illustrate that the SP4 cabinets are 3-ways; this means that the audio signal is split in 3 frequency bands by what is called the "crossover" Ultimately, what makes that so critical is that the 15" woofer in each cabinet, that is lowest to the ground, is actually a subwoofer, by definition. It is receiving just bass frequencies, and is a Black Widow edition as well, with more peak handling than necessary. 🎸
Bass takes the most juice to create those sound waves, so that power is needed. This is exactly why I have upgraded amplifiers from the Yamaha at 900 watts, to the new Crown at 2,700 watts. I think that 3x the power will get the bass boost we desire. I also added a dbx 15 band EQ in a rack, for any extra mega bass needed.
So, yes, in conclusion, fundamentally now I don't need to add extra subwoofer cabinets. It actually is quite a bit more costly to go this route, in equipment purchases. The truly powerful amplifiers are so expensive that it almost takes the fun out of it, and they do not impress the ladies at the yard either, so sound guys generally will go for lots of big looking cabinets and subs, that all combined will still pale in comparison to this single set of SP4s paired with a Crown XLi 3500, boosted by dbx EQ.
Having a 3-way crossover, also makes for a pleasant distribution of frequency load across the speakers! The truth is, that the SP4s I have are actually quasi 3-ways. The difference being that the middle woofer get the mids + bass also. I am assuming this is so there's more bass, which is a good thing out there in the field. Even with all this, the sound quality is fantastic; I actually like listening to them as much as my studio monitors.