Philosphies on subwoofers: as I see it.

From what I have read and heard, there are a couple of philosophies on the use of subwoofers.

1. The subwoofer is used to add the low frequencies that the mains leave out. For example, if the mains don't go any lower than 50hz, then the subwoofer is used to cover frequencies belowe 50hz. From modest, personal experience, I have found that this is tough to do as you can never tell where the mains actually leave out and where the sub actually kicks in. There is a chance of sever overlap or worse, some frequencies will get left out.

2. The other way I have seen subwoofers used is to augment the mains. I have seen this done where the mains will go down really low, 35hz or below, but the amplifier used does not do very well in the lower register and the sound tends to roll off and disappear. A subwoofer is used to augment the very low frequencies and boost the bass. This can also be tricky, but not as hard as the previous method, in my opinion. With this method, I have found that the subwoofer does not do as much work ,depending on the crossover used, and can sometimes go unnoticed until it comes across a low frequency and a pleasant surpise comes around.

I have also seen and heard about people using subwoofers in stereo. Low frequencies are supposed to be un-directional, but some subwoofers, like the Vandersteen, are capable of reaching and crossing over at very high frequencies, producing clean sound, and thus, I think, directional waves.

I have a question for Vandersteen subwoofer users; is it possible to have one Vandersteen subwoofer in a system that crosses over so high that it could change the focus of a system. I would see this as a good reason to have two Vandersteen subwoofers instead of one.

Comments?