Vandersteens and subwoofers other than the 2Wq?

Sek, how does he acomplish this cross at 75Hz? Perhaps you mean he has 75K fixed X-2 filters(their is no 75K setting on the switchable unit that comes with the woofer).

Bigtee and Scott, I have a question my self. It is my understanding that the low pass portion of the X-0ver built into the 2W's is fixed at 80 cycles, and that the feed forward correction does nothing to compensate for input impedance variations and theirfore lowered or raised High pass starting points. i.e. a 75K fixed filter into a 100K amp gives a high pass value at roughly 63Hz and thus an overlap of frequencies being produced by the woofer with its low pass x-over point at 80HZ. Or is their some mechanism that I am unaware of built into "Dick's" feed forward correction set up to compensate for this?

He started with the variable crossover that came with the 2WQ and from there, after consulting our local Vandersteen dealer, determined the proper value for the higher quality fixed Vandersteen crossover for which he paid an additional charge. 75 Hz. is my best recollection.

You can change the crossover "Hinge" point by adjusting the value of the capacitor in the crossover vs. the input impedence of the amp. Using the formula 6.28 x input z x crossover frequency, you can adjust for whatever sound you want by allowing the main speakers to operate further down in frequency or up in frequency. For example, if you set the crossover at 80hz and then re-adjust say at 70 hz, the sound will be more bass heavy. If you do the opposite and go from 80 up to say 90hz, the sound will be leaner. You can always adjust the level control on the sub to compensate for some of this. The 2wq error correction is designed to exactly match the rolloff of the 6db filter at 80hz with a boost in exactly the same fashion creating a flat frequency response. However, room acoustics affect this considerably. That is why Vandersteen says try a value above, equal to and a value below. Since the lowpass on the 2wq is non-adjustable, this is the only option you have. In the owners manual, it shows this. The boost created by the "Error correction" remains the same. You just adjust the crossover point for the sound you prefer.
I can't imagine with some effort not being able to make the 2wq work in any position.
One of the problems the 2wq corrects is the phase shift created by faster slope subs. This was designed into the error correction based on Vandersteen's trials. Everything is going to be a trade off of sorts. But with a little patience and an open mind, you can get this bad boy to work!