crossover question

The crossover (at 600hz) will decrease the volume of the driver gradually (the slope) so that the mid-range speaker will take over and produce the sound until it hits the next crossover for the tweeter. So the crossover creates a downward slope for the driver and an upward slope for the mid, that sort of intersects at the crossover point.
The driver will still be producing some sound at 700hz and 800hz and above, but it will be reduced by 6,12,18,or 24db per octave, depending on the degree of the slope. The reverse is true of the mid. It might start out at 300hz and be 24db down. It will gradually get louder until around the 600hz mark, where hopefully it will blend perfectly with the driver. Such is the plight of the speaker builders!
The crossover doesn't "deliver" from 30-600, but it does slow down and stop the speakers from delivering above and below that point. Hope this helps a bit!
Sonny

Yes, the crossover would block hi frequencies from the woofer.

But be careful here. Even if you pick a driver with the same nominal impedance and sensitivity, probably it won't blend very well with the other drivers until the x-over is adjusted for it.
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Are you trying to modify the Vandersteen's? If you have questions about Vandersteens you may want to read posts by Bigtee. He is very knowledgeable on most things Vandersteen.

Oh boy am I modifying them. When I am done I will post a pic.
You won't recognise that they are Vandersteens.
I believe that the 8" driver is not OEM. And I don't want to pay Mr Vandersteens prices. I would rather buy a stock Vifa driver and save 50%. But I am also being told that the Vifa in the 2c's is not stock. That it is modified in some way.
Either way. It has to be better than this plastic piece of shit that's in there now.

Not to rain on this parade but it takes a LOT of knowhow to do what you are attempting. Vandersteen has refined the 2's design over some 28 years. I for one would not second guess him in this area.
If the speaker was previously modified, I would try and bring it back to the original design.
When you start dealing with a time and phase speaker, the 6db slope is just the beginning. The drivers are used over a much wider frequency spectrum than steeper slopes and does require custom drivers. Vandersteen modifies his or has them built to his specifications to serve the intended purpose. The 6db design is probably the hardest to modify because of this.
After all of that, then you must deal with the phase characteristic of any driver used. Correction is then applied to bring phase relationships into line using those selected drivers. Each one is individually tested in all parameters. This is one of the reasons the drivers cost more from him because they are a known quantity.
What you are attempting is a re-engineering of the design. Unless I had vast experience, I would leave it alone. Vandersteen didn't get where he is at with hit and miss engineering. He is one of the more knowledgable individuals in the industry and his designs are extremely sophisticated. His bass loading using an 8" driver in a sealed encloseure and the 10" radiator in the rear are unique. The system acts sealed and passive because the "Acoustic coupler" in the rear is also actively driven below 35hz. It is not truly passive. This "System" is pretty remarkable in the world of speaker engineering and speaks highly of Vandersteen's knowledge.
If you mess with the 8", then you have to also deal with the 10". What I'm saying is it is MUCH to complicated for a novice and I wish you the best of luck.