Vandersteen 2C contour controls +-

It sounds like, all things being equal, the Vandersteen 2C models - with back firing woofer, need to be placed closer to the front (or back behind them) wall to amplify the bass. I experimented with my 2Ci model and moved them from 24" to 16", considering mine are on the sides of a bay window, and it shrunk the depth of the soundstage but did add a tiny bit more bass. Just like everything else, it all boils down to tradeoffs. For me the presentation of the soundstage is more important than the extra bass.

Update:

After letting the cables sit without change for over a week the bass came back 80% which is fine - I was a little bass heavy before. More importantly, it really only shows up after letting the entire system warm up for a few hours. Previously I'd get up to full range in an hour or so.

I've now put a bit shy of about 200 hours on the cables.

I think this lends to the dielectric properties theory. The new cables are just more difficult to charge than the other ones. The end result is a better sound in my system.

That is great to hear. I bet when you hit 400 hours, things will be even better.
Bob

Alternatively, perhaps the mid and treble controls are turned up too high in relation to the bass at any given sound level.  Their relative setting to the bass may have changed from the old to the new wires.

@jetter 

I've set the contour controls on the speakers at 0 during this time.

I don't use tone controls on the pre amp at all and I'm not inclined to. They are bypassed entirely.