I wonder if i ask real nicely if they would make one for me? lolSVS does make custom order subs. Time to order is longer, and I'm not sure the warranty is the same. It would probably have to be a passive model, as the powered models must go through all sorts of fire/electrical safety certifications before being OK'd for regular production.
I'm not saying for sure a 16-46 CS Ultra is in your future, but it can't hurt to ask Tom and Ron - more accomodating people you will not find.
I would love to get a 16-46 PC Ultra if such a thing existed ;-)Well, you can plug one of the ports on the current Ultra. Though I don't think it's necessary, as the Ultra seems to defy it's on stock tunig point by a couple of hz.
I believe an Ultra has about a 2db advantage over a 2039 CS+. A 2039 CS + has about a 2db or so advantage over a 1646. If this is accurate, it would lead me to believe that an Ultra with one port plugged would have comparable output to the 1646 between 15 and 20 hz and play louder above those frequencies.
Although you pay SVS a premium (by industry standards it's not much) for an Ultra, I've always felt, as far as SVS cylinders are concerned, that the Ultra is the true switch hitter of the bunch. Meaning, in it's stock tune, it plays very close to the 2531 in sheer SPL output and plays very near the 1646 in spl extension. This my opinion as I've not done any side by side testing to validate but the conclusion is drawn from professional and independent reviews.