I have an original VMPS larger subwoofer, bought in 1988, and upgraded with mega woofers in maybe 2000 or so. I also added a plate amp.
I've never upgraded the PR, so I started looking at a TC Sounds solution. I ran some numbers through a speaker design tool, modeling it as a 145L box with two 15" TC Sounds drivers and a 15" PR (the modeling software only supports one type of speaker, but with multiple instances).
What I found surprised me. As a straight install, the model shows a 6 - 9db rolloff from about 50Hz down to 17Hz. This clearly isn't the kind of performance we expect from the larger subwoofer. The model said I would need about 1kg of washers on the PR, and 150g of added weight on the driver cones, to get a reasonably flat response.
Anybody done a TC Sounds upgrade, AM I missing something?