Velodyne high pass filters: modifiable?

I'm considering purchasing a Velodyne sub. I had a ULD sub years ago and modified the high pass point by soldering different resistors onto a little plug-in board in the amp. Is that the way they still do it? I'm really after bottom octave replacement, so I want the high pass much lower than factory standard 80 Hz.
E-mail Grant at, he knows how to do it, has scematic for ULD 15, 18