I had a similar sub but sold it. The SVS Ultra 12" was a TC Sounds underhung sub with a Ti basket. When I got it, I thought "That motor looks like an Audiomobile". Yep. I pulled the magnet boot off and there was an Audiomobile serial number on the motor. TC Sounds was re-using parts but at least they were good parts.Thanks.
I had a Audiomobile Mass for a while and loved it.