I had a Veloydne DD-15 and it is a great sub that can be dialed in given the sub's room correction software (manually or automatically). It was a little much for music in my room but great for HT. I sold it and replaced it with two DD-12 subs and I like this set-up better. Faster and more balanced throughout my large room.
I have no reservation in recommending the DD-12.
I have no reservation in recommending the DD-12.