Seems like it either works really well or really poorly depending on the install. My biggest issue is most people have no idea how to set gains at all, so when the thing doesn't work right, they are basically screwed. It's not foolproof enough to be put into anyones hands.I loved the DD-1, it was simple, and safe. If you know how to use it along with the level you normally listen to its a perfect tool. I get plenty of poutput along with a perfect blend using one. Its nice to listen to something that raises the volume of all amps at the same time.
You do have to have a understanding of how everything works to get the most out of it JUST like a scope. Most people I have seen burn up subs using one set it with the -15db tone and played dirty music. For all we know the OPs SS filter is set at 50hz, that would cause a lack of excursion.Seems like it either works really well or really poorly depending on the install. My biggest issue is most people have no idea how to set gains at all, so when the thing doesn't work right, they are basically screwed. It's not foolproof enough to be put into anyones hands.
Odds are you can fit bigger if you don't go with all right angles in construction of the box. From my testing a 12" in 3 or 3.5 cube is as loud as a 15 and has generally more low extension. I can get more out of a 10 than a 12 up to a little over 3 cube.Can you even get 5 cubes in the trunk of a car without building it inside it? The external dimensions are 31.5 wide, 16 high and 19 deep, a single inch in any area would cause it not to fit in the trunk. This box almost wedged. I think I'm limited there and my builder accommodated for that with the best I could get.