I've read this support forum all the way through and have learned a lot.
My room is has 9' ceilings and is 16' x 25' with a 16' x 16' L shape off the back resulting in 6,000 cubic feet in the primary space, plus two openings to a kitchen and hallway resulting in another 3000+/- cu ft. of secondary area = 9,000 cu ft. total.
Right now I'm using a single Definitive Technology SuperCube I (14 x 14 x 14), which was a big improvement over nothing, but not the state-of-the-art experience I want. It is physically located in an area specifically boxed out and recessed flush in the wall for it (made of 1' thick plywood) located under a stairwell to the right and 3' back from the front wall.
From previous questions and answers in this thread, I'm already expecting a recommendation of a Velodyne DD-18. This will not fit in the existing boxed alcove under the stairs, so it would have to be located in the corner or along the back wall.
My questions are:
1). Can I keep and use the SuperCube I in the existing location (Front Right) in conjunction with a new Velodyne DD-18 in the Back Left? Or are these subwoofers too dissimilar in size and timbre character?
2). If I replaced the SuperCube I with a Velodyne DD-12, which dimensionally is the largest DD subwoofer that will fit in the existing boxed alcove, would the Velodyne DD-18 and Velodyne DD-12 work and blend OK together?
In other words, is it always best when using two subwoofers to use two of identical size or is it acceptable to mix and match sizes, if not brands?
The high level of exacting support evidenced by this forum has been the deciding factor for my plans to purchase one or more Velodyne DD subwoofers.