velodyne spl1200r or dd12 differences

What is the difference? DD12 has low bass like bigger subs, even though it is small size. They have remote and equalizer, I think.
Why not send Velodyne an email with your question? BTW, I've wondered the same thing. I spent a little time comparing the two, but nothing striking jumped out at me.
DD has the OSD with a 8 band EQ that can be adjusted manually. The SPL only has a 6 band auto EQ. You can't adjust it manually.

The DD also has a larger amp at 1,250 RMS, dual 3" coils, and servo control monitoring the voice coil 16,000 times a second. Much lower distortion.

Volume wise there won't a huge difference, but the DD plays much lower with lower distortion. The two subs aren't in the same league.