Well OP I fixed you right up, no need to post and then get told to feed the chickens. I suppose you know when to feed my chickens. BUT it would be better if you learned that REL is the issue not my chickens, rabbits , goats or posting.
My point is pretty simple REL doesn’t know what they are doing. Really no need to explain why.. They just don’t.. The difference is I NEVER built speakers to make money only to learn from and fund my personal speaker projects.
BUT I have fixed REL subs. It’s not that hard and less so with a stack. You only have to add the slot to the bottom cabinet.. I did 2 sets, each with 3 per stack, all at 90 degrees from the one below in the stack. The directions those slots face make a difference just like the main drivers direction and location. I used 1.5" butcher block for the butt plate and spring loaded casters for the V control
Rel is not a bad sub it is a bad idea that THEY refuse to learn about. Vibration or destructive harmonics is not your friend.. And how much more does it cost to enclose the bottom or move the passive radiator to the side or remove it all together and have no port.
That plate they use is different too. DSP? PEQ, GEQ, mic input, PC interface, XLR all the stuff a Parts Express plate amp has REL doesn’t.. Go figure.
I know what I know.. Boom Boom in the Room Room.. No shake, rattle, and roll at my digs. Neighbors either for that matter. :-)
BTW "REL subs are NOT DESIGNED TO DECOUPLE", That is my point they ARE NOT DESIGNED at ALL. They are copies from the 1970s and they use a pretty cheep plate amp to boot. Nice paint though. Lipstick anyone? Bigger :-)
Regards