Downward porting, with a passive radiator solves a few problems. Add that with side firing active drivers, you get a few things more. Quicker roll offs, and easier blend between sub and bass.
The material used is important in the drivers and PR, paper has great property, in the DOWN firing position, you can pick up on in the forward firing position, but not downward. Woven carbon fiber, is my favorite sounding active driver (it has NO SOUND).
I did find some Alu cones with light enough spider and surrounds that work better with higher XMax drivers, in the Passive position. I also add "More-Tite", non hardening putty, you pinch to get the mass weight correct. Under your fingernail sizes of adjustment, VERY accurate, for main and sub blending..
The weight and rigidity of the driver cones has a lot to do with the quality and speed of the sound.
I like phase plugs also, it makes a LOT of difference at the sub/bass driver. It LOWERS distortion, through deflection. Because they are outward facing, (even if they are facing the wall), the standing wave doesn't effect the cone face with phase plugs..
The phase plug design shape and length, help a lot also..
I use a bullet shape from 300-1500hz. A half round, pretty long one from 1-300, and a short flat and sometimes concaved from 20-100hz.. It's paid me great dividends in distortion reduction, bass clarity, and cleanup.
I make it sound pretty rough in application, In reality, I use some pretty precise measurements for lengths and shapes.
Regards
The material used is important in the drivers and PR, paper has great property, in the DOWN firing position, you can pick up on in the forward firing position, but not downward. Woven carbon fiber, is my favorite sounding active driver (it has NO SOUND).
I did find some Alu cones with light enough spider and surrounds that work better with higher XMax drivers, in the Passive position. I also add "More-Tite", non hardening putty, you pinch to get the mass weight correct. Under your fingernail sizes of adjustment, VERY accurate, for main and sub blending..
The weight and rigidity of the driver cones has a lot to do with the quality and speed of the sound.
I like phase plugs also, it makes a LOT of difference at the sub/bass driver. It LOWERS distortion, through deflection. Because they are outward facing, (even if they are facing the wall), the standing wave doesn't effect the cone face with phase plugs..
The phase plug design shape and length, help a lot also..
I use a bullet shape from 300-1500hz. A half round, pretty long one from 1-300, and a short flat and sometimes concaved from 20-100hz.. It's paid me great dividends in distortion reduction, bass clarity, and cleanup.
I make it sound pretty rough in application, In reality, I use some pretty precise measurements for lengths and shapes.
Regards