Subwoofers down-firing or side-firing? Why?

I favor a pair of front firing subs located adjacent to the main l/r to create and preserve stereo imaging.

If the subs don't go above 80Hz they won't affect imaging at all. The harmonics of the bass instruments do the imaging, and they will be in the main speakers (unless the mains don't make it to 80Hz- then you have a problem!).


Downfiring subs allow the bass wave to move in several directions in the room at once. The problem you have with bass in a room is standing waves which can cause cancellation at some places in the room and re-enforcement in other places. By having the bass radiate in several directions at once, its easier to place the sub or subs so you can get more uniform bass because some of the standing waves can be less pronounced.

Of course to really deal with standing waves you need 3 or 4 subs. Then you can have really even bass everywhere in the room.

My ML subs are downfiring and placed in opposite corners of the room and are set to work from about 70hz down.
I honestly can NEVER tell they are on, in other words I can never detect where they are by "hearing" bass emanating from a particular corner located sub.
But turn them off?
Who killed the bass player!!

Have never had side firing in this setup so no idea if better but figured that ML know what they are doing........

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

There are so many variables involved, seems like whether driver faces down or sideways is not the major factor... 

In my case (Martin Logan), I did not notice any sound difference so I opted for safety and I use them down firing to reduce any cleaning and/or small children accidents which may happen and destroy the woofer.