Sub placement

Marty, the orientation of the subwoofer can make a big difference as the
interference patter in the room, i.e. position of the bass nulls and peaks,
depends sensitively on the relative orientation of the cone (and port) with
respect to the walls.

To be more explicit, because of interference, i.e. the way wave interact, the
bass response is not the same across the room. There are places with very
strong bass, i.e. these are places where constructive interference occurs for
some specific frequencies (the room modes), and also places with very little
bass, here destructive interference occurs (again for room modes). The
position of these bass nulls and peaks in the room depends on where the
subwoofer is located in the room. Thus, by changing the position/orientation
of the subwoofer one is looking for a position that does not give any
significant resonances (constructive and/or destructive) at the listening chair.

In conclusion, because our ears are somewhat insensitive to the position of
the bass source one can (and one should) move/rotate the subwoofer around
in the room in order to improve the bass response at the listening position.

NVP,

Not IME. For the last 6 years, I've used a RTA to measure FR at the listening position. If the subs are in a good spot, I get good results irrespective of orientation. There may be small differences, but if you're setting up subs by ear, I wouldn't characterize the delta as significant.

Of course, different rooms and/or different ears might yield a different conclusion

Marty

Hi Marty, what you report it can certainly happen but it is not the general rule. Sometimes the interference fringes may be less affected when rotating and/or moving the sub. I am sure that you have often noticed while setting up your sub that moving the sub in one direction can induce significant changes while moving the sub in other direction has only a minor effect, if at all. Since one can never predict this, as it depends on the room and subwoofer, it is best to experiment like you have done. However, as I have mentioned in my previous post, this has nothing to do with our inability to detect the position of the source of law waves.

I've used a REL Stentor 3 (a down firing ported subwoofer) for four years and I have set it up in three different rooms. In one of them rotating the sub made very little difference, while in the other two the difference was significant.

I use a similar method as suggested by Polk432, except that I align the subs (2 15" sealed), facing each other from the outsides of the speakers. Basically, you will aim the subs towards each other across the sides and slightly to the rear of each main speakers. I use a Velodyne SMS-1 sub controller to address any issues. This could also aide in mitigating phase issues.

I have used this process for years with satisfying results. Also, the sound stage seems to open up greatly using this method. Observe that a cutoff below 60hz also removes localization issues associated with bass.

Integrating a sub into a system is utterly room and system specific so rendering suggestions on this is tough. Another reason why I can't get the "put your head where the sub sounds best" thing is that it takes the main speakers out of the picture...and the sub/main synergy is where the mojo lives.