Sub placement

Wolf_garcia, regarding your comment:

The "put the sub in your listening spot" suggestion is ridiculous (but amusing) so ignore that one

You are simple incorrect. Placing the sub in the listening position and then walking/crawling across the room to find the place with the most even bass response, helps one find the place in his/her room that beside having an even bass response it is also the acoustic equivalent of the listing position, i.e. the interference pattern of the low waves in that place is very similar to the one in the listening position. The method is not ridiculous at all, in fact it is based on simple 3-dimentional Euclidian geometry.

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.

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.

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.

Wolf_garcia, you are incorrect again. As I have mentioned in one of my previous posts, when putting the sub at the listening position one tries to find a place that is roughly the acoustic equivalent (for the low notes) of the listening chair. That means that 1) the bass will be very similar in the listening chair and in the place where you would like to put the sub, 2) all bass sources (i.e. room, main speaker and subwoofer) have been accounted for. (Only this paragraph is addressed to you Wolf_garcia.)

One has to realize that below 200 Hz, the listening room (and the neighboring rooms too!) has(have) a very significant effect on the sound that you hear in your listening chair. This is because the room can significantly amplify or absorb specific frequencies, i.e. the room modes. In fact, it often happens that when listening to big speakers what one hears below 100 Hz is dominated by the room response!

The main advantage of adding a subwoofer is that one can place the speakers in the position that gives the the best stereo image and most natural midrange, and place the subwoofer in a different place that minimizes negative bass resonances induced by the room.

I really do not want to be condescending and/or impolite, but people should understand that in order to properly integrate a sub into a system one has to understand how waves interact, i.e. the interference phenomenon. It is really not a difficult phenomenon (it is taught in high school), plus one does not need to understand the math to be aware of its consequences. (It is pretty much like with the water, one does not need to work out the theory or look at phase diagrams to understand that water can exist in different phases, e.g. solid, liquid and gas).