Sub placement

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.

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).

Sub placement is too complicated. Ditch it and get some speakers that slready put out decent bass...
Or, experiment. I think placing one sub just to the outside or right in front of each speaker might be best, try that.
Another option would be to place the sub in your listening chair, crawl around the room, find out where it sounds best and then adjust your monitors accordingly so that they sound best also, in your new listening position on your hands and knees in the corner of your room.
Seriously though, just get some speakers that have decent bass to begin with; if not, you'll always wonder if the sub is just muddying the waters and whether or not it's fast enough to keep pace with your monitors. I liked subs for about a month, then I realized a good set of speakers is all you need for the best bass response (vandersteens made me come to this conclusion, blame them, not me ). If you want really deep, big boom, go with a sub. If you want mixed well, articulate, fast, look into speakers. Just my oppinion.

Risking redundancy: For my tastes the low notes generated by the sub are part of the musical whole, and I wouldn't hear a proper mix with my head on the floor in the corner. It's easy to get an accurate, musical main/sub blend in a listening space...and not complicated at all. Do not be afraid. Otherwise, maybe you could carefully balance a stack of your main speakers in a pile on top of your sub at the "sweet listening spot", crawl around on the floor until your knees ache and your head becomes crammed into a place where the moon don't shine.