You can use the splitter to run both subs off the "LFE out" of your receiver assuming you have only one LFE out. Another option is to use the second sub as a dedicated front sub by running speaker wires from the receiver's L & R to the second sub, then speaker wires from the second sub to the L & R speakers.
How to wire dual subs has been answered, but now you must place them properly. Usually placing the main sub to the front left corner a little from the walls works well. Then place the second sub in the first half of the room, to the right a little from the wall (placed asymmetrically with the first sub). Staggered, lack-of-balance sub placement can help tame standing waves in lower frequencies. Experiment pushing them around, or do the crawl test, or use a parametric or 1/3 octave EQ and RTA to fine tune the placement.
ive connected 2 subs to my reciever via a splitter.. and i am puzzled to where to placed the 2nd sub.. at the moment i have the 2nd one placed behind me and the 1st in the front left corner of the room.
ive heard that placing it behind me is a bad thing to do. why is this..?
and how important is it to "break in" a subwoofer..? do i need to do this to speakers as well? for how long should i do this for before i can pump ground shaking bass throught them?
You can stack two sub cabinets in a front corner. You could also place one in a front corner (not too close to the walls) and the second to the opposite side of the front corner sub halfway into the room. I can't remember if it was Dolby, THX, Polks Guide to HT, Crutchfields HT book, or on M&K Sounds site where I saw sub placement in the rear of the room is not as good. It may be because the sub if placed in front would splice better with the mains. But 80Hz and below is omni-directional. Just experiment with various placements. I know commercial theaters, including IMAX has their subs up front. Break-in theory is debated among audiophiles. Some say playing lower frequency tones all day for a month will make the sub less stiff and sound more articulate. Tests have been done in chambers. I do not have any web sites to back it up, but I have seen valid reasons why stiff woofers perform better after break-in.
Multiple subwoofers placed asymmetrically yield a smoother response with the mains. They also smooth out standing waves. Another benefit of more than one sub is you "feel" the bass more.
I heard at one time that at about 6 feet they will couple as that is the optimum distance for the wave length out of the sub. When two subs couple it is supposed to be awsome. Myth?
If the subs are located in the same plane and implemeted in mono, yes. Coupling is creating an even bass response. Physically locating subwoofers in five locations in a room usally results in wildly varying bass response on all channels. That is why using the bass management feature in a pre/pro creates 5, or 7 full-range speakers with identical 20-20K Hz response. This designer has 32 12" subs in one location that couples with with the sound of the room: http://www.priceyoursite.com/FiLeZz/