I currently have an Energy S12.3 subwoofer.  However, the listening area is quite large (7000 Cubic feet).  I would like to add a 2nd S12.3 subwoofer.  Logistically, it would be very easy to place the 2nd. subwoofer right next to the first subwoofer.  The subwoofers would be sitting about 1/2" away from each other in a bookshelf that is open on all four side, has a wood floor, and is about 8" from the wall. 

Although it may not be optimal, would it be a bad idea to place the subwoofers right next to each other?

The primary purpose of using 2 subs is to smooth out the swells and nulls in the room.  If you place them in the same spot, then they'll generate the same swells which will mess up your bass even worse than just having the one sub there.  Start with one subwoofer in each of the front corners (for a room that size, you want the best bass response you can get) and see how that sounds.  And pull them out further from the wall... 12" at least to give the port's room.

energuy:

The primary purpose of using 2 subs is to smooth out the swells and nulls in the room. 

 

Thank you for the response.  However, in my case I am not trying to smooth out the swells and nulls, I am just trying to provide enough "sound pressure" in this large room to better experience the bass.  I guess I am really asking if putting them right next to each would help or hinder increasing the room sound pressure. 

 try stacking the one on top of one other i seen that done , but not sure how well it might work or sound, no harm should occur.