Lots of bass at walls, lack of bass in center of room/listening position


I guess this is relatively common in listening system. Is there any way to smooth this out so I get more bass energy at my listening position? This happens with our without my 2x 18 inch subs. Room is 12 x 16 x 8 ft, speakers 4.5 ft apart on long axis and I am sitting 4.5 feet away. I tried moving back and forward but the entire middle center of the room except near the walls has decreased bass.
Is this a boundary effect or could it be due to bass cancellation effects?
smodtactical

Showing 3 responses by atmasphere

Yes! It might make a difference between a standing wave or none- at your listening position.
Right now they are about 10 inches off the wall and they probably need to be moved out more.
@smodtactical  If your bass is rolled off, you're usually better off moving the speaker closer to the wall behind it. This is particularly true in the case of a sub- as it gets closer to the wall, the boundary effects start to come into play. So the bass goes up not down. But standing waves will also be more pronounced, so you should try the sub pointed in different directions, with different phase and in different locations along the wall if you can. The right spot might only be a few inches wide so if you're playing with a single sub this requires patience!
Lots of bass at walls, lack of bass in center of room/listening position
@smodtactical  This is the classic description of a standing wave in the room.

While room treatment will help a little bit, its effect is marginal. You have two solutions both of which will work fine, depending on how you want to handle this.

The first is as others have suggested, move your subs around until you find a location that allows you to hear bass at the listening position. This can be tricky but can be done even with only one sub.

Now if you think you might want to hear the bass properly in any position in the room, then you need to break up the standing waves. The only way to do that (you can't do it with room treatment) is to use multiple subwoofers. You'll need at least 4 to do the job. This type of subwoofer approach is called a 'Distributed Bass Array' and is very effective- with the qualification that none of the subs operate above 80Hz. But its likely that your main speakers go lower than that, so this should be fairly easy. Below 80Hz your ear cannot tell where the bass is coming from- and the harmonics of the bass instruments will make you think that the bass is coming from in front of you.


Two of the subs would be placed in front of you, and the other two placed asymmetrically in the room, with one maybe on one side wall and other other in the rear on the opposite side. You might get better results by putting one of the latter two out of phase with the rest. They can all be fed a mono signal- again, if kept below 80Hz this will work fine. To get bass evenly distributed at all frequencies this is the most elegant approach. There is one subwoofer that is built specifically for this purpose, the Swarm, made by Audiokinesis in Texas.  Good Luck!