Raising Subs?

Imo an advantage of using more than one subwoofer is that  you can distribute them far apart and asymmetrically such that each is a different distance from the room boundaries.   The result is a significantly different room-interaction peak-and-dip pattern from each sub, the sum of which will be smoother than either sub alone.

@secretguy ime it is beneficial to distribute the locations of multiple subs in the vertical as well as horizontal plane, such that you get the aforementioned summed-room-interaction smoothing in all three planes.  If you can, I'd suggest raising one sub closer to the ceiling than to the floor, and leaving the other on the floor.  

Duke

subwoofer manufacturer

secret guy

When you say " significant improvements", what exactly are the improvements that you would like to hear? Can you define them please. 

Well I pose this question to anyone. What would be " significant improvements " 

When I had subwoofers in my system the biggest reason for moving them in any direction was to make the response as even as possible in their output band. 

through measuring and listening you find that if they are too close to a wall or other boundary the response might be peaked and have an overly dominant note or frequency.  

moving them away from the bounday is a way to reduce the peak and make the sound more balanced.  

raising the subwoofers off the floor could be a way to make the response more even, especially if your room and furnishings put limits on how much you can move them away from vertical boundaries.  remember, the floor is a bass reinforcement boundary.