Subwoofer

Very timely thread!  I am thinking about adding a sub to my Sonus Faber Guarneri Evolution monitors.  These have a -6db response at around 43hz and starts to roll off at 72hz.  My room is small (10x11, though the back wall is only 3' high and opens up to my family room) and I do not listen at high volumes.  The sub I am looking at has a -6db response of 32hz.  I am hoping that adding a sub has the effects that Stingreen mentioned above.  I have also read that adding a sub will help to "open things up" and "expand the soundstage" though I have no idea how.

 You're not extending the low end, but making mids and treble better....also you change the acoustics of the room by evening out the "bumpy" low end.  

tboooe,
I swear to you adding subs has "opened things up and expanded the soundstage." I don't know why, but it's easy to hear.
What has been difficult is blending them perfectly!

I sure hope so!  I am going to pull the trigger on a REL T-5i sub.  I think in my modest room and style of music  this sub should work for me.  

Where do you guys suggest I set the crossover point?   My speakers start to roll off at 72hz and its -6db point is 43hz.

So while adding a single subwoofer will offer the benefit of improved bass extension, adding multiple smaller subs and spreading them around intelligently will additionally result in smoother bass throughout the room.

Duke, does your opinion change if I am only interested in good bass at a single location in the room?  In my case, I have a dedicated, albeit small listening room where I listen from a fixed location.  

Bass blossoms all around, it submerges you, yet not to overwhelm. In turn it highlights contrasting frequencies. That I believe is what gives a greater sense of depth and realism to the sound stage. 

Thank you for this.  This is probably the best explanation yet I have heard on why a sub seems to improve overall experience.  

I finally got my Rel T/5i sub set.up with my Sonus Faber Guarneri Evolution monitors. The sub is crossed over at a little below 40Hz.  Using my spl meter I verified that I am getting pretty flat response from 100Hz down to 20Hz!  I am completely satisfied with how my setup sounds with the sub.  I didn't realize how much low freq information I was missing.  My only complaint is waiting so long!   Now I wonder if adding another one would improve things even more?