How does adding a second subwoofer improve your systems SQ?

@erik_squires Another great post! Really well done, and attractive to boot. I’m wondering if you can tell me what the sonic difference might be if I added a second subwoofer? 
The reason that I ask is that in my present set up, my single subwoofer provides enough bass and it is fairly clean and tight. I had to connect the subwoofer to the two mono blocks and that provided a speaker level input into the sub.

 Many people have said that I really need to have a second sub woofer but if I were to get another one what would I notice about the sound (assuming that I could place them correctly)? 

Thank you for the kind words @hilde45

It's hard to tell without measurements, honestly, but before you get to your second subwoofer, the room treatment and EQ could be considered. With 1 sub, and good room treatment, properly set up, it can be magnificent.

A second sub, if you are free to place it anywhere, can certainly compensate for any big nulls, but what if you don't have any, or what if you use an open layout which does not lend itself well to standing waves to begin with?

Best,

E

Please pardon my ignorance, but what is SQ?

sound quality

markj941 OP
How does adding a second subwoofer improve your systems SQ?

Amazingly so! because bass is done in stereo on more albums than you think.
People that use one subwoofer have no idea that they’re screwing up any stereo imaging that the bass has. You need two subs L & R close to the mains if you are to faithfully reproduce what the studio recording engineer wants you to hear.

I have many albums (CD’s) even from the 80’s 90’s that have <100hz bass notes that come out of either left or right channel. So to mon’ize these recordings into just one mono sub is not what the recording engineer wanted you to hear.

EG: Just listen to the second last track "It’s A Miracle" on Roger Waters "Amused to Death" at the end there is a kettle drum roll that rolls around the room on the ground from right to left and back again. If you had just one sub it would ruin that mesmerizing effect totally.
And the harmonic structure of bass notes like this above go right up into the midrange
Another that comes to mind is Ricky Lee Jones self titled album, it also has tracks where the bass only comes from one channel or alternates

Cheers George