Is it better to have two matched subs or one

More is better unless you can't afford them or don't have room for them.

2 is better than one, especially if you can locate each in the optimal locations, which is usually not symmetrical.

unsound/duke, how does it subtract some bass signals?

I use single-end stereo out from an Ayre preamp to a Velodyne SMS-1 bass manager that presumably sums the channels into one balanced channel that I split between two HGS-15s subs.

There are at least two alternatives:

• The SMS-1 has three single-ended outputs. I could take two of those to the subs. Not sure if they are summed outputs.
  
• I have a spare SMS-1. I could take balanced LR from the preamp to each SMS-1 then balanced out to each sub. Set up is more complicated.

With the current setup, I’m unaware of the subs unless a pipe organ pedal note is invoked, but they do seem to make the setup sound a bit larger with large orchestrations.

Any advice-- and from you too erik -- would be appreciated.

db

There's a lot of unfounded info around subs, and this idea of summing bass losing info is one of them. At the 80Hz and below frequencies used for subs all bass is mono. Don't take my word for it. Hook em up yourself and listen. It simply does not matter. There is no such thing as stereo bass. Just because there's two channels doesn't mean they aren't the same. Even if they were, how would you know? We are unable to hear low bass frequencies less than a full wave. Low bass frequency wavelengths are as long or longer than the room. The sound travels clear across the room and back before we even hear it. So even if it was stereo, how would we know where its coming from? We can't. So not only is low bass not directional, we cannot hear where its coming from, and so we couldn't hear stereo bass even if it was there, which its not.

Contrary to popular belief bass can be stereo. If the bass driver from one channel is moving in the opposite direction of the other channel, when summed they can cancel out the signal between them.