Hm, ive heard many people on this forum suggest to use Mono drives for the low end. So im a little confused here...
This caught my eye, as did Jens intriguing reply.
If you want to know the response of a listening environment, then both separate and together is best (since the combined response of room modes and SBIR is not as easy as just add together, it’s the sum of a lot of vectors with different phase). If you are trying to understand the behavior of modes in a room, then one driver is the way to go.
I reckon any short answer is destined for failure but I will give this a shot.
Based on ISO and other test methods the best way to investigate modal behaviour is to place an omni speaker (most are at LF) in the corner on the floor. Two or even four are preferred. This ensures that the largest number of modes are most evenly stimulated.
Our real life situation entails two actual speaker positions, considerably constrained e.g. tweeter at ear height, not in the middle of the room.
The speakers can be placed close to the front boundary for added LF pseudo soffit, or at particular distances from it for various reasons, e.g. to create SBIR action to compensate for something else. Similarly the side boundary.
Speakers may be placed in nulls of a particular mode to diminish it's action.
Typically in the nulls of the x2 side mode.
And so on. I reckon all cylinders have to be fully firing to deal with this one.
However, to reduce all of this, I am afraid I have to disagree and agree with Jens...
Two speakers in and around their final locations will give the best measurement of reality. One at a time helps with optimising the positions.
And just in case... one at time for Full Range, HF, or ETC.