If you ever play gigs at small to mid-sized venues or at private parties, you have probably decided to only bring one bass cab sometimes. Typically one with a 4×10″ speaker configuration.
However, sound is very sentitive to direction and surface reflections… If you place a 4 x10″ cab on the floor, sound waves will bounce off the floor, which is great for getting that fat low-end impact – but the downside is that you can’t hear the details of your playing. Well, your knees can, but not your ears.
One solution is to place the cab on a chair, a rack case or similar. Now, you can hear the mid and high frequencies much better, but now the downside is lack of low-end presence. Since you elevated the cab, you loose the early reflections boucning off the floor.
In other words, no matter what you do, using only one 4 x 10″ cab means a compromise on sound quality.