Does your monitor system need a subwoofer?
Monitoring in the recording studio control room has two functions. The first is to tell you exactly what it is you are recording, otherwise it would just be guesswork. The second is to tell you what your mix will sound like to your eventual listeners.
These functions are contradictory. For the first, you need the most accurate monitoring available, which would probably demand electrostatic loudspeakers as all moving coil loudspeakers are horrendously colored. For the second, you need a system that has an average of the characteristics of typical listening systems. And remember that people listen at home, in the car, on their iPods, and even on TV and radio. So ideally your mix monitors have to be an average of all of that.
Nearfield monitors have developed in popularity tremendously since the concept first caught on. They are placed close to the engineer's ears so that reflections from the room are low in level compared to the direct sound.
But also they are small, like typical hifi speakers. This inevitably leads to a lack of bass response compared to full-size loudspeakers.
This is OK in the sense that you'll probably wind on just the right amount of bass for other people's small speakers. But you won't actually know what's going on in the low end on your recordings. Microphones can pick up a lot of unwanted low frequencies - footfalls etc. - without you noticing.
So perhaps the answer is a subwoofer.
It could be, but putting all the bass into one speaker, and then siting it apart from the monitors themselves isn't really the right thing to do. A listening comparison between a subwoofer system and decent full-size speakers will quickly demonstrate that.
But on the other hand, people just don't buy big speakers, apart from hifi buffs that is. But having a subwoofer in the home is becoming a popular activity.
So to reflect the needs of your listeners who have subwoofer systems, perhaps your monitoring system should have a sub too.
Just set things up so you can switch it on and off, and make sure your mixes sound good both with the sub and without it.