As I have said many times in the past, few loudspeaker systems are truly full range. They are helped with the addition of a subwoofer. But one is enough? Or do you require a stereo pair? Perhaps more?
Here's a good rule of thumb for making this simple decision (other than 'can I afford only one or two?'). Small or large speaker system? The answer here might seem counter intuitive.
In every small system I have ever installed I have one subwoofer augmenting the system. In every large speaker system, I have two. I say this runs counter intuitive because one might think the smaller the main speaker woofers, the higher in frequency the sub must go to match. The higher in frequency, the more directional the sub gets. The opposite is true with a bigger set of full range loudspeakers; they couple to the sub at a lower frequency, thus their directionality is less important. So, why do I always do the opposite?
It has to do with two things: practicality and, most importantly, room and soundstage size.
If you're running a set of bookshelf loudspeakers on stands, it's not all that practical to add a set of subs; kind of defeats the purpose of 'small is beautiful'. Secondly, your expectations of soundstage size, as well as the room size you'll likely place these in are smaller than that of a big pair of speakers. In these situations I've managed make seamless full range music more than a few times. In Music Room Two, for example, I had a small pair of Thiels with a single 6" coaxial driver that, with a single REL sub setup properly, one could have a full range presentation. It was so seamless, in fact, that just for fun I'd turn the REL sub off to show just how wimpy the Thiels really are. On, the Thiels were perfect, the sound coming from them, nowhere else. It's a very instructive demo.
In a larger room with full range loudspeakers other aspects come into play. Here, more can be better. Let's look at this tomorrow.
