This won't be quick or easy if its to be explained correctly.
Let's start with some basics. The Sound Labs Albert refers to are absoutely wonderful speakers, which create sound by vibrating an extremely thin sheet of Mylar, or at least a Mylar like material, a very short distance, by using an electrostatic charge. Because the excursion of the mylar is very minimal, it must move a large portion of the air to create life like 'volumes'--this is one reason why full range electrostatics are large--one moves a small amount of air a great distance, or a great amount of air a small distance.
The stated advantage of the Sound Lab is it's control of this almost infinitessimal weight of the Mylar (or Mylar like material). The SL's are very low in distortion, as the Mylar is, because of this lack of mass, relatively easy to keep in check.
Because the radiating surface of the Sound Lab is so large, it is generally thought to be impractical to have this large of a radiator in a small space. Why?
All rooms, depending on their shape,that is proportions of length to height to width, have resonant 'modes'and "standing waves" that is frequencies,(pitches) which can be disproportionately excited causing, for want of a better explanation, an over reaction to the amount of energy put into the room at a given frequency or frequencies. The rooms also have the liklihood of cancellations of (calculable but not for the typical, "I want music in this room person"). So the result can be a very uneven (frequency anomolies) playback from a very good (tonally correct) speaker if the room can't handle the amount of energy put into it by the loudspeaker.
Here's a cut from a 'resonant mode text':
"The modes of vibration associated with resonance in extended objects ...have characteristic patterns called standing waves. These standing wave modes arise from the combination of reflection and interference such that the reflected waves interfere constructively with the incident waves. An important part of the condition for this constructive interference...is the fact that the waves change phase upon reflection from a fixed end. Under these conditions, the medium appears to vibrate in segments or regions and the fact that these vibrations are made up of traveling waves is not apparent - hence the term "standing wave".
With this in mind, one can increase the liklihood of room excitations being so great as to 'obscure' the basic sound output of the loudspeaker.
Dynamic loudspeakers which usually, (usually) fire out the front--but they have what is known as an omnipolar output. Which is to say, sound coming away from the cabinet in a full 360 degree fashion. The amount of output is determined by how 'active' the cabinet happens to be. Since many of today's dynamic speakers are made of MDF (medium density fiber board) with wooden supports internally, they resonate, giving off these sounds in all directions. How much they give off, is dependant on the amount of mass, (call it weight)that the speaker has to absorb the energy, AND how stiff the cabinet is. The more 'active' the cabinet, the more energy, (additional to the front firing drivers)that the speaker puts into the room. The larger that 'picture' the more room excitations you will typically end up with.
As a designer, one has a choice to make--do I try to 'kill' the cabinet sound by using something almost completely non resonant--or do I try to use that output in some way, and try to make it less of a problem?
It seems that more designers over the past few years have begun to radius the sides of the cabinets. This seems to have the advantage of loading the energy room in such a way as to make that omnipolar energy somewhat less of a problem. It also helps within the cabinet by helping to lessen cancellations, standing waves, (just like those that exist within the room).
After all that, we can now conclude that the amount of energy that a speaker puts into a room, can simply be too much for the room to 'handle' or at least too much to allow for acceptable sound.
Clear as mud, no?
Hope this makes some sense.
If you have a good dealer, do some listening in your room and try to get a feel for what does work in your space.