Jafox makes some good points. The Maggies love lots of power, the more the better, and often but not always are preferred with tubes driving them. Due to their flat profile, the larger models can produce a bit more chest-thumping bass than dipoles with different radiating characteristics, although conventional cone woofers deliver more impact, yet in my experience dipoles deliver much greater pitch definition.
The radiating characteristics of cone woofers and planar or line source dipoles are vastly different, however. In an anechoic environment the sound from a point source decays at 6 dB for every doubling of distance between the source and the listener, due to the logarithmic relationship of the proportion of areas of the corresponding spheres.
A cone woofer isn't exactly a point source, it doesn't quite radiate in all directions, and most of our rooms are somewhat reverberant - the latter has the effect of reducing the decay some by room reinforcement and room resonances. As with most speakers, a hybrid planar/cone woofer speaker is designed for even response at what the designer considers to be the typical volume at the typical listening distance in the typical room. Getting the right balance between woofer and planar element in such circumstances thus is a balancing act.
Conversely, the sound from a line source or virtual line source drops off at 3 dB for every doubling of distance between the source and the listener, since the logarithmic relationship is computed based on areas of cylinders at those distances. Again, this is based upon the theoretical anechoic environment, and actual room acoustics affect this some but less than the point source.
A speaker using a flat planar diaphragm falls somewhere in between a line source and a point source, although much closer to a line source dependent upon frequency. A speaker with a flat diaphragm, whether a planar magnetic or electrostatic, often can produce greater sound pressure levels than one with a curved or faceted membrane, due to the way acoustic energy stays concentrated along the axis perpendicular to the diaphragm, although it depends upon the speaker. Conversely, the response especially at high frequencies drops off as one moves off axis, giving a small sweet spot for optimum listening. An example of this is the Quad ESL (I have owned a pair for quite a while) which fortunately has a bass panel on either side of the treble panel. Ribbon tweeters can counteract this by virtue of the width of the ribbon being small enough in proportion to the wavelengths, but then one has the effect of two parallel quasi-line sources and the challenge of timing between them dependent on listening position.
Aside from the radiating characteristics. there is the matter of moving mass and thus how responsive and resolving the speaker can be, especially at low volumes. Thicker membranes simply cannot get out of the way as quickly as lighter ones, without requiring power several magnitudes greater. A related benefit of low moving mass is smooth frequency response across a broader range of volume levels. Large horn speakers and full range dipoles, while radically different, tend to excel at different volume levels. Because there are exceedingly few horns I consider relatively uncolored (the Siemens Bionor being one - it's much too large, though), I've made my choice of full range dipoles that are virtual line sources and bought Sound Labs, later to become a dealer (there's my disclaimer - hopefully not sounding like a pitch). I guess I got hooked on planars the day I heard a properly triamped set of Magneplanar Tympani IIIA's many years ago, an epiphany at the time.
Brian
