Posted by John on July 22, 2004 at 00:30:43:
In Reply to: Re: Re: That's cool... posted by Lew on July 21, 2004 at 12:42:09:
Lew,
You are right about the spacious imaging that you can get out of dipole planar loudspeakers. But the point that I was making about either dipole/ bipole speakers is their weakness in the domain of precision and pinpoint imaging. Acoustic guru Dr. Floyd Toole makes the point about the vague imaging of bidirectional speakers while also stating that some would prefer the spacious sound of such speakers. I quote him: "As discussed earlier, 40-some years with two-channel stereo have yielded nothing in the way of a clear
direction. Although the majority of loudspeakers sold are traditional forward-facing “cone and dome” designs, it
is also true that the majority of listeners are not very critical about the imaging of their systems. Among those
who are, the “high end audiophiles”, those designs figure strongly in their preferences. However, so do designs
of very different kinds, like, dipole, bipole and directional horns. The perceptual consequences of speakers this
diverse are not subtle. Bipole designs have approximately omnidirectional sound radiation properties, and
therefore produce energetic reflected sound fields in listening rooms. Conventional forward-facing systems, and
horn-loaded systems will place the listener in a sound field in which the direct sound is more prominent. The
more directional the system, the more dominant will be the direct sound.
It is probably correct to say that the majority of listeners find stereo to be pleasantly embellished if the
room reflections are energetic. The sound tends to be open and spacious, with a good sense of depth, but the
specific images can be rather vague – in other words, not unlike real concerts. A positive effect of this vagueness
is that the stereo listening region is enlarged.
However, there is also a category of listeners who respond unfavorably to this kind of reproduction, and
prefer to have a very specific, almost pinpoint, sense of image position. Interestingly, this category includes
many recording engineers who, in their studios, require that they be able to hear, very precisely, the results of
their manipulations. Consequently, recording studios are often acoustically rather dead, and the loudspeakers
directional (often horn loaded), or placed very close (so-called near-field listening). However, these same
people, at home, frequently revert to the more spacious version of stereo. So, go figure." From page 14 of: http://international.infinitysystems.com/homeaudio/whitepapers/audio_art_science.
Also a note from award winning recording engineer Michael Bishop about dipole speakers: "...that diffuse character may destroy the directionality and individual mix components that would be present in a music-only surround recording. I have successfully used dipoles in a surround monitoring setup, but getting "focus" with them is difficult and requires very careful placement and consideration of wall treatments."
from: http://www.wired4music.com/Setup_Tips.htm Although the latter is about surround speakers the same holds true for a two channel setting.