jdm56;231317 Wrote: > ""Monopole: Any speaker that encloses the backwave of the speaker device > even though part of this backwave may be released via. a port or duct. > The primary radiation at most frequencies will be from the driver > front. If the driver is not enclosed it becomes a dipole." > --AudioLinkServices. That too, is my definition as the term relates to > loudspeaker systems. What one do you and "everyone else" use?
So apparently some other people also use the term incorrectly. Congratulations. See below. Note the last quote (from the Journal of the Acoustical Society of America) in particular. the Oxford English Dictionary Wrote: > > c. gen. Anything which has a spherically symmetric field around it and > so can be treated as a point source. > 1957 Jrnl. Acoustical Soc. Amer. 29 743/1 We shall consider monopoles. > dipoles and quadrupoles built up out of constant volume flow elementary > sources. 1972 Celestial Mech. 6 384 These can be shown to correspond to > the [gravitational] field of two fixed monopoles. 1981 A. D. PIERCE > Acoustics iv. 160 The concept of a point source (or acoustic monopole) > generating waves governed by the linear acoustic equations is a > convenient extrapolation. 1989 Nature 14 Sept. 131/1 A solid spherical > object of constant density is a monopole for newtonian gravity. 1997 > Jrnl. Acoustical Soc. Amer. 101 3343/1 Many noise sources are > directional and do not behave as simple monopoles particularly at close > range. Better yet, look at the plot here: http://www.linkwitzlab.com/rooms.htm#B Siegfried Linkwitz Wrote: > > Practical loudspeakers are neither pure monopoles nor pure dipoles > except at low frequencies where the acoustic wavelengths are large > compared to the cabinet dimensions. > > The ideal monopole is omni-directional at all frequencies. Very few > speaker designs on the consumer market approach this behavior. > > ... > > The typical box speaker, whether vented, band-passed or closed, is > omni-directional at low frequencies and becomes increasingly > forward-directional towards higher frequencies. > jdm56;231317 Wrote: > > I don't know that they are less sensitive to the room. They just > interact with it differently than bipoles or monopoles or > omni-directional designs. And I maintain that, in-room, the dipole > system's spl will not drop off with distance at a greater rate than a > monopole, but quite the opposite. It seems to be a simple enough > proposition to prove or disprove. Just measure an example of each > system in the same room. If memory serves, monopole speakers drop off > at about 6db with every doubling of distance from the source, while > dipoles drop off at 3dB. I admit I may be off on the specifics, memory > being less than perfect most of the time. Well, I haven't tried that, and the argument I made was for infinite space. So I suppose it's possible that for some perverse reason the pressure falls off less rapidly for dipoles in small rooms even though it falls off more rapidly outside. Doesn't sound very likely, though. In any case, what may be more important is that the dipole radiates less total power to achieve the same SPL on axis, so there's simply less acoustic power bounding around in the room to cause problems. -- opaqueice ------------------------------------------------------------------------ opaqueice's Profile: http://forums.slimdevices.com/member.php?userid=4234 View this thread: http://forums.slimdevices.com/showthread.php?t=38593 _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
