Jerry, a bare ribbon would in fact behave like a dipole. However, in many designs material is put on othe back side to try to damp out resonances. > -----Original Message----- > From: rollei_list-bounce@xxxxxxxxxxxxx > [mailto:rollei_list-bounce@xxxxxxxxxxxxx] On Behalf Of Jerry Lehrer > Sent: 15 February, 2005 21:49 > To: rollei_list@xxxxxxxxxxxxx > Subject: [rollei_list] Re: Completely OT- Loudspeaker info > > > Richard > > The people in the audio world refer to the planar speakers, such > as the ones made by SME , Magnaplanar, and Martin-Logan, as > dipoles. Some "dipole" speakers have the backwave absorbed > almost completely. Then, are ribbon speakers "dipoles"? All > that I have used, absorbed the backwave. > > Jerry > > Richard Knoppow wrote: > > > ----- Original Message ----- > > From: "Jerry Lehrer" <jerryleh@xxxxxxxxxxx> > > To: <rollei_list@xxxxxxxxxxxxx> > > Sent: Tuesday, February 15, 2005 10:06 AM > > Subject: [rollei_list] Re: Completely OT- Loudspeaker info > > > > > Akhil, > > > > > > We have had Likwitz as a guest speaker at our audio club. > > > > > > I am intimately familiar with his and his associate, > > > Riley's, > > > theories on crossovers > > > > > > I have an active crossover in which I can plug in a card > > > which can be configured to any order. The Likwitz- > > > Riley 2nd order is not to my liking. > > > > > > Jerry > > > > > > "A. Lal" wrote: > > > > > Boy is this a name from the past. I still worked for HP > > when Linkwitz published his paper on crossovers. He was not > > the first to suggest the use of low level crossovers nor of > > phase matching crossovers. I remember my friend Richard > > Heyser, who had some fame in audio himself, being very > > skeptical of this system. > > Low level crossovers and individual amplifiers are a very > > good idea for several reasons but this is a different issue > > from the nature of the crossover itself. Crossovers are > > still something of a compromise but the ability to introduce > > delay at will using digital circuitry allows a much closer > > approach to the ideal where the acoustic fields of the > > individual speakers add in a way that approximates a single > > source. > > I have no idea what he is doing with the very strange > > looking cabinets shown on the web site. Dipole suggests to > > me that the backwave is being radiated directly. I remember > > some talk of dipole speakers in the distant past and, by > > memory, that the idea was based on a misunderstanding of the > > way loudspeakers radiate. The text on the web site is chock > > full of the sort of hype which is so familiar in consumer > > audio. My once golden-ear hearing is no longer good enough > > to make judgments about some aspects of audio system > > performance but I can still tell the difference between > > loudspeakers, at least other than the very top frequencies. > > It would be interesting to compare is speakers with good > > conventional systems. > > Many years ago I worked with Dick Heyser on his method of > > making acoustical measurements called Time Delay > > Spectrometry. I tried at the time to get HP to buy the Cal > > Tech patents, they wouldn't and assured me that the system > > wound't work. In fact, I was making such measurements using > > a standard HP spectrum analyser at the time! HP then tried > > to break the Cal Tech patent. Cal Tech has very good patent > > attorneys so they had no luck. Cal Tech would have sold the > > patent rights for very little so I think there was a large > > dose of "not invented here" about the whole thing. Another > > company finally picked them up and made the equipment > > commercially. HP had to modify the tracking generator in its > > spectrum analysers to avoid an infringement. > > > > --- > > Richard Knoppow > > Los Angeles, CA, USA > > dickburk@xxxxxxxxxxxxx > > >