ST801804@brownvm.brown.edu (steve liebling) (02/28/90)
I was wondering if someone could possible go into the fundamentals of the structure of electrostatic speakers and also electromagnetic speakers that are not the conventional cone type. [I second this... I haven't the time to do it myself. Mail me first so we don't have a duplication of efforts. - tjk]
bala@research.att.com (Balachander Krishnamurthy) (03/02/90)
speaking of which, can someone enlighten me via mail, or, if of general interest, on the net, re the wisdom/mechanics of satellite speakers? danke. cheers, bala
allen@b11.ingr.com (John Allen) (03/06/90)
in article <2649@uwm.edu>, ST801804@brownvm.brown.edu (steve liebling) says: > Approved: tjk@csd4.csd.uwm.edu > > I was wondering if someone could possible go into the fundamentals of > the structure of electrostatic speakers and also electromagnetic speakers > that are not the conventional cone type. > > [I second this... I haven't the time to do it myself. Mail me first so we > don't have a duplication of efforts. - tjk] I am curious too, but if we could go a step further: Speaker Builder Technology type 1) Magniplaners (dipole?/electromagnetic?) 2) Quads (?) [Electrostatic -tjk] 3) Apogies (ribbon?) 4) Accustats (electrostatics) 5) Magnet (plasma flame) 6) ?? (asetolene flame ) I would like to know (understand) the technology used by these various displines. I threw in the asetolene flame because one of my co-workers mentioned that he built one in colledge. I have not questioned him on the technology, but maybe now is the time. The magnat (SP-?) was a speaker that I read about that used a plasma flame speaker for its tweater ,I not certain about the source of the flame just but remember that it was ecologically dangerous and was only being sold in europe. Well this is high-end audio, which means (I Suppose) that we are all into the stupid-end (extreme) of things. I am serious about the above posting and will try to follow-up with notes on the asetolene flame speaker, assuming my co-worker will talk. [Then there's the Hill Plasmatronics, that used ionised helium jets for the tweeters. Sounded great, but they were huge and expensive... not to mention you had to buy two full-size tanks of helium! -tjk] Speaking of flames.. Maybe this discussion will go relatively unscortched, since this is recreational high-end.audio [No flames allowed. -tjk] -- * /- _______ ingr.b23b!allen!jallen@uunet.uu.net * * */ | V | John E. Allen * * |^^^^^^^^^^^^^^^^^^^^^| (205) 730-8627 * * |---------------------| *
steve@ncsc.navy.mil (Mahan) (03/06/90)
In issue 15 John Allen expands on the unconventional speaker question with the following list: >I am curious too, but if we could go a step further: > I can't answer for all of them, but will try for those I know about. >Speaker Builder Technology type > >1) Magniplaners (dipole?/electromagnetic?) (Magneplanars) electromagnetic/electrodynamic These speakers including Magnepans use linear magnet strips on a supporting framework to provide the field. The diaphram is imprinted with conducting ribbons of some metal. The metal strips are aligned with the magnetic strips on the framework. The magnetic field runs in opposite directions for each adjacent conductor and the conductors zigzag so that current is in opposite directions for each adjacent conductor. This provides a fairly uniform drive over the entire surface of the membrane. The opposing directions of current flow result in a fairly low reactive component in the speaker resistance and an easy load for an amplifier. The tympani 1D was 8 ohms and sounded best biamplified (poor internal crossover) and with a subwoofer. Positioning was extremely important as the membrane radiated sound in both directions. >2) Quads (?) The Quads along with the Infinity Servo-Stats, the Dayton Wright Mk 8, the Martin Logan, and a few others are electrostatic types. The operating principal is electrostatic attraction/repulsion. In general a charged diaphram is positioned between two conducting grids. The output voltage from the power amplifier is applied to the two grids thereby providing a fairly uniform electrostatic field. The electrostatic force applies a uniform acceleration to the diaphram and thereby moves air. Most speakers of this type have relatively poor bass response, the exception being the Dayton Wrights. Martin Logan uses a crossover to an air suspension woofer in the Monolith. These speakers typically have a relatively poor efficiency and present a difficult load to an amplifier. Dayton Wrights need at least 300 W/channel and start sounding good with 1Kw/channel. > >3) Apogies (ribbon?) > I thing the speaker is similar in design to the Magneplanar. Heard them a few weeks ago. Beautiful highs but cannot match the bass of my Kef 107's. >4) Accustats (electrostatics) > See under 2 above. >5) Magnet (plasma flame) > >6) ?? (asetolene flame ) > There was a speaker about 10 years ago that used a plasma driver. You needed a tank of helium to provide the plasma. The speaker applied a magnetic field to the ionized gas to move it directly. It was an ultimate low mass diaphram. Supposedly it had fabulous high frequency response but had serious usability flaws. It required 500 w/channel tube amplifiers (supplied with speaker) that made great space heaters, needed a helium tank and regulator, was very large, and had an annoying hiss from the helium feed. [This is the Hill Plasmatronic I mentioned earlier. It ionized the jet and the AC signal was applied across the bias supply to provide the modulation. The biggest problem with the sound was the regular cone drivers weren't as fast as the modulated helium jet. - tjk] Other interesting varients include ESS with the Heil Air-Motion Transformer. This was a small frame with plastic encased ribbon conductor folded into a zigzag so that the conductor ran parallel to the fold directions. When suspended in a magnetic field the conductors would squeeze together on one side and spread apart on the other and thereby move air. Not particularly impressive. The only other one I can recall at the moment is the Walsh driver from Ohm Acoustics. This is a conventional cone mounted face down. The cone is fairly flexible and supposedly the ripples propagating down the cone create a cylindrical sound wave moving outward. The inside of the cone is filled with damping material. Stephen Mahan steve@ncsc.navy.mil