rjs@hpfcla.UUCP (rjs) (07/24/85)
A salesperson at a local audio store recently pointed out to me that
there is a difference between electro-static and ribbon speakers. Could
someone explain to me the difference, and how electro-static speakers
work? Thanks in advance.
Bob Schneider
{ihnp4|hplabs}!hpfcla!hpfclo!rjsrdp@teddy.UUCP (07/29/85)
In article <42400009@hpfclo.UUCP> rjs@hpfcla.UUCP (rjs) writes: >A salesperson at a local audio store recently pointed out to me that >there is a difference between electro-static and ribbon speakers. Could >someone explain to me the difference, and how electro-static speakers >work? Thanks in advance. > >Bob Schneider >{ihnp4|hplabs}!hpfcla!hpfclo!rjs Ribbon tweeters consists of a small ribbon of metal, or some metallized plastic (mylar, etc) held in a magnetic field. The direction tf the magnetic field is parallele with the plane of the ribbon thusly (a front view): +----+ N <--- | | <--- S O <--- | | <--- O R <--- | | <--- U T <--- | | <--- T H <--- | | <--- H +----+ WHen a current is passed through the ribbon, from the top to bottom or vice-versa, a force perpendicular to the magnetic field and the current is applied to the ribbon, so it moves in or out Electrostatic speakers have two grids spaced evenly apart, with a tightly stretched film of metallized plastic in between them. The seperation is on the order of a fraction of an inch (say 1/4 inche between the film and the front and rear grids) The front and rear grid have a moderately high (few thousand volt) charge applied. The signal is then applied to the diaphram. The difference in potential between the grids and the diaphram cause the diaphram to be attracted to either the front or rear grid (and repusled by it's opposite) causing the diaphram to move in a manner (supposedly) proportional to the applied signal. Other differences that are important: o Ribbon drivers are often VERY low impedance devices, requiring an input coupling transformer. For the most part, these devices are used for tweeters, as it is nearly impossible to generate a large and sufficiently linear magnitic field over the wide area needed for a low=frequency driver. In addition, they are frequently of very low efficiency, requring horn loading or sone other such kludge. They can have, because of their very low moving mass, a very wide bandwidth. o Electrostatic loudspeakers are very HIGH impedance devices, also usually requiring an input matching transformer (with the exception of things like Acoustats, which driver the speaker directly from a high voltage, high-impedance, high power source). The can be made large sizes, so have been used successfully for full-range use. The necessity of the polarizing voltage makes for all sorts of problems in humid or dusty environments. Again, because of the low driven mass (or more specifically, a low mass-to-force ratio) thay can be capable of very wide bandwidth In both case, the addition of the input transformer almost totally negates any bandwidth advantages. In fact, many otherwise good designs are trashed by simply awful input transformers. Oh, well... Dick Pierce
shop@uwmcsd1.UUCP (Electronics Shop) (07/30/85)
> A salesperson at a local audio store recently pointed out to me that > there is a difference between electro-static and ribbon speakers. Could > someone explain to me the difference, and how electro-static speakers > work? Thanks in advance. > > Bob Schneider > {ihnp4|hplabs}!hpfcla!hpfclo!rjs If I recall correctly, ribbons work by electromagnetic induction through the aluminum ribbon voice coil. Electrostatics are full range speakers ( I've seen ribbon midrange but not ribbon woofers :-) . The basic 'static is a thin piece of film-like material, such as mylar, that is driven by the audio signal. This film is suspended between two perforated metal plates that are charged to a couple of kilovolts. The audio signal is also stepped up through a transformer. One plate is charged positive and the other negative, and the mylar moves toward one and is repelled by the other due to electrostatic attraction/repulsion. The major difference is that the ribbon is 'just' a tweeter (or mid) but a 'static is a full range, although many complain of lack of lower bass. A subwoofer helps, but is sometimes too slow, and there might be an audible delay. Some disadvantages of 'staics are the low impedance, sometimes as low as two ohms -- need an arc welder to drive them sometimes. Another is the high cost -- my Koss ESP-10 headphones retailed for $350, and Quads can cost up to $2K or more. If you have a limited budget, ribbons can be bought to upgrade your existing speakers, or if you have bucks and an amp that can power New York City, electrostatics can be the best investment you ever made. Thomas Krueger -- Engineering Electronics Shop U of W - Milwaukee ihnp4!uwmcsd1!shop uwmcsd1!shop@wisc-rsch.arpa
rdp@teddy.UUCP (07/31/85)
In article <351@uwmcsd1.UUCP> shop@uwmcsd1.UUCP (Electronics Shop) writes: > >The major difference is that the ribbon is 'just' a tweeter (or mid) >but a 'static is a full range, although many complain of lack of lower >bass. A subwoofer helps, but is sometimes too slow, and there might be >an audible delay. AAAARRRRGGGGHHHH!!!! A subwoofer is "slow" for on reason only, because of it's limited bandwidth! If you were to take something like an electrostatic, and limit it's upper cutoff frequency to the same as a subwoofer, it would be just as "slow". This nonsense about "slow" and "fast" woofers is so silly. The "speed" of a linear system is a function of it's bandwidth. If something is causing it to respond to signals slowly, then it's bandwidth will be appropriately restricted. Period. As to the "audible delay", unless it is approaching many hundreds of milliseconds (given a crossover of less than 200 Hz), there will be NO audible delay. There might (read WILL) be some phase anomolies, but nonbody is going to hear a delay. > Some disadvantages of 'staics are the low impedance, >sometimes as low as two ohms -- need an arc welder to drive them sometimes. >Another is the high cost -- my Koss ESP-10 headphones retailed for $350, >and Quads can cost up to $2K or more. If you have a limited budget, >ribbons can be bought to upgrade your existing speakers, or if you >have bucks and an amp that can power New York City, electrostatics >can be the best investment you ever made. > >Thomas Krueger This is simply not so. What is required for driving electrostatics is an amplifier that can handle highly reactive loads without instability problems. The only thing you might need high power for is to overcome an inefficient transducer. This is not a function of impedance. For example, take a Klipsch horn loudspeaker, which is very efficient. Put a 2 ohm to 8 ohm matching transformer on the input. You now have a very efficient, very low impedance loudspeaker. So what? One of the most pleasing systems I configured was a double pair of Quad ESL-1's driven by Lux MB3045 tube amplifiers, each running about 5-10 watts class A or about 75 watts class AB. The system played very loudly, very nicely, not because there was gobs of power (there sure wasn't!), not because tubes were used, but because the amplifiers were stable with the load presented. This falacy exists, I suspect, because many smaller amplifiers are not stable into these reactive loads (higher dynamic output impedance maybe?) On the other hand, higher power amplifiers that people are inclined to hook these things to are usually more stable, inherently. Remember that the part of the impedance that constitutes that part that the amplifiers is actually doing work against, the part of the power that ends up producing sound, constitutes a very small part of the total electrical impedance presented by the speaker. (Try going through and reflecting the radiation impedance back through to the speaker inputs. It turns out the, except for in the deep bass, the impedance presented by the loudspeaker would change nearly immeasurably if operated in a vacuum!) Is there a net.audio.unsubstantiatable_myth news group? :-) Dick Pierce
shop@uwmcsd1.UUCP (Electronics Shop) (08/01/85)
> > Some disadvantages of 'staics are the low impedance, > >sometimes as low as two ohms -- need an arc welder to drive them sometimes. > >Another is the high cost -- my Koss ESP-10 headphones retailed for $350, > >and Quads can cost up to $2K or more. If you have a limited budget, > >ribbons can be bought to upgrade your existing speakers, or if you > >have bucks and an amp that can power New York City, electrostatics > >can be the best investment you ever made. > > > >Thomas Krueger > > This is simply not so. What is required for driving electrostatics is > an amplifier that can handle highly reactive loads without instability > problems. The only thing you might need high power for is to overcome > an inefficient transducer. This is not a function of impedance. I seemed to have made an error.... I meant that high current output was needed for some electrostatics such as older Accoustats. Not many amps can put out that kind of current. I will agree that maximum stability is very desirable. Accoustat's Trans-Nova MOSFET amps have a zero (or claim to, anyway) output impedance. If I recall the load impedance should be the same (ideal condition) or higher than the source impedance to minimize problems. Sorry for inadvertant foulups. Thomas Krueger -- Engineering Electronics Shop U of W - Milwaukee ihnp4!uwmcsd1!shop uwmcsd1!shop@wisc-rsch.arpa
dep@allegra.UUCP (Dewayne Perry) (08/02/85)
<ribbons make fine food, but static electricity really gives zip> Krueger may well be right about the technical details about the two but I think he is incorrect about ribbon speakers being just tweeters. Stuart Audio in Westfield NJ (another good snob shop, though not quite in the league of Lyric HiFi) had a pair of large (2' wide by 5' tall) pair of ribbon speakers. We heard a cd version of a Bach organ work - completely blew the speakers away - gave the bass pipes a real buzz (which is ok if they are reeds, but these were not - oh well). So in one sense he may be right in that the speakers certainly could not handle the woofer end very well at all. I suppose that all this ribbon technology gives new meaning to the song line "round her neck she wore a yellow ribbon". Dewayne Perry
pearse@hound.UUCP (S.PEARSE) (08/04/85)
Recently there has been talk about "fast" vs. "slow" woofers. Someone indicated this is only a function of limited bandwidth of the woofer. Could someone explain how a, well, bandpass or lowpass system results in a time delay? Is it just like how an equalizer introduces phase distortions? Surely an equalizer doesn't introduce audible delays, does it? -- Steve Pearse ihnp4!hound!pearse
dca@edison.UUCP (David C. Albrecht) (08/05/85)
> > Is there a net.audio.unsubstantiatable_myth news group? :-) > actually it is net.audio.scienceandmagicmixedwithtotalegobasedbullshit and you are reading it. David Albrecht General Electric
2212zap@mhuxm.UUCP (putnins) (08/08/85)
> > Recently there has been talk about "fast" vs. "slow" woofers. Someone > indicated this is only a function of limited bandwidth of the woofer. > Could someone explain how a, well, bandpass or lowpass system results > in a time delay? Is it just like how an equalizer introduces phase > distortions? Surely an equalizer doesn't introduce audible delays, > does it? > -- > Steve Pearse > ihnp4!hound!pearse *** REPLACE THIS LINE WITH YOUR MESSAGE *** Yes, it is just like the "phase distortions" of an equalizer. And yes, equalizers do introduce delays. Whether they are audible depends on the gold content of your ears. Any phase distortion produced for a particular frequency corresponds to a time delay. ex: COS (WT + D) == COS( W*(T + D/W) ). So a phase distortion of D radians corresponds to a time delay of D/W seconds at frequency W. If D is linearly related to W, then we have a constant time delay across the spectrum, and the effect is just a time delayed version of the original. If the phase distortion is not linearly related to frequency, then you will get a distorted version of the original. Whether this type of distortion is audible also depends on the gold content of your ears :-).