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On Wed, 23 Mar 2005 07:24:11 +0000 (UTC), Stewart Pinkerton
wrote: On Tue, 22 Mar 2005 20:15:28 -0500, wrote: On Tue, 22 Mar 2005 02:32:03 GMT, Chris Hornbeck wrote: On Mon, 21 Mar 2005 20:33:06 -0500, wrote: In the case of an E-spk membrane, the tightness would determine it's resonance, just like a drum. I would imagine the membrane would be loose enough to put the resonance out of the audio band, could even be less than 1hz. Unfortunately that high of a compliance isn't possible given the constraints of practical diaphragm-stator spacing. Practical electrostatic speakers have fundamental resonances in the tens of Hertz range. The QUAD Mark 1 from 1957 has a design center F-sub-S of about 70 Hz, for example. Choice of fundamental resonance frequency is actually one of the toughest and most interesting parts of the design, because the resonance is used to extend response lower than a free-air diaphragm of those dimensions would achieve. I don't know what you mean here, I've seen 12" cardboard speakers with a resonance of 15hz... what does size have to do with it? In any open-baffle dipole, size i.e. path length from front radiator to rear radiator, determines when the FR starts to drop at 6dB/octave. Wouldn't the resonance have to do with how tight the membrane is installed? Yes, and in a good design the fundamental drumskin resonance can be set so that it starts to peak up just as the natural FR starts to droop. Below the dimensional limit all diaphragms' responses fall at 6 dB/octave. Choices must be made. I thought system fall off was 12db? That's for a sealed box, a dipole falls at 6dB/octave. I have to say I don't know much about E speakers... had some E headphones once, had no bass... Well, they should have, since they are conventional direct radiators, not dipoles. Stax 'phones have as deep bass as any other type that I've heard. I can't remember the brand, it was in the 70s... but they really lacked bass response... they were supposed to be among the best at the time. I remember they had a 'self power' switch or could use a power supply. I replaced them with I think Koss Pro 4AAA or something like that, which had the bass but not the transparency. They proved to be defective and non-repairable... I no longer use headphones... |
#83
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#84
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On Wed, 23 Mar 2005 14:04:48 +1100, Patrick Turner
wrote: wrote: On Wed, 23 Mar 2005 00:10:30 +1100, Patrick Turner wrote: Wait a minute, you are wrong Pinky. The percussion sound you hear from an ESL is produced by signal applied to the whole surface of the diaphragm. And although it is conceivable that such signals might excite some resonances, its not in any way like when a dude hits a drumskin with a stick, temprarily deforming the skin in a local area, and sending ripples out across the skin, and exciting a mass of trapped air. I think this 'hit with a stick' thing is a red herring... You are in effect saying that one can't play a drum by hitting it with a book or something that affects the whole head - you are wrong! (it will just sound different) Also, there are pre-tuned drum heads, no drum shell required. And have you ever seen roto-toms? No shell either, so no air-mass. The sound of a drum re-produced by an ESL is done in a very different way to how the sound is genarated at the drum. The drum sound is due to a very asymetrical distribution of waves waves across the drum skin, which has considerable weight compared to an ESL membrane. The ESL membrane is excited over its total area in an evenly spread fashion by an amplified mircrophone signal. The ripples across the membrane don't occur, The almost massless diaphragm does not like to ripple or swing back and forth in air to any great extent like resonant things do, and the resonaces of ESL are renowned for being less than most other transducers. Also, putting a mass into resonant vibration can be done with anything, including an electrostatic force, ANYTHING that excites it to move. Well show us all what terrible resonaces exist in ESL. As I said, I don't think the resonance is great or terrible, just that it probably exists. The fact the resonance of the diaphragm of an E speaker doesn't affect the sound doesn't mean it has NO resonance, just that it is damped and very small, and is well controlled by the amplifier's feedback. We are saying ESL resonance is small. I have not done the math to support any idea how effective NFB control of the diaphragm is. But if you tap a diaphragm, or play music alongside an ESL connected to an amp with no signal, you'd expect to see an error message in the amp as it tries to resist the motion caused by the external sound or excitation. I have never done this test. I've only done it with normal magnetic speakers, but I imagine the effect is the same. Now I forget the original OP topic! BUT in practical terms, I'd agree that the resonance in an E speakers diaphragm isn't a factor in it's sound, and the light diaphragm with 'full wide drive' is what gives it the advantage over a cardboard/magnetic motor spk. All this talk about those speakers makes me want a pair now! Hey Phil, got a set to sell? I doubt he has, but why not try brand new ones from http://www.eraudio.com.au Patrick Turner |
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On Wed, 23 Mar 2005 02:46:45 GMT, Chris Hornbeck
wrote: On Tue, 22 Mar 2005 20:42:54 -0500, wrote: The fact the resonance of the diaphragm of an E speaker doesn't affect the sound doesn't mean it has NO resonance, just that it is damped and very small, and is well controlled by the amplifier's feedback. I'd just like to agree with all of your post, and to add a piggyback comment. Electrostatic speakers are often considered to be "inefficient", therefore poorly coupled to the driving amplifier and therefore indifferent to amplifier source impedance. But actually, the "motor" in electrostatic speakers is of very high efficiency and coupling is therefore very high. The misconception arises from the considerable parasitic capacitance present. (But it's "outside" the motor). That's good to know... Your English is better than mine, and that's all I really can use, but your syntax is extremely provocative. I can't place your childhood language, even to within a continent. Sometimes it seems north European; sometimes southeast Asian; very intriging. Care to share? Thanks, Chris Hornbeck It's interesting that you wonder about my language... I actually have quite poor language skills, I have to work at it, my brain is better attuned for visuals then for writings. Do you know that test where there are a bunch of words that are the names of colors, but the words are colored, and the colors don't match? Example, the word 'BLUE' is green, then the word 'YELLOW' is purple, and on and on...? The answer to the test is to say the colors of the actual words, NOT to read the word. For the example I gave, the answer would be 'green, purple'. You have to read it aloud at a good speed, and most people start making mistakes right away! Well, this test is no trouble for me... I can zip thru in no time, looking at the colors and ignoring the writing. This shows that one side of my brain is dominant... and it isn't the language side! All I can say about my origins is that my parents were a mix of British and French, with some German grandparents mixed in... Parley vous la Francais? C'est possible que les deux langues me donne des autres problems encore! |
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#87
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wrote: On Wed, 23 Mar 2005 07:24:11 +0000 (UTC), Stewart Pinkerton wrote: On Tue, 22 Mar 2005 20:15:28 -0500, wrote: On Tue, 22 Mar 2005 02:32:03 GMT, Chris Hornbeck wrote: On Mon, 21 Mar 2005 20:33:06 -0500, wrote: In the case of an E-spk membrane, the tightness would determine it's resonance, just like a drum. I would imagine the membrane would be loose enough to put the resonance out of the audio band, could even be less than 1hz. Unfortunately that high of a compliance isn't possible given the constraints of practical diaphragm-stator spacing. Practical electrostatic speakers have fundamental resonances in the tens of Hertz range. The QUAD Mark 1 from 1957 has a design center F-sub-S of about 70 Hz, for example. Choice of fundamental resonance frequency is actually one of the toughest and most interesting parts of the design, because the resonance is used to extend response lower than a free-air diaphragm of those dimensions would achieve. I don't know what you mean here, I've seen 12" cardboard speakers with a resonance of 15hz... what does size have to do with it? In any open-baffle dipole, size i.e. path length from front radiator to rear radiator, determines when the FR starts to drop at 6dB/octave. Wouldn't the resonance have to do with how tight the membrane is installed? Yes, and in a good design the fundamental drumskin resonance can be set so that it starts to peak up just as the natural FR starts to droop. Below the dimensional limit all diaphragms' responses fall at 6 dB/octave. Choices must be made. I thought system fall off was 12db? That's for a sealed box, a dipole falls at 6dB/octave. I have to say I don't know much about E speakers... had some E headphones once, had no bass... Well, they should have, since they are conventional direct radiators, not dipoles. Stax 'phones have as deep bass as any other type that I've heard. I can't remember the brand, it was in the 70s... but they really lacked bass response... they were supposed to be among the best at the time. I remember they had a 'self power' switch or could use a power supply. I replaced them with I think Koss Pro 4AAA or something like that, which had the bass but not the transparency. They proved to be defective and non-repairable... I no longer use headphones... I had someone give me a pair of Stax phones, which were quite stuffed. Yes, they were "self powered". I removed the transformers and chucked out the rest; I haven't the time and space for every electronic orphan that lands on my doorstep. Patrick Turner. |
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