They sound, but to hear them and with an obvious problem in the medium-low range, you have to turn up the volume a lot. a lot!
is there any chance that they can be recovered? they asked me if I want to take them back at a price... but
I wanted to know from you if they are repairable and how complicated they are to fix.
is there any chance that they can be recovered? they asked me if I want to take them back at a price... but
I wanted to know from you if they are repairable and how complicated they are to fix.
Be careful applying too much power when the speaker has problems. You can damage other parts doing that.
Many electrostatic speaker diaphragms fail electrically at some point. If you search for diaphragm replacement threads, you can see what's involved with that.
Bias supply failures are also pretty common. You need a high voltage probe to measure that or a workaround. Get familiar with the methods before you attempt anything. The voltages involved are high, and the current of the audio signal can be substantial also.
Are both speakers behaving the same way or is it just one of them? Swapping parts between good and bad speakers can help narrow down the issue even if you can't measure everything.
When you said "medium-low range", are you talking about the frequency range or volume setting? Depending on how you answer that: is the treble range at normal sensitivity? Can you do acoustical measurements to back that up? If you move your ear over the speaker very near to it, is there an obvious drop in output anywhere?
There are other things that could be wrong, but without a better idea exactly what's going on, it's hard to suggest where to look.
If you're careful, have some mechanical aptitude, and know what you're trying to do, they are often repairable.
Many electrostatic speaker diaphragms fail electrically at some point. If you search for diaphragm replacement threads, you can see what's involved with that.
Bias supply failures are also pretty common. You need a high voltage probe to measure that or a workaround. Get familiar with the methods before you attempt anything. The voltages involved are high, and the current of the audio signal can be substantial also.
Are both speakers behaving the same way or is it just one of them? Swapping parts between good and bad speakers can help narrow down the issue even if you can't measure everything.
When you said "medium-low range", are you talking about the frequency range or volume setting? Depending on how you answer that: is the treble range at normal sensitivity? Can you do acoustical measurements to back that up? If you move your ear over the speaker very near to it, is there an obvious drop in output anywhere?
There are other things that could be wrong, but without a better idea exactly what's going on, it's hard to suggest where to look.
If you're careful, have some mechanical aptitude, and know what you're trying to do, they are often repairable.
both sound the same and as if lacking in low range, if you turn the volume up a bit you can hear the classic - noise that a woofer emits when it is cooked or goes out of revs, but it does so in a light tone.
I think I will also try a measurement, but I think the sound is lacking from 400hz and below.
I think I will also try a measurement, but I think the sound is lacking from 400hz and below.
Audiostatics typically fail in one way only and that is the coating going bad. This results in severe loss of sensitivity and in bad cases loss of tonal balance. Cranking up the power to compensate will kill the audio transformers so don't. The noise you hear could be arcing in the transformers, I strongly advise not to repeat that test. And hope for the best it's not too late.... You can check resistance of the secundaries of both transformers but make sure to discharge them properly beforehand. Both secundaries should measure exactly the same (somewhere around 1100 ohms iirc).
In general, if you need more than a few watts for substantial output, they are ready for a rebuild. Another tell tale sign is that the output is uneven over the surface of the membrane, let them play at very low volume and move your ear close to the surface to check this. With bad coating, output can increase temporarely when you breathe on the lower part of the membrane, due to the moisture.
Rebuilding them involves replacing the membrane, not that difficult but it is time consuming and a lot of work. On the other hand it's a very rewarding job, imho these are among the best electrostatics there are.
In general, if you need more than a few watts for substantial output, they are ready for a rebuild. Another tell tale sign is that the output is uneven over the surface of the membrane, let them play at very low volume and move your ear close to the surface to check this. With bad coating, output can increase temporarely when you breathe on the lower part of the membrane, due to the moisture.
Rebuilding them involves replacing the membrane, not that difficult but it is time consuming and a lot of work. On the other hand it's a very rewarding job, imho these are among the best electrostatics there are.
no no, obviously we didn't keep them at high volume for a long time, just for a few seconds. if you tell me that replacing the membrane takes time, but it's a very doable thing, this is already a good step and I will try to understand what type of membrane and how to proceed for the replacement. I will also check the value of the resistance when everything is perfectly discharged.
Unfortunately it's not so much a matter of prolonged overloading, arcing only once is enough to potentially kill a transformer. But let's hope for the best for now. Bad coatings or connections can also cause weird sounds. And replacement transformers are not completely unobtanium.
First step would be to verify it is indeed the coating. Since both have the same problem, it is very likely but still. Switch them on, no input signal. Listen in a quite room with your ear close to the membrane and interface for hissing or craking or popping sounds. If all is quiet, feed them a small audio signal (max 1 Watt). Listen again if the output is uniform in volume all over the surface. Try breathing on the membrane, at the bottom end. Don't remember if the coating is on the back or front so just try both. When breathing on the membrane increases the output, you can be pretty sure the coating is gone.
Next step would be to open up the interface. Remove mains and audio connections, leave them for a few hours to discharge. Remove the plastic cover at the back. Use insulated wires to short all three wires that go to the ESL element without touching them with your fingers. Leave the shorts in place for half an hour. Then you can safely work on the speakers. Check for loose connections, oxidation, signs of arcing etc. Post a picture.
Measure dc resistance on the secundary windings of both audio transformers, the connections near the top edge of the PCB. If you get strange unstable readings, use another multimeter. Some meters use a pulsed signal that interferes with the large inductance. Any cheap multimeter should do fine.
For rebuilding you need to completely disassemble the speakers and remove the ESL element from the MDF frames. Everything is glued together so it might take some serious force to separate the element from the side frame parts. Next step is to split open the elements, again it's all glued. Depending on the year of production and/or possible previous rebuilds you can expect all kinds of glue. Some easy to break, some not so... Then you have to remove the old membrane, clean everything, restore any broken joints etc. Most important is not to damage or bend the stator wire/crossmember assemblies. All the rest is easily fixed or replaced.
The original membrane is 6um mylar, but 4 works fine too and gives slightly better high frequency detail. There are several sources that will sell you suitable mylar. You'll need coating, this is the most difficult part. There are some recipes out there that seem to work, or you can order a ready-made coating in Australia that works very well. You will need to construct some sort of tensioning rig to stretch the mylar to the correct tension, this probably will take some trial and error as each batch of mylar is different and you need to get the resonance frequency just right.
The electronics seldom fail but it is a good idea to at least rebuild the high voltage multiplier and replace the large electrolytics in the interface.
First step would be to verify it is indeed the coating. Since both have the same problem, it is very likely but still. Switch them on, no input signal. Listen in a quite room with your ear close to the membrane and interface for hissing or craking or popping sounds. If all is quiet, feed them a small audio signal (max 1 Watt). Listen again if the output is uniform in volume all over the surface. Try breathing on the membrane, at the bottom end. Don't remember if the coating is on the back or front so just try both. When breathing on the membrane increases the output, you can be pretty sure the coating is gone.
Next step would be to open up the interface. Remove mains and audio connections, leave them for a few hours to discharge. Remove the plastic cover at the back. Use insulated wires to short all three wires that go to the ESL element without touching them with your fingers. Leave the shorts in place for half an hour. Then you can safely work on the speakers. Check for loose connections, oxidation, signs of arcing etc. Post a picture.
Measure dc resistance on the secundary windings of both audio transformers, the connections near the top edge of the PCB. If you get strange unstable readings, use another multimeter. Some meters use a pulsed signal that interferes with the large inductance. Any cheap multimeter should do fine.
For rebuilding you need to completely disassemble the speakers and remove the ESL element from the MDF frames. Everything is glued together so it might take some serious force to separate the element from the side frame parts. Next step is to split open the elements, again it's all glued. Depending on the year of production and/or possible previous rebuilds you can expect all kinds of glue. Some easy to break, some not so... Then you have to remove the old membrane, clean everything, restore any broken joints etc. Most important is not to damage or bend the stator wire/crossmember assemblies. All the rest is easily fixed or replaced.
The original membrane is 6um mylar, but 4 works fine too and gives slightly better high frequency detail. There are several sources that will sell you suitable mylar. You'll need coating, this is the most difficult part. There are some recipes out there that seem to work, or you can order a ready-made coating in Australia that works very well. You will need to construct some sort of tensioning rig to stretch the mylar to the correct tension, this probably will take some trial and error as each batch of mylar is different and you need to get the resonance frequency just right.
The electronics seldom fail but it is a good idea to at least rebuild the high voltage multiplier and replace the large electrolytics in the interface.
when you say coating, what do you mean. besides the mylar membrane?
keep in mind that as soon as I take them apart (in a few days), I will understand what you mean by - coating - but if you update me, I will have a better idea of what I will encounter.
keep in mind that as soon as I take them apart (in a few days), I will understand what you mean by - coating - but if you update me, I will have a better idea of what I will encounter.
The membrane must hold an electrostatic charge for the speaker to operate. This implies the membrane must be able to conduct electricity to some extent. This is what the coating is for. It should have a very high surface resistance, stick well to the mylar and be stable over time. The coating is the most difficult and mysterious part of the speaker, with most manufacturers carefully keeping their recipies secret.
I think everything maudio wrote is very accurate.
I wonder if the transformers are very sensitive to breakdown. At what voltage should this happen? Never seen a transformer of audiostatic being broken down. Saw a burned stator once, probably caused by fried resistors. My gut feeling it is 99% coatingproblem all the time
I wonder if the transformers are very sensitive to breakdown. At what voltage should this happen? Never seen a transformer of audiostatic being broken down. Saw a burned stator once, probably caused by fried resistors. My gut feeling it is 99% coatingproblem all the time
I've seen 3 or 4 bad transformers on Audiostatics that I rebuilt. All had open secundary windings on one of the transformers. And all of these speakers had coating that was so bad there was hardly any output left.
I think what happens is that the owner keeps cranking up the power as the coating breaks down, until flashover occurs in the transformer winding. That damages the insulation, resulting in one (or a few) shorted turns. In the shorted turns very high local currents start flowing that burn out the shorted windings. The wire is extremely thin. Resulting in the final stage, an open winding.
I disassembled one of these transformers and ideed found a few burned turns.
I think what happens is that the owner keeps cranking up the power as the coating breaks down, until flashover occurs in the transformer winding. That damages the insulation, resulting in one (or a few) shorted turns. In the shorted turns very high local currents start flowing that burn out the shorted windings. The wire is extremely thin. Resulting in the final stage, an open winding.
I disassembled one of these transformers and ideed found a few burned turns.