Washing panels without taking them off speakers

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jasonz1121

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My vistas have been hissing for the whole summer when humidity is higher than 60 percent. Vacuuming doesn't help with this problem. So I thought the panels have got dirty again due to my non-ideal environment. Since last time I washed them in the shower and it was quite a bit of effort, I decided to try a new way. This time I used a small carpet cleaner, a fine makeup brush and a spray bottle with distilled water. The process is quite simple. First, I sprayed some distilled water onto a small section of the panel. Then I agitated it with the makeup brush. I payed close attention not to spray too much water to the places which are close to the edges so the water doesn't get into the seams. After I've done with brushing. I sprayed more distilled water onto the panel to perform a flush while I was holding the vacuum head to suck all the water out the same time. I clean a small section a time and then move onto the next one. After I finished vacuuming, the panel is 99% dry. Finally I set my hair dryer to lowest heat to give the panel a good blow to dry the last 1 percent. The result is very significant. I only did it on the front side of a single speaker to test out, and the hissing is pretty much gone. I think after I finished cleaning the back side, the hissing problem will be completely cured.
 
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hillbilly

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That sounds promising!
If there's any way you could post pics or video, it would really help:)
Please let us know the final results.
 

sleepysurf

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Hah! Perhaps those of us with the later models (those with metal frames) could rig up a system to hold the entire speaker upside down in the shower, so no disassembly required. Who wants to go first? 😁
 

roberto

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Yes, only one side, this is reason why you should wash only front side. The conductive coat is located at the front only. Believe it or not.
The diaphragm is so thin, that only one side is necessary to have the bias voltage.

Happy listening!
 
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jasonz1121

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I should have been more specific with the result of washing only the front side of the panel. So I’d say 95 percent of the noise is gone. I can only hear the hissing with my ear “on” the panel, which I don’t consider it as a problem anymore.
 

roberto

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Hola Jason1121,
That hissing noise, do you have the power amplifier turned on? Do this: play 10 seconds of a song, and then, turn off the power amplifier. Do you still have the hissing noise? The hissing could be the output stage of your power amplifier, this is called signal to noise ratio and this hissing is normal. If you have a distance of 3 feet away from the speakers, can you still hear the hissing?

Happy listening!
 

jasonz1121

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Hola Jason1121,
That hissing noise, do you have the power amplifier turned on? Do this: play 10 seconds of a song, and then, turn off the power amplifier. Do you still have the hissing noise? The hissing could be the output stage of your power amplifier, this is called signal to noise ratio and this hissing is normal. If you have a distance of 3 feet away from the speakers, can you still hear the hissing?

Happy listening!
It’s nothing to do with my amp. With everything off except for the speaker with the music sense indicator on, the hissing is still there.
 

Robert D

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It’s nothing to do with my amp. With everything off except for the speaker with the music sense indicator on, the hissing is still there.
Did you try unhooking the speaker cable to see if the sound is still there?
 

jasonz1121

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In that case, your PSU must be changed. Ask Martin Logan service dept about this.

Happy listening!
How can power supply be affected by humidity tho? I found 55% of RH is the threshold for the noise to appear. If I blow on the panel lightly, the noise level will dramatically increase due to the increase of moisture level.
 

roberto

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The noise could be at the bias voltage. A noisy electronic component of the PSU could be the culprit. I am guessing only. I had that problem previously.
The service team of ML could help you more. When a debris is causing the noise, you can locate the exact point from where it is produced. I am understanding that this is not the case.
Happy listening!
 

Tosh

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Jason,
Do you have a winter update?
Both panels are capable of hissing? Not just a faint squeal?

On the subject of cleaning the rear, 'dirt' can still get on the rear and cause HV shorting to the stators. But as the speaker is usually leaning back a little, dirt on the rear is much less than on the front. I regularly find exploded insects in mine....
 

roberto

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Hola Chicos,
I had tested the back of the panel for voltage, and my Fluke tester does not read a thing. At the front, I do have a reading. Using a special probe, I can measure high voltages. The reading says that the supplied bias voltage is near 1.900 DC on my Summits. Is this reading correct? Well, with my experience with ML, this bias voltage might be between 1700 to 2200 DC V. Now, only at the front of the diaphragm the voltage is present. At the back, there is no voltage.
The conductive coat is applied only at one side, at the front. The back of the panel, there is no conductive coat.

Happy listening!
 

spkrdctr

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Roberto, you are correct. If anyone hears hissing without the speaker cables connected, it is the speaker. For ML speakers it is the power supply causing this. Now the issue becomes at what level is it normal? If you have to stick your ear on the metal perforation grib, does it matter? ANY sound will immediately drown out the miniscule hiss at 25db or less? But a quick call to ML and they can tell you if there should be any hiss or none at all. Power supplies don't usually go bad until many years after purchase. Usually any very quiet hiss ,crackling and popping can be a bad capacitor. Capacitors are the weak link in any extreme performance circuit like the ML speakers.

Oh and I want to throw in my normal caveat. If the speakers are 20 years old, ALL of the power supply/crossover capacitors need to be changed out. At 20 years old they are really getting long in tooth. Some may go at 15 years. But at 20 it's usually a good idea to refresh the speaker and it will return to like new performance. Plus it does not cost all that much to have done.
 
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