Martin Logan CLS panel distortion


Dear Audiophiles,
My original Martin Logan CLS speakers developed harsh distortion at higher spectrum of frequencies (mostly audible at high pitched soprano voices). Distortion disappears at low volumes of sound. Are my panels getting too old (they could be 10 years old, I am a third owner)? Is there a way to clean/tighten them (the panels, not owners ;-)? Your comments and suggestions will be appreciated. Thank you.
meta
Meta,
There are several threads on this subject if you do a search for Martin Logan.

It is possible that the panels need to be replaced. This is about the expected life, but my Quests are about the same age and still doing OK. You may be able to solve the problem by unplugging the panels and letting them sit for several hours. Then vacuum them. Humidity or smoke can also cause problems.

Good luck and write me if you can't find what you are looking for in a search.

Happy listening.
Meta:
If you e-mail Jim at Martin Logan he will send you back an E-mail describing the use of a hair drier passed quickly over the panels in an attempt to tighten them and remove distortion. It would be worth trying since you would have nothing to lose if you had to replace the panels anyway (about $800).
arlenm
I a re-posting Jim Power's advice which I think is already in the archives - see below. You can ruin the panel...but it is already broken you may have nothing to lose. Also, you can call ML, give them the serial # on the panels and they can tell you when the panels were built.

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There are a couple of possibilities that may be occurring. One would be that the panel is simply resonating because it has perhaps lost a bit of tension. The other possibility is that the clear 'damping strips' have come loose from the backside of the panel. There is a difference in performance between the two.

A resonating panel will only buzz on certain notes and at somewhat higher volumes.
A loose damping strip will buzz at almost any frequency and at any volume.

From your description, I believe that you are hearing a resonance. We fondly refer to the phenomena as "Kazooing" because it sounds like a kazoo. This can usually be improved by heat treatment. All CLS panels are heat treated initially before they leave the factory. Some times with age, they will stretch themselves slightly loose. They need heat to re-tension them. There is a very specific technique to heat treatment. If you wish to try it, Here are the instructions.

CAUTION!!!!
There certainly is the risk of damaging the panels by melting a hole through the membrane. Bad thing. If you are careful however, I think you will do just fine.

The heat can be applied with a strong hair dryer. A heat gun may be too extreme. I recommend starting with the heat source about 12 inches away from the speaker. Complete the entire procedure and if it has no affect, move the heat source about 2 inches closer and repeat the entire process. Patience is required.
The heat must be applied ONLY to the side portions of the panel, never in the center zone indicated by the horizontal spars or ribs. The side sections are the 'bass' sections that are about 6 inches or so wide and run from top to bottom on each side of the panel.
The heat must be applied from a constantly moving heat source but at a very slow steady rate of movement. Specifically, start applying heat from the dryer at the top of the panel along the edge of the wood frame moving toward the bottom. Keep the heat source moving at the rate of 1 foot per 3 seconds. Next start at the top again but this time, move inboard just slightly, about 2 inches and make another slow downward pass. Repeat until you are near the vertical spar defining the beginning of the center section.
If you first treated the left bass zone, now do the right bass zone.
If you have a good light source on the membrane, you may be able to determine if it is receiving enough heat to have a good effect. You should be able to see a slight shimmer of the membrane directly under the heat if light is so that you can see the reflection of the light. As you move the heat past, the area that was shimmering will draw tight. I hope this helps.
If all else fails, you can purchase new panels and receive an new 5 year warranty on everything. New panels are $890 including shipping within the US. We accept Visa, MC. Call me if you have any questions or need new panels. (785) 749-0133.

Happy listening!
Jim Power
service manager