And you used full strength simple green with no dilution? I'd be worried that would take the coating on the mylar right off. Your experiment proved that wrong !So, yesterday being Thanksgiving I decided it was the day to finally take a shower with my SL3's. I've had them apart before for panel slippage and the resulting repair of a lead so I have no fear of disassembly. I've not been religious about vacuuming or cleaning them over these +20 years of ownership (they are serial #SELE000 and SELE001 to give you an idea of age) and they've been sounding dull to my ears for quite awhile. (I built some full range speakers recently and was stunned by the high end detail and air that had apparently gradually slipped away from the Martin Logans.)
At any rate, I was more than skeptical that a quick rinse was going to do much beyond getting them wet. I convinced myself that something more aggressive would be needed if cleaning was going to be effective...and of course increased the potential for damage. But everything I had read said that the panels were a lot hardier than given credit for. I figured, what the heck, I'm looking at panel replacement if I mess them up or don't touch them - either way. I had already contacted ML service about replacement panels (12-16wks delivery, yikes!) so I knew what that looked like.
Full-strength Simple Green in a spray bottle. I drenched both sides of the panel. I then took a very soft bristle brush (like a really soft varnish brush; it was actually a kitchen basting brush) and brushed both sides of the panel. This caused them to foam up, lots of wet suds. I didn't want to chance leaving a residue but I let the panel soak like this for perhaps a minute and then rinsed them under the warm shower. Not hot-hot but definitely not lukewarm - about the same temp as you would take a normal shower.
I held the panel up close to the spray, say, 4-6" and rinsed the panel. What ran off was a combination of green (the soap) and black...something. A lot of it. I thought for a fleeting second the paint was washing off - that's how much black was running off. Most of the grime came off the front of the panels, I'm guessing due to polarity.
After rinsing to clear water, I shook the panels a bit and stood them up. I wiped them down with towels, more to get the major droplets than anything, turning them around a few times in the process (water did drain from the corners when turning). I then used my shop vac (it's a commercial grade dust collecting vacuum for woodworking, so rather serious CFM) with a bristle brush and went over the panels thoroughly. After this, I stood them outside to air out. After about an hour I turned them end for end and let them stand another hour or so before assembling them (replacing all the nasty rubber strips that ML used on these with self-adhesive foam strips). I then let them stand overnight.
I'm listening to them now. They sound absolutely amazing - just like they did when I first heard them and had to have them. Your mileage may vary but this worked incredibly well for me. I'm thinking it's going to be a part of annual maintenance.