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since this appears to be KLH week.
I have a KLH Eight FM radio I'd like to restore. From my inspection of the speaker, I cannot see how to get inside short of destroying the grill cloth or using a Saws-all on the back of the cabinet. What's the secret with the old KLH boxes?
If this is a D_ question, please be nice!
On mine, the grille cloth is sorta stiff like it's starched and it's exterior dimensions are about 1/8" larger than what appears to be the front opening. It's held in place by being fitted into a notch that's routed around the inside perimeter of the speaker box. To get the cloth out I just used a precision screwdriver to pull the cloth out of the notch on the short side of the box. It becomes obvious once you see how it's done.
The baffle board is mounted to the box by six or eight slotted wood screws around its perimeter. However, KLH used some kind of hardening sealer glop betw the baffle board and the cleats behind it that the screws screw into so you must be very careful when you pry the board up else you'll break it. The drivers are rear mounted to the baffle board with rivets and are a royal PITA to remove because the speaker baskets themselves are plastic and rather fragile. The speakers are wrapped in black scrim cloth which is tied in the back with wire twist ties of all things. Besides the appearance thing, the scrim is needed to keep the fibreglas fill from getting into where it shouldn't be. The speakers are wired in series.
The reason I know all this is that I was hearing a buzzing sound during heavy bass passages at higher levels and thought I could fix the problem. Turns out that the speakers are pretty high compliance and even though the box is sealed more or less, the speakes will bottom out easily. I tried sealing the interior seams of the box with caulk and then sealing the interior walls with a couple coats of shellac. I also used a high quality, non-hardening 3M automotive rope caulk betw the baffle and the cleats. Not surprisingly, the condition persists so I just listen to less than head banging levels.
At some point I'm going to build a replica of this speaker using modern 3" full range speakers from Tang Band. I wouldn't be surprised if there isn't much improvement in sound but there will definitely be an improvement in power handilng capability.
Bottom line: Digging into an operating KLH Model 8 speaker is not a recommended exercise.
Steve, and thanks for your thorough reply. Based on your experience, think I'll wait until the electronics have been checked out so I can listen to it first. I just assumed that 40+ year old surround would likely be rotting.
I replaced all electrolytics and what I thought were paper-n-foil caps in mine. Turns out that the paper caps were really some kind of polymer film and were pretty close to marked value AND not leaky at all. Even though these caps are pretty cheesy looking, they didn't need replacing. I do feel better with metalized PP film in there however.
I was also going to align the RF/IF sections but couldn't find alignment instructions so I don't know if the thing uses single peaked, undercoupled IFs or if it's a double peaked over-coupled design. As it turns out, it's reasonably sensitive and dial calibration is acceptable as-is so I've decided to leave it be for now.
The KLH 8 is a dated design that to my ears sounds oh-so-good. They really got it right with this radio. It totally blows away the Tivoli Model One in terms of sound quality and is close in RF performance. I think you'll really like it. My only disappointment is the incredibly crappy FM programming polluting the airwaves these days. The Model 8 was clearly designed for a long past era when FM was truly a HiFi medium and good programming was important.
The speakers use some type of treated cloth roll surround that has remained totally pliable over the years. If the surrounds had somehow gone bad, I don't think there would be any practical means of fixing them w/o totally screwing up their performance characteristics.
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