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Another Model Twelve Contour Box


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Got these recently--just the contour (crossover) boxes--not the speakers. One box cover looked just awful inside--all moldy. The guts of that box were a little dirty but not bad. Everything else was good but 2 knobs were missing. Wood veneer had some small chips and one gouge or dent.

First step was to scrape the mold off with a putty knife, then brush on pure bleach. Rinsed it off and dried with a hair dryer.

The gouge was steamed out. Wood was stripped using lacquer thinner, steel wool and paper towels. The chips were filled with a mixture of epoxy and walnut sanding dust. The cabinets aren't finished yet. Still have to decide whether to use lacquer or oil. Also have to get some yellow paint for 2 of the terminal screws.

This was odd: The instructions say "The terminals marked 'GND' and '8 Ohms' on the Contour Control's rear panel should be connected to the corresponding speaker terminals on your amplifier".  Surprise! KLH used some spare FM Antenna terminals for this pair! So I decided to remove those, blank the hole with sheet aluminum and install 5-way binding posts. That's a first for me but I think it's an improvement.

All of the caps were replaced with ones I had on hand: Two 50uF NPEs, one 16uF Erse mylar, three 4uF Dayton polys and one no-name 3uF mylar. I used to replace all of the resistors but Roy advised me that the only truly undersized one is the 5 Ohm 5 watt in the woofer circuit so I replaced that with 2 10 Ohm 10 watt Rs for an effective 5 Ohm 20 watt.

Because of the two missing knobs I used some stove style knobs to replace them.  I think they look right, with a vintage vibe but I just bought a single "parts donor" crossover with 4 knobs, so I can use originals and have 2 to spare.

I tested these two with some raw drivers just to make sure everything works.

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Here's a shot of the back with the new 5-way binding posts. I put them to the side because space is limited in the middle. The old hole is blanked off. The pic also shows my "custom interconnects." The originals had a flat color coded 4-conductor cable but that was missing. Fortunately I had just pulled a bunch of ~20" wires from a speaker (my next project--Dynaco clones). Trying to figure out how to tie them together I Googled "4-strand braid" and found lots of instructions. I had the crimp connectors and heat-shrink tubing on hand so these cables were virtually free. I like the look. Still need to paint the 4th screw head yellow.

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