Warped Grill Repair--A Success Story

motorcityguy · January 2019

A recently acquired pair of Polk 10's suffered from badly warped grills. Here is what I did to successfully repair them.

Apparently the prior owner had removed the grills from the speakers, and stored them in a flat position. They may also have had something lying on top of them. They did not have water damage but apparently had been exposed to enough humidity that they were both warped along long sides (top-to-bottom). When I tried to install them, there was a gap of nearly a half-inch to the cabinet.

Worse yet, prior owner had attempted to flex them in a reverse curvature, to remove the warp. All that did was crack the frame at the location that was scalloped for the mid-woofers. :-(

Although the cloth was dirty, it was in good shape. And I really did not want to scratch-build new grills, or purchase used ones. So I figured I would take a chance on fixing the warped ones I had.

First step, was to repair the cracked frame. To gain access to the grill frame and to avoid getting glue on the fabric, I carefully removed the original grill cloth staples along an area about 6 inches long. I pulled the broken area apart and applied Loctite Go2 glue on the surfaces. I used a small nylon ratchet strap to pull the broken areas tightly together. I used a piece of tin foil around the front surface of the frame to ensure that no glue escaping from the repaired area would contact the fabric.

After 24 hours, the glue was cured and I used a razor blade to trim the small amount of excess that had squeezed out of the joint. Then I reattached the grill cloth using the original staples back into the original holes. (If you straighten the removed staples back to their original dimensions, you can easily press them back into the existing staple holes. Then it looks like it has never been touched!)

Now to fix the warp....

I wanted to reintroduce some moisture into the wood and considered using steam. But I had read where some folks had successfully washed their grills in the bathtub. Normally I would not take such desperate measures, but the cloth was dirty and I needed to get the frames "softened".

I put a few inches of warm water in the bathtub along with a small amount of Dawn dish soap. At first I thought all the darkness in the water was from the dirt in the fabric. But I came to realize that much of it was the black paint on the speaker frames dissolving. (If you've ever tried to wipe the dust off the inside of your speaker frames with a damp cloth, you have already discovered this!) So, the lesson is don't leave them in the water longer than you need to.

After rinsing the grills well with clean water, I patted them dry with some white towels. (Tip: don't use the wife's good towels!)

Now here is the key to the un-warping process. Before washing the grills, I purchased four (2 per grill) 36" lengths of 1/8" thick aluminum "angle iron". These are incredibly stiff and perfectly straight. The idea is to clamp the moist grills to the metal channels and let them dry in a perfectly flat condition. What you do, is to put one metal channel on each long side of the speaker grill, so that the warp is lifting the ends of the grill. (Does that make sense?) Then tightly clamp the 4 corners flat onto their respective metal channels. This will be clearer if you look at the first photo.

After 3 days of drying, I removed the clamps, and the grills were completely flat! SUCCESS!! Now they fit the speakers beautifully and are nice and clean. :-)

motorcityguy · January 2019

By the way, a big advantage of the metal channels (as opposed to just stacking something heavy on the grill) is that the grill is fully open to the air, for quick drying.