That looks good. Or the following works for me. Take a piece of veroboard, draw a circle slightly smaller than the speaker on it with a drawing compass, the sharp leg should be located in a middle hole. Firmly tape board to the case where you want the grill. Then drill thru all the veroboard holes inside the circle with a small drill. The board keeps the holes aligned even if you wobble a bit. ? A drill press makes it much easier (and cheaper on drill bits). ?
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