I am in the process of building dual passive subs. I recently purchased a pair of Polk Rti-a9's. These beauties are fairly large and have a curved teardrop shape, as they taper from front-to-back. I like the look, and the mid-bass performance is solid, so I've set out to build matching subs to extend the low end.
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I've been researching different ways to bend MDF so that I can form arcs for the sides of the enclosures. My budget is tight and tools are limited, so I can't afford too many failed experiments. I've read about kerfing, but I'm afraid that I won't get a smooth outer finish, and that I'll go through several sheets of wood trying to get it right. I've also read about bending several thin sheets then laminating them together, but the only sizes available at the local lumber yards are 1/2" and 3/4" (can't afford 8 sheets of birch either).
The idea that intrigued me the most came from terryj at home theater shack in his thread
My speaker build...about time I showed you - Home Theater Forum and Systems - HomeTheaterShack.com. Thanks for the idea. I set a 4X8 sheet of 3/4" MDF on 2 sawhorses. As you can see, the board is very stiff and hardly bends even with about 80 lbs. of weight on it.
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I used a bottle of household ammonia mixed 50/50 with water and rubbed it on with a wash cloth. I applied the ammonia/water mixture evenly across the board until it had soaked about 1/3 of the way through. I flipped the board over and applied the mixture to the other side until it soaked 1/3 of the board's thickness. This left the inner 1/3 dry. Amazingly, the board began to bend!
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My intent in this thread is to help anyone who is considering different ideas around DIY speaker building. I am not an expert by any means, so I welcome any feedback pros/cons (particulary cons) from any experts who could add to this thread. Ultimately, this idea worked great for me as I am very pleased with the results.
