I haven't used it, but from the posts I've read, I'd say truckbed liner spray paint. You can also buy it in cans and apply it with a roller. Next would be plain black countertop laminate. You can get it a Lowe's or Home Depot for about $40 for a 4'x8' sheet. Very easy to apply with contact cement and it is the most durable "finish". I've used to to build subs and also use it on the backs of most speaker cabinets.
How about going for an antique grained finish? The steps would be as follows:
1) Prime the cabinet 2) Paint the cabinet with a base coat of paint (e.g. - a rust color would work.) 3) "Dry brush" a very small amount of black gloss paint - going in one direction on the cabinet. Let dry. 4) "Dry brush" a very small amount of gold gloss paint - going in one direction on the cabinet. Let dry.
This would give the enclosure a great "WAF" factor because it would look like a piece of nicely finished furniture. When it comes to the black and gold paints that I mentioned, RustOleum sells small pint cans @ your local home center to carry out the job. By "dry brushing" you only get a very small amount of paint at the ends of the bristles on the brush. Then, dab the brush slightly on a paper towel to make sure any excess has been removed before taking the brush to the cabinet.
I will be applying this painting technique in a few weeks when I finish my sub enclosures. At that time, I'll be able to supply some pictures. I've seen this technique done before by another family member - and the piece of furniture looked wonderful when completed.
i used rustoleum american accents stone creations granite spray paint. (wow, what a long name!) it comes in several colors, but i settled on the dark granite, because my wife figured the speakers should disappear when the light level is low in the room for movie watching. tough to do with 4 foot high by 18 inch wide speakers. from a distance they look pure black, but up close you can see the grey and white flecks in the mix. very rough texture, like bed liner. i did 2 coats of brush-on flat black to hide the mdf and wood putty, and then sprayed the granite paint. looks very nice!
after living with vinyl-clad speakers for 25 years (my fake walnut advents) i am trying to get away from that look. i even "granitized" my advent center channel speaker. it was black vinyl.
I just bought a can of the Rustoleum Black Hammered Metal spray paint. I really like the way it looks. Much classier looking than the truck bedliner sprays. It may be a bit to shiny though. I'm going to see if I can sand it lightly with 1000 grit paper and see if I can get a more satin finish without screwing up the paint.
IF you leave MDF nekkid, it turns a darker brown color depending on environment. I have an unpainted subwoofer sitting in the corner of my room for about 2 years and it looks the color of the earth. heh
There are a lot of ideas at home improvement stores in the painting section. From textures to sponges, you can even cover it with a table cloth. hehe
Stone type paints are easy to do if ave good technique. They look very good too. I also like "gravel guard", it is essentially a very heavy-duty rubberized textured black spraypaint.