Since most "glossy" speakers use a high quality automotive finishes, the same rules would apply.
As one poster suggested, a "quick detailer" and microfiber cloth should do the trick for general maintenance. Just be careful of overspray. Your raw drivers won’t appreciate being sprayed with contaminants.
If your speakers have a little age on them (3+ years) the finish might have gotten a little lazy or neglected and may need some attention. My general rule on this is to take a clean microfiber cloth and move it about the surface. If it doesn’t move effortlessly, then the material made need a little motiviation to deliver its orignal shine. IF the surface is nearly perfect. a good automotive wax is a good starting point. If you see some swirl marks, or light scratches, then you may need to take it to the next level(s)
Mequiar’s "Ultimate Compound" is slightly more aggressive than wax, cleans better and will "remove" some slight scratches and/or swirl marks. I use the term "remove" in parenthesis because you are not actually removing those scratches. The compound comes in contact with the indented surfaces and "polishes" them to a degree that they don’t draw as much attention to themselves. I also use this material on turntable dustcovers. Works great for me.
If you really want to get after it, "glaze" takes it another level, with a slightly more aggressive material than the compound mentioned above. You can get "hand" or "machine" glaze depending on how big a surface you’re working with. This will remove small surfaces scratches and swirl marks, but be prepared to devote a little work to get there.
Actual "scratches" are a different critter. In this case material is missing (gouged out). Minor scratches (with solid color throuout the scratch) can be helped with the compound or glaze mentioned above, concentrating on the scratch itself. You won’t remove the scratch. It will just be less noticable. Deep scratches will require that the damage be repaired. A good technique is similar to taking "rock bites" out of cars. Find the matching paint. Fill in the scratch with the paint with brush or q-tip not paying much attention to how it looks at this point. The idea is to build up the material in the void so that it will be higher than the other surfaces. Then sand it down even with the other surfaces. and polish. It may take several layers of paint to to this. Don’t try to fill in deep scratches with one coat. Solid colors are easy. Metallcs, no so much.
Shine on (you crazy diamonds)
