Changing a speaker color

Two points to weigh in on IMO:

- Are you talking about a “usual” satin or flat black refinishing or a gloss black refinishing ? I would not try the latter requiring multi-coat applications, sanding, and fine polishing as a DIY project.

- Without prejudice to the above, a bespoke non-OEM new radical refinishing color ; ( and especially in a DIY effort even with your advanced woodworking skills) will kill its successor owner appeal pool , and especially kill its FMV resale value should you wish to ever sell them later,

No matter what color you choose, I would leave the job to a reputable auto body shop. They will cost more, but they'll do a far better job than you could, and as @akg_ca  said, it will be better for your resale value if you decide to sell.

I've never painted speakers, but back in '02 I was working in a composite shop and I brought in some wooden window shutters, sanded off the old finish, shot them with two coats of USAirways blue and then a coat of clear and they are still holding a gloss shine to this day, so I do not see why it could not be done with wooden speaker cabinets.  . 

Are the speaker cabinets actually made of wood?  I've sanded some stuff before that wasn't wood, and some of it does some goofy stuff after the paint comes off.  I have no idea what it will take to get that gloss white to start coming off . . . maybe just start with a small inconspicuous area with some 80 grit (or even 100 grit) and see how it goes before you start sanding a large area.   

If the original paint is in good condition, it does not need to be stripped, only sanded to a matte finish. After removing all sanding dust, the original paint should function perfectly fine as a primer, assuming it had an automotive-grade finish to begin with. 

Remove the drivers and binding post plates prior to any of this of course, and mask off the holes. 

There is no way to achieve a true piano grade finish without a very controlled HVLP spray system/gun. I recommend that be handled by a professional, otherwise you’re likely to end up with runs, orange peel effect, or trapped debris.  
 

@akg_ca you underestimate the talent of many home enthusiasts.  While I am not a painter, there are many areas where I do the work myself because my work is better than the pros.  

I don't know about @jeff7630 but I wouldn't assume he is talentless.

Second, used speakers sell at half of new anyway.  if the paint isn't perfect, you still can get 7/16 of new. Don't pay 40% of new for a pro paint job.

And changing from an unusual color to black, probably improves resale.

Jerry

What’s 7/16, a new grading system ? 

Depending on what color you like, I've sometimes considered using a vinyl wrap instead.  Removable. 

I would also recommend doing the vinyl wrap. Similar to what they do with vehicles.

It is very durable, has no problem being applied to a high gloss surface and can be removed if circumstances change.

Added bonus is that you can literally any surface treatment you can imagine. All you need is a digital file.

Never tried vinyl, but it sounds plausible.

In 1990, I took my raw MDF cabinets to a classic car painter. He sanded, filled, primed, sanded some more, and applied coats of black and clear lacquer. Aside from a few inevitable minor dings, the paint job looks unchanged in 30+ years, where they’ve resided in the living room of my large family. No cracks, peeling, wrinkles, crinkles, bubbles, runs, or other defects, and has even proven to be quite resilient to liquids.

wrap it in linex it seems to help to kill resonance even more.

I'm actually thinking about linex as well on my Aerial speakers 20+ years old vintage. Their look will definitely benefit and since it's not a vehicle not much disturbance the finish will face cuz it ain't a vehicle. 

I'm no painter so I would find a local auto body guy to do it for me.  I'd just remove the drivers, speaker terminals, etc. and drop them off.