How To Clean Piano Black Speaker Finish?

They're speakers but its really automotive paint so clean the same way you would a car you wanted to concours. Only difference is the car would be a lot bigger, and dirtier. But same technique.

Fold your soft microfiber cloth. Clean in straight lines. Do not go in circles. This way, if you do make a scratch, it will be visible from one angle only. Circles you can see from everywhere. Which I'm sure you have. The halo of swirls that moves around as you go. So don't be That Guy.

You can spray detailer like Griot's Speed Shine on the speaker or on the cloth. Or just dampen with water. Speakers aren't dirty so you'll be fine.

Whatever you do, fold that cloth, and use very little pressure, and clean with a rolling motion that keeps lifting the leading edge of the cloth pulling the dust and dirt up and away from the surface. Make your first pass like this. Then once you have removed all the dust like this if there are finger prints or whatever you can go back and use a little more detailer to get those. When cleaning those you can go back and forth if you are careful but never anything but straight lines until you are sure the surface is clean.

Now if you do get a scratch, well if its not too deep you can remove it. First use Griot's Paint Cleaning Clay. (Which you can do anyway, and will be floored how good your speakers will gleam if you do.) Then use Machine 4 Polish, a very fine polish. Finally, not necessary because indoors but Best of Show Wax will bring out depth you never knew was there.

Overkill, especially in a dark listening room. Then again it is piano black. Do all this and your speakers won't just disappear in the sense of throwing a sound stage. They will disappear because they have such a mirror finish you won't even see the speakers but only the reflection in them.

Miller gave good advice. I just use a premium detailer spray like Meguiars or Mothers and I get a very satisfying shine on my piano black von Schweikerts

+1 Millercarbon.  Griots speed shine is awesome stuff!  I use that on my car, after 3 days of wet sanding, buffing, and waxing of course ;) Primo stuff.

But yeah, treat it like a cars finish.  Pretty much exactly as Millercarbon describes.  Once you have the finish dialed in Speed Shine is all you need.  I would recommend spraying it on your microfiber towel, not directly on the speakers as to not get overspray on the drivers.  I’ll only use damp microfibers on the fronts next to the drivers.  I’ll also use a soft paintbrush to dust the my mid bass drivers (particularly on the surrounds).

I sprayed mine with furniture Pledge and fingerprints show much less.  I suspect anything containing light wax can do the same.

Millercarbo I will certainly not let you near any of my Porsches. Stereo 5 you are going a fabulous job if you have not got swirl marks so far.
Instead of using water you could use an instant detailer like Meguires 34
which has a little wax in it and will remove finger prints. If you polish the surface do not wipe in straight lines! Polish in brisk circles never staying in any one place. Here is the reason. If you wipe in straight lines the swirl marks you generate will all be visible from one angle and from that angle the finish will look like absolute crap with hundreds of straight line marks. If you wipe briskly in circles constantly moving, the marks you create depending on the light will only have very short segments visible at any one angle in a very random pattern which is not near as noticeable as all the marks going one way. If you do develop swirl marks Menzerna 3800
will take them out safely with a clean microfiber cloth and polish the surface at the same time. Autogeeks carries Menzerna which is the German version of Meguires. The difference between a scratch and a swirl mark is the swirl mark you can not feel but the scratch will catch the edge of your finger nail. If you were to get a scratch, leave it alone. The paint on this stuff is very thin and it would be easy to rub right through it then you have a real mess. It would have to be filled first then flatten out which is a whole other process
Millercarbon, Paint cleaning clay is only for use on the most contaminated surfaces before rubbing the car out. I never use it on my cars because they never get that contaminated because nothing ever sticks to them 
(CQ UK 3.0) Clay is a swirl mark generator. Mequires #4 will take the paint right off his speaker. He would use Meguire's 205 (they changed their numbering system just to confuse everyone.)