Wood finishing 101: there are two types of wood finishes. Those that seal the pores and require no ongoing maintenance (most synthetic and some natural finishes, e.g. lacquer, epoxy, polyurethane, etc), and those where the pores are unsealed, will dry out, and require repeat application (oiled finishes).
Nearly all wooden finishes require no ongoing maintenance if kept indoors. The people who make and sell speakers know their customers are audiophiles and not woodworkers. So the most common finishes are polyurethane (if a matt finish is desired) or lacquer for gloss finishes.
Real oiled wood finish are always matt, never satin or gloss. IMO they look more natural and beautiful. The disadvantage is requirement for ongoing maintenance (re-oiling every few years), and susceptibility to stains if not promptly wiped off. Because they are more fragile, they tend not to be used on furniture or speakers. They are used on chopping boards because you don't want to be ingesting polyurethane. For this reason, chopping boards need to be periodically oiled with a food-safe oil. At a pinch, cooking oil will do but it does not last very long. The curing oils (Tung oil, linseed oil) are preferable, but this means your board will be out of action for a week.
Do not apply one type of finish on top of another because unpredictable results might follow. If a woodworker is asked to refinish furniture, the old finish is sanded off before a new finish is applied. Oils work by penetrating the wood and then curing with exposure to Oxygen. The reaction is exothermic (generates heat) which is why oily rags can catch fire if not disposed of correctly. Do NOT throw an oily rag into the trash with your wood shavings and sawdust. Rinse it off and put it on a clothesline to dry for a couple of days. Then you can discard it.
My recommendation for your speaker: chances are, it is polyurethane. It only needs cleaning, it does not need maintenance. Avoid solvents because it dissolves the finish. Use mild soapy water and wash it off.
If it is a high gloss finish like lacquer, absolutely nothing needs to be done. If you want to make it shine, you can use automotive wax or synthetic wax (wipe it down first to avoid scratches). The sole exception is if it is French polished shellac, but chances are it isn't (this is a very labour intensive process, so it is expensive and any furniture piece with French polished shellac will boast what it is). French polished shellac is maintenance free, unless used on high traffic furniture like dining tables. So it needs periodic application of shellac and more polishing. You will typically find it more on jewellery boxes or cigar boxes and not on speakers, unless you own a luxury speaker.
Example of an oiled finish, in this case Tung Oil. Note the deep colour and natural appearance of the wood.
This speaker is likely finished in high gloss polyurethane. It will require no maintenance. I hate all gloss finishes on wood (and in fact all polyurethane finishes). I rarely use them on my own woodworking projects, but then I make stuff for my own use so I know how to maintain them. I do use polyurethane
These March Sointuva's are most likely satin polyurethane. I can tell from the plasticky finish. No maintenance required unless the finish is damaged, resists (but does not reject) stains, very durable, easily repairable - provided the same type of polyurethane is used.
Outdoor wok burner. The one in the foreground has no finish, the one in the background is finished in satin polyurethane. I chose polyurethane because this piece is going to lead a tough life. It will be outdoors in a shaded area, subject to heat and food spills and all sorts of abuse.
irrelevant to the current discussion -- back in the old days it was not uncommon for commercial (i.e., professionally assembled) loudspeakers to be offered in an unfinished option. The primary driver was economic (i.e., a cheaper option for a given loudspeaker), but the secondary driver was for custom finishes.
A few such floatin' around here.
, but, empirically, it is pretty good.
. We used it as a printer stand, but it had gotten quite wobbly. My son built us a nice bespoke printer table. I pulled the old table out of service and put it in the basement. After "discovering" the Watco product (used initially to rejuvenate an antique humidor table that we have), I decided to rehab the aforementioned mystery table for our daughter's new house. I repaired the wobbly legs and used the Watco. The results were transformative.
so in the meantime I put it up at the top of the stairs to my hifi room. At this point, it looks too nice to be in the basement. 
