How to protect the wood finish of speakers.

curtains on windows work pretty good

Photon46 is correct. Two options, curtains, or a UV filter film (made by 3M) installed on your windows. Also, periodically, switch your left with your right speaker around to get an even tan.

Try to protect the grills too.Also the sun may shine through the grill,damaging the drivers.

I just had my west facing windows covered with window tinting. It will achieve 3 major improvements to a room. First 98% of the uv light will be blocked-the most critical portion of light that causes fading. Second it will block 50-85% of the infrared wave length( infrared accounts for 50% of light's thermal energy). Third it will improve the accoustic's of the glass which is often a source of reflected sound perceived as bright,and fatiguing. 3-M is a good brand but there is a German brand Huber that is the best if you want your window protected but no tinting. This brand is used by museums that want maximum light but blockade of the uv and infared. It uses 3 layers of plastic each tuned to a different wavelength. It has no metallic sheen to it like 3-M. It is the best.
David Pritchard

Yes, as mentioned above theres little that can be done to totally stop yellowing of Maple, or any veneer for that matter. Some alter colour more than others, wether exposed to uv light or not. Wenge for example, a timber which is known to be dark brown, with almost black streaks, is in fact blonde when first cut, the exposure to light changes the colour to the dark we know. So your Maple will yellow over time regardless. The amount of yellowing will be affected by several aspects, ie exposure to light, and the anti-yellowing properties of the lacquer used. Some are better than others in this regard, and i'm not sure what Totem use, but most likely either a 2 pack Acid Cat, or a 2 pack PU, which is better if good quality catalysts are used. The thought that they may still be using pre-cat is possible as it is low cost, and will change colour.

So there is unfortunately no magic protection that can be applied to stop this. All modern coatings are designed to be maintenance free, application of waxes or oils is not necessary, and will build up over time and look cloudy.

The best advice is to cover them when not in use, and at all cost avoid direct sunlight!

Enjoy them above all though, they are tools to do a job at the end of the day..

Regards,
PS