Very practical but conspicuously unappealing to the eye. The garbage bags are the most economical in case of rain. Using those as sun-shields will only add to the heat buildup around the speaker. Some speakers may cope others may not!
I didnt find them "conspicuously unappealing to the eye" at all, just the opposite because they were craftfully constructed.. Tyvek, may not be water proof but its very water resistant and the material somewhat breathes. Hence, releasing more heat than that big black heat absorbing hefty bag.
This was at 12,000 ft. So there was NO problem with heat. Weather was perfect with highs in the low 70s. But thunderstorms popup so quick up there its best to keep the covers on even if there is not a cloud in the sky.(And it did rain later that day) Anyway they match his suit.