Some designers can tailor the crossovers to lessen/eliminate sibilance along with careful driver selection. Others, like Daniel Emonts of Revival Audio uses his own proprietary formula to coat his dome tweeters to help deal with it as well. Lots of ways to skin this cat's hiss but in the end, there's really no reason nowadays to have to deal with it.
If one is experiencing a surfeit of sibilance beyond what's normal on a certain recording, then it may lie in the recording/mastering and you're stuck with it. If that's not it, then cabling and noise pollution can be the culprit.
I can only remember one speaker I had that exhibited more sibilance than what normally occurs and for the life of me, I can't remember the brand and only that it didn't last long before I moved on.
All the best,
Nonoise