Considering that they're some of the most manhandled components of a pro audio system, it's no surprise that speakers are designed and built tough. They can stand up to a lot of abuse, but even they have their limits - and that's where speaker cases, gig bags and covers come in. They'll make your cabinets easier to stack in a truck full of gear, not to mention easier to pick up and transport, and well-protected when they're sitting in storage between uses. Cases, gig bags and covers will also go a long way to preserve the appearance of your speakers so your setup will always look professional, and even defend them from the elements so they can work in any weather.
There's no rocket science behind picking out speaker cases and bags. It's just a matter of matching the features you need in the case styles you want with the speakers you're buying them for - either by choosing speaker-specific enclosures or general-purpose ones that have the right dimensions. For a really big cabinet, a case with built-in casters like the Gator G-TOUR SPKR-215 Speaker Transporter can be a real lifesaver. When the speakers are smaller, you'll be all set with a pick-up-and-go solution such as the JBL EON15 Deluxe PA Speaker Carrying Bag (3rd Generation), which gets its portability from its light weight and lots of carrying straps and handles.
Of course, transportation is only part of owning speakers. When it comes to storage and in-use protection, your best bet will probably be covers rather than cases. Many of these, including the QSC K12 Outdoor Cover and the Electro-Voice Cover for ELX118 Speaker, are custom-fitted to perfectly match certain models of speaker cabinet. And there are even some covers - the JBL EON15 Speaker Cover (3rd Generation), for example - that come complete with an unzippable front panel, which allows you to leave the cover on the speaker full-time: just open it up when the show is ready to start, and let the audience enjoy.
With as many speaker cases, gig bags and covers as there are to choose from, it's safe to say that you can find something for just about any pro audio system. In storage, on the road or onstage - wherever your speakers need protecting, a good collection of enclosures will make sure you're prepared to handle it. And if there's one thing that any audio professional knows, it's that being prepared is about 90% of the recipe for success.