A solid sound and decent battery might be the first things you look for in a Bluetooth speaker, but if you plan on using it when you're out and about, the most important factor might just be its durability.

Ideally, any parts like buttons or switches should be firmly embedded in the loudspeakers, rather than sticking out, so that there's no danger of them breaking off, is the advice of product testers at inspection agency Tuev Sued.

Also, when picking a model, look for a speaker that has rubber guards or flaps covering the ports. This will protect your charging port and any other connections from being clogged up with dirt or damaged by water.

Most speakers can play between 6 and 10 hours of music but if you are on the road for longer, then you may want to make sure your loudspeaker has a USB port that lets you charge from a power bank.

Normally, this information is written directly on the connector, and you'll see for example "Input 5V/max. 1A". That's where you can plug in a power bank with the appropriate voltage.

It's classic advice but make sure to read the operating instructions first, just to be on the safe side.

 - dpa