How to find out if the speakers are 20khz compatible? + need to be a native speaker?

[fab10]

Can someone recomment a cheap small speaker which ist 20khz compatible and which is mobile and easy to transport. So that I can use it where-ever I sleep and work?

I am currently using Edifier R12U- they are small, cheap, look really sleek, rated 30Hz to 20kHz and pass the speaker test with no cracking. However, it’s two speakers (which is better for subs anyways) and it needs to get power from a phone charger or a USB port, I’m not sure if that would work for you.