How to prevent unauthorized access to bluetooth speakers?

Seems the Harman Kardon Soundsticks Wireless Speaker System automatically enters pairing mode and becomes discoverable by other devices when turned on, and has no discrete Bluetooth button. As such I don't see any way to limit access to them while they are turned on, and for a product being sold at at such a premium price this seems to be an extremely surprising omission. (Strangely, no widespread complaints about this either as far as I can see.)

As for alternatives, we don't do product recommendations here so just look for a set of speakers that has a physical Bluetooth pairing button. There are lots available.