Sony GTK-XB60 Basic Information page 2

In addition, similar to how forgetting someone's phone number means that you cannot call him
or her, if the pairing information stored by your Bluetooth device is deleted (e.g. device reset),
you will be unable to connect it to the device you previously registered.
Should that happen, you will have to pair them again in order for them to be able to connect to
each other. In the same way, when you change your mobile device (e.g. when you buy a new
smartphone), you must create a new pairing between the new device and the headphone or
speaker.
Refer to the following pages for the pairing procedures for Bluetooth devices.

How to pair Bluetooth headphones with a source device.

How to pair a Bluetooth speaker with a source device.