Sennheiser MX W1 Instruction Manual page 12

Associating a second pair of earphones to the transmitter
With one transmitter you can associate up to two pairs of
earphones. If you want to use another pair of earphones, you
have to pair your transmitter and the new earphones:
Switch the new
Switch the transmitter and the already paired earphones on
(see page 14).
ON
Switch the transmitter off (see page 14).
ON
Press and hold the operation/pairing button of the
earphones until the LEDs flash rapidly.
ON
10
earphones off (see page 14).
ON
4s
OFF
OFF
OFF
OFF
ON
7s
new