An update speaker kit is available for the TX16s. Please contact your favorite RadioMaster dealer to order.
To install the speaker remove the rear case, fit the sponge in the speaker cavity shown in the picture below and use the 3 supplied screws to fit the speaker with the black side facing out.
Disconnect the front speaker from the main board as shown below and connect the rear case speaker then connect the front speaker to the second connector of the rear case speaker. Both speakers are now connected and working together.