The Scale Trains SD7/9 simply uses either the SXTH-UNI1 or SXTH-UNI2 speaker with the mounting ears nipped-off. The stock speaker and wire bracket are discarded with the Scale Trains Universal speaker slipping into place. A strip of tape over the top holds everything nicely in place. No modifications are required. See the second set of photos for installation procedures.
 
The speaker comes fully assembled and tested.
 
Dimension: 12.5mmH x 16mmW x 25mm