This is a Rectify Series drop-in speaker system for various Walthers Proto and Mainline locomotives using the 28mm round speaker encased within two weight halves held together by screws. No modifications are required to replace the factory speaker.
 
The speaker is a press-fit in the stock cavity, firing down through the frame. The loose half of the weight is discarded.
 
If you have a factory sound model, you can reuse the 2pin speaker harness. If you need a 2pin harness, most of these Walthers models use the small, SH1.0 JST harness: https://www.scalesoundsystems.com/product-page/factory-pcb-speaker-harness-small
 
Originally available in two different heights from the flat-side to the curve’s apex, the 18mmH version has been discontinued, leaving the 16mmH version to be truly universal, fitting all models.
 
I have installed these in Mainline Phase II GP9s and Proto U30Bs, GP20s, SD9s and some GP30s (GP30s with the thick ridge behind the cab should use the GP30 speaker).
 
The speaker comes fully assembled and tested.
 
Dimensions are: 16mmH x 15mmW x 28mmDia
 
VIDEOS: 
Proto GP30 https://youtu.be/RnyLdApHPCM
Mainline GP9 https://youtu.be/E2h9RBZvyJE