This is a Rectify Series drop-in speaker system for Atlas Classic & early-run Master GP38/40 locomotives. The speaker is a beautiful press-fit between the rear weight and motor mount. No frame/weight/shell modifications are needed! The factory PCB will need to be removed. Decoder installation can by simplified with a Nix Trainz Decoder Buddy and a 21-pin decoder, or you can hard-wire a decoder in. Board-style decoders will not work (Soundtraxx PNP, LokSound Direct), as they take up all of the space between the two weights and leave no room for the speaker.
 
The speaker comes fully assembled and tested.