The manual indicates the speaker cavity will accept 2 11mm X 15mm sugar cube speakers or 1 16mm X 35mm speaker. I seem to recall the rear weight is hollow underneath. You need to remove the weight to see this cavity.
Mark.
¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ
The TCS site shows an installation of a WoWSound with oval speaker in an SD40-2 (not SD40T-2). In their case they are replacing the main board with a TCS board.
For that model, the 2-piece frame has a void over the rear truck that can accommodate a speaker. I would prefer 1-2 micro speakers to an oval, but that's me. Two of the photos show the speaker space, facing down over the rear truck. In one of the last photos, you can see where the (blue) speaker wires come out.
https://tcsdcc.com/installation/ho-scale/1479
Paul
Modeling HO with a transition era UP bent
Got a ST SD40T-2 DCC ready. Has anyone done an install of a decoder and speaker? I know the Decoder just pops into the plug, but where does the speaker go?
(My Model Railroad, My Rules)
These are the opinions of an under 35 , from the east end of, and modeling, the same section of the Wheeling and Lake Erie railway. As well as a freelanced road (Austinville and Dynamite City railroad).