These are Rectify Series drop-in speaker systems for Bachmann Soundvalue S2/S4 locomotives.
 
Two versions available:
 
The BAHO-S2S4-RC1 replaces the original full-length speaker and mounts with double-sided mounting tape and features a hole for the factory PCB mounting screw. This can be used with the stock Soundtraxx decoder. Some of the later runs moved the same decoder forward (using a smaller speaker) so if you have that version, simply move the decoder toward the rear like the original models. No modifications are needed to replace the factory speaker.
 
The BAHO-S24S-RC1 is a shorter version designed to work with the Tsunami2 TSU-BH1 decoder. The shortened length clears the CurrentKeeper socket on the PCB. It also mounts with double-sided mounting tape and features a hole for the factory PCB mounting screw. No modifications are needed.
 
The speakers come fully assembled and tested.
 
VIDEO: https://youtu.be/zBci-eZz4SA