This round speaker fits many of the Atlas locos that were designed for sound – they usually use a pair!
If you are using two of these speakers together, they need to be in series and in phase. What means is that the red wire on one speaker connects to the black wire on the other speaker – yes you can shorten them. Make sure this connection is insulated, we recommend 1/16 inch shrink tubing for the task. Then you connect the remaining red and black wires to the decoder.