I was not sure what to expect after the SD45s from Atlas regarding speaker location, etc.
I have received my B23-7 and U23B silver engines. The speaker is not in the fuel tank, like earlier Atlas Silver engines. It is mounted under the circuit board at the rear. The speaker wires plug into a connector on the board. There is another small, white plug toward the front which I assume is an E24 decoder connection - it's way too small to be a Next18. Unfortunately, there is no info on the parts diagram included in the box that clarifies this.