Has anyone ever put sound decoders in a bowser Decapod? The tender has no floor.
You will need to build a soundbox for it, .030" or thicker styrene is a good choice.
That could be a blessing in disguise. That means you have more flexibitily mounting the speaker. Is the tender body plastic or metal?
I just found a monster speaker that I’ve been experimenting with. I made a stand alone custom sound box for it out of styrene, but for comparision built a sound box directly into an Athearn dummy F7B unit. The built in one is much bigger and hence produces much better lower frequency sounds.