Installation Notebook:
Sound Installed in HO Scale Atlas RS3
The Soundtraxx’ Atlas light board type decoder is used.
The weight had about 0.3 inch removed with a belt sander. Speaker mounting holes were enlarged to fit the Atlas mounting screws.

Two 1/4-inch holes were drilled through the weight beneath the speaker cone for the sound pressure to escape toward the truck. The speaker is sealed to the weight with adhesive, making sure no adhesive gets on the cone.
When the shell is installed, an infinite port enclosure is created. Note: the sound is virtually inaudible until the shell is installed.