Installation Notebook:
Sound Installed in a Kato HO SD70MAC
by Mr. DCC
This SoundTraxx decoder installation is fairly straight forward. The speaker needs to be angled to clear the light pipe for the rear bulb.
SoundTraxx does some things in their LC series decoders which make the rear bulb glow occasionally if you use LEDs. While I prefer LEDs, this loco had room enough to abandon the LEDs and use 14 volt bulbs! If you choose to keep the LEDs, add the extra parts to stop the glow.
I am frequently asked for details on my “semi-infinite baffle” design, so I charted out the air flow on the lower photo. Look at the magenta arrows and imagine that the shell is in place. The speaker is close enough in width to the shell that the positive pressure (noted by a +; created when the speaker cone moves away from the magnet) can only flow out through the rear truck. A divider or baffle is created with styrene (white was used for clarity) which channels the negative pressure (-) above the motor and decoder and forces it to exit around the front truck.
Parts #8 and #9 shown in magenta below are only needed if you want to eliminate the glow in the "Off" LED.
FRONT VIEW - Wiring view from the front of the engine. These components are installed external to the decoder and are needed only if you want to eliminate the "glow" in the OFF LED.
REAR
VIEW - Wiring for the Front LED. Parts in magena are only needed to
eliminate the glow in the off LED.
The Advantages installing sound using this approach:
- No speaker “box” is needed - saving money.
- The sound is better than it would be with an enclosure
- Less room is needed for the installation.
Be aware that the sound will be virtually inaudible until the shell
is in place.