Athearn SD70ACe Sound Improvement Technical ... - Ulrich Models

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Athearn SD70ACe Sound Improvement Technical Note
Revised: November 16, 2010
Author: Steve Gill
The Athearn SD70Ace sound model has low volume and does not acheive its full bass
potential as shipped from the factory.
The sound fidelity issue is due to an improperly designed speaker enclosure. The speaker
enclosure is open on the inside where the driveline tunnel goes through. I assume this was
done to allow clearance for the driveshaft around tight radius turns. However, there is
ample clearance for the drive line even when the opening is closed.
When a speaker cone is open on both sides to the same area, positive sound waves from
the front of the cone are canceled by negative sound waves from the backside of the cone.
This is why it is important to isolate one side of the cone from the other with a baffle of
some type.
Fortunately this design flaw is easily corrected; that is, if you consider having to remove and
reinstall the shell on a supposedly ready-to-run Genesis engine an easy thing to do.
Outside View
Completed Enclosure Modification
Inside View
SD70ACe Factory Enclosure Sound
SD70ACe Modified Enclosure Sound
Sound samples are recorded at factory settings and identical recording environment. Click
on the links to hear samples. The change is even more impressive when listening to the real
thing.
The factory setting for the horn is 225 it can be set a little louder by changing CV229 to
255.
Remove the shell from the SD70ACe.
There are two screws in the frame located near the fuel tank ends. One secures the front
part of the frame to the shell and one is for the rear section of the frame. Remove both
screws.
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Remove the front and rear coupler boxes. Slip the shell off but be careful to watch for the
four wire detail parts (sanders) that extend from the body down past each truck side. The
wires also need to be watched especially close on reassembly. The rat’s nest of light bulb
wires between the decoder and the shell also need watching.
Remove the speaker enclosure from the frame. It is held by one screw.
Remove the speaker from the enclosure; it is held in by two screws.
Cut a piece of .020 sheet styrene to fit over the open area.
Apply Goop, E4000 or some other silicon adhesive to the cut styrene piece and place it over
the opening in the speaker enclosure. Hold it flush long enough to set.
Once the cover for the opening is installed and the adhesive has set, reinstall the speaker
into the enclosure. We recommend applying a 1” Soundtraxx speaker gasket to the speaker
for an airtight fit.
Install the enclosure back into the frame and reassemble the engine using great care.
Note: The parts for the enclosure upgrade will be included in our Athearn LED and sound
upgrade kit coming out soon.
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