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Athearn SD70Ace with Sound: Another Fiasco!

Athearn Locos

Here is another example of a supposedly quality locomotive with sound that is being shipped with a major defect. It amazes us how many so called top-of-the-line offerings are being shipped with glaring defects.

This problem is by no means exclusive to Athearn, we have seen this across the board. To some extent we believe the US manufacturers have little control of what their Asian vendors actually do but after years of this continuing to occur I am not inclined to let them off the hook.

The irony is that all other aspects of the loco like detail, finish and smooth running appear excellent! It would seem that the only remedy for the manufacturers to resolve this is to send a "well informed" inspector to the Asian factories to inspect and accept the final products before they hit the water!

The report that follows is from Steve at Ulrich models. Thanks Steve for giving model railroaders a "heads up".

Revised: November 16, 2010
Author: Steve Gill

The Athearn SD70Ace sound model has low volume and does not achieve 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.

Completed Enclosure Modification

Outside View - SD70ACe Factory Enclosure Sound

Outside View - SD70ACe Factory Enclosure Sound

Inside View - SD70ACe Factory Enclosure Sound

Inside View - SD70ACe Factory 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

The factory setting for the horn is 225 it can be set a little louder by changing CV229 to

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

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.

Hi Tony,

I just received a Genesis SD70 Ace and did the speaker enclosure mod suggested by Steve Gill in the Tony’s Tips labelled: Athearn SD70Ace with Sound: Another Fiasco!

Congratulations to you and Steve for a great article. I have an additional suggestion: When you have the speaker removed from the enclosure (2 screws) and before glueing the piece of styrene in the hole, remove the two screws that hold the two halves of the enclosure together. Coat the metal to metal mating surfaces with a thin film of Silastic (or other goo) and re-screw the two halves together. This further ensures an airtight chamber.

I did this as well as the suggested fix and, when it was all back together again, the sound was so loud I have to run it at quarter volume.

Best regards,
Erik B.


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