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A Sound Improvement
By Steve Bourdon,

A Sound Improvement
Enhance the Sound in a Rapido Trains FPA-4

Many modellers would agree that a sound-equipped locomotive is much more pleasing to operate than the alternative. That is probably why most of us reserve or purchase locomotives having factory installed DCC with sound.

However, although manufacturers may strive to produce high quality models, factory-equipped DCC and sound doesn’t always mean you are getting the best sound.

A case in point is the recently released Rapido Trains FPA-4 with factory-equipped ESU DCC and sound.  I must admit that I was favourably impressed with the sound and performance of this model when I first operated it on my model railway.  However, after I attended an ESU Loksound workshop in Scranton, PA., I learned about how to make a simple improvement in the sound produced by this model.

At that conference, one of the attendees, Roger Eicher, asked if I had purchased any of the Rapido Trains FPA-4 locomotives with DCC/sound, to which I confessed that I had.  After I told him how happy I was with my model, he indicated that he improved the sound simply by changing out the OEM speaker and installing an ESU Loksound 28mm speaker (PN 50333). Since the decoder in the Rapido FPA-4 is an ESU product, the 4-ohm ESU Loksound speaker is compatible.

After Roger completed his installation, he turned on the sound and blew the windows out of his basement! (His words.) Of course he was exaggerating, but after he explained how easy it was to do the modification and the impressive results, I thought I’d give it a try. 

Compare the original speaker with the ESU Loksound 28mm speaker assembly (PN 50333).


The first step is to remove the shell.  The instructions in the manual state that all you need to do is to remove the couplers, and then wiggle the shell off the chassis. It’s that easy, so says Rapido.

Well, folks, it ain’t that easy. They forgot to mention one little detail. The side railings that are located halfway down both sides of the body are attached to the chassis at the bottom. Removing them is easy, simply by gently pulling them out using tweezers. After you have removed the bottom part of the four railings from the holes in the chassis, as well as the couplers, then you can easily remove the shell.

The next step is to remove the original speaker, which is installed on top of the chassis next to the decoder assembly. The speaker is held in place by a bracket that is screwed into the chassis.  Remove the two screws and lift out the assembly. Next, remove the speaker from the assembly, slide the two insulation tubes back and cut the wires from the speaker terminals.   Set aside the speaker assembly for future use in another project.

To prepare the ESU 28mm replacement speaker for installation, first remove it from the baffle. Then solder short wires to the terminals on the speaker.  I used brown 36ga ESU Loksound wire (PN51948). Before placing the speaker back into the sound baffle, cut off the lugs from the side of the baffle and sand the exterior surface until smooth.

Install the speaker in the baffle, with the two speaker wires exiting from one of the pairs of slots on the side. After the speaker and wires are in place, seal around the top edge and in the three sets of speaker wire slots---including the slots where the speaker wires exit.  I applied clear silicon sealant using a toothpick to seal the speaker in the baffle.  Allow the sealant to dry before installing the speaker on the chassis.

To mount the speaker over the rear truck on the chassis, you will need to build and install a pair of shims. These shims will support the speaker above the rear bolster, as well as leaving plenty of room for the pick up wires and the wires running from the back-up light to the decoder. You can go ahead with installing the shims while the speaker sealant is drying.

First cut 4 pieces of Evergreen 0.080” x 0.080” styrene strip (Evergreen PN164). Each piece should measure about 1 ¼” in length.

Next, glue together the styrene pieces, one set of two pieces for each side of the chassis, using a liquid plastic cement such as Plastruct Plastic Weld.  NOTE:  The pieces for the engineer’s side where the backup light is located may need to be shortened a little to fit.

After moving any wires out of the way, glue the shims to each side of the chassis.   For this purpose, I used a thin layer of a product called Plasti-Dip (Home Hardware), but silicon sealant or connector coating would also work. (I also use Plasti-Dip as a connector coating.)

After the sealant on the speaker has dried, it is time to install the speaker to the chassis. Simply tuck the pickup and rear light wires out of the way, and glue the speaker assembly to the shims with the speaker wires facing the decoder.  Again, I used a thin layer of the Plasti-Dip for this purpose. It dries in an hour or two depending on temperature and humidity.

After the speaker is solidly in place, then only a few steps remain.  Cut the speaker wires to length and solder them together. Then, slide those two insulation tubes over the solder joints and heat them with your soldering iron until they are melted in place. Finally, tuck the wires down to the top of the chassis where the original speaker had been located.

Below are some photos of the completed project, shown before taping the speaker wires to the chassis.

You may wish to test the chassis with the new speaker to make sure it is working properly. Wear ear plugs!  Test the back-up light as well to ensure it operates, too (Function 12).

Now all you have to do is wiggle the shell back onto the chassis and install your couplers. Just don’t forget to reinstall those side railings!   It’s that easy. 

You may find that your new speaker does come close to rattling the windows in your layout room. I certainly had to lower the volume on mine after testing to ensure it didn’t blast my friends during operating sessions.  

We tested my Rapido FPA-4 with the newly installed speaker next to an FPA-4 with the original speaker. Quality of sound is certainly a subjective issue, but in my view the MLW rumbles that emanate from my locomotive are certainly very rich by comparison.