Class 37 by Bachmann

Items required: Zimo MS440D or ESU 58429 LokSound 5 21-MTC decoder DCCSound premium speakers for Bachmann Class 37 model.

Microscale Micro Kristal Klear glue & applicator

Note: The speakers only suit the Class 37 with new tooling, released from 2022.

This installation features a Zimo MS series decoder, though it works equally well with an ESU LokSound 5 decoder.

The body is removed from the chassis via 8 screws on the underside of the chassis. Remove the 8 screws then gently pull the body off from the chassis. There are four wire looms connecting the body to the main motherboard on the chassis; these need to be unplugged prior to fully removing the body.

Next, unscrew the motherboard from the chassis. Save all screws in a safe place.

Remove the small 11x15mm speaker from on top of the motherboard. It will be replaced by a much larger speaker that sits in the chassis, underneath the motherboard.

Also, remove the round speaker and its black plastic frame from underneath the motherboard. The round speaker will be reused, and housed in a new enclosure to enhance volume and bass.

The new speakers sit under the motherboard, wired in parallel back to the 2 pin connector.

The red dot on the round speaker is wired to the LHS contact on the 13x18mm speaker driver, such that they may pump in phase for optimal volume and sound quality.

Prior to soldering the wires to the round speaker, the wires are first passed through a small (1.5 mm) hole in the enclosure. The round speaker driver will then be placed in its enclosure.

Once soldered, the round speaker is placed inside its new enclosure and a small bead of MicroScale Micro Kristal Klear around the rim seals the speaker to the enclosure. Also be sure to apply some glue to the small hole where the speaker wires pass through the enclosure; it needs to be air-tight.

Both speakers are then placed in the chassis as shown below. The speaker drivers are 8 ohm each, which together presents as 4 ohms at the decoder / 2 pin connection.

The motherboard is then refitted to the chassis, along with the body back onto the chassis having plugged in the 4 looms previously disconnected.

The final step is to reduce the volume level of your decoder as the new speakers will be considerably louder!