SurroundTraxx: How It Works

SurroundTraxx stores a roster of locomotive sound settings in a database called the Roundhouse. This is an extensive library that you can set up and adjust to match your model's prototype or to sound like your favorite horn or whistle, prime mover, or exhaust chuff. Each engine can have a unique sound profile!

Once you have entered your locomotive roster into the Roundhouse, you can use the internal “dispatcher,” which allows up to six trains to be in operation at one time. SurroundTraxx can be set up to pick the first six locomotives detected, or you can assign these slots to the locomotives of your choice (perfect to make sure your favorite engine never goes silent!). These locomotive “slots” used by the dispatcher are called Auto Dispatch (AD) slots.

After the trains have been dispatched, the block detector will identify the trains' locations, the speed they are traveling, and the point where they will cross into new blocks. SurroundTraxx uses this information to move the appropriate sounds to the corresponding sound channel (six are available) on the SurroundTraxx unit. SurroundTraxx uses an intelligent cross-fade algorithm that factors in train speed, direction, and distance between speakers. This reproduces the sound in such a way that it appears as though it is being emitted directly from the train rather than the speakers on the layout.

The multiple trains running on the layout can all be in the same area or spread throughout the layout. SurroundTraxx will still dispatch and reproduce their respective sounds in full audio richness. It truly is a complete layout sound system with multiple trains and operating sessions in mind!

Note: If using single-channel mode (default), the sound will feed through all six channels at once and does not follow the train. In order to set up the other modes of operation, you must use Digitrax® transponding block detection on your layout.

SurroundTraxx includes the following items:

  • SurroundTraxx system
  • 5V power supply
  • Network cable
  • Speaker harness for six sound channel outputs (6' sections of each)
  • Quick Start Guide
  • Owner’s Manual CD
  • Customer registration card

Additional items needed for operation:

  • Up to six 8-ohm speakers
  • Optional subwoofer
  • The appropriate DCC mobile decoders equipped with transponding or a TL-1 transponder
  • Digitrax DCC Command Station, cabs and power boosters
  • Additional speaker wire if using a distance greater than 6’
  • Digitrax BDL-168 (or older BDL-162) Block Detectors
  • Digitrax RX-4s (eight total)



SurroundTraxx can accommodate up to six speakers per system, or five speakers and a subwoofer. The size and quality of these speakers are up to you and should be based on your layout design. However, we have a few helpful guidelines and requirements to help you achieve the best audio experience.

The speakers must be passive 8-ohm speakers rated between 5 and 25 watts. We recommend choosing speakers with a frequency response ranging from 80 to 16,000 hertz. If you plan to use a subwoofer, speakers with a frequency response of 150 to 16,000 hertz are sufficient, as the subwoofer will provide the bass.

Mobile Decoders and Transponders

SurroundTraxx is designed to operate on DCC layouts. In order to operate SurroundTraxx in transponding mode (multiple trains in multiple sound zones), you must have DCC mobile decoders with transponding installed in your locomotives. Alternatively, you may add separate transponders to any DCC mobile decoder that is already installed. To emphasize this point, when using SurroundTraxx to its full capabilities, you must either use decoders that come equipped with Digitrax transponding or purchase a TL-1 transponder to add to the locomotive. Sound decoders can also be installed in the locomotive, but are not required. Locomotives that aren’t equipped with transponders will still run on the layout, but will not be able to be dispatched or produce any sound through your SurroundTraxx system.

DCC Command Station, Cabs and Boosters

SurroundTraxx requires a Digitrax LocoNet-equipped command station in order to operate in any of its modes. For now, SurroundTraxx cannot be used with other systems.

Additional Speaker Wire

SurroundTraxx comes with 6’ sections of speaker wire for each sound channel output. If your layout requires more wire, you can add your own wire to the end of the wire harness included with your SurroundTraxx unit.

BDL-168 Block Detectors

To achieve the effect of sound traveling through your layout with your train, you must use Digitrax bi-directional block detectors known as BDL-168s. One BDL-168 will operate eight different blocks. Therefore, if your layout has more than eight blocks, you will need more than one BDL-168.

Digitrax RX-4s

Digitrax RX-4s are required in conjunction with BDL-168s, and you must have one for each block on your layout. For example, if you have 10 blocks you, will need 10 RX-4s for your layout.