I am open to correction here, but I think that people either used custom LokSound decoders or MM 121 Class decoders for the original run of 141's.
There were other options, too, and Bachmann even released their own non-sound decoder, but the previous two seem more common.
The new 141 sound decoders should work, if you install a speaker, as the original batch had no factory speakers. They just won't be covered under warranty.
EDIT:
This is the thread I was thinking of on the original run:
https://irishrailwaymodeller.com/topic/1270-141181-class-and-best-bachmann-decoder
The original Bachmann non-sound decoder was item 36-554.