The Heljan / Hattons OO Beyer Garratt...
Carefully remove centre housing underneath as instructed in the leaflet that comes with the model. Be especially careful not to
pull any of the wiring too hard, as it is quite spaghetti-like inside, and the wires are brittle!
Remove the boiler top to access the speaker area and remove the factory-fit speaker, which is not powerful enough to make it
worth keeping, unless you fancy building a proper enclosure for it.
The Zimo SugarLump will fix into the old speaker's place with a double-sided pad, soldering to the provided contacts, or direct
to the MX645 decoder. A stay-alive capacitor can also be placed inside the boiler - the standard 220uF/25v capacitor is shown
here, but you could easily fit a larger one in - although probably not necessary as the model has good pickups and good weight.
NB Even better would be an IceCube18X13X12-1W speaker.