I may be asked to fit a sound decoder into a Spreewald loco.
Any tips, especially regarding speaker size and location?
When I did mine a few years ago I put the speaker in the cab roof. I did a post about the whole thing for GScaleMad - I've probably still got the photos somewhere. Also, I remember I had to ditch the boiler weight to make room for the decoder (it was only the 3rd loco I'd chipped so maybe these days is do it diffetently). To compensate I used some spare lead flashing offcuts from building work we were having done and created a kind of sleeve to fit inside the boiler; decoder plus wired went inside this sleeve and, as mentioned above, speaker went in cab roof.
Fitting the speaker meant removing an inner perspex "shell" that forms cab windows and cutting out a hole for speaker. Bit fiddly as I recall.
As far as the overall installatoon went, to quote Mike Duffy, "it may not be the right way but it's my way". Other folks will no doubt know a more appropriatevway of doing this.