Dc to dcc

[Edv]

Hi everyone,
Need help
I have a HO spectrum 80 ton 3 truck shay (8 pin dcc ready) and want to install a Soundtraxx 750 sound decoder.  Soundtraxx offers what decoder and speaker to use so I am satisfied about that.  The help I need from this forum is where I would install the speaker and how to go about it.  Is there is a different brand decoder and/or speaker I should be considering also.
Any help or advise would be appreciated.