I was curious so I also looked at the manual for the unit, it is the same audio output as you would have in a car or pickup etc. Front, Back - Left, Right speakers with fade and balance. Being installed in a new TT makes me go back to your original question and I would think Forest River would have installed some kind of switches to select inside/Outside etc or not include outside speakers on the unit.
Now having rambled on, I am wondering if the speaker system might be covered in your TT user manual? Perhaps some switches behind a panel door, just a thought I know has already gone through your thought as well. I am not familiar with your TT so good luck with figuring this out.
Enjoy your toy hauler and camping -
Dale & Terri, Lulu & Tiki (our Chihuahua's), New rescue puppy Prince - Pom/Pug mix.
2013 Tundra, Double Cab, 5.7, TRD Off-Road, 4X4, Full Tow Package
2013 Wildwood T26TBSS - Sold
2000 Gulf Stream Sun Voyager M-8357 MH, Ford Trident V10 Gasser, 35 foot.