In a bookshelf? They would have to be horizontal to fit. Does horizontal vs. vertical make a difference?

My TV is in a built in cabinet that takes the entire wall...

THanks,

JB

Your stereo imaging won't be as sharp if the speakers are horizontal because the sound source will be spread out but everything else should be OK -- assuming the speakers are protruding a bit over the edge of the shelf and they are not "in a box" formed by the sides and upper shelf of the wall unit.

If you are essentially putting the speakers "in a box" within the wall unit then you will get more colorations and less accurate sound as a result.

Any chance you could post a picture of the wall unit ?

JB, welcome. Yes, a vertically configured speaker is designed to have have wide and smooth horizontal dispersion and relatively narrow vertical dispersion. Placed on its side the patterns are reversed and this should be avoided if possible.