Dining/kitchen in-wall speaker height

My brother-in-law purchased a pair of JBL in-wall speakers and now wants to know where to install them for stereo sound in his combined dining/kitchen area. His son wanted to install them in an exterior wall with the magnets against the exterior sheathing, leaving no room for insualtion. With winter temps down to -5 degrees here, I suggested an interior wall that faces the dining, then kitchen area. I'm wondering about height. There's a bar/counter between the dining and kitchen area that get's used everyday for meals, while the dining table gets used less often. I thought the speakers should have their non-adjustable tweeters about 5 feet high. What do you think? Thanks, Roger