http://www.lansingheritage.org/images/altec/specs/home-systems/model-19/page1.jpg

When I built my XPL 200'S I wanted to maintain the original driver spacing so I scalled it from a photo. What you can do is use a picture editor too take a know dimension in pixels and use that to determine the unknown. If you knew the woofer diameter it would be easy using the brocures to figure out the height of the lower box. You already have the width and depth. Then you can calculate the volume to see if that make more sense.

Just in case you didn't already think of doing this.

Good luck