This is how I built mine (click on link). If you go with 13" wide x 16 deep as Wayne specifies and you use my type of corner bracing then you will barly have enough room for the 10 driver so be careful. Mine are 14 1/2 width outside dimension and as you can see in the pics that the hole for the woffer is pretty tight. You don't have to build as I did but there have been a couple here that have showed some intrest in this type of construction and I did it this way because even though it is a bigger job in some ways it simplified the construction for me because I am not a cabinent maker with high quality tools. In fact Home Depot cut all the plywood for me.They sound darn good. I will be doing some A/B test with some other speakers this week. I don't know if they differ much in sound or not from the 13 x 16 version. I have read that this shaping of the box can lead to a version of a "pipe" and may be more prone to standing waves and such.
Have fun!