This suggests that (a) EVI-10 was the model name for these generic ten-inch speakers, (b) the EVI-10 and Force 10 were closely related (as seems obvious), but (c) the EVI-10 may be somewhat different from the Force 10 and distinctly different than heavier (18-pound) EVM models (see below). Within the first seven- or eight-digit number the 10 signifies ten-inch, as many 12-inch speakers listed in that spreadsheet have either 812- or 1812- prefixes. However, what do the second four numbers of the model number mean specifically? And why do some models (e.g., Force 10; EVI-10) have more than one model number? Furthermore, what are EVM-10 (lacking any letter designation) speakers?