The following is a brief summary of the model naming conventions used by JBL over the years. Model numbers on the professional side have been a lot more consistent than model numbers on the home speaker products. However, there seem to be more exceptions than rules on both sides. This post attempts to summarize some of the patterns that JBL has used in product naming. I'll limit this post to pro studio monitors and home speakers since they represent the products with the largest interest among our readers.
I'll start with the easier stuff - the pro monitors. Throughout the 70's and into the 80's, the monitors all had model numbers in the 4300 series. Generally, the higher the number, the larger and more expensive the system. Thus the 4301 represented the bottom end of the scale while the 4355 was the top end.
In 1981, the 4400 series of monitors was introduced and generally followed the same naming convention with the 4401 representing the entry level and the top of the series being the 4435. However, some models of the 4300 series remained in production so you really can't use model numbers to compare market positioning from one series to the other. Lately, the LSR series has thrown that numbering system out the window. However it is interesting to see that they have started a sub series that is utilizing the old 4300 numbering.
The home speaker model naming history is much more complex. Throughout the 50's and into the 60's, the official system model number consisted of the enclosure model and component kit combined after a "D" prefix. For example, the C30 Hartsfield enclosure with the 085 component kit installed became the D30085. The enclosure and kit numbers did not carry the same significance as the pro numbering with inexpensive systems having low numbers and vice versa. Most people seem to refer to the systems from that era by the enclosure names (Hartsfield, Harkness, Olympus etc.) and there was no real pattern the development of these names.
The mid sixties saw the launch of the "L" series which became the mainstay model line for JBL through the 70's and into the 80's. As a general rule, higher numbers corresponded to higher priced systems. The mid 80's saw JBL's product line splinter into many subgroups like TLX and J series. At that time, the "L" series name was temporarily retired to make way for the "Ti" series at the top of the line. Again, higher numbers generally represented higher prices. Starting with the 1990's, even I begin to lose track of the model lines. Where product life spans exceeding a decade were not uncommon from the 50's and into the 80's, product turnover in the 90's was so high that I would suspect the nominal product life span was 2-3 years. The decade started off with the XPL series being the top of the line, later replaced with another stab at an "L" series and culminating with the "Signature" and "SVA" series.
The absolute high end, starting in 1989 and continuing today, is the K2 series. Until recently, few of these have been marketed domestically with Japan being the primary market focus. At any rate, click on the "Library" button along the menu bar at the top of this page and go to the JBL catalog section. There you will see all of the models discussed and get a feel for the product line evolution.