There are a number of threads on this in the archives if you want to search.
It has been some time since I was "up" on the differences but let me make one clarification. The new models have dropped the "N" from the name, where the old model was the N803, the new is the 803S. That said, many have not recognized this and may still use the "N" in their ads, causing confusion.
The newer models have a new tweeter, different surround on the mid driver, new Rohacell bass drivers and new design crossovers. There can be more, these come to mind. While they look the same, there have been many changes.
An easy way to tell the difference is look at the model name stamped by the speaker inputs. Using 803's as an example, they will either say N803 for the older or 803S for the newer. The diamond series would be 803D.
It has been some time since I was "up" on the differences but let me make one clarification. The new models have dropped the "N" from the name, where the old model was the N803, the new is the 803S. That said, many have not recognized this and may still use the "N" in their ads, causing confusion.
The newer models have a new tweeter, different surround on the mid driver, new Rohacell bass drivers and new design crossovers. There can be more, these come to mind. While they look the same, there have been many changes.
An easy way to tell the difference is look at the model name stamped by the speaker inputs. Using 803's as an example, they will either say N803 for the older or 803S for the newer. The diamond series would be 803D.