JBL SR4726A and SR4726X Why do these two models exist?

I am not sure but I have been under the impression that the model "X" came after the model "A". The two models are so very much alike aside from one using a 4 ohm woofer and the other an 8 ohm woofer. I am curious to know what was the rational which necessitated designing the model "X". The two models share seeming identical performance characteristics. I have not listened to the "X version so I cannot say if one sounds better than the other or not. I am hoping someone with JBL knowledge can enlighten me as to the reason two such similar products exist. I need to know if the model "X" came second or first, if I were to make an assumption it woould be that a later version would be done to realize some design improvement of at least result a significant decrease in cost. I don't see any significant different in cost so I would guess that the later version sounds better or is more reliable.
 
I would think a later design was to satisfy a market rather than some esoteric technical spec.

Only difference is nominal impedance? How about that right there? I recall my dad buying a car. He chose a Chevrolet model, but had to decide if he wanted a two-door one or a four-door one. Otherwise the same. Maybe some buyers prefer one impedance over another, to suit their amps better, or to facilitate multiple speakers on one amp.
 
I have a set of 4732A's and know the 4732x has a few differences:

1. Different finish
2. Cabinet updated
3. Full grill
4. Different crossover (not sure if it's electronically different, could just be the i/o plate)

Similar situation for the 4726 maybe?

Todd
 
seems that JBL wanted to market an 8 ohm version with a more dressed up look. I had a response on a different forum from a member who provided an overlap of the tweeter response of all three listed models, the 4726A the 4726X and the 4726FX as well as a much later model using a 2226 and a 2447. Overall the 4726A was about as good (smooth and extended horn wise) as this pro model seems to get. An L-Pad was suggested to make top end response for this rather hot speaker adjustable in a domestic setting. It was also pointed out that sliding off axis by 10 degrees with this horn would roll off the horns top end peak which is well worth a try to see if that helps and it will cost nothing but the time to try. Thank you for your response.