JBL 4429, deep bass ?

It is very hard if not impossible to make a driver that is effective at 18 Hz go all the way up to 800Hz gracefully. This is why subwoofers exist. You can make a midrange driver that makes it down to 100 Hz especially if you use them in multiples such as in a D'Appolito array. Then you can go right down to 12" subwoofers and skip the standard woofer altogether. 
This design approach Is used by several companies the Goebel Divin Nolesse is a great example. God knows what they cost. I have not seen JBL do anything really creative in home speakers in a while. Back in the day they were ahead of the curve. Anyway there is not speaker of this design type that makes it very low with authority. Real bass is a beautiful thing.

You know that the L100 Classic and the 4429 share the same woofer. One has a white damping material sprayed on the front. The other is sprayed on the back. Low end should be the same.

Well, the porting is different, the cabinets are different, and I don't know but wouldn't be surprised if they cross over differently.

Zowie. I would think the cabinet volumes are close. But you could research that. I have a plot of the response of the 4429s' in my listening room. I will look for it and submit it if I can find it. To my ears the 4429s' seem to dive into the 30 range. It took awhile before they went that low. Probably a year before the suspension loosened up. That woofer has a dual spider setup.

It does not look like I can insert the PDF file here. The rolloff starts at 40Hz, but judging from the file date the speakers were only a couple of months old. I know the bass improved quite a bit after a year.