I'm quite sure that the voicing of all the newer class 15" woofers has been moved upwards by a partial octave.
You can check ( for yourself ) my contention by manipulating a woofer's TS parameters .
Divide Qes into Fs ( Fs/Qes ) to arrive at the EBP.
The EBP figure is a good determinate of the ( low-end ) voicing available through box alignments.
I'll give you a few examples ( & then you are on your own to figure out the EBP figure for any woofer you're interested in );
2245H ( EBP ) = 20hz / .27 = 70 ( hz )
2235H ( EBP ) = 20hz / .28 = 71.5 ( hz )
1501fe ( EBP ) = 29.5hz / .25 = 118 ( hz )
2226h ( EBP ) = 40.0hz / .33 = 121 ( hz )
So a conclusion ( of sorts );
- The 1501fe has a naturally higher "voice" when compared to the 2235H or 2245H.
- This woofer is voiced as more baritone than bass ( just as in a singers choir ) .
- It'll have better mid-bass characteristics than the 2235 ( at the expense of low-bass reproduction ).
ADDEDUM; Why Change ( the EBP ) figures ?
- JBL has been making sub-woofers for decades now ( & it all started with the somewhat anemic 18" K151 / way back when ).
- They have obviously ( from the numbers ) made a conscious effort ( since the early 90's ) to give their newer 15" woofers a higher voice ( & by extension leave the reproduction of real low bass job to their line of dedicated subwoofers ).
A bigger enclosure size won't change the inherent voice of the woofer / it'll just change the ( box/woofer ) alignment ( & that might extract a tiny bit more low bass ).
As you have quoted ( GT ) here a couple of times, these newer woofers can easily be EQed to get more low bass ( since they have good power handling and decent Xmax figures ).