Hello Chungjh:
Sorry for the delay in response.
After the break in, yes, there is a clearly more bass as expected with double the bass panel area. With the PX/BF, the whole spectrum is improved and envelopes the room( ie. right sized for this speaker in my environment) No reduction is HF either. The imaging with the BF is improved. The whole experience has motivated me to challenge the positioning of the speaker. I now have a more acute toe-in, and with the original Pristine 2 frame at a rack angle of about 3 degrees backwards, I have slowly elevated the rear to about a 1 percent rake. Combined with the toe in and the the midrange set to + 3db, the whole system has launched up big time. Very satisfying! I have a home made sallies in the rear, angled to the rake, 5’ high as well. All combined, it snaps up the front projection nicely and reduces the backwave.
Other improvements include a fixed resistor over on the tweeter pot which resulted in a surprisingly improvement is HF smoothness and imaging.
As for the amp, I am using VTL 225T mono blocks, heavily modified and update, with Winged C El34, 12au7 Brimar NOS and and sylvania black plate 6350. The 12au7 is not standard, and was modified to this tube along with other updates. All caps and resistors upgraded. Output is about 110 watts in a 8 ohm load( form the standard 5 ohm) and hard wired in triode mode. Lots of drive for the pristine 2 with a Toroid 1 update.
Let us know how you make out….
Ken