I have a pair of JBL 4349’s in my main room. These speakers will play at whisper quiet levels, though the use of subs may be advised for extended low frequency response at those low levels. However, at 55 dB or less, something like a 4349 or 4367 may be a bit overkill.
Would JBL’s 4309 or HDI 1600 cabinets be a better match for what you wish to accomplish? Still horn loaded, but probably much more suited to lower listening levels.
Finally, keep in mind that human hearing at quiet levels is rolled off at both low frequencies and high frequencies. Hence the inclusion of loudness contour filters (tone controls) on some equipment that can compensate for our hearing at low levels.