Here's my take on how to compare the sensitivity of the 210HT and RM22....
Looking at Erin's chart I see he shows a mean SPL (in a very relevant range) of 92.5dB @ 2.83V.
Since 2.83V is used for specifying 1W/1m sensitivity at 8 ohms, and the 210HT is listed as 4 ohms, a -3dB adjustment need to be made if I want a 1W/1m spec.
So I'd call the 210HT's 1W sensitivity about 89.5dB, based on it being a 4 ohm nominal box.
Here's the test voltages necessary for common nominal impedances and 1W specs.
2 ohm, 1.4V; 4 ohm, 2.0V; 8 ohm, 2.83V; 16 ohm, 4V.
If manufacturers aren't matching their test voltage to those nominal impedances, dB adjustments need to be made with each step being 3 dB.
(Note that JTR used a correct 2.0V for the specified 4 ohm impedance)
Looking at Fulcrum's RM22 charts, on top we see the raw response for both the LF and coax sections, both specified as 8 ohm nominal.
Fulcrum chose 91dB sens for the lower section, and 104 dB sens for the upper section. Both appear realistically well chosen (not inflated).
2nd down is processed response.
Note the lower section's green trace is about the same as the raw, other than raised a bit from 45-100Hz, smoothed, and hpf and lpf added.
It's sens probably is unchanged at 91dB.
But note the coax section's black trace has been brought down throughout it's entire range. Basically, the it's curve and smoothing necessary to sum well below 1000Hz with the lower section, define the overall sensitivity of the entire speaker. This is because the coax has more than enough to match above 1000Hz.
Fulcrum specifies that combined sum sensitivity as 95dB, which again looks very realistic, if not conservative, vs the Axial Processed Response.
So I'd say the 210HT is 89-90dB 1W, and the RM22 96dB 1 W. That's a pretty huge difference, with at least 4x the wattage needed for the 210HT.
It's the dang passive xovers in the 210HT....passives always have to bring sensitivity down to the lowest producer........
The RM22's active bi-amping of course avoids that.
I'm a fan of JTR, having owed a pair of 3TX, and still owning a pair of Orbitshifter subs.
That said, Fulcrum's stuff is exemplary imo,.....great boxes, accurate extended specs, great support with processing packages etc...
(Fulcrum put's out DSP presets for almost all major prosound processor/amps.
https://www.fulcrum-acoustic.com/support/processor-configurations/ )
I likes what they do !!!!