Roughly. Spl does depend on other things as well. You also have to take into consideration the speaker design.
The difference in the xmax is due to the difference in overall length of the voice coil. Xmax=voice coil length minus the gap height. The difference in efficiency is due to a different number of windings in the gap. The current passing through the coil generates a magnetic field which is distributed along its length. On a shorter voice coil, more of the generated field is in the magnetic gap producing a slightly stronger motor but with a shorter stroke. You can make a speaker really efficient by designing the voice coil to fit entirely in the magnetic gap. This would likely yield a sensitivity of 104 or so. This speaker may work very well if powered by a low powered amplifier because of the high efficiency but would not be able to produce high SPL at low frequencies because it would have a very small xmax.
You also have to consider the frequency played, as well as the xmax of the speaker. Efficiency alone should never be used to find the db's a sub will hit.
ok, I see what you mean by high sencitivity put with high x-max. So in other words when the cone is at high excursion it leaves the magnet gap witch reduces the sencitivity b/c its not as close to were it once was in the normal position in the magnet gap.
please correct me if im wrong. I did not know that. I geuss it is true you do learn somthing every day
Not a good basis to go by really. Once you put a couple hundred watts on a subwoofer, results change. The sensitivity of a subwoofer (or speaker for that matter) does not relate to it's efficiency, which would be the power in compared to the power out, and it won't dictate how loud a subwoofer is capable of getting. Many manufacturers rate sensitivity differently, you have to consider the type of enclosure they used, whether free air, sealed, etc. and also the location they put it in when they measured it. An example is the Infinity Kappa Perfect subwoofer, the 96db figure may look good, but they measured that with 2.83V instead of the typical 1W/1M sensitivity, and also put that subwoofer in a car for the measurement and not anechoic, which boosts the sensitivity by a huge amount. Independant tests have measured that sub in the 80s with normal methods of testing at 1W/1M. You also have to consider the frequency they measured at and other factors. High sensitivity is usually accomplished with lightweight materials, such as a light cone, foam surrounds, and looser suspension, also motor strength plays a big part of it. Lightweight can be bad or good depending on what you're looking at, too light can result in a lack of damping of the driver, degrading SQ. Subwoofers are capable of moving out of the magnetic gap with enough power, but of course it usually isn't recommended. If you have the suspension to handle it, you can stay somewhat linear doing so, but you do lose motor strength and a lot of control, like Joe stated. This is typically done in sealed boxes with high power, especially at the resonant frequency of the system.