???Why The HUGE Discrepancy in Sensitivity Ratings???

freediver,
i'm looking at the M-L 35XT speaker manual & on the last page, the specs read:
Sensitivity = 92dB @ 2.83V / meter.
You can find the manual here:
http://www.martinlogan.com/pdf/manuals/manual_motion_35xt.pdf

The speaker is clearly noted as a 4 Ohms speaker.
If you input 2.83V into 4 Ohms (after you calculated V^2/R) you get an input of 2W.
Usually the standard is to input 1W into an 8 Ohm speaker. 
So, for the M-L Motion 35XT we have to compensate/normalize to bring Sensitivity number to an equivalent 8 Ohms so you can do an apples-apples comparison with other speakers.
We need to halve the number of input watts to 1W Or double the input speaker impedance to 8 Ohms (which will also yield an input of 1W).
In either case, the output SPL should drop by 3dB (assuming the speaker SPL response is linear in this region & is being fed by power well within its handling capacity. This should be the case as 1W is well within the power handling capacity of the speaker which also means its not distorting hence response should be linear).
So, in effect the M-L Motion 35XT Sensitivity is 92-3 = 89dB.
You say it's measuring 87dB ( I could not find a review that said this. Can you please provide a link? Thanks).
it's not out of the ordinary to lose 2dB due to measurement setup issues. And, like others wrote, the spec could be in-room & the measurement could be in an anechoic chamber. 
Anyway, you should view the M-L Motion 35XT as an 89dB sensitivity speaker; not 92dB. 

thanks for the kind words nonoise :-)

What bugs the crap out of me is that amplifier manufacturers used to do the same thing with power ratings.I don't know how this was changed but IMO it's high time the same pressure was brought to bear on speaker mans.to provide honest & accurate specs!

that would certainly help but..............
i dont think there is a IEEE or AES or similar standard instituted by an industry institution. That leaves the door open to fudge specs.
You confront the speaker manuf & he'll tell you that his speaker spec is correct because (for example) his spec sheets quotes in-room spec (but he's not obligated to put that in the spec notes so you are left guessing). There's nobody to enforce this spec.
What we can do is educate ourselves & ask the right questions during purchasing. That'll let manuf know that they cant pull wool over our eyes.
I still remember the marketing slogan from Syms Mens Clothing " An educated consumer is our best customer" - that's what we have to become....