I have always used C weighting, slow response on my trusty Rat Shack SPL meter and I use test tones off a Stereophile Test CD.  You have to adjust your measurements as documented for the Rat Shack meters response in the lower ranges, but this has always provided "reasonable" results for me that coincide with what I was "hearing".

I have Audio Nirvana SCF 12" Alnico's in CommonSenses' 5.6 cu.ft. ported box... and I have measured them, using the above method.  Nothing scientific.  Just measured at my listening position, with the speakers where I normally place them.  After all... this is where and how I listen to them, and what is important IMO.  I don't listen in an anechoic chamber and neither do most people.
Anyway I always felt they sounded "generous" in the 55-60hz region... which I like.  These speaks have a warm, juicy sound that is never fatiguing.  And that is exactly the way they measure as described above.

I also have Audio Nirvana SCF 15" ferrites.. in Open Baffles - I have heard these in an 8 cu.ft. reflex box of CommonSenses' recommendation - and I did not like them in this config at all - very forward and fatiguing.  Not even worth the effort to measure, because I didn't care how they measured - they were unlistenable to my ears. I think most of the problem was probably poor box construction and lack of damping.  But these drivers in the OB's sound pretty darn good.  I have been listening to them in an OB for a few years - driven by a Torii MK.3 and enjoy them quite a bit.  I have never attempted to measure them - except with my "ears" - that's all that matters when you get down to brass tacks.
I also have Wild Burro Betsy's and Betsy W.O.W.'s and the Lii Audio 15's that I play with from time-to-time as well.  Like all things "audio", they each have their own strengths and weaknesses, but I have been able to make them all produce music that I enjoy....