If you add in the mids, does it become less efficient?
Also, are we talking efficiency over 100hz?
And what kind of extension down low would you guess?[/QUOTE]
All bass cabinets base their efficiency claims north of 100 hz. In looking at Bass Gear Magazine, tested efficiency is based from 200 to 2000hz. I think that this is typical. The only reason I'm saying this is that I want an apples to apples comparison with other cabs. Unfortunately, many manufacturers choose the most optimistic point between 200 and 1000 hz. I think that for bass players this is wrong and misleading. Our volume is largely perceived by the region between 150 and 300 hz, I think. An SVT has very little output below 80 hz but most perceive it having a "huge" bass sound.
I also think that we can agree that a speaker with an efficiency of 101db will perform pretty admirably with a 50 watt tube amp. One with efficiency of 96 db will not. In looking at Eminence's graphs, I can predict efficiency of 101db down to around 150hz. This is a lower frequency than the yardstick used by most. The MVW enclosure typically increases efficiency by around 3db.
As far as extension, I'm getting pretty good at predicting this---based on measurements of my other speakers. I would say mid to high 50's as a -3db point. This is pretty much in line with the Kappalite LF speakers. Most of the "super" 12's and 15's using the Kappalite 3012lf and 3015lf have minus 3db point in this region. I've seen some misleading specs where someone claimed a usable frequency response to 37hz where the -3db point was in the 50's and the -10db point was at 44hz!
So I guess that in answer to your question---in comparing "apples to apples" this would be in line with other speaker manufacturers claiming 101 to 102db efficiency. And said speakers would kick butt with a 50 watt tube amp. My other speakers go lower, but this would compete in extension with other "super" 12's and 15's. (Andy Lewis's Acme speakers are an exception---they go really low)
And not to open up a big can of worms---but my real world experience has shown me that a 50 watt tube amp competes with a ss amp of much higher wattage. (oops---here we go). When I was in Nashville I was trying Kevin Shaw's 150 watt tube amp. A 150 watt ss amp will barely get my 112 going, but you could hear and SEE that that woofer was working overtime with that 150 tube watts!
oh and I was serious about an interest in the possibility of a 2x12 
