Ampeg gives two low end specs...one for -3db from flat, one from -10db from flat (otherwise known as the "usable low frequency"). Most companies only quote the -10db figure in their specs but Ampeg does both. The -3db point is, indeed, 71 hz, but the usable low freq for the 212av is 40 hz. That means that while it starts rolling off noticeably at 71 hz, you can still get down to 40 hz out of it. It's pretty high tuned, but a lot of folks (like me) like the rolled off low end because it keeps the bass from getting too muddy in the lows. Those who like low tuned cabs like the SVT 410hlf may not be interested in the 212av, but the higher tuned cabs have their fans as well.
Ampeg Portaflex Club #1