Actually if it was tuned to 30hz it would start a t 30 and peak out somewhere around 40 before it would start to slope off.Tuning freq and peak freq are 2 different things.Tuning means you are designing your box for what its peak output will be. My box is tuned at 30 hz, so my box would (all other conditions being perfect and equal) have the most output at 30 hz , and slowly slope down in output from there. Of course, many other things affect tuning as well, but thats a VERY simplistic definition. Squeak could probably explain better.