you can tune to any fq, but depending on box size, the roll off is what is going to make it sound good, if you tune to 28hz and it is a hard sharp peek, your highr fq might sound like crap, but tune it a little higher like 33-34 and the roll off is not as sharp the sound for lower notes and higher notes will be much better, i have built thousands of boxes, and done both built to customer specs and then let me do it my way, always a 33-34 hz box has been best for a daily setup....... now onto a bandpass differnt story - 42-45hz.......... with a 1:2 ratio seams to always work great, and handles good power.