A sealed box isn't going to give you much below 35-40hz anyway. Build a ported box tuned to 30-33hz you will get the lows you want and it will still punch the higher notes some bit.! I had one of these in 2.7suft tuned to 32hz off 1.5Kw and it was a pretty musical box, maybe a little small but musical. I sold it and 2 years larter its still goind strong