big box and super low tuning doesn't help with sound quality, all it does is create a large peak in the tuning frequency while sacrificing a lot of output above tuning frequency and have massive group delay which degrades sound quality. Which means if his main music is rock and metal, he literally gave up a lot of output thats needed in that range just for some whale notes that he'll never even touch on. low 20hz tuning is to bloated low notes which most of the times music doesn't ever come close to reaching so all you are doing is just giving up output/bandwidth in most usuable ranges and accuracy for no reason unless all you listen to is rebassed music that digs to the low 20hz and teens.. Sometimes boominess is completely out of your control as well depending on the vehicle acoustics and overall cabin gain, even a giant sealed box or a small sealed and a perfect sealed with a qtc of .707 may sound like a peaky 50hz fart box purely due to cabin gain where the only thing that can fix is a parametric EQ to flatten out along with some deadening to lower peak cabin frequency.
