You'd be suprised what has notes that low, it's one of those things when it's there you notice it, but if your not used it, you can live without it. Plus tuning in the low 30's upper 20's generally removes the "peak" near tuning and you end up with a very low playing fairly flat response. I find for music honestly, audibly flat response to 25hz is pretty much a necessity or I will notice it's missing. Maybe not on your typical rap songs that have a pretty much constant 40ish hz tone, but stuff that gets lower, you notice it, especially 25-32hz. People always mention where a song "peaks" on a termlab, but peaking and where it has bass are NOT the same thing. Do you really think a song that peaks at in the low 30's really has no bass below that? Of course not! My current box basically crushes anything from 20-50 and you can def notice when the SSF goes above 30hz. My last 2 setups used passive radiators, I can change tuning from 25-45 in literally a minute without taking any tools, so I've messed with tuning quite a bit. Mid 30's tuning generally does leave a bit to be desired on some songs and when it does come up lacking, you can hear it.
Anyway off the top of my head, the bottom note of put on is pretty low, TI's "let my beat pound" has a pulsing note in the beginning that most cars miss, obviously "love for money" and like I said, anything that has peaks down low like that has pretty strong audible notes down to around 25hz. Plus some people do it for the flat response too, generally if I tune a box low it's more to remove a peak than it is to crush 20hz. I know the build I just did for a friend, he wanted "loud and low", but I knew he didn't listen to that much low stuff, so I tuned him at 33hz. On all the songs I mentioned you can cleary tell he's missing notes compared to my car. However it's not stuff he usually listens to. I remember the first time I played the stuff I listen to in mycar like the screwed version of "on my level" in my car he about **** a brick lol. He's like WTF mine don't sound like that! So I showed him a song in the mid 40's where we are alot closer in SPL to show him the trade off. Then I retuned the passives for a mid to upper 30's to show him the trade off the other way, where I was now way louder than him on the mid 40's peaking song, but lost quite a bit of my low end crushing abilities.
For daily drivers I find 25-30hz tuning often works the best in terms of overall audible response. Just depends though, i've tuned as high as 35 for the right subs and car, it always comes down to the end response, the tuning that gets you there is just the means to the end.
