I run 2 18 lvl 5's in a Tahoe box is tuned to 32hz 6.3 per driver on 5k clamped doing a 153.8 on music around 37 not as really a small enclosure but dc's like smaller boxes where most 18's would like 7 per driver
my car has to have a small box unless you go with a wall,,i was worried the 18 wouldn't perform well in it.im hoping to get a 53+ by the time im done with the box ,replacing the batt and the hatch.
I have a diamond d6 10 in 1.2 cubes at 33 hz. Did a hair over 140 on a TL. Almost as loud as my type r 12 was. Neither had a high tuning for db numbers, but both are great on music. Did a Tang band 8 ported, but didn't meter it. Very impressive to the ear though.