I need to do some more work to lower the variables down at play here but apparently everything i thought would happen didnt so now i'm a noob again, lol.
I have 4 18" XL M1s in ~27cuft Net right now with no port length except for baffle which is 1.5".
I have ability to switch on\off 1,2,3 or 4 subs on at once.
When i had 1 or 2 subs going, i had 0 low end audible below 40hz.
When i have 4 subs going, low end barely is audible to about 36hz but thats it.
I threw in 7 35" long 2x4s in the port and BAM, low end came back just great down to the low 20s and clearily audible.
Now, i decided to test to see what the wall is peaking at right now before i seal the wall off and record a cabin gain sweep graph of the car before i start tuning..
Well, this is where it gets even more weird.
I have 2 ~6sqin holes in the port wall that need to be sealed up but thats the only 2 air leaks so far in the enclosure.
The car, at passenger side head rest ~28" from glass did 46hz sealed, 45hz outlaw.
Something weird going on here...
When only 2 subs are playing, it peaks at 57hz sealed, outlaw unknown.
So my first of many questions is-
Do these 18" XL M1s like extremely small enclosures?
I used to run Level4s and they liked large enclosures in my vehicle with street and wall enclosures but these XLs are confusing the hell out of me.