Maybe its the sub?
I've had it in 3 boxes
1 cu ft sealed
1 cu ft @ 40hz
1 cu ft @ 34hz
(all off my 1200d)
and 1 cu ft @ 34 hz with my 225hcca
the only constant is the sub and pretty much the 1200d (aside from the one time I used my 225 on it)
think the e8 could handle the 225 @ 4 ohms, sealed?