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[CertifiedHoodClassic]

I borrowed some else's DATS and measured it. All coils in series (4 ohm nominal):

It's supposed to be tuned to 28 but that dip at the resonance appears to be closer to 25/26. Maybe that's the issue? If it's tuned that low, the port is probably not helping much at all even in the 30's.

 

[Buck 5,000+ posts]

I borrowed some else's DATS and measured it. All coils in series (4 ohm nominal):
View attachment 69564

It's supposed to be tuned to 28 but that dip at the resonance appears to be closer to 25/26. Maybe that's the issue? If it's tuned that low, the port is probably not helping much at all even in the 30's.

The math behind your box should be simple to see if it's tuned to 28 hz on paper

 

[shredder1 10+ year member]

Maybe that's the issue? If it's tuned that low, the port is probably not helping much at all even in the 30's.

I'm always suspect of a under 30hz tuning unless I'm in control. No shade thrown but its the laws of diminishing returns tuning super low in a ported enclosure. A tuning that low can definitely kill numbers while being demo-loud. Ported enclosures are a one trick pony in most cases with a peak sought more than delivered and cabin gain being something not considered. After decades of usage my go to is Winisd as I've become cognizant of all the other factors and how they affect final output. For this exact reason I prefer 6ths when bandwidth and power handling are sought. Plus big #'s. Space makes bass they say and those 3laws still apply.
I'm not trying to be cute... I'm just sayin'