Question: Sub with Fs 54, but response remains above 95dB down to 27: How can I best build

"I've got a driver with free air Fs at 54 1w/1m, but free air response remains fairly even down to 27Hz above 95dB"

This sounds unusual to me.  What woofer is this? 

@audiokinesis  Its an 15" OEM sub from AliExpress, was accompanied with the impedance & FR graphs, and I liked the Bl 23.  

@hsbrock , do you have the other T/S parameters?   Qes, Qms, and Vas at a minimum? 

Imo 54 Hz is an unusually high free-air resonance for a 15" home audio subwoofer.  Is this a car audio subwoofer?  Or a prosound driver? 

The driver is 15", VC4", Bl 23, Vas 2.2 cuft., fairly stiff suspension w/ Qms 14.5, Cms 0.05mm/N, double spider, so for this reason & the Bl I was leaning towards a corner horn, not relying on excursion w/ an Xmax of 7.5mm. Primarily will be used from its low end to 150 Hz, & in this range it averages about 98dB. The above measurements are at 1W/1M, & compared to most subs I've looked at its fairly flat +-3-4dB up to about 1100Hz, where it begins dropping off or breaking up. Primarily considering a corner-horn cabinet, facing into the corner, with maybe with a passive radiator above it. What more would be helpful to know? Qes: .51, Qts. .50, Sd 881, Vd 661, so displacement is not the greatest for a 15", but the PR and corner placement should help. Thinking of a sealed cabinet w/ PR facing into corner w/ rear chamber could be 2-4 cu.ft. This is as far as I've gotten. The Qts. suggests an open back or infinite baffle, and with the stiff suspension (which I also liked) so I hoped the sealed rear chamber w/ the PR might better load the horn. ??? 

@hsbrock,

See articles below:

Mike

https://www.lansingheritage.org/html/jbl/reference/technical/1983-subs.htm

https://www.lansingheritage.org/html/jbl/plans/1979-manual.htm