PS: This product link have 2 order options which is for HiVi D8 and D8.8+, which have different suspension material so that have different Fs too.
D8.8 adopt grey foam as suspension material with a Fs=32Hz
D8.8+ adopte Black rubber material as suspension with a Fs=35Hz
1, Here is the datasheet of D8.8 subwoofer speaker unit, as following
2, Here is the D8.8+ subwoofer speaker unit datasheet, as following
