Actually I remember it was Coral PRF400. Should be exactly the same as Peerless Resolution R15.
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Electrical data
Nominal impedance Zn 4 (ohm)
Minimum imp./at freq. Zmin 4.2/71 (ohm/Hz)
Maximum impedance Zo 51.2 (ohm)
Dc resistance Re 3.2 (ohm)
Voice coil inductance Le 5.7 (mH)
TS Parameters
Resonance Frequency fs 29.1 (Hz)
Mechanical Q factor Qms 7.72
Electrical Q factor Qes 0.51
Total Q factor Qts 0.48
Force factor Bl 18.7 (Tm)
Mechanical resistance Rms 7.28 (Kg/s)
Moving mass Mms 307 (g)
Suspens. compliance Cms 0.10 (mm/N)
Effective cone diam. D 33.7 (cm)
Effective piston area Sd 892 (cm²)
Equivalent volume Vas 106.9 (ltrs)
SPL 2.83V/1m at fmin 91.1 (dB)
I'm building two sealed subs from these. Real bang for the buck as they did cost only 100€/pcs.