2027 Iron Driver T/S measurements: SB13PFCR25-XX

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I just measured the T/S parameters on my 2027 Iron Driver woofers. I thought that other builders might be interested in comparing measurements, so I am starting a new thread. Measurements can vary quite a bit based on break-in, VAS method, mounting method, piston diameter assumption, etc., so I will detail my methods as best I can. My drivers are the SB13PFCR25-08 (8 ohm) version, broken in at 15Hz 1/4" peak to peak for 2 hours. I used the test box VAS measurement method using a sealed 0.327 cu. ft test box. Piston diameter assumption was 4.1875 inches center to center of surround. Driver was simply held in my hand for the first measurement, then pressed into the gasket of the test box for the VAS measurement. Equipment used was an HP Win7 laptop and the DATS V2 software/hardware. I think the Le measurement is about half the spec because DATS V2 measures this at 10kHz.

TS Parameter Driver A Driver B Mfg Spec
Re 5.7 ohms 5.7 ohms 5.6 ohms
Fs 44.4 Hz 44.4 Hz 45 Hz
Qts 0.3257 0.3248 0.33
Qes 0.3792 0.3805 0.39
Qms 2.307 2.22 2.2
Le 0.37 mH 0.37 mH 0.77 mH
Mms 9.9 grams 9.9 grams 10 grams
Vas 0.51 cu ft 0.51 cu ft 0.473 cu ft
SPL 87.1dB 87.1dB 87dB 2.83V/1M

SB13PFCR25-8 TS measurements
SB13PFCR25-8 TS measurements1357×705 161 KB

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That’s impressive! I too had excellent matching between my SB15CAC-08 drivers and they were only a tiny bit different than SB’s published specs. But as usual, when you plug the specs into a box modeling program like Unibox, the small differences don’t mean anything response wise. I have always used the added mass method for Vas.

BTW - you can choose whether to measure Le at 1k or 10k with DATS. I think that selection is on the preferences tab.

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Thanks. Didn’t know you could do that. I changed it over to 1kHz and the Le changed to 0.8678 mH for driver A and 0.8587 mH for driver B. Much closer to factory specs.

I have always done added mass method as well, but am moving back to the test box method. The sticky mortite or other material that I used for added mass always leaves a mark on the cone that I cannot remove later. I didn’t want mess up these brand new, nice looking paper cones.

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