Strange /incorrect impedance measurement in REW

[d_burban]

Hello,

I've measured few speakers with REW 5.2 beta1 ( loaded in cabinet for B&C8PE21 or coupled to an Horn for rCF ND1411-M ) and "free air" for vifa XT25SC90-4.

I have incorrect impedence measurement for all of them . I 've check my Rig several time with Rsense= 47 ohms, but all measurement show values above 25ohms (cf enclose capture)... static measurement with ohmmeter shows 6.2 omhs for BC 8PE21

strangley, if I replace the speaker with a 47 ohms resistance, the result is correct in REW (purple line). Do you guess what is going wrong ?

 

[John Mulcahy]

All unusually noisy at higher frequencies as well. What audio interface are you using? It may be struggling to drive the loads.

 

[d_burban]

Hello,
It's a small usb sound card : https://www.amazon.fr/Hercules-Surround-Pocket-Carte-externe/dp/B002R5W1SK .... Used with a T-amp 2022 for the output signal.

i will try an other card ....

thanks

 

[d_burban]

Hello,

I've tried with my old M-Audio ultra fast pro. After drivers installation on W10, and mass loop issues correction. I succeed to measure something more relevant :

... compared with RCF documentation for the compression :

Thanks for your advices ;-)