# Interpreting Impedance: Manufacturer vs me



## grokaudio (Feb 11, 2013)

Hi all,

First time post in this Forum, and need your brilliant advice:

Some background: I'm building speakers and using REW for measurement of Driver in order to get T/S, Frequency response and impedance curves (to ultimately use crossover designer and Mathcad) to finalize my build.

The drivers I am using are SB15nrxC30 - 8 ohm uncoated and SB29RDC 4 Ohm 

I've already done some measurements (impedance) and have come across an interesting situation.

SB Acoustics states measurements are on drivers broken in. My Z max for impedance on un-broken in drivers vary significantly.

I'm in no way questioning the MFR. However they are far enough off to question my setup before proceeding with this build with additional info here: http://www.sbacoustics.com/index.php/download_file/-/view/191/

I'm using linux, rew Java version and built in soundcard for measurements - so far it is fairly consistent across measurements - so I know its not REW or the impedance rig.... I know MFR used a 150 Ohm sense resistor during impedance measurement, what I don't know is output voltage during testing.

Can anyone shed some light on the post in rew forum as posted here:

http://www.hometheatershack.com/forums/rew-forum/67216-checking-mdat-impedance-files.html

I can post images of measurements in the case REW is not available.


Thanks

:huh:


----------



## fbov (Aug 28, 2008)

Replied to wrong thread...
http://www.hometheatershack.com/for...ecking-mdat-impedance-files-2.html#post609941


----------



## grokaudio (Feb 11, 2013)

No worries - Thanks for the post!

I found it interesting there was at least the published data saying measurements were taken broken in...

And that at least they used a 150 Ohm Sense Resistor


----------

