# Impedance measurement and cabling mess



## buggyboy (Mar 10, 2011)

Hello.

First of all THANK YOU for this great Software,it's a piece of free gold that can do anything you want even compared to commercial competitors.

Lately i want to make impedance and thiele/small calculation on some unknown drivers i have.

I use a Xonar Essence STX but i could NOT calibrate it,the result was hairy,so i've gone with the onboard sound card,that gave me the results i wanted.

But then again i still have problems.

Before i continue,i want to ask about the impedance connection because i don't really know if i have it right.

I've made and connected the cables exactly as on this schematic:
http://www.hometheatershack.com/roomeq/wizardhelpv5/images/impedancesetup.jpg

I assume that the left/right input/output are the positive wires of each side,but where is the common?
I mean,i don't really get where the speaker is connected,i see the one to the (assumed) positive cable,but the other one on the graph connects to nothing.

I ended up do the following:

1) Make a bridge from the +right output to the -right of the input after the Rsense - I still get anomalies,nothing fixed.
2) Connect the +right output after the Rsense to the speaker driver then the negative of the driver to the -right of the input - I hear the driver whistling but still a flat 22ohm line.

Does someone knows anything more than i do? 

As for the calibration part.

I connected the inputs to the output as the help page says and assumed that i had to connect the common of the input as i did mentioned above,i did the calibration with a 22ohm resistor that reads exactly 22R on the multimeter,everything seemed fine,but then ALL the times when i do a measurement the output on the graph is a flat 22ohm line,even if i have everything disconnected from the sound card's input.

I've spend 2-3 days trying to do a measurement with various Software but nothing "felt" friendly,and now i have the best of them but i have no idea what's wrong with what i do. :scratch:


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## robbo266317 (Sep 22, 2008)

Hi, the Right headphone out goes to the left soundcard input and the RSense resistor.
The other side of the RSense resistor goes to the right soundcard input and one connector on the speaker.
The other speaker connector goes to earth or common.
I hope this sorts it out for you.

Cheers,
Bill.


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## buggyboy (Mar 10, 2011)

Hello Bill.

Thank you very much for willing to help me,this actually sorted it out for me,i see now that goes output positive - input positive and i don't connect anything to their common except the speaker.

Just a finalizing question,do you recommend the speaker to get connected to input's or output's common? :scratch:

Thanks again!


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## robbo266317 (Sep 22, 2008)

I would connect it to the headphone output common.

Cheers,
Bill.


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## buggyboy (Mar 10, 2011)

YEY!!! Thanks again Bill. :R

I did my tests by the way,i measured the Impedance of a Dayton Tweeter i've had and compared it with the Impedance Vs Frequency Graph of Dayton.

The measurements are getting done in an environment as silent as possible and they are very accurate i can say,though Dayton's is smoothed,so when mine's unsmoothed it's a nightmare,when it's smoothed to 1/1 and to 1/2 looks almost exactly like their's,though it's off by up to 1ohm,but i'd say i cannot use it to determine my accuracy as the Tweeter is new out of the box,thus it's NOT Broken in yet!

What concerns me is the fact that when i'm trying to measure the leads' Impedance i'm getting random results,i mean,each time i run it the same line appears but it's down 0.2-0.5Ω to up to hundreds each time,while nothing in the room or on the setup has changed,and they are done seconds after between the previous one.

I will try to sort this mess out aswell.

Thanks again Bill and to whoever spend time to read my problem. :T

EDIT: Well with the leads shorted and the measurement smoothed i'm getting around 232mohms but i can't set it.

EDIT2: Nevermind,i clicked on the arrows and got it there.


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## djryanash (Nov 5, 2015)

Hey buggy boy,

How you coming along with the impedance measurements? I'm trying it now and running into problems.


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