Using Behringer UCA222 to measure speaker impedance

[jabar102]

I have a 2-channel setup with a couple of different DACs feeding a tube amp and some Tannoy speakers, which apparently have some wide impedance variation, from 3 ohms to 40 ohms! Having muddled my way through the frequency response section of REW, created some filters (applied through Audirvana), I'm now looking to measure this impedance myself.

One of the two DACs does not have a USB input, and I use a Behringer UCA222 to gain a Toslink output, using a Macbook Air.

So the question is: can the UCA222 be used as a the "in" and "out" for an impedance measurement, and does an additional resistor need to be added into the loop? If this rig can work, any thoughts on the proper way to connect it all?

Thanks in advance for any insights.

J.

(tried posting a link to the UCA222 page for reference but couldn't)

 

[John Mulcahy]

Impedance measurement is explained in the help.

 

[roger2]

Here is an interesting thread where a UCA222 is used to measure impedance. The UCA222 was showing high impedance on the lowest frequencies when tested with a resistor as the DUT.

Posts 6, 20, and 23 give a good summary of the most relevant information.

Problems with impedance measurement

Hey, i recently got myself a pair of Dayton Nd105-4 drivers, and now im trying to measure the impedance curve with a crude self-build circuit and REW/Arta. The cable with the yellow connector is connected to the output of my behringer u-controll UAC222, the red rca is connected to the right...

www.diyaudio.com

 

[jabar102]

Thanks for the thread Roger, much appreciated! Looks like from reading through it that I might be better off not going down the route of using this UCA222.

 

[roger2]

I don't know jabar. The 3 graphs in post #20 show that when using headphones out (instead of line out) , the discrepancy is very slight and only occurs below 50Hz. So it may not matter much some cases.

I am new to this and learning. Not trying to influence your decision, just thought that the thread was relevant for you.

 

[Antonio Di Motta]

The Behringer UCA222 sound card has a serious low frequency crosstalk problem due to the input buffer that generates the error in the measurement of the impedance below 50Hz.
I was able to use it by bypassing the entire input buffer section and sending the signal directly to the integrated Audio PCM2902.
In addition, the board is also very noisy due to the lack of the integrated low noise stabilizer that adequately filters the + 5V of the USB socket.
Therefore, if you are not familiar with hardware changes, I do not recommend using this card.
Regards
Antonio