Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Software Tools SPICE, PCB CAD, speaker design and measurement software, calculators

Measuring loudspeaker impedance with HolmImpulse - possible?
Measuring loudspeaker impedance with HolmImpulse - possible?
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 12th June 2012, 09:46 PM   #1
IG81 is offline IG81  Canada
diyAudio Member
IG81's Avatar
Join Date: Feb 2008
Default Measuring loudspeaker impedance with HolmImpulse - possible?


I use a Behringer UCA222 USB interface, which is supposed to be full duplex and has 2 channels, input and output sections.

I'd like to have HolmImpulse read the voltage at the input of the UCA222, which would be the voltage accross the 8ohm resistor in series with a driver. I'd export the voltage vs frequency data to a spreadsheet to convert to impedance vs frequqency, much like I do manually.

It did not work when I tried and I'm not certain why. One thing I'm not sure of is, where you choose the I/O devices, there is no distinction between the input or output "section" for "USB audio codec", much like how I can set the microphone for the ouput device (I don't know why this is allowed). So I am not even certain it even tried to read the UCA222's input.

Is this even feasible?

  Reply With Quote
Old 8th January 2019, 04:44 PM   #2
Lojzek is offline Lojzek  Croatia
diyAudio Member
Lojzek's Avatar
Join Date: Feb 2012
Location: Croatia
Lightbulb Better late than never!

I was playing around and arrived at a solution how you could achieve that. Basically you connect a circuit like it is drawn and measure voltage drops across resistor and driver. These 2 plots will have to be manipulated by introducing a division of these two responses, driver voltage drop being in the nominator part of the fraction. HolmImpulse calls it C=A/B. Once you are done with that, remains to multyply the result by 15, and that means you would have to increase the resulting response by +23.52 dB. This comes from:


Now this resulting response is your impedance in dB, and in order to appear in ohm is needed this:

Z(ohm)=10^(Z/20); Z being you end result of measured impedance in dB.

Funny though, HolmImpulse can switch the amplitude scale from dB to linear scale and that is actually your Z in ohms. Still, the exported file will be in dB, so it needs a little work on the file to appear in ohms.

There has been a thread on Behringer uca 202 having issues with measuring impedance because of the capacitor in the sound card, so its own impedance rise at low frequencies adds to the one of the device under test. Perhaps doing the impedance measurements this way, will make this sound card a little more practical.

0 dB in the plots equals 1Vrms.
Attached Images
File Type: png Z measurement.png (25.2 KB, 80 views)
File Type: png V R15.png (39.3 KB, 81 views)
File Type: png V dr.png (43.8 KB, 81 views)
File Type: png Vdr divided by Vr15.png (44.3 KB, 81 views)
File Type: png Vdr divided by Vr15 and multiplied by 15=Z in dB.png (45.4 KB, 81 views)
File Type: png Amplitude in linear scale=ohms.png (48.1 KB, 11 views)
  Reply With Quote
Old 8th January 2019, 06:00 PM   #3
Pano is offline Pano  United States
diyAudio Moderator
Pano's Avatar
Join Date: Oct 2004
Location: SW Florida
Measuring loudspeaker impedance with HolmImpulse - possible?
Thanks for that. These days we could also use REW and get a direct reading in ohms.

FWIW, I've tried to use my old WT3 with both HOLM and REW and can't get good results. Too bad, as the hardware still works, but the software for the WT3 isn't current.
Take the Speaker Voltage Test!
  Reply With Quote
Old 10th January 2019, 05:02 PM   #4
tthorsten is offline tthorsten  Germany
diyAudio Member
Join Date: Nov 2008
you can measure impedanz also with SATlive SATlive Audio Measurement Software
  Reply With Quote


Measuring loudspeaker impedance with HolmImpulse - possible?Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
HOLMImpulse: Measuring Frequency- & Impulse-Response askbojesen Software Tools 1088 10th February 2019 02:51 AM
Measuring a loudspeaker close to a wall wigginjs Multi-Way 2 3rd April 2009 03:02 AM
loudspeaker measuring/design software Jean Multi-Way 11 20th November 2002 06:51 AM

New To Site? Need Help?

All times are GMT. The time now is 04:09 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio