3rd Order Harmonic Distortion in my in-room measurements

wigginjs · 23rd November 2009, 12:35 PM

I've been doing some in-room measurements of my speakers at my listening position and I'm seeing large amounts (~10%) 3rd order harmonic distortion throughout the entire measurement, but very low (~0.1%) 2rd order harmonic distortion. Is there something in particular about a measurement setup that would result in this? Or is this possibly due to room interaction? Why is 2nd so low, but 3rd so high?

breez · 23rd November 2009, 01:27 PM

What frequency range are you measuring? Low frequency measurements may not be very useful because of modes amplifying and attenuating both the fundamental and distortion components.

What kind of measurement is it? Perhaps logsweep or just a single tone with spectrum analyzer?

Pano · 23rd November 2009, 01:31 PM

Yes, please tell us more about your measurements.
And do you get similar results if you measure the speakers up close?

wigginjs · 23rd November 2009, 01:44 PM

I'm measuring 10Hz - 20KHz with ARTA "Steps", so I guess that's a series of single tone measurements. I have not compared it to up-close measurements. That would probably be a really good diagnostic step.

doug20 · 01:49 PM

Quote:

Originally Posted by wigginjs

I'm measuring 10Hz - 20KHz with ARTA "Steps", so I guess that's a series of single tone measurements. I have not compared it to up-close measurements. That would probably be a really good diagnostic step.

Are your measurements Gated? I would say if you are measuring below 200Hz then they probably aren't ?

btw, I use ARTA too so I do have a side question. Did you get ARTA calibrated so its displays the right SPL values? I can never get the SPL calibrated to show the right values

Andi · 23rd November 2009, 01:50 PM

use the logsweep with arta to confirm. normally you might not necesserly hear this 3rd order distortion, it is hard on the boarder of perception i would say. are the other harmonics also very high, when you go on distortion d%, you can see the others too. if there also high, than it might be distortion in your measurement set up, or maybe dirt in the voice coil....????

JohnPM · 23rd November 2009, 03:14 PM

Odd harmonics may be an indication of clipping somewhere in the measurement chain.

Pano · 23rd November 2009, 06:21 PM

Yes indeed! That's why a closed mic'd measurement would help.

23rd November 2009, 12:35 PM	#1
wigginjs diyAudio Member Join Date: Dec 2003 Location: Columbia, SC	3rd Order Harmonic Distortion in my in-room measurements I've been doing some in-room measurements of my speakers at my listening position and I'm seeing large amounts (~10%) 3rd order harmonic distortion throughout the entire measurement, but very low (~0.1%) 2rd order harmonic distortion. Is there something in particular about a measurement setup that would result in this? Or is this possibly due to room interaction? Why is 2nd so low, but 3rd so high? __________________ The Four Chairs DIY Home Theater

23rd November 2009, 01:31 PM	#3
Pano diyAudio Moderator Join Date: Oct 2004 Location: North Carolina Blog Entries: 4	Yes, please tell us more about your measurements. And do you get similar results if you measure the speakers up close? __________________ Take the Speaker Voltage Test!

23rd November 2009, 01:44 PM	#4
wigginjs diyAudio Member Join Date: Dec 2003 Location: Columbia, SC	I'm measuring 10Hz - 20KHz with ARTA "Steps", so I guess that's a series of single tone measurements. I have not compared it to up-close measurements. That would probably be a really good diagnostic step. __________________ The Four Chairs DIY Home Theater

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23rd November 2009, 01:27 PM	#2
breez diyAudio Member Join Date: Jul 2004 Location: Finland	What frequency range are you measuring? Low frequency measurements may not be very useful because of modes amplifying and attenuating both the fundamental and distortion components. What kind of measurement is it? Perhaps logsweep or just a single tone with spectrum analyzer?

23rd November 2009, 01:50 PM	#6
Andi diyAudio Member Join Date: Nov 2009 Location: south Germany	use the logsweep with arta to confirm. normally you might not necesserly hear this 3rd order distortion, it is hard on the boarder of perception i would say. are the other harmonics also very high, when you go on distortion d%, you can see the others too. if there also high, than it might be distortion in your measurement set up, or maybe dirt in the voice coil....????

23rd November 2009, 03:14 PM	#7
JohnPM diyAudio Member Join Date: Oct 2008	Odd harmonics may be an indication of clipping somewhere in the measurement chain.

23rd November 2009, 06:21 PM	#8
Pano diyAudio Moderator Join Date: Oct 2004 Location: North Carolina Blog Entries: 4	Yes indeed! That's why a closed mic'd measurement would help.

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