# Stereo measurement - why does averaged L & R look so different from actual stereo measurement?



## nicknace (Feb 10, 2011)

Measuring my friend's Focal 816 speakers in my garage this morning. Each speaker produces a very flat wave, but together very different. (Thicker orange line is the averaged). I think I understand but am only 51% sure.

The speakers are side by side 3 feet apart, against a wall, no toe-in. Umik-1 was placed 5 feet away, between the speakers. Room is about 20x20 ft vaulted ceiling with a lot of exposed concrete and wood paneling.

Many thanks,

Nick


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## nicknace (Feb 10, 2011)

Never mind. I figured it out. Comb filtering.


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## AVoldMan (May 15, 2011)

nicknace said:


> Never mind. I figured it out. Comb filtering.


Isn't it the interference pattern caused by both of the speakers having the same signal and not measuring exactly in the mid-point between them? If the mic was precisely placed between the speakers and they a matched speaker set the measured output should be 6 dB (or is it 3 dB) higher in level.


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## rhtjytku (Jan 21, 2021)

Comb filtering.






192.168.100.1 192.168.1.1


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## valer (Apr 16, 2018)

It is why when you are listening a speaker pair that is in the same showroom than other speakers you will never ear the real speaker reproduction: the non powered drivers are moving due to the energy provided by the powered speaker.
The same phenomenon is happening stereo mode when the right speaker generate a sound and the left speaker is not.


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## Ed Oz (Mar 29, 2018)

So...which graph most closely represents what a listener hears?


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## valer (Apr 16, 2018)

It is the individual speaker graph that is used.
You are trying to have each speaker able to produce your target curve .
you need to correct each speaker one by one with EQ or room correction.
Stereo is easy to do manually.
Multichannel system is easier to correct with the AVR room correction process.


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## Ed Oz (Mar 29, 2018)

Thanks!


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