Waves on the graph

Adeptuz

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How can these waves be explained?
Where do they come from?
Measurements in the car, at the same volume.
e-mu 0204
dayton audio imm-6
2.jpg
1.jpg
 

John Mulcahy

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Is there some monitoring active? If any of the input is fed back to the output it creates feedback. Make sure the direct monitor level on the 0204 is completely off.
 

Adeptuz

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No, monitoring is disabled, with it I would not be able to sit in the car, my ears would have broken from the terrible increasing noise.
With the internal sound of realtek the same problem. Strange, it disappears and appears again, I don't see any pattern.
Any more ideas?
 

John Mulcahy

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The problem is a peak in the measurements around 327 ms before the true peak, sometimes the early peak is larger than the later peak and gets chosen instead. Because of the left hand window width both peaks are included in the response in that case, and the large time delay between them results in the small frequency spacing of the ripple. Does the system have a lot of latency? FIR processing, for example?

37083


Looking at the frequency response of the early peak it might be crosstalk in the interface.

37084
 

Adeptuz

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The problem is a peak in the measurements around 327 ms before the true peak, sometimes the early peak is larger than the later peak and gets chosen instead. Because of the left hand window width both peaks are included in the response in that case, and the large time delay between them results in the small frequency spacing of the ripple. Does the system have a lot of latency? FIR processing, for example?

View attachment 37083

Looking at the frequency response of the early peak it might be crosstalk in the interface.

View attachment 37084
When i made measurment with acoustic timing reference, difference between R and L always about 315-320 ms. May be it is DSP processing of amplifier or slow android sound system in the car?..
In attachment measurments of line out (renault rlink), without any peak. Realy terrible SPL)
 

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John Mulcahy

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The early peak is much smaller in those measurements so no risk of REW thinking it is the measurement peak.
 
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