REW graphs do not align with experience

AlexRossFan

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Preamp, Processor or Receiver
Denon X3700H
DAC
Soundblasterx G6
Universal / Blu-ray / CD Player
Sony X700
Front Speakers
JBL Stage A130
Center Channel Speaker
JBL Stage A125C
Surround Speakers
JBL Stage A130
Front Height Speakers
Polk V60
Rear Height Speakers
Polk V60
Subwoofers
SVS PB-1000 Pro
Video Display Device
LG OLED C9
My sub is svs pb-1000 pro. I'm trying to find out why the sub has port chuffing noise at one position in the room (Position 3) but not at another position (Position 14) after Audyssey calibration. I used REW (ASIO4ALL, LFE channel only) to generate graphs in order to visualize Before vs After Audyssey but it made little sense to me. Please see the process below:

1) First, these were the post-Audyssey results:
Position 3: speaker preset 1, sub trim = -4.5, sub gain = -19
Position 14: speaker preset 2, sub trim = -4.0, sub gain = -15
I usually watch movies with master volume = -15, DEQ enabled

2) I started the investigation by placing the sub at Position 3, selected speaker preset 1, put the sub gain at -19, and turned off MultEQ XT32. I then lowered the master volume until the REW SPL meter read 76-77db. The master volume settled at -19.5. I started the measurement. This should show "Before Audyssey" (Blue):
53822


I then enable MultEQ XT32. This should show "After Audyssey" (Yellow):
53823

So it seems like Audyssey didn't touch the dips at around 24hz (which was where the chuffing noise was the loudest I suppose) and only cut down on the peaks.

3) I then placed the sub at Position 14, selected speaker preset 2, put the sub gain at -15, and turned off MultEQ XT32. I kept the same master volume level from before and the SPL meter still read 76-77db, which made sense. I started the measurement. This should show "Before Audyssey" (Red):
53824

I then enabled MultEQ XT32. This should show "After Audyssey" (Green):
53825


As we can see, Audyssey now clearly boosted the dips at 24hz. Plus the sub gain is at -15 (higher than -19 of Position 3). So if there is chuffing noise from the sub, it should occur when the sub is at this Position 14 instead of Position 3, no? Hope someone can explain this for me. Thanks.
 
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