@WiiM Team,
These are the results of a preliminary test of this feature.
■Test Equipment
WiiM Ultra
Main speakers: Focal Chorus 806
Subwoofer: Polk Audio MXT10 (down-firing)
Measurement microphone: Dayton IMM-6C
First, I positioned the microphone 100 cm from the main speaker and 220 cm from the subwoofer, and tested each at crossover frequencies of 60 Hz, 80 Hz, and 120 Hz.
(We have conducted the same test multiple times and confirmed that the results are nearly identical. We found no particular issues in this regard.)
▼Test Result 1-------------------
<Test Environment>
Distance from microphone to main speakers: 100 cm
Distance from microphone to subwoofer: 225 cm
Crossover:
60 Hz
Results
Main speakers: +9.229 ms delay
Subwoofer: +0 dB Level
▼Test Result 2-------------------
Crossover:
80 Hz
Results
Main speakers: +8.479 ms delay
Subwoofer: +0 dB Level
▼Test Result 3-------------------
Crossover:
120 Hz
Results
Main speakers: +7.833 ms delay
Subwoofer: -4 dB Level
Well, I ran into an error here.
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Next, I moved the microphone and tested it in the same way.
Mic -> Main speakers : 200cm
Mic -> Sub: 150cm
▼Test Result 4-------------------
Crossover:
60 Hz
Results
Main speakers: +4.125 ms delay
Subwoofer: +0 dB Level
▼Test Result 5-------------------
Crossover
80 Hz
Results
Main speakers: +3.813 ms delay
Subwoofer: -6 dB Level
▼Test Result 6-------------------
Crossover:
120 Hz
Results
Main speakers: +3.333 ms delay
Subwoofer: -14 dB Level
I’m not an expert with 40 years of experience in this field, so I can’t say for sure whether these results are accurate. I’ll run a verification test using Gemini later, but at first glance, the delay correction seems to be working fine. However, I still have some doubts about the volume adjustment.
So, I used RoomFit’s evaluation feature to compare the raw responses before and after calibration. Here, we compare the response with that of "Test 6," which had the widest range of sub-volume adjustment.
First, here is the response before calibration.
This is the response after calibration.
The WiiM calibration function reduces the gain by 14 dB, using the subwoofer’s loudest frequency (70 Hz) as the reference point.
As a result, if you run RoomFit in non-boost mode after calibration, the subwoofer’s frequency can't be corrected.
As things stand, if such adjustments to the sub-volume are made during auto-calibration, I believe it will be necessary to readjust them manually.
Well, since this alone is clearly too few test cases, I also looked at the response when calibrated with a crossover at 80 Hz. These are the raw responses for "Test 5" before and after calibration.
This is before calibration.
This is after calibration.
Unlike when the crossover is set to 120 Hz, you can see that the gain is adjusted starting from 30–40 Hz.
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Finally, I restored the Ultra to its official firmware and tested the current sync functionality. I conducted this test under the same conditions as "Test 6."
I’m not entirely sure why, but a delay of +39 ms was added to the subwoofer (rather than the main speaker).
And this is a response based on the evaluation.
...Following the verification results from Gemini.
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