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Did the WF-1000XM4 just pass through the FCC? (update 4)

Sony YY2948 WF-1000XM4

So what do we have here, Sony YY2948. The model name gives nothing away, but that label photo looks awfully like a charging case for wireless earbuds. The model number is intentionally left out in the documents, but the product name remains "Wireless Noise Canceling Stereo Headset". 

Sneaky Sony, sneaky.

Update 1:
While I initially noticed this difference in the power rating of the unit versus the WF-1000XM3, I did not think much of it. But mirai160525 on twitter pointed out something interesting. The WF-1000XM4 appears to have monopole antenna versus the dipole antenna and they mention that such a change should lower the power use, but the WF-10000XM4 has a higher rating. mirai160525 goes further to suggest that maybe the higher power rating could be for LDAC, no idea, could be. The version of the WF-1000XM4 tested was a prototype where as the WF-1000XM3 was pre-production. I am attaching the antenna information from the reports below.

Sony YY2948 WF-1000XM4
Click on photo for larger size

Sony YY2948 WF-1000XM4
Click on photo for larger size

I also looked at the other WF models, the WF-H800 and WF-SP800N are both monopole antenna as well, the WF-1000X has an inverted-F antenna design. I only information for the WF-XB700 I can find is that it uses a  FPCB antenna. I can attach the antenna design photos if people want me to.

Update #2
The WF-1000XM4 has appeared on the Bluetooth certification site. The YY2948 has been certified for Bluetooth 5.2. Comparing it to the WF-1000XM3, the supported layers are identical, so not sure if the device was tested for LE Audio (unlikely), but the MT2822 which is part of the certification does have the required support layers for LE Audio. The MT2822 certification also confirms that the SoC is an Airoha chip, part of the AB156x family. Photos attached below.
Sony YY2948 WF-1000XM4
The combined designs, 157713, 163117 correspond to Airoha Hummingbird Duo 5.2 and MT2822 respectively. Perhaps this Bluetooth certification could indicate a much earlier release date and not the late September date if we go by the End of Short Term Confidentiality.
Update 3: 
The model has gone through E-postel, but I missed it earlier. So far nothing on any other website, like Anatel, but here is hoping it will show up soon. Apple has said they might face some product shortages, likely due to the current electronic parts shortage globally. Although not sure if this will affect headphones or just high end devices like smartphones and computers. Hopefully there will be no delay in the release of the WF-1000XM4 but even if announced relatively soon, I suspect the model would not go on sale for another month or 2.
Sony YY2948 WF-1000XM4

Update 4:
I rarely update these that late, but I was finally able to find Industry Canada's website for their certifications. Unfortunately no new information from here, the RF exposure is less than the WF-1000XM3 (0.95 W/Kg), now rated at 0.36 W/Kg.
Sony YY2948 WF-1000XM4

Sony YY2948 WF-1000XM4
For comparison, the WF-1000XM3 numbers.

End of Update
Clearly we are looking at some new wireless earbuds from Sony. In the documents, the right part is only tested since both the left and right are the same as mentioned in the FCC filing:

* Only right part was representatively tested by client request since left part and right part are the same specification.

Sony YY2948 WF-1000XM4

Likewise, a charging case is mentioned in the label document, so we are definitely looking at a wireless earbud headset here.

Since headset part to be applied is small and there is no space,
it is described in charging case and manual

But is this the WF-1000XM4? Unless Sony has another wireless earbud headset coming, my guess is yes, this is the WF-1000XM4. Digging deeper into the documents reveals the new Bluetooth SoC being used for the new model, different than the Mediatek MT2811 found in the current model

Sony YY2948 WF-1000XM4 MT2822S
So we are looking at a new Bluetooth SoC, MT2822S in the new WF-1000XM4. Similar software was used on the WF-SP800N in its FCC filing, but with M2811S_BT_Test instead. The WF-1000XM3 also had MT2811S_BT_Test as well in its FCC filing, but since I had no knowledge of the Mediatek MT2811 back then, I had no idea what MT2811 was. When 52Audio posted their teardown of the WF-1000XM3, did I then only realize this software was in reference to the Bluetooth SoC.

Mediatek MT2822S

So what is the MT2822S? I believe this is a rebrnaded Airoha AB1568. My reasoning is based on 2 pieces of information, first, a post on reddit by AMD_Fanboy_Wavpro who confirmed the AB1568 and MT2822 are the same; second, a linkedin account which mentions the AB1568 and MT2822 as the same chip. This individual works at Airoha.

The full specifications of the AB1568 are up on Airoha's website here and one can compare it to the MT2811/AB1552x here.  Here is a quick table comparison of the 2 Bluetooth SoCs, some aspects like power management are a mystery to me.

AB1568/MT2822 AB1552x/MT2811
CPU ARM® Cortex®-M4 up to 208Mhz
192kB memory
ARM® Cortex®-M4 up to 156Mhz
embedded 4MB flash
DSP Cadence® HiFi Mini®Audio Engine DSP coprocessor
-Maximum speed: 416MHz
-704kB memory
Tensilica HiFi mini Audio Engine DSP
-Maximum speed: 312MHz
Bluetooth Bluetooth 5.2 Qualified
BR, EDR, Bluetooth Low Energy, Dual-mode Bluetooth
Supports Bluetooth low energy isochronous channel
Bluetooth 5.0 dual mode, including low energy profiles
Highly integration PMU built in LDO and bucks
Supports BC1.2 charger detection
Li-ion battery charger from for internal charging
Over-current and thermal overload protection
Precision voltage measurement for fuel gauge
Integrated Li-ion battery charger supports over-discharging protection
Integrated Buck and LDO regulator
Audio Support 24-bit 192KHz HD Audio and Hi-resolution codec
Side-tone filter
Hardware Active Noise Cancellation(ANC)
-Feedforward ANC
-Hybrid ANC
16/24-bit data addressing format
mono or stereo data transactions
Hardware gain control
Noise suppression
Support 24-bit 192KHz HD Audio and Hi-resolution codec
Noise suppression and echo cancellation
Multiband Programmable EQ and Dynamic Range Control
Ambient sound
TWS Hybrid Active Noise Cancellation
-Feedforward ANC
-Feedback ANC
Memory System in Package (SiP) 64Mb flash memory
Software FOTA
Voice assistant support
Reference IOS and Android smart phone APP
Voice prompt
Voice assistant support
Reference IOS and Android smart phone APP
Voice prompt
Package 5mm x 5mm TFBGA package 6.2mm x 6.2mm BGA Package
(MT2811 - 4.8mm x 4.8mm)

If anyone wishes to comment on anything here in the comments to explain any further differences, please go ahead. 

The biggest differences I can see are the faster CPU, different DSP, new Bluetooth version 5.2 support (most likely for LE Audio, Isochronous channel), and more embedded memory. I would imagine Sony will be pairing the SoC with their QN1e again like in the WF-1000XM3 for superior Noise cancellation and sound quality.

Going back to the charging case, the shape and size looks like it is wider but not as long as the WF-1000XM3 charging case. The new shape of the case does look like it could fit the new rounder design seen from the leak in February. Using the text height from the label (1.5mm), I get an approximate size of 64.44 x 28.1 mm for the case (width x length).

I am assuming the photo of the case from the label document is correct and not just an estimation. Regardless, the shape of the case is definitely different when compared to the WF-1000XM3, more closer to the WF-SP800N and WF-XB700. Both headsets with more rounded earbuds.

Apart from the FCC, the model appeared on the Korea's FCC as well. Not much was revealed in the filing this is why I did not post it up, but now that we know these are new wireless earbuds, the Made in Malaysia makes more sense and does help support the WF-1000XM4 theory.

Sony YY2948 WF-1000XM4

Of course I could be wrong and this might be something completely different. But I suspect this is the WF-1000XM4. 

Reveal date

The short term confidentiality ends on September 27th 2021, so I would imagine we will see the new headset revealed before that date. 

Comparing to the WF-1000XM3, its short term confidentiality ended on July 5th 2019 and the press release was July 4th, so 1 day before. This does not mean Sony will wait until September 26/27th for a reveal, they could just as easily introduce it earlier (IFA 2021) but if it shows up on the September 27th, I will not be surprised. 

As always, if anyone has any more information please leave a comment or contact me through the contact page.


  1. Cool, thanks buddy up!

  2. just hoping it is announced earlier than september.

  3. Great news! Any chance they will release this month?? ha

    1. April? unlikely I was told the retail box design was supposed to be confirmed in march/april, so that still wasn't finished. Likewise the device on FCC was a prototype, not pre-production, so still sometime before it comes out.

    2. How about May?

    3. unlikely, too early, especially after such a recent filing.

  4. I do hope I will see a substantial upgrade in XM4 from XM3

  5. I see Sony released the white WH XM4 to coincide with 75th anniversary in May. I hope they also release the WF xm4 in May

    1. Would be great, but I wouldn't hold my breath.

    2. B+W's just announced PI5 and PI7 are really tempting me right now, especially since one review said the PI7 is the best sounding pair out there right now. Would prefer to go with the WF-1000XM4 so tough decision lol

    3. if you can't wait and need a headset now, get what is best out there.

    4. This is the same boat I am in. Killed my old xm3. Have tried the momentum 2s (huger senn fan), mw07 plus, mw08, jabra 85t. So far the jabra are the only ones that sound good enough, anc works well enough, and stay in my ear. Trying to decide between returning the jabras and trying the pi7, or keeping the 85t and waiting for the sonys. Ugh! Hurry up sony!

    5. Both of the B&W products looks enticing, especially the PI7. If Sony's WF-1000XM4 doesn't come with hybrid drivers or even a larger drivers than the current 6mm, then I'd rather get these from B&W. Back when the XM3 came out, the competition was not as big, now Sony needs to step up their game to be at the top.

  6. They will be bigger than 6mm

    1. Looks like this information was wrong.


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