Sony WF-1000XM4 teardown by 52Audio

We finally have a full teardown of the new Sony WF-1000XM4, time to see what secrets it reveals. The teardown was performed by 52Audio.com. Check out their full teardown for all the photos. Photos courtesy of 52Audio.

First a close up of the new earbud tips.

My Sony XBA-A3 tips also use polyurethane foam in the middle but I with regular silicone rubber on the exterior. Looking at the WF-1000XM4 tips, they appear o be a different material than rubber. Maybe someone can confirm this in the comments.

I looked at the notes in the Sony’s help guide for the tips and I am kind of alarmed from what I read. For instance:

Do not subject the polyurethane foam portion of the earbud tip to pressure for over long periods of time. It may cause deformation and it may be difficult to return the earbud tip to the original shape.

Hmm, what does long periods of time mean? Hours? Days? The longest one can use the earbuds nonstop is 12 hours, so beyond this time the deformation occurs? In addition Sony states that through long-term use and storage, the tips may deteriorate. Understandable, things wear out, but does Sony (outside of Japan) offer these earbuds for purchase once you need to replace them? If not, I suspect users will be importing them from Japan or other areas where these replacement tips will be sold. The replacement tips are the Sony EP-NI1000, I only see them on Amazon Japan, but not sure if these can shipped outside of the country.

Finally I will point out something important from the guide, do not use any detergents, alcohol or other cleaners to clean off the tips, only use a dry cloth. I have seen a reddit post where an individual used rubbing alcohol to clean the tips and this damaged them severely.

Looking at the feed-forward microphone hole, 52Audio says the design is special to minimize wind noise, and if wind noise is detected, the earbuds will turn on wind noise suppression. I do hope dirt and grime do not build up in the holes because the do not look the easy to clean.

Charging Case

Looking with the bottom removed, we can see the wireless charging coil. While I have seen some users attaching a USB type-C wireless charging pad to their WF-1000XM3 and then covering them in a case, I wonder if it would be possible adding such a coil to the inside of the original case?

I wonder if such a coil could be added to the WF-1000XM3? I know there are wireless charging coils that connect via USB type-C, so perhaps that could be somehow integrated into the WF-1000X3M3 inside the case? But that is an idea for another post.

In this post, I speculated the coil would be soldered to the PCB and the battery in the case could be disconnected for replacement, looks like I was right.

I would have preferred if Sony used a connector for the wireless charging coil as well, easier/quicker assembly and repairs but I understand that most people would not be replacing the this part often, unlike the battery which can just be unplugged and might need replacing in the future.

The battery is rated at 3.85V 2.0Wh (520mAh), the WF-1000XM3 battery in comparison is rated at 4.2V 2.59Wh (700mAh). The model is SP702428, meaning 7.0mm tall, 24mm wide and 28mm long. There does not appear to be much extra space around the battery, so I doubt a larger one can be installed. Looking at Aliexpress, I could no find any battery with similar dimensions.

While you can just unplug the battery from the PCB, there is a surge protection PCB attached to the battery which must be replaced or come with the replacement battery. I would imagine most replacement batteries, especially from Sony would ship with the surge protection PCB.

And now looking at the PCB. The upper portion of this PCB is the power management and the lower portion for the wireless charging according to 52Audio.

1. Texas Instruments BQ25618 charging IC
2. Renesas Electronics IDT P9222-R
3. Texas Instruments TPS6124x
4. 2047 323 input protection chip.
5. Voltage regulator – Mitsumi A33

The other side of the PCB has one main large chip, NXP K32 L2 MCU. This apparently controls the case functions like charging, discharging, battery power management, headset communications, etc. 52Audio claims it is a custom chip designed for Sony.