Sony LinkBuds Teardown: Using a hollow diaphragm to achieve a sense of air

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In early 2022, Sony launched the LinkBuds open-ear earbuds, which subverted our perception of traditional TWS earbuds in terms of appearance and function. The earbuds adopts a new ring-shaped drive unit, and the hollow design enables users to hear the external environment sound when wearing it. In terms of control, the earbud supports wide-area click control, and tap the cheek to realize earbud control.

The earbud supports adaptive volume control and can automatically adjust the volume after intelligently identifying ambient noise levels. The built-in microphone monitors external ambient sounds. When you need to talk, earbuds will automatically pause or resume playing music to achieve intelligent pick-free. In terms of configuration, the earbud is equipped with a V1 processor and supports the DSEE digital sound enhancement engine. It supports Bluetooth 5.2, the total battery life is about 17.5 hours, and it supports IPX4 waterproof rating.

52audio recently got the Sony LinkBuds earbuds and dismantled them. The appearance of the ring-shaped sound unit and the internal structure of the earbud will be revealed by our teardown in this article. Let’s take a look at the teardown of the earbuds.

Sony’s true wireless products disassembled by 52audio include: Sony WF-1000XM4, Sony WF-XB700, Sony WF-H800, Sony WF-SP900 true wireless waterproof sports earphones, Sony XPERIA Ear Duo open-back true wireless headphones and earlier TWS earbuds.


01/ Sony LinkBuds Unboxing

The outer packaging of Sony LinkBuds is designed in a square box, with hanging ears on the top for easy display. The front of the box shows the appearance of earbuds and the product name: SONY LinkBuds.

The top of the box shows that the earbud has a single battery life of 5.5 hours, and the charging case supplements the battery life of 12 hours. Total battery life is up to 17.5 hours.

Information on the back of the box, the packaging is made of environmentally friendly materials without plastic, and the product model is WF-L900.

Packing list: earbuds, charging case, earbud support bracket (XS/S/M/L/XL), USB A to Type-C cable.

Remove the outer paper cover and the LinkBuds LOGO is embossed on the top cover of the box.

There are suggested graphic instructions in the package to describe the linkage and wearing of earbuds and mobile APP.

The back of the instruction manual shows that the earbud supports the use of curved support brackets to fix the position. The factory is equipped with different specifications of curved support brackets such as “XS/S/M/L/XL”, which are suitable for different ear canals.

Remove all accessories from the box.

USB A to C data cable.

The charging cable interface is printed with Vietnamese production and Sony logo.

The included Arc Stand is loaded in a separate package with the Arc Stand dimensions marked on the package.

Curved support frame in XS/S/L/XL size, made of transparent high-toughness material.

The Sony LinkBuds charging case is made of matte material as a whole, the shell is made of renewable material, and the SONY logo is printed on the top.

There is a physical button on the front of the charging case for opening and closing the charging case. An LED light is also provided at the position where the case cover is in contact with the bottom case of the charging case to indicate the working state of the charging case.

The Type-C interface for charging the charging case is designed at the back end of the charging case. There is also a function button on the left side of the charging interface, which is used to realize the bluetooth connection, initialization and reset functions of earbuds.

Information on the back of the charging case. Model YY2953/WF-L900, rated voltage 3.7V, rated capacity 300mAh/1.11Wh. Output 5V⎓80mA, input 5V DC.

Open the charging case and you can see that the space inside the charging case is relatively compact. The inner side of the charging case indicator is provided with a buckle structure for fixing the charging case cover. The charging case adopts a stacked design, and the raised structure is used to provide storage space for the charging case battery.

Sony LinkBuds Earbuds

Take out of the earbuds.

The headphone cockpit is designed according to the shape of the earbud, which is more in line with the earbud. Above the three-pin charging contact is an elastic buckle that fixes the earbuds.

The Sony LinkBuds are completely different from any TWS earbuds on the market in appearance. It adopts a figure-eight design in which two circular parts are connected together. Among them, the ring-shaped design is a ring-shaped drive unit, and the circular design integrates components such as batteries, earbud motherboards, and microphone circuit boards.

In terms of materials, the earbud uses a matte textured material as the shell. The circular shell of the earbud is also provided with a microphone opening for providing a pickup function for voice calls.

The earbuds are placed in the palm of your hand.

In the hand-held state of earbuds, the front design is unique, which can provide an air feeling and comfortable wearing.

In the position between the battery cells, metal contacts for charging earbuds, sensor windows for in-ear detection, and L/R logos are designed. The circular shell also has arc-shaped brackets for fixing the earbuds on the ears.

There are multiple speaker openings on the inside of the earbud corresponding to the ring drive unit, allowing more music to come through.

There is a microphone pickup hole on the back of the circular unit, which is used to pick up the external sound to realize the adaptive tuning function.

The earbud has a ring-shaped structure and an arc concave hollow design, so that you will not miss the sound of the outside world when listening to songs.

The L/R logo is printed on the inside of the earbud to facilitate the distinction between left and right ears. On the edge are metal contacts for charging earbuds. The dark window on the right is the in-ear sensor location.

The production address Malaysia is printed on the side of the earbud.

The earbud’s charging current is 5V DC.

Use a portable power tester to test the wired charging of the Sony LinkBuds charging case. The charging voltage is about 5.23V, the charging current is about 0.29A, and the charging power is about 1.50W.

After actual measurement, the total weight of Sony LinkBuds earbuds + charging case is about 41.6g.

The Sony LinkBuds charging case weighs about 33.4g.

The total weight of the Sony LinkBuds earbuds is about 8.1g.


02/ Sony LinkBuds Charging Case Teardown

First pry off the earbud cockpit along the parting line.

The bottom shell structure of the charging case is equipped with multiple buckles to fix the earbud cockpit.

Above the earbud cockpit.

Below the earbud cockpit, the back battery is mounted on the midframe.

Behind the earbud cockpit, there is a Type-C charging interface and a micro-motion button.

On the side of the earbud cockpit, the battery is held in place using a custom bracket.

The hall sensor of the charging case is connected to the top of the board through a connector.

On the front of the earbud cockpit, there is an LED light guide column in the middle position.

There is a spring structure for opening and closing the charging case above the position of the light guide column in the earbud cockpit.

Information on the external label of the charging case battery, the battery is from Shuopeng Technology (Shenzhen) Co., Ltd., model 621733. Rated capacity: 300mAh/1.11Wh. Rated voltage: 3.7V.

According to 52audio’s tracking, plus the Sony LinkBuds, there are currently 16 products from 4 brands including Sony, JBL, GARMIN, DJI, etc. that use batteries made by Shupeng Technology.

Uncover the external label, earbud battery silkscreen information, model 621733, rated voltage 3.7V, rated capacity 300mAh/1.11Wh.

The battery is equipped with a circuit protection board, and the protection board has an IC for protecting the circuit and a MOS tube.

Remove the battery and use double-sided tape to hold the battery in place.

Remove the battery holder, there is a magnet under the holder to attract the charging case cover.

On the back of the battery bracket, there is a positioning column for fixing the motherboard. The spring is used to rebound the open key.

On the back of the charging case motherboard, the motherboard is fixed with screws, and two circular magnets are used to attract earbuds.

Remove the charging case motherboard.

The spring structure on the back of the earbud cockpit is used to fix the earbud. Even with the charging case cover open, the earbud will not fall off if you shake it hard.

Take out the independent module in front of the charging case, which is equipped with a light guide structure.

Standalone modules feature custom bracket mounting locations.

The back of the stand-alone module.

Remove the stand-alone module holder.

The screen-printed “XBK” Hall element, by sensing the magnetic field change (Hall effect) when the charging case cover is opened/closed, notifies the charging case control chip, and then informs the earbuds to connect/disconnect from the paired device to open the box and pair devices automatically function.

The back of the charging case motherboard.

The front of the charging case motherboard.

The Pogo pin connector that charges the earbud is protected by a plastic base.

The LED light on the main board is used to indicate the working status of the charging case.

Type-C interface female socket, used to charge the charging case.

The micro-motion buttons on the motherboard correspond to the function buttons behind the charging case.

Screen-printed “L3N6” TVS input protection tube for input overvoltage protection.

Mitsumi silkscreen A33 Zener tube.

TI BQ25618 charging IC, which integrates charging, boost converter and voltage protection functions, supports 22V withstand voltage, and is used to charge the earbud built-in lithium-ion battery.

TI BQ25618 details.

Silkscreen “17C1” booster IC for boosting the built-in battery to charge earbuds.

Silkscreen 20401 IC.

Silkscreen “75SY” voltage regulator IC.

NXP K32 L2B series microcontroller, built-in ARM-M0 core, customized model for Sony. It is used to realize charging case control functions such as charging and discharging module management, battery power management, indicator light control, and earbud communication.


03/ Sony LinkBuds Earbuds Teardown

First, remove the annular front shell and the circular rear shell along the mold line. The earbud shell is composed of a figure-8 shell in the middle and the other two shells.

The internal structure of the ring-shaped front shell is fixed with glue around the unit. The sound outlet of the unit is not provided with a dust filter.

Earbud ring unit.

Earbud ring unit side.

After actual measurement, the size of the ring diaphragm of Sony LinkBuds earbuds is about 13.09mm.

The ring-shaped unit voice coil is connected to the base by welding, and the welding position is glued and reinforced.

The front and rear shell circuits of the circular part of the earbud are connected by FPC cables.

The earbud battery is mounted in a circular case via a transparent plastic bracket and reinforced with glue.

The earbud motherboard is designed in the circular rear shell.

Heat up to remove the glue, take out the battery and expose the sub-board of the earbud.

The back of the button-type lithium battery is fixed on the rear shell of the earbud with a custom bracket.

The button battery is from ZeniPower, model Z32H, rated voltage 3.85V, rated capacity 0.12Wh.

52audio has learned that Sony WF-1000XM4, Sony  WF-H800, Philips SHB4385 and other products have adopted ZeniPower button batteries.

The motherboard on the inside of the earbud round front shell.

Remove the ring-shaped sound unit of the earbud.

The earbud annular shell has a special design on the inside corresponding to the sound unit to improve the acoustic performance of the earbud.

On the front of the ring-shaped sounding unit, the diaphragm is directly exposed.

The back of the ring-shaped sounding unit is embedded with a metal ring.

On the side of the ring-shaped sounding unit, the solder joints of the voice coil wires are full. The two pins are used to connect the earbud motherboard, and the connection method is soldering.

earbud circular back shell circuit.

The internal structure of the front shell of the circular shell, and the position of the charging contact is provided with a circle of silicone sleeves for waterproofing.

On the front of the earbud charging board, the black sealing double-sided tape occupies most of the area of ​​the sub-board.

Remove the bracket on the round rear case to fit the bracket of the button battery in a fixed position.

Round back case battery holder. The bracket can not only fix the main board on the casing, but also fix the battery part.

Remove the motherboard of the circular rear case.

A small circuit board is also arranged inside the circular rear shell, and a metal contact is arranged above the small plate.

Remove the circuit board. The position of the microphone pickup hole is provided with a milky white waterproof membrane.

A MEMS microphone is fixed with white glue in the middle of the circuit board, and the microphone is connected to the metal contacts of the circuit board through metal connecting wires.

Another metal contact on the circuit board is connected to the bluetooth antenna on the back of the board. In the center is the microphone pickup hole.

The front of the main circuit of the earbud circular rear shell is connected by an FPC cable.

Earbud round back shell main circuit back.

On the front of the earbud charging board, there are metal contacts for charging the earbud and an in-ear sensor.

On the back of the charging board, there is a metal shrapnel in contact with the button battery.

Connect the negative terminal of the button battery to the negative metal shrapnel that supplies power to the earbud.

Silkscreen 761PK4U1 integrated battery protection IC.

Metal contacts for charging earbuds.

The sensor for in-ear detection enables you to listen to the sound when you put on the earbud, and automatically pause the music when you take off the earbud.

The back of the earbud motherboard.

The front of the earbud motherboard.

Connect the Pogo pin connector to the positive side of the coin cell battery.

Regulator IC with silkscreen “BVL”.

Silkscreen “C1GA” storage IC.

Silkscreen “XF 3X” IC.

The silk-screen “5N1EA” acceleration sensor is used to realize the acceleration induction of earbud.

Connect the metal shrapnel of the bluetooth antenna on the back of the circular back shell microphone board.

The earbud motherboard has another 3 metal shrapnel, which are used to connect with the metal contacts of the microphone board to supply power to the microphone.

The main control chip of Sony LinkBuds adopts MediaTek/Airoha MT2822 platform solution. This chip supports the latest Bluetooth 5.2 version, is equipped with Airoha MCSync TWS dual-transmission bluetooth transmission mechanism, supports LDAC encoding for wireless high-resolution sound quality, and helps WF-1000XM4 obtain Hi-Res Wireless sound quality certification.

Sony’s leading noise cancelling technology combined with the active noise cancelling filter function integrated on the MT2822 platform can provide consumers with an excellent listening experience and enjoyment. It has the characteristics of fast operation speed, good noise cancelling performance, and low power consumption.

All components of Sony LinkBuds open-ear true wireless earbuds.


04/ Summary

In terms of appearance, Sony LinkBuds has subverted the image of the previous earbuds. It adopts an 8-shaped open design and has a built-in hollow ring diaphragm to provide an open listening experience.

The main control chip of the charging case adopts NXP K32 L2B series microcontroller with built-in ARM-M0 core, which is customized for Sony, and is used to realize charging case control functions such as charging and discharging module management, battery power management, indicator light control, and earbud communication. In terms of charging, earbud uses TI BQ25618 charging IC, which integrates charging, boost converter and voltage protection functions, supports 22V withstand voltage, and is used to charge the built-in lithium-ion battery of earbud.

The battery of the charging case is from Shupeng Technology (Shenzhen) Co., Ltd., model 621733. Rated capacity: 300mAh/1.11Wh. Rated voltage: 3.7V. It can provide an additional 12h of battery life for earbuds stability.

In terms of internal configuration of earbud, the main control chip adopts MediaTek/Airoha MT2822 platform solution and supports Bluetooth 5.2 version. Equipped with Airoha MCSync TWS dual-transmission bluetooth transmission mechanism, it supports LDAC encoding of wireless high-resolution sound quality.

The earbud has a built-in acceleration sensor, which is used to realize the acceleration sensing of the earbud and realize wide-area click touch. There is a MEMS microphone at the position of the circular rear shell of the earbud to realize adaptive volume adjustment and call pickup functions.

The button battery of the earbud comes from ZeniPower, model Z32H, with a rated voltage of 3.85V and a rated capacity of 0.12Wh. The size of the ring diaphragm of the earbud is about 13.09mm.

Source: 52audio


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