Sony LinkBuds Engineer Interviews

Sony unveiled their new Linkbuds last week, and as is the case from time to time, Sony Japan has released an interview with some of the designers and engineers. I will not be copy and pasting the entire interview here, having read through it, I will post some of the interesting bits and post my thoughts about what the interview reveals. The full interview can be found here, but it is in Japanese, so you will need to translate it.

The interview starts off discussing the concept of the LinkBuds and what were the factors which shaped their design, specifically the rise of streaming music services like Spotify. While I personally do not use Spotify, or other music streaming services, I can see their appeal especially if you have an unlimited data plan on your phone for such a service. It seems that the new LinkBuds are partly directed at "Generation Z" with the interview making the point that this group of people a lot time listening to music. From what I have seen, this seems to be a general trend, with many people having their headphones on the street, in stores or on public transit. I suspect the rise of truly wireless headphone is also one main reason why so many users have headphone on all the time. 

                    

But I question what percentage of users want to hear the outside world when wearing headphones? I know personally I would rather keep outside noise out. Maybe there are users who wish to be aware of their surroundings and hear outside sounds, like in an office. I would not mind testing out a pair to see how well they work and how they sound but I would rather wait and save up money for whatever the YY2950 is, just in case it is something special.

Ide, who was in charge of acoustic design, explains that Sony was able to achieve a good sound response from low to high frequencies even with the open design. Turning down the volume allows the outside noise to enter the ear, giving a sensation of the music being played in the background, like in a store perhaps. But turning it back up will drown out the outside noises and sounds. But the SoundGuys review points out the sound quality is not anything to get too excited about. The bass is rather poor and but indoors they seem adequate. Still I would not mind testing them out to see how they perform.

The headphones are designed such that they should lie and fit well inside the ear. But I am sure there will be users who will have issues with keeping these earbuds in their ears. Sony puts the LinkBuds size down to something they call "じこうかい" or Jikokai according to Google translate. I cannot find anything specific to to word online, so perhaps someone can explain it better in the comments. Update, thanks to the anonymous comment, the translation is just the part of the ear concha, the place where the main unit sits. The size of the earbuds seems rather small, so I am curious if the battery capacity is the same as the WF-C500/WF-1000XM4 or smaller. Looking forwards to seeing a full teardown online, again most likely from 52Audio.

The Sony interview provides us with a glimpse of some the internal parts, but for the time we will use a render from Sony of the internals. We can see that the unit is divided into 2, the driver part, and the main body. While the render does not show any rubber seals, I do believe the main body is IPX4 certified so there should be a rubber surround between the body and cover.

Looking at the render, we can see there are 2 PCBs visible, the main top one with the Mediatek MT2822 (V1) and the second board under the battery which should include the optical sensor and charging pins. The ribbon cable might either connect to another smaller PCB or will just have the battery contact on the actual ribbon cable. I do wonder how the bottom board is connected to the rest of the unit, perhaps the ribbon cable extends around to the other side and down to the board.

The main board has what appear to be 4 on board contacts situated the right and top of the main chip. We will see later on, but these connect to the printed wireless antenna and to the MEMS microphone connections on the plastic piece under the main cover.

Thanks to the interview, we have our first look at the new ring-type driver.

Photo courtesy of Sony.jp

In the interview, Ide from Sony explains that with a hole in the middle of the unit, the diaphragm would lack the power to provide adequate sound pressure, and apart from the sound quality, the bass would not be as deep. So the engineers at Sony experimented with various designs and came up with the design we can see on the right in the above photo. But the SoundGuys review seems to refute this pretty much.

The ring design is composed of 2 transparent rings with the black ring the actual diaphragm from what I understand. This black ring vibrates to product the sound. Even though the surface area looks rather small, Sony claims they were able to engineer it so that sufficient bass and sound pressure were produced. This is because the new ring diaphragm uses special high-compliance material which permits the diaphragm to move as much as it could. I am guessing the left side shows a standard driver unit.

 

To achieve a proper mid-range frequency, the way the LinkBuds sit in the ear, the driver unit sits in front of the ear canal and in turn the eardrum. Therefore the headset is able to reproduce the mid-range clearly, confirmed in the SoundGuys review.

One main obstacle for Sony with the LinkBuds was size and shape. A larger ring-driver would produce better sound quality, but this would come at the expense of making the ring structure bigger and would make wearing the LinkBuds uncomfortable. The objective was to make the best sounding headset at the most compact size.

This is why the ring-driver housing and diaphragm protector have been integrated into one. In addition the Mediatek MT2822 (V1) with its integrated functions like power management and DAC, also removes the need for separate chips with these functions. To further reduce the size, Sony has moved the call microphone from the main PCB to the underside of the wireless antenna piece. I do believe this is a first for Sony.

Photo courtesy of Sony.jp

We can see the MEMS microphone attached to the underside, along with some surface mount resistors. The pads do not really match up to the connectors on the main PCB, so I guess the CGI render of the internals is not 100% accurate. This makes me wonder what else in the render will look different on the real LinkBuds.

One issue Sony had during the development was proper fit of the headset in the ears without them feeling uncomfortable after a prolonged use and keeping them in place during movement. Since everyone has a different ear shape and structure, Sony came up with the idea of special fitting supporters that would fit under the antihelical fold and hold the headset in place. Sony will be including 5 different sizes with the LinkBuds, XS, S, M, L, XL. The photo on the left shows the XS size attached to the headset. I really hope Sony will sell replacements of these, since people will lose them. Because if you lose them, keeping these in your ears might be an issue.

With the new LinkBuds, Sony has gone a step closer in their Green Management 2025 program. Sony launched this program in 2010, with the final goal of having zero environmental impact by 2050. The packaging of the LinkBuds contains no plastic whatsoever, with the entire package made from paper, but I am not sure if this is from recycled paper. The same type of packaging can be found in the WF-C500 and WF-1000XM4. I would imagine that the upcoming WH-1000XM5 will also use this paper packaging.

In addition the body of the headset and the charging case both use recycled plastic which is why both the white and gray colours have a speckled appearance.

A newly developed microphone that makes full use of AI technology makes the
user's voice natural and clear.

I have read a few reviews and reports that mention that the quality of the voice microphone on the LinkBuds is superior to the WF-1000XM4 and comparing the audio quality on the SoundGuys reviews for both headsets, it does seem like the LinkBuds have superior microphone quality.

Sony claims the new AI algorithm filter for voice and ambient noise is based on more than 500 million samples using machine learning. Perhaps Sony can also transfer over this new AI algorithm to the WF-1000XM4 in future firmware updates to improve their voice call quality. After all, both use the same SoC, the MT2822. But then the LinkBuds have their call microphone more or less as close to the pickup hole as possible, something not present in the WF-1000XM4.

The new MT2822 is supposed to be very power efficient and Sony claims a music playback time of up to 5.5 hours and 2.5 hours for voice. This seems a bit less than stellar, considering the WF-1000XM4 with the same SoC, with NC off and DSEE Extreme on Auto, can get up to 8 hours of playback. The LinkBuds do not even use DSEE Extreme, only DSEE. So the question is, is the battery in the LinkBuds smaller? Or does the new ring-driver use that much more power versus the smaller 6mm driver on the WF-1000XM4? Again we will have to wait for a full teardown.

In the press release and product website, Sony mentions IPX4 water resistance, but you will need to click the tiny little note which says that this IPX4 rating only pertains to the main body unit, excluding the ring driver and the charging case. Funny thing is, the driver unit will not be fully covered in everyone's ears so there will be scenarios where some users will experience water damage when running in the rain.

As for other precautions, Sony recommends cleaning the unit with a soft dry cloth but in extreme situations one can use a diluted neutral detergent, making sure to ring out the cloth before cleaning.  Do not use any alcohol based cleaning products on the device as this will damage the surface. The same precautions exist for the WF-1000XM4.

                     

Finally unlike the WF-1000XM4, there is no touch sensor, instead a tap sensor is used to control the headset. The function is called the Wide Area Tap, which requires the user tapping near the ear to control the volume, skipping tracks, etc. Click here to see the various functions of the Wide Area Tap. The headset does have an automatic volume adjustment setting that can be turned on in the Sony Headphone app, but SoundGuys report that this function is quite disorienting and they would rather use the Tap function. Besides the Auto volume control also drains the battery faster and with a mediocre 5.5 hours of use, best to keep the function off.

Small update from an AV Watch interview

There is an AV Watch interview (link at the end) with Yutaka Nakamura, who is the General Manager of Mobile Products Division, Sony Home Entertainment & Sound Products Business Division.

First off, the development took 3 years with the aim to develop a unique product. There was discussion of using bone conduction but Sony decided against this as the sound quality is not that great. But Sony does mention that they are still developing/investigating bone conduction for possible future products.

The development of the ring-driver was a separate endeavor and the LinkBuds are the first product to use them. The interview goes on to point out the main body with the Bluetooth chip is half the size of the WF-1000XM4, ie "no wasted space". From the WF-1000XM4 teardown, while there are some empty spaces inside them, I do not think there is wasted space. Perhaps Sony could have used a larger battery or maybe used a larger driver if there was extra room.

Apart from the chip, the LinkBuds do not share anything else with the WF-1000XM4, so I guess this also means the battery is different, perhaps a smaller capacity? I do feel the MEMS microphone could be the same as in the WF-1000XM4, so perhaps Nakamura meant other major components. 

Nakamura brings up an interesting piece of information regarding possible future products. Where as before Sony started with a high end product like the WH-1000X series and then they would move down to expand the lineup. It seems this is no longer the strategy with Sony now reducing its lineup of products. Maybe headphones like the WF-C500 or WF-XB700 are no longer on the cards for a future lineup or we will only get high end and middle range devices with no more low end?

The interview also addresses the LinkBuds name and how the model number WF-L900 is not being used in marketing, since LinkBuds would be easier to remember and search for. Likewise Western market prefer a name to a model number. That being said Sony will not be moving to a model name for future products and will continue to use the model number like 1000X for example.

Finally the interview finishes on the current semiconductor shortage if it will this affect the LinkBuds. Sony claims this will not be the case. So perhaps they have enough stock of chips and parts, but I do wonder if the profit per each unit has dropped due to rising prices of parts.

Just in case anyone is wondering, no I did not get paid to write this post, nor is it sponsored. And now we wait for a teardown. If people wish to donate any money to help me save up for a LinkBuds and perform a teardown, you can always donate on Paypal.

Sony Interview | SoundGuys Review | AV Watch