Design: Interview with ZX1 Designers

With uncompromising attention to detail, the NWZ-ZX1 achieves truly realistic sound that resonates in the heart of the listener. We went behind the scenes of history’s best-ever Walkman model to learn more about its development, and discovered a team of professionals who were passionately dedicated to achieving the best possible audio quality.

Full story after the break.

Concept
The Ultimate Hi-Resolution Experience
Delivered in a pocket-sized package.

Attention to detail has been the focus of every aspect of the Walkman® ZX1, but the audio quality is particularly exceptional. What was the background to its development?

Sony’s Home Entertainment and Sound Business Group developed a comprehensive strategy to open up a new market by simultaneously launching a group of Hi-Res (High-Resolution) audio playable products, from mobile devices through to home entertainment systems. So on this occasion, the Walkman® was developed as part of this group of products, rather than as a standalone project. Our flagship ZX1 model was developed as a product that would symbolize the mobile side of this Hi-Res strategy.

- Yasuhiro Onogi, Product Planning

What aspects did you concentrate on when planning and designing the concept for this model?

Our product concept is the ultimate audio experience delivered in a pocket-sized package. The complete audio experience comprises not only audio quality, but also facets of usability such as ease of operation and connectivity, so these are areas that we considered carefully.

For example, we wanted to ensure compatibility with iOS, as well as supporting a variety of different codecs such as Apple Lossless, AIFF, and FLAC. Furthermore, we believed that the ultimate audio experience would need to offer customers a full-featured, stress-free environment in which to listen to music, so we ensured that the user interface of our music player would be clear and easy-to-understand, with sharp operations. In addition, the specs allow for seamless connectivity with other Hi-Res devices in the various categories being developed by Sony, as well as with websites offering downloads from Hi-Res sound.

- Yasuhiro Onogi, Product Planning

Who do you envisage to be your target users?

Well naturally, we hope that consumers who already enjoy Hi-Res content will love the ZX1. But we also want people who don’t yet have Hi-Res content to listen to it. That’s why we say that the ZX1 is for “all music lovers.” Every generation has consumers who long for the ultimate audio experience, so this product is targeted at a wide variety of ages.

- Yasuhiro Onogi, Product Planning

Until now, Hi-Res was really only aimed at high-end audio users. However, we hope that the arrival of our ZX1 and F880 series Walkmans®, which are Hi-Res audio file playable, will expand this consumer base to include regular users. As a portable audio player, the quality is really exceptional.

- Tomoaki Sato, Project Leader

A special feature of this model is that we began its development by taking cost out of the equation. Usually, the planning process begins by deciding on the sales price, and then determining which device specs we will be able to use within this price framework. However, in the case of the ZX1, our slogan was simply to “create the ultimate portable audio player.” Quality was always our leading priority, so we proceeded to develop a product that would have a value and sales price within the range of 50,000 to 100,000 yen.

As for audio quality and design, factors which directly influence the price, we left it completely up to the respective professionals, instructing them only to “Do whatever you like, regardless of the cost. We just want you to create the ultimate device.” We intentionally refrained from specifying too many requirements, because we wanted to leverage the maximum effort from everyone on the team. The creative process was a complete departure from regular models, and I think this is what has resulted in the quality of our ZX1.

- Yasuhiro Onogi, Product Planning

What did the engineers think when they were told that they had such a high degree of freedom in the planning process?

When we were first told that there were no cost restrictions, I actually felt that, as an engineer, the job would involve more pressure than usual (laughs). I had heard that there were several people within our company who had taken a commercially-available Walkman® and then customized it by replacing certain components for even better sound quality. Since we had been told that for the ZX1, our overriding priority was to improve the sound, I decided to call upon several of these audiophiles to form an audio quality design team.

- Tomoaki Sato, Project Leader

I’m one of the members of this audio quality design team. The existing Walkmans® also produced great sound, of course, and knowing that the components had been carefully selected for the balance they offered in terms of cost and size, I believe they achieved the best sound possible under those conditions. But personally, I felt there was still room for improvement. As a kind of hobby, I had been quietly experimenting for two or three years by opening holes in the body of my Walkman and then somehow cramming in and soldering large components that would not normally have fit, in the hope of achieving even better audio quality.

We had several possible ideas for producing superior audio quality, and basically, they have all been incorporated into the ZX1. I have to confess that I never thought that we would be allowed to use so many great ideas in one device!

- Yasuhiro Onogi, Product Planning

Sound
The Quality Aspired to by the ZX1
Endless days of unrestricted trial and error. Our goal was to find ‘pure’ audio quality.

Did your quest for pure sound proceed smoothly?

We spent many days repeating experiments and testing audio in our search for improved sound quality. Based on many new ideas accumulated by the Audio Quality Design team, we tried various things such as increasing the thickness of the battery wiring and boosting the power supply...

There were components that we knew from the outset we would not have been permitted to use in other, regular models due to their unsuitability for volume production. However, with the ZX1, the attitude was consistently more like “Right. We need that for the best audio quality - how do we go about making sure we can include it?” This stance was maintained right to the end, and really expanded our options. With plenty of issues needing to be fine-tuned, our team members meticulously waded through the process of trial and error while continuing to refine the sound quality.

- Tomoaki Sato, Project Leader

As you can imagine, changing a single component could require a complete reshuffle of the internal layout, and that was our challenge in Mechanical Design. For us, this was fraught with problems, and we suffered long days of agony as we tried to accommodate countless minor adjustments (laughs).

- Ryo Tsuchiya, Mechanical Design

Yes, that’s true. Our main priority for the ZX1 was audio quality, so we frequently found ourselves shifting the extra burden to Mechanical Design. Not only that, this new model is equipped with AndroidTM, so it also contains radio wave-related features such as Bluetooth®, Wi-Fi, and even GPS.

- Tomoaki Sato, Product Leader

These elements cannot be completed individually, but must be comprehensively integrated. Numerous components had to be carefully incorporated together within a limited space while maintaining the overall balance, so we really had a tough time with the ZX1 in comparison to other models.

- Ryo Tsuchiya, Mechanical Design

What advantages were to be gained by removing the coupling capacitor?

The coupling capacitor is a component that blocks the direct current (DC) signal and allows only the alternating current (AC) signal to pass. If either the positive or negative power source has direct current, the electromagnetic movement of the headphones will be one-sided and could cause a fault. The capacitor therefore acts as a kind of safety filter, but being a high-pass filter, it has serious disadvantages such as causing low-pass levels to fall, and generating phase lag.

From this perspective, the S-Master HX does not require a coupling capacitor because its system uses both positive and negative power sources, and voltage applied to the electromagnet transits to both the positive and negative sides centering on 0V. Normally, this technology would be avoided due to the expense and space required on the circuits, but our focus was on the benefits of achieving crisp, sharp bass sounds.

- Hiroaki Sato, Audio Quality Design

So what kind of audio quality did you aim to achieve with the ZX1?  

In a nutshell, we were after as robust and pure a sound as possible, with no embellishments. We wanted a sound quality that leveraged the unique characteristics of the various headphones available around the world. However, we also had to consider that the ZX1 was principally a portable audio device that would be used in a mobile environment, so instead of focusing solely on large, open-back headphones used in the home, we also tested the sound using a variety of headphones from other companies, in addition to Sony-branded accessories. I believe that the pure audio quality found in Hi-Fi sound is characteristic of the ZX1.

- Hiroaki Sato, Audio Quality Design

Why did you decide not to include any headphones with the ZX1?

The ZX1 is a product in the upper price bracket, and we’re confident that the type of consumer who purchases it will be a true music lover. Accordingly, there is a high probability that they will already own a pair of quality headphones. So rather than have Sony dictate which headphones should be used, we intentionally decided that the customer should have the freedom to enjoy music with the tone color characteristics provided by their preferred headphones.

- Yasuhiro Onogi, Product Planning

What are the benefits of having four power sources (Left, right, positive, negative) for S-Master HX full digital amp?

Portable audio amps generally only have a single power source, and in some rare cases, perhaps two. For the ZX1, we wanted to remove the component in front of the headphone output known as the coupling capacitor, so we opted for a system that creates waveforms using both positive and negative power sources.

In addition to the push of the positive power source, the pull from the negative power source facilitates increased braking performance, and by equipping the device with four power sources, a sufficient supply of electrical current can be ensured. This provides a much stronger driving force, which has led to an extremely powerful device that produces robust, reliable audio output even for headband-type headphones, while complete isolation of the independent L/R power sources prevents mixed signals between left and right for a superb stereo sensation.

Compared to analog amps, the S-Master is more susceptible to the effects of power supply noise, so the number of power sources was increased to secure a higher grade power supply. Although this involved an added cost component, it was vital given that our highest priority is audio quality.

- Yasuhiro Onogi, Product Planning

The device is now equipped with DSEE HX technology. This handy feature is sure to be highly valued, as it enables compressed sound to be upgraded to Hi-Res-equivalent quality.

Yes, that’s right. As we previously mentioned, there are bound to be many customers who purchase the ZX1 but who do not yet have Hi-Res content. That said, it seems unfair to have to re-purchase songs you already own in MP3 format, just to obtain the same song in Hi-Res.

Naturally, customers will want to make the very most of the content they already have, and we wanted them to be able to enjoy the wonderful sound of their favorite songs in Hi-Res-equivalent quality. It was this realization that prompted me as a member of the Product Planning team to insist 1that we add this feature to the ZX1, right when development was being finalized. It was a bit of a bombshell for the engineers (laughs).

- Yasuhiro Onogi, Product Planning

Architecture
Uncompromising Design for Superior Audio Quality
A complete revamp with audio quality as the highest priority. Unanimous agreement on the clear difference in sound.

Could you elaborate on what your objective was in enhancing the power supply, particularly in adopting the large OS-CON capacitor?

Personally, I really wanted to use this component, but it was not normally used in portable audio devices due to its size. It’s a component with a lot of height, so usually, companies shy away from using it. We created a substrate fitted with the OS-CON, together with another two candidate capacitors, and together, our team tested the audio quality of the three varieties. We unanimously agreed, hands-down, that the OS-CON clearly offered a different sound, with powerful bass notes, extended high ranges, and sleek vocals in the mid-ranges, so our decision was made!

- Hiroaki Sato, Audio Quality Design

In what ways does the POSCAP charge pump power source excel?

This component is mounted at the base of the power source, and is characterized by its low ESR (equivalent series resistance). It acts as a capacitor in a wide frequency band. Clean electrical current, from which noise has been removed, is passed from here to the OS-CON to ensure that the final sound is crystal clear.

- Hiroaki Sato, Audio Quality Design


The cables connecting the battery to the amp substrate power source seem to be thicker than usual.

If based on calculations alone, a thinner cable might have been sufficient and would not have caused any power-related issues. However, our testing revealed that a shorter, thicker cable resulted in reduced noise. This really affected the degree of power in the bass notes and the extended high ranges, so we decided that keeping this component would also have to be non-negotiable.

- Hiroaki Sato, Audio Quality Design

At first I was skeptical (laughs) about whether having a thicker cable would truly make any difference, but then I heard the difference in the actual sound… The difference was really remarkable.

- Tomoaki Sato, Project Leader

The FET (field-effect transistor) used for the power supply switch on the battery protection circuit was also modified to accommodate bigger electrical currents, and this has also been effective in improving audibility.

- Hiroaki Sato, Audio Quality Design

Electrical current flows through the circuit constantly, even when the protection circuit itself doesn’t function, so we made the wires thicker. Impedance (resistance of electrical current) was lowered by making all wires thicker, including the cables connecting the battery to the amp substrate power source and the traces used inside the circuits, and I was amazed to observe just how much the sound actually improved when I listened, not to mention the heightened expressiveness of the audio.

- Tomoaki Sato, Project Leader

Is it true that a dedicated crystal oscillator has been mounted for the clock in the D/A converter?

For digital audio, the base clock is extremely important. Waveform quality has been improved by using a crystal oscillator that outputs the frequency with high precision, thus reducing jitter (temporal difference in signal waveforms) and accordingly, producing clearer sound. The installation of this dedicated oscillator is a huge strength of the ZX1.

We use an extremely thick, low-resistance OFC (oxygen-free copper) cable for output from the substrate to the headphone jack. It was really important that we were able to transmit the sound to the headphones without loss, so right from the start, I insisted upon using OFC for this purpose, and we proceeded from there.

However, the development team later questioned whether OFC was really necessary, so we substituted it with a generic cable of the same thickness. However, as expected, the transparency of the sound fell dramatically. These results confirmed just how much the OFC cable contributed to the audio quality, so after that, I insisted a little more loudly (laughs).

- Hiroaki Sato, Audio Quality Design

OFC cable is rigid and difficult to manipulate, so we in the Mechanical Design team felt it was a bit of a nuisance (laughs). Furthermore, the specified OS-CON occupied approximately double the space of a regular capacitor, so no matter how efficiently we tried to assemble all the components, the front-bottom portion remained stubbornly thick.

- Ryo Tsuchiya, Mechanical Design

We have also made improvements to the low-pass filter for removing unnecessary noise from the digital amp. This circuit is formed from a coil and a capacitor, and generally uses a ceramic capacitor. However, film capacitors deliver much sleeker vocals in the mid-ranges, so while monitoring the overall balance, I decided that a film capacitor was better suited to the audio quality we were pursuing, and we adopted it accordingly.

- Hiroaki Sato, Audio Quality Design

The robustness of the headphone jack also deserves special mention.

We have used metallic components to increase rigidity and ensure a structure that resists rattling. This enables the correct contact pressure to be maintained, so that noise caused by vibration when a user is walking around can be prevented.

- Hiroaki Sato, Audio Quality Design

Design
Natural design
A design that naturally expresses the personality of the product

How did you feel when you were first asked to design and create the ultimate product any way you liked?

When the Product Planning team first mentioned that there were no cost restrictions, I was really surprised, because it was the first time I had ever heard anyone say such a thing at Sony (laughs). I felt incredibly inspired, and very excited. There was no pressure at all.

- Shogo Yashiro, Design

The shape of the ZX1 represents the product’s strong determination. I’m interested to hear more about the concepts behind your design.

Everyone has their own interpretation of design, but personally, I believe that a design should express the personality of the product as much as possible in order to create good, strong architecture. For example, the ZX1 has a distinctive bump on its back. The bump occurs due to the shape of internal components such as the OS-CON. It would have been difficult to attempt to absorb this shape as part of a normal design, so instead, we decided to make the most of it by incorporating it as a feature. As soon as I saw it, I felt inwardly happy, as it seemed like a little treasure trove with its own unique look.

That’s why, more than anything, our design was intended to link together, as seamlessly as possible, the various factors needed to achieve our high audio quality. The result is this highly desirable, natural ZX1 shape. As with our concept for audio quality, we wanted to ensure that our design would have no superfluous embellishments or colorings – we just wanted the polished quality and degree of perfection to speak naturally for itself.

- Shogo Yashiro, Design

It’s immediately apparent that the ZX1 is completely different to the flat style that is characteristic of smartphones and some other devices

Yes, we really wanted to make sure that the ZX1 was distinguishable from smartphones. After all, the Walkman® is an audio player, and we felt strongly that we should aim for a shape that could only be achieved by a dedicated music device.

Although smartphones are great products with various features condensed into their thin, flat cases, I feel that other features have probably had to be sacrificed in order to achieve this thin shape. I hope we have succeeded in drawing a clear line between that kind of device and the shape of the ZX1. Rather than focus solely on how thin a device can be, we decided to pursue a shape that would enable us to unleash the maximum potential of the product.

- Shogo Yashiro, Design

So the bump on the bottom-rear panel is proof that you never gave up on high audio quality, but rather that you gave it the highest priority.

Yes, that’s right. If the rear bump was required to accommodate the high audio quality capacitor, then we decided that we would show it off as a feature of the design rather than attempt to conceal it. We felt that it was much more straightforward to draw the user’s attention to the bump and let them know that something special was contained within.

It’s true that some people may not find the shape to be ideal because of the way the device leans when laid on its side. It’s also true that partway through the process, the suggestion was made that we make the device completely flat to match the thickness of the bump. I may be biased, but I believe that objects and humans are all more attractive when they have some kind of special noteworthy feature.

- Shogo Yashiro, Design

What is the purpose of the rubber grip on the back of the device?

We made some fine adjustments to the undulation and gradient of the surface, to take into account the center of gravity of the device when held in one’s hand. We then affixed some soft-touch rubber and tweaked it so that it would function as a grip, to ensure that the bump would not have any negative elements when used. The soft rubber gives the device a much more comfortable feeling when held than metal or plastic.

- Shogo Yashiro, Design

Although rubber is not a material that has been associated with Walkmans® in the past, Sony has plenty of experience using rubber with digital cameras, including single-lens reflex cameras, so we were able to accomplish this task smoothly.

- Ryo Tsuchiya, Mechanical Design

The world of the ZX1 seems to be dominated by the monochromatic colors of silver and black, so the gold headphone jack on the ZX1 is a welcome accent.

The brass housing for the jack component was not originally part of the design requirements. I personally suggested that we add it in order to firmly affix the large-model jack. Incidentally, the 3.5 mm stereo mini plug is a standard that was developed by Sony for the first generation Walkman®. It has now become the global standard. Knowing this background, I thought it would be meaningful to make this component an iconic focal point of history’s finest Walkman®.

- Shogo Yashiro, Design

It’s clear that the included carry case is also an extension of the design concept.

As with any fashion item, consumers have their own preferences when it comes to color and style. So for our carry case, we requested a simple, tasteful design that anyone could happily use.

- Yasuhiro Onogi, Product Planning

We used only simple, planar, minimalistic elements to achieve a natural shape when encasing the device body. As with the device itself, we have avoided adding any unnecessary colors.

- Shogo Yashiro, Design

Body
Chunky and highly rigid
A framework to solidly support high audio quality. Sturdy machined aluminum body.

Why did you decide to use a machined aluminum frame for the body?

At the beginning of development, as a kind of field trip, our team went to Akihabara together to thoroughly observe the various kinds of high-end audio devices available. We looked at the uniform mood and grade of the product casings, and checked to find reasons why certain products might look less desirable. The results of our investigation led us to the conclusion that we needed to adopt machined aluminum as our main material.

- Shogo Yashiro, Design

A lump of thick aluminum undergoes various processes until it is finally machined into “single layer formations,” which have a much higher rigidity than regular materials. Naturally, this texture can be confirmed directly by the users themselves when they hold the device. I believe that it is the machined aluminum body itself that achieves the simple, strong world view projected by the ZX1.

-  Ryo Tsuchiya, Mechanical Design

This material also contributes to our superior audio quality, because the body’s increased rigidity works to isolate ambient static electricity, which causes noise. This is a huge advantage for portable audio devices, which by nature are used in a variety of locations, including at home and outdoors.

Although it is not possible to fully suppress unnecessary vibration from the drive section as with a CD player, a robust sound can be achieved by firmly mounting the device, which is another benefit.

- Yasuhiro Onogi, Product Planning

Another advantage of single layer formation is that ground is stabilized.

The machined aluminum body is a component for the external appearance, and has been designed specifically to double as a structural framework. All electrical components, including the substrate, have been firmly affixed to the interior of the aluminum casing, and electrical connections have been placed in strategic locations.

- Ryo Tsuchiya, Mechanical Design

When several layers of structural components are screwed together, voltage lag can occur between the two ends. However, the ZX1 uses a simple construction with a single substrate firmly affixed to the interior of the body. This ensures that ground is stabilized and the unit overall will be electrically flat, demonstrating that single layer formation is also desirable from an audio quality perspective

- Tomoaki Sato, Project Leader

The hardware buttons on the side of the device are also packed with various features

The first thing we conveyed to the Mechanical Design team was that we wanted users to have to press slightly harder than the usual light touch to which they are accustomed. We also wanted the buttons to be round and simple, so we set ourselves a challenge to see how much we could improve the user-friendliness of the device using only simple elements such as differences in pitch and size.

We created many prototypes with button sizes that differed by only 0.1 or 0.2 mm each, making adjustments according to operability or the rhythm of their appearance. The high precision of the machining contributed greatly to this attention to detail and fine-tuning.

- Shogo Yashiro, Design

The aluminum is machined using a circular motion, so it makes sense that circular holes are the easiest to create. Therefore, a round button design is able to leverage the full properties of this processing technique. As just mentioned, the difference in the size of the buttons can be extremely important. For example, a user may sometimes need to operate their Walkman without visually confirming which buttons they are pressing, such as when the device is located inside a bag. This would be difficult to accomplish if all the buttons were designed to be the same size, and located at equal intervals from one other. From this perspective, we have tweaked the layout design of the ZX1 so that the volume button is instantly recognizable and easy to use, with its large shape and slightly overlapping edge.

- Ryo Tsuchiya, Mechanical Design

Each area of the device body seems to feature a slightly different finish on the surface of the aluminum, such as the spin finish of the buttons.

That’s right. Although we didn’t color the aluminum in any way, we were able to achieve a variety of different finishes and looks by manipulating the surface of the metal. For example, the buttons feature a spin finish with metallic gloss, which was achieved by using a spiraling process.

A blasting process was used on the main face of the model, as well as on the portion of the rear surface that does not have a rubber covering. This achieves a matte look for a more subtle metallic finish. Additionally, hairline processing has been performed on the sides of the device to achieve a sharper image. This is extremely rare in other products due to the technological difficulty in creating a hairline that can extend all the way around the perimeter of the device. Please note the difference in contrast when compared to the finish obtained using the blasting process.

- Ryo Tsuchiya, Mechanical Design

To conclude, do you have any messages you would like to share with ZX1 users?

The ZX1 was created by a group of engineers who love music, and who love the Walkman®, and we had a lot of fun doing it. We have every confidence in this product. The device contains a lot of tricks of the trade for improved audio quality that we had developed as hobbyists for our own personal enjoyment, without much thought for incorporating such tricks in a commercially-available device. We really hope you will be moved and inspired by the superior audio quality, and we definitely recommend that you try it out for yourself.

- Tomoaki Sato, Project Leader

We were given free rein so long as our objective was audio quality, and it’s true that we had a lot of fun making it. Conversely, it meant that we couldn’t cut corners, and that sometimes put pressure on us (laughs). It may seem like an exaggeration, but I truly feel that I have put everything I could into this project, and I am willing to stake my professional reputation as an engineer when I say that this device represents the fusion of sound and sincerity. Everyone has their own personal tastes when it comes to music, so I hope you will slip on your preferred headphones, play a few of your favorite songs, and allow yourself to enjoy the full ZX1 audio experience.

- Hiroaki Sato, Audio Quality Design

I may be repeating myself, but I really hope that consumers will take the opportunity to savor the look and feel of the complete ZX1 as soon as possible, from the rigidity of the body through to the natural color and appearance of the aluminum material itself, the luster of the gilding covering the brass, and the soft touch of the rubber on the back of the device.

- Ryo Tsuchiya, Mechanical Design

Naturally, we believe that consumers will be able to use this high-end device for many, many years to come, and we have aimed to create a design will continue to look fantastic even ten years from now, regardless of trends that may come and go. It would bring me great joy as a designer to know that our customers will love the ZX1 and get many years of pleasure from it.

- Shogo Yashiro, Design

The ZX1 delivers the best possible audio experience that Sony can currently achieve from a portable audio player. We have all spoken at great length (laughs) about the many wonderful features of the ZX1, but to be honest, the best way to fully appreciate these features is to listen for yourself. I heartily recommend that you drop into a nearby Sony Store to experience the audio quality of the ZX1.

In conclusion, I’d also like to mention that our user interface boasts many meticulously-chosen features, so I hope these are not overlooked. We have tried to incorporate a true sense of fun into the device. For example, the icon buttons on the screen have the appearance of aluminum to match the actual buttons on the side of the device, while the story line of the three pre-installed wallpapers encourage the user to polish rock until it transforms to metal. Furthermore, we have prepared a large music player widget to ensure that when the customer opens the box and connects the power, the device will unquestionably take on the appearance of an audio player.

Although these last aspects are not directly related to audio quality, they are an important part in terms of creating the world view of ZX1, so I hope that you will take the time to look closely at the ZX1, because our team of UI designers has worked above and beyond the call of duty to perfect this product for you.

- Yasuhiro Onogi, Product Planning

Source: Sony Canada