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HT-A7000 engineer interview

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matthewcornwell
Contributor

HT-A7000 engineer interview

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Soundbars that can enhance sound when placed under your TV are gaining attention nowadays, as we spend more time at home. Today, we take a look at HT-A7000, the new Sony flagship soundbar. Read on as the developers of HT-A7000 explain just what it can do.

 

Developers

Itagaki

Home Product Planning Department

Home Product Business Division

Sony Corporation

 

Sonoda

Home Mechanical Design Department

Home Product Business Division

Sony Corporation

 

Negishi

Home Product Technology Department

Home Product Business Division

Sony Corporation

 

Yana

Home Product Technology Department

Home Product Business Division

Sony Corporation

 

Hashimoto

Home Product Planning Department

Home Product Business Division

Sony Corporation

 

Sato

Home Product Planning Department

Home Product Business Division

Sony Corporation

 

Watanabe

V & S Software Engineering Department Development Department 2

Home Entertainment & Sound Products Business Group

Sony Corporation

 

Yoshida

Studio 1

Creative Center

Sony Group Corporation

 

HT-A7000 is the new flagship soundbar.

 

First, can you tell us about the most recent trends in the home theater market?

 

1.jpgHashimoto: Home entertainment demand has been increasing while televisions have been steadily growing in size and improving in resolution. With this, there has also been a big growth in subscribers for video streaming subscription and live streaming services.

 

Under these circumstances, soundbars have been attracting attention as devices that can be connected to TVs and really enhance sound experience. Sony has been selling a wide range of products in this market, from high-performance flagship models to more affordable entry-level models and “minibar” models. This has been helping to enrich the time we spend at home with our families.

 

 

What kind of product is the one we’re talking about today, HT-A7000?

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Hashimoto: HT-A7000 is our new flagship soundbar which features 7.1.2-channel. The greatest advantage of this product is that it has an enhanced surround sound feel, as well as sound dispersion that is compatible with the increase in size of recent televisions. To go into detail, the up-firing speakers that reflect sound off the ceiling and newly developed side beam tweeters that reflect sound off the walls combine with Sony’s original signal processing technology in this model to create impressive sound dispersion, and sound space expression, for sound experiences that feel rich and real.

 

Itagaki: This product is the successor to HT-ST5000, the 7.1.2-channel flagship soundbar we released in November 2017. We designed the new model to surpass the predecessor not only in functionality, but also in sound quality.

 

Next-generation sound experience in a single soundbar

 

How exactly is Sony’s new flagship soundbar HT-A7000 an advanced version of its predecessor? Can you first tell us a bit about how it’s a more advanced version hardware-wise?

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Yana: What we primarily aimed to achieve was a device that fits big screen TVs, expands the sound space, and creates immersive sound. The process of achieving these things isn’t quite as simple as just expanding sound along with the expanding size of the screens. By expanding sound beyond the screen, we aimed to create a sound experience that would make it feel as if you were really entering the space you see on the screen.

 

To do this, we installed five speakers on the front face of the soundbar, two up-firing speakers that recreate height and direction of sound, and beam tweeters on the left and right sides of the soundbar. Unlike the subwoofer that came with the previous flagship model HT-ST5000 as an external attachment, we installed two of these within the new soundbar itself.

 

Can you explain each of these features, starting with the front speakers?

 

Yana: For the five front speaker units, we are using Sony’s original “X-Balanced Speaker Units”. When it comes to soundbar sizes, demand ends up leaning toward soundbars with limited height. However, for speaker units with the same sound power level, the smaller the area of the diaphragm, the more difficult it is to generate sound pressure. With the X-Balanced Speaker Unit, the shape of the diaphragm is made as close to a square-like ellipse as possible to maximize its effective area so that a large diaphragm can be used even when there is limited space.

 

On the other hand, the problem with non-circular diaphragms is that they make it difficult to maintain amplitude balance. Here, we would like to draw your attention to the pattern embossed along the edge of the soundbar. This is the feature that improved the amplitude balance even with the elliptical diaphragm.

 

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Can you tell us more about the benefits this has in terms of sound quality?

 

Yana: With the enlarged effective area of the diaphragm, we were able to increase sound pressure. Since we’re now able to maintain amplitude balance, minor distortions have been further reduced and the sense of realism is enhanced.

 

Can you explain the placement of the front speakers? There is one speaker unit in the center (C), two to the left side (L), and two to the right side (R) of the soundbar. Why are two of the same speaker units used for the ones to the sides?

 

4.jpgNegishi: As Hashimoto mentioned earlier, we developed HT-A7000 with the aim of improving sound dispersion and expression in the sound space. On top of this, there was also one other thing we focused on during development of this new soundbar, and this was making it easier to hear dialogue. We thought that having clear dialogue should be just as important as having good surround sound.

 

 

That’s true. But wouldn’t dialogue be unrelated to the front speakers to the left and right sides of the soundbar?

 

Negishi: As you imply, in general with 5.1-channel audio, dialogue is usually assigned to the center speaker unit. For HT-A7000, however, we made it so that the dialogue signal is also reproduced by the two pairs of front speakers at the left and right sides of the soundbar. By doing this, we’re able to increase sound pressure while maintaining clearer sound than if we just were just playing dialogue on the center speaker.

 

What an innovative idea!

 

Negishi: I think it might be Sony’s first time doing something like this. We aren’t simply playing the same audio for the center speaker unit on the left and right interior speakers. The signal is being split into the appropriate frequency bands through signal processing. The audio would not sound clear without this processing.

 

Watanabe: Because this was our first attempt at achieving something like this, a lot of work was put into building, then modifying, building, and then modifying again. But it’s thanks to this process that we were able to achieve clear sound. We would like everyone to be able to experience the dialogue elements of this product in addition to everything else it has to offer.

 

Expansive sound dispersion through the reflection of sound off not only the ceiling but also the walls

 

Next, can you tell us about the up-firing speakers? The up-firing speakers were the centerpieces of the previous flagship model HT-ST5000. How have you added on to them for HT-A7000?

 

Yana: We used the X-Balanced Speaker Unit just like for the front speaker units, increased sound pressure, and improved the articulation of height and direction of sound in the sound space rather than maintaining amplitude balance. The HT-A7000 up-firing  speakers look similar to the front units, but the edges have been slightly changed to improve their ability to reflect sound off of the ceiling.

 

Negishi: We also put attention into our selection of the acoustic cloth (fabric) material for the speakers. The way sound passes through the cloth varies quite a bit depending on the material, so Yana, Sonoda, Yoshida, and I tested through trial and error over and over to find the material that would be able to really bring out the characteristics of the up-firing speakers.

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Yana: The attention we put into the acoustic cloth material is an example of this, but in order to really enhance the reflection of sound off a ceiling by the up-firing speakers, we believe it is of the utmost importance that we pay attention to what makes it more difficult for the sound from the speaker to reach the listener’s ears directly. By reducing the amount of sound that is reaching the listener’s ears directly, the sound that is reflecting off the ceiling before reaching the listener sounds louder in comparison, making the sound more three-dimensional and improving the expansive sound dispersion feel. With HT-A7000, in addition to the amount of consideration we put into the hardware we just talked about, we’re also working to reduce the amount of direct sound through the use of signal processing.

 

Watanabe: That’s right, on top of three-dimensional expression of sound through the reflection of sound off the ceiling, we are also using a hybrid approach to virtually eliminate any direct sounds from the up-firing speakers to further enhance three-dimensional sound.

 

Can you tell us more about the kind of processing being used?

 

Watanabe: Sony soundbars without a built-in up-firing speaker have something called a “Vertical Surround Engine” that is used for signal processing to make it sound like the sound from the front speakers is coming from above. In the case of HT-A7000, this Vertical Surround Engine is processing sound from the up-firing speakers. This makes even the smallest direct sounds produced sound like they are coming from above, enhancing the effect of the reflected sounds.

 

I see! So, the sound actually being reflected off the ceiling and the hybrid direct sound created with the Vertical Surround Engine enhance the effect of the reflected sound.

 

Watanabe: That’s it.

 

Next, we have the side beam tweeter, which is a new built-in component starting with this model. Can you tell us about what kind of component this is?

 

5.jpgYana: Maybe it will make more sense if I talk about the side beam tweeter like the sound version of a laser pointer. The way it works is that the sound emitted by the tweeter is passed through a duct (acoustic duct) with holes that give the sound direction. The sound is then reflected off the walls. Through this reflection off the walls, wide sound dispersal is created that make it sound as if the sound is coming from points from beyond the wall. We made improvements to the beam tweeter that came in the 360 Reality Audio-certified SRS-RA3000 speaker we launched in April. These improvements made it possible for the beam tweeter to work with soundbars, and we put the new and improved beam tweeter into this soundbar.

 

What kind of improvements did you make?

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Yana: With SRS-RA3000, the beam tweeter is positioned in a vertical position. For HT-A7000, it’s positioned horizontally, enabling it to reproduce sound fields in a way that works with the soundbar. To add to this, we are also paying special attention to the materials we are using for the acoustic ducts as well as the configuration of the holes. Also, as we mentioned earlier when we were talking about the up-firing speakers, with the side beam tweeters as well, it is important that sounds that reach the listener directly are removed. To do this, we selected the material for the acoustic duct based on the sound resonance we’re looking for and tried to include as many design ideas as possible within the 1 mm of thickness for the configuration of the holes to enhance the effect of the sound reflection.

 

Itagaki: Easy to say, but these parts actually cost quite a lot. (laughs) In order to considerably reduce the amount of direct sound, we used very expensive resins for these parts.

 

Yana: Even so, it was worth it, because we were able to achieve a sense of sound dispersal that exceeds the TV screen size.

 

Were there any innovations with the signal processing like what you mentioned earlier with the up-firing speakers?

 

Watanabe: Oh, of course there were. This is also relevant to the up-firing speakers, but HT-A7000 is equipped with an automatic Sound Field Optimization function that adjusts internal processing according to the distance between the soundbar and the walls and ceilings, something measured in advance, so that sound reproduction can be appropriately adjusted to suit any room.

 

Are there any other sound-related points you would like to make regarding HT-A7000?

 

Yana: Of our soundbars, HT-A7000 is the first to accommodate Sony’s original “360 Reality Audio” technology. I think users will be able to enjoy an immersive, three-dimensional sound experience that rivals the 360 Reality Audio-certified SRS-RA5000 and SRS-RA3000 speakers that were released earlier this year. I’d love for people to experience the sense of immersion this soundbar can offer for not only movies but also music.

 

Pursuit of high-quality sound through attention to structure and part configuration

 

Can you tell us more about the amps on this soundbar that contribute to the high quality of sound?

 

Sato: Despite the size of the HT-A7000 body, it contains the side beam tweeter and the interior subwoofers in addition to other features. Because of this, the circuit board had to be pretty compact. It took a lot of work to achieve the current size.

 

Can you tell us more about the new ideas you used for this soundbar?

 

Sato: The S-Master HX amplifier we’ve been using up until now had a 2 chips per 2 channels configuration, so with a product like this one that requires an amp with 11 speakers, the need for a circuit board with a bigger surface area is inevitable. But by using single chip amp this time, the number of chips on the circuit boards was reduced along with the overall surface area. What’s more, the switch to a single chip amp comes with merits like stable and pronounced performance, so it is actually better in terms of sound quality. A high product grade is being maintained for the filter converting sound back to analog signal through the utilization of tried and tested parts of predecessor models such as HT-ST5000.

 

Was there anything you focused on for the circuit board design?

 

Sato: It might be something you could notice just by looking at it, but we really focused on creating a beautiful layout for the parts. By positioning the parts symmetrically with the center of the soundbar being the center of symmetry, the parts to the left and the right are aligned, keeping with a basic stereo parts layout. By focusing on these points, we ensure that the timbre of each speaker matches, improve connectivity and density of the sound in a space, and maximize the quality of the user’s experience with the product.

 

With respect to the finished product, it sounds like there are only benefits to making the soundbar more compact.

 

Sato: That actually isn’t true. (laughs) What we struggled with even more than with the sound quality was the countermeasures for the overheating that occurs with a more compact device. Our electrical team wasn’t able to do anything about this, so Sonoda’s mechanical team built a heat dissipating mechanism that is so big, it almost looks as if it’d be too big for the circuit board. They also designed a casing that could conduct heat so that we had a way to carry the heat away.

 

Sonoda: Generally speaking, a heat sink would only be placed on the IC part that generates the heat, but in this product’s case, the entire circuit board is covered with a heat sink. (laughs) While the circuit board itself is really small, it generates a large amount of heat, so the big problem was how we could dissipate this heat. But we knew that we could somehow disperse the heat if we could figure out a way to make the most out of the space available in the body. So, after putting in a considerable amount of effort, we finally succeeded in dispersing the heat by fitting the heat sink with its complex yet monumental structure into the housing.

 

Speaking of structure, compared to the previous flagship model HT-ST5000, HT-A7000 is a lot bigger horizontally, isn’t it? It doesn’t come as a surprise since you have added so many new features. But what is the soundbar interior like?

 

Sonoda: First off, there is an independent box behind each speaker for sound to properly resonate. S-Master HX and the heat sink Sato just mentioned are then situated at the back of the subwoofer box.

 

By attaching a wave shape component to the bottom of the subwoofers, vibrations from the subwoofers are dissipated very nicely. Usually, there would be ribs (reinforcement) inside the casing to absorb vibrations, but this design kept giving us muddy sound. For this product, we went with these wave shape components to keep the shape of the interior simple while maximizing reinforcement. It may look like ordinary wave shapes at first glance, but the waves are actually not the same size, and each part differs from the others in random ways.

 

A system that can be updated to fit the different ways people enjoy content

 

HT-A7000 has built-in subwoofers while subwoofers were external components with the previous flagship model HT-ST5000, but optional external subwoofers can also be purchased and added on to this soundbar. What was your reason for creating this feature?

 

Hashimoto: HT-A7000 is fully capable of reproducing bass sound, but for those who are looking for even more powerful bass, we made it so that subwoofers can be added on via wireless connection. We have two different subwoofers available for this soundbar, and people can choose based on the bass sound they want and the space they have available. We would recommend SA-SW5 for those who want the maximum low bass and intense sound experience and the compact SA-SW3 for those who want to easily enhance bass even with limited space.

 

It’s great how you can just get the soundbar first and then upgrade the system as you need to later.

 

Hashimoto: That’s right. There are all kinds of ways people are viewing and listening to content. In order to respond to each one and allow for our customers to enjoy more options, we also have an optional speaker, SA-RS3S, available in addition to the subwoofers. Adding this on to HT-A7000 can allow for an even more expansive surround sound experience. And of course, these add-ons are connected wirelessly, so there is no need to deal messy cables.

 

Can you explain to us how adding a rear speaker to HT-A7000 can enhance sound quality?

 

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Optional subwoofer SA-SW5 / SA-SW3  and optional rear speakers SA-RS3S 

 

Negishi: HT-A7000 is already able to use all of the features we’ve talked about so far to create a three-dimensional soundscape, but by adding a rear speaker as well, you'll be able to hear sounds from behind even more clearly and distinctly. This especially smooths out the flow of sounds in the horizontal orientation and reinforces the feeling of being surrounded by these sounds.

 

Yana: SA-RS3S is a 2-way speaker with both a tweeter and woofer driver and features a very flat characteristic throughout both the low and high-frequency ranges. It creates a natural and expansive surround sound experience with any kind of sound source.

 

Watanabe: Of course, it also supports the automatic Sound Field Optimization function and is also really easy to use because the optimal settings are automatically set on the speaker.

 

Is there anything you would like to add regarding the expandability of the soundbar?

 

Hashimoto: A function called Acoustic Center Sync can be used by connecting HT-A7000 to a Sony BRAVIA television. This function links the soundbar to the BRAVIA TV’s “Audio” to enhance the synchronization of the visuals and audio and create a more immersive experience.

 

Negishi: By connecting HT-A7000 to a BRAVIA TV’s “Audio”, the “Acoustic Center Sync” processing is up-firing to localize the positions of voices within the TV screen. Specifically, HT-A7000, with its high low-frequency sound reproduction capability, reproduces the low frequencies of the voices while the TV reproduces the high frequencies. By adjusting the frequency range and playback timing for each, we have improved the synchronization of the visuals and audio. I think you will really enjoy the sense of immersion that comes with being able to hear voices from the screen itself.

 

Hashimoto: When HT-A7000 is connected to BRAVIA, operations that are used from day to day, such as Sound Mode and bass adjustment, can also be accessed from the BRAVIA remote control.

 

Meaning in every aspect of HT-A7000

 

Can you tell us about the design as well? We can start with the concept you worked off of when designing HT-A7000.

 

9.jpgYoshida: “A Series” products, including HT-A7000 and the optional subwoofers and rear speakers, were designed based on the common theme that came to be called the “Omnidirectional Block” concept. It feels natural even if the products in this series are used together in the same room. In fact, I think you would find that they go really well together.

 

The main feature of the Omnidirectional Block is a design that allows for sound to be heard 360 degrees in any direction. This is a design that also makes the products feel like one solid entity and contributes to the experience of the sound that is reproduced. It was because we were pursuing solidity to our design that we were able to minimize the lines that divide each part of the entity. Also, while the colors and finishes of the products are all based on black, we’ve slightly changed the shades and textures for each product and component. I think each component harmonizes with each other, and when viewed as a whole, it gives off a sense of sophistication. I also think it would be easy for them to blend into a room’s interior.

 

With each product in the series different in its own way, how did you go about designing HT-A7000?

 

Yoshida: First off, in terms of the shape, the same radius (rounded corner) size is used for all the edges of the body, which emphasizes the feel of each product being a part of the same entity under our Omnidirectional Block concept. This radius size actually also makes sense acoustically.

 

Negishi: By including this radius, we can reduce diffraction where sound from the speakers reflects off the corners of the body and create unwanted vibrations.

 

Yoshida: And since we wanted to choose a material that would suit a model that offers the optimum acoustic experience, we used a thick, flat sheet of glass, as used in architecture, for the top. Not only is this the most distinctive feature of HT-A7000, but it also makes functional sense.

 

Sonoda: The hard, heavy glass top helps reduce vibrations generated by the subwoofers and other components. Together with the wave pattern components on the bottom that we talked about earlier, this further enhances the anti-vibration capability of the soundbar.

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Wow, this design really embodies the very   essence of the saying, “beauty in practicality”, doesn’t it?

 

Yoshida: The metallic paint used on the back of the body is a color especially made to make the surface appear solid and resemble stone. The result is a rugged surface texture with metallic flakes that shimmer in the light. Combined with the glass on top, I think we were able to create a really elegant look for the product.

 

We also took a new approach to the acoustic cloth, which we discussed earlier with the up-firing speakers. We wrapped even the ducts in fabric to keep the design looking as simple as possible and create a “solid” look. Normally, this kind of material is used only for the speaker, and different parts would be used for the ducts on the sides. However, doing that would differentiate the look of the parts from each other, so we went with this configuration and finish even though it would take more time.

 

Experience the spectacular sound with this new-generation flagship soundbar

 

Finally, would you like to say something to our readers in closing?

 

Yana: This time around, we took on the challenge of making something that would make people impressed enough to go, “Whoa!!!” It all comes down to that reaction. While I’d also worked on the previous flagship model HT-ST5000, for HT-A7000, as illustrated by the side beam tweeter, we really took the approach of making something we have not seen before. We created this product while half worried and half excited, but I think we were able to create a soundbar that will allow you to experience it even before you hear it.

 

Negishi: This is a product that we’ve been working on for a long time and one that we feel very strongly about, so we’re happy to finally be able to present it to you all. We really focused on creating a “straightforward” sound for HT-A7000. This is in part through the “impressive sound” that Yana referred to. We aimed to create a sound that could convey the exceptional nature of the soundbar even without explanation. We hope you’ll visit a Sony retailer to hear it for yourself.

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Sato: HT-A7000 was actually my first time working on a soundbar. And because it was my first time, I think I was able to bring design ideas to the table that were different from those for past soundbars. I’ve worked on many amplifier products over the years. I’ve put all of this expertise into making this small circuit board, so I hope you’ll experience the resulting sound for yourself.

 

Watanabe: HT-A7000 has a number of unprecedented signal processing technologies incorporated into it. Not only has the “DSEE HX” function, which upscales standard resolution sound to high-resolution quality, become more advanced since it became available on the predecessor model HT-ST5000, but the acclaimed “DSEE Extreme”, which is available on WH-1000XM4, is also available on a soundbar for the first time. We really hope you’ll enjoy these technologies on the new soundbar.

 

Sonoda: While it is quite large as far as soundbars go, a great number of functions and designs are incorporated within. I hope the new sound experience brought by this collection of functions will be enjoyed by as many people as possible.

 

Yoshida: We were very meticulous with the look of the textures on components, including the subwoofers and rear speaker for HT-A7000. I know it’s difficult to go out to a store these days, but I’d love customers to see the actual product. I hope they love the design as much as they love the sound.

 

Itagaki: As a designer that worked on this product, I’ll never forget working on this during the COVID pandemic. There were many unexpected difficulties, such as restrictions on coming to work which made it difficult to communicate with other members of the design team, and the inability to make trips to the factory for prototyping. However, I’m satisfied we were able to overcome these challenges and create a good product in the end.

 

Hashimoto: Sony has released a number of soundbars up until now, but even among these, HT-A7000 is the product with the best possible sound and functions. I think we’ve put together a wonderful product that could also be upgraded with the optional subwoofers and rear speaker to really upgrade your sound system according to your environment at home or your own preferences. I hope people who’ve purchased a large-screen TV will consider this product. You definitely won’t regret it!

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matthewcornwell
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Updated with additional info :slight_smile: