Sony’s unique “360 Spatial Sound Mapping” technology delivers
a revolutionary new listening experience via HT-A9,
the next-generation home theatre system
With the popularization of large-screen televisions and the growing demand for home entertainment, attention to sound within home entertainment is increasing.
In the midst of this trend Sony introduced HT-A9, a home theater system with a new concept that makes it different from any other existing product. Sony’s unique 360 Spatial Sound Mapping technology creates an expansive, 360 spatial sound experience using only four wireless speakers. How was this brand-new product made? Read on, for the developers’ answers to this question.
Suzuki (Masaki): The HT-A9 is a home theater product unlike any before in multiple aspects, including the form factor. With the increase in the size and quality of TVs and the popularity of video streaming services nowadays from stay-at-home demand, it has become easier to enjoy movies at home. This has led to a significant increase in demand for better sound to be enjoyed in the home. However, the reality is that many people do not have enough space in their living rooms to install a full-fledged home theater system. There are also many who feel that it would be difficult to install a full-fledged home theater system on their own. That is where the HT-A9 comes from. HT-A9 features Sony’s new original “360 Spatial Sound Mapping (hereinafter 360SSM)” technology and automatic Sound Field Optimization technology to reduce the amount of time and effort required for everything from installation to usage, making it easy for anyone to enjoy an amazing 360-degree three-dimensional audio experience.
Suzuki (Masaki): The HT-A9 is the product made up of four separate wireless speakers and a control box. The speakers are connected wirelessly, so there is no need to run cables connecting speakers at the back of the room to a control box at the front of the room. This gives the user the freedom to maintain a neat, minimal look. The wireless speakers are made up of a horizontal front speaker and an up-firing speaker facing the ceiling. By pairing these with 360SSM, Sony’s revolutionary 360 Spatial Sound is achieved.
Sakai: The up-firing speakers’ project sound upwards, reflect it off the ceiling so that it feels as if the sound is “showering down” from overhead. All four speaker units of the HT-A9 are equipped with up-firing speakers, which play the essential role of making sound resonate in three dimensions through 360SSM.
Sakai: 360SSM uses Sony’s original distance measurement technology to measure the distance between speakers, and from the speakers to the ceiling, and then combines it with physical sound field reproduction technology. The system uses two microphones on each wireless speaker to measure the relative positions of the speakers and reproduce sound wave fronts from up to 12 “phantom speakers” (simulated sound sources) that are assumed to exist somewhere outside of the physical speakers. Because the simulated speakers exist beyond the actual speakers, it can make you feel as if you are in an extremely wide and expansive space that seems to extend beyond the room.
Sakai: No, it’s a bit different from virtual surround sound. Virtual surround sound is the technology that uses something called psychoacoustics to create the illusion that you’re listening to three-dimensional sound, but for 360SSM, it’s not an illusion. It is actually generating a sound field.
Sakai: The way a virtual surround sound effect sounds varies from person to person, and as a result, there may be differences in the way the sound field dispersion is perceived. 360SSM, however, can reproduce an actual sound field, so there are no differences in experience depending on the individual, and realistic surround sound can be experienced across a large area of space.
Suzuki (Takashi): That’s right. As Sakai explained, the two microphones in each speaker are used to determine the relative position of the speakers and compensate for the sound produced by each. Distance is not only measured horizontally, but also vertically (for the distance to the ceiling), making it possible to achieve a complete surround sound effect even if the height of each speaker is different due to space restrictions.
Suzuki (Masaki): Creating an expansive sound field area that is larger than the actual area of space where the physical speakers are installed allows users to feel as if they are “there” in whatever it is they are enjoying, even if they are in a living room of an ordinary home. If it’s a film, it would be like being in the movie theater, and if it’s live music-type content, it would feel like being there at a concert. Being able to experience sound as if you are where the action is, even while you are in your own home, is the characteristic that defines HT-A9.
Horiuchi: I’ve worked on a number of different products up until now, including AV receivers and soundbars--basically what you would call “high-end” audio systems--but when I first learned about 360SSM on the HT-A9 prototype, I was astonished by the expansive sound field, something which was different from the products I’ve worked with up until now. In particular, I was amazed by the way the sound could move up and down and the way the sound could rotate upward. I’d like for everyone to experience this exciting technology.
Suzuki (Masaki): Object-based formats such as Dolby Atmos or DTS:X for video content and 360 Reality Audio for music are supported, but conventional 5.1-channel surround sound sources can also be processed in a way that delivers three-dimensional sound.
Sakai: Originally, 5.1-channel surround sound channels only contain signals on the horizontal plane, but with signal processing technology, height information is being generated from the original signal. This allows for it to sound like ambient sounds, in particular, are filling the space.
Sakai: Yes, even 2-channel content can be enjoyed with three-dimensional sound.
Horiuchi: There was so much hard work involved, I don’t really think I can describe it all. (laughs) But I’ll start by talking about the control box that controls the four wireless speakers. In the end, we were able to get the control box down to this size, but at the beginning of development, we thought it would have to be as large as a standard AV receiver for it to work.
Horiuchi: Yes, that’s right. The reason why we were considering such a large size is to, first of all, ensure wireless performance. We needed to develop a new system and configuration that is not only capable of communicating with the four wireless speakers, but is also optimized for a wireless operation to ensure communication stability when used with external devices such as Chromecast and AirPlay.
Horiuchi: We developed brand-new antennas with the cooperation of our in-house wireless specialist team and mechanical engineers. We gradually refined the arrangement and shape of the multiple antennas so that they would not interfere with each other. It was through dozens of repeated simulations and prototypes that we were able to achieve the current compact size.
Ninomiya: There are three circuit boards for the antennas in the control box, and because we had to fit them into this small body, it was pretty difficult to keep them completely isolated from each other so that they won’t interfere with each other. The two layers of metal plates and other parts inside the box are there to separate the front and back antennas. We also paid attention to many other details to improve sensitivity, including angling the antennas.
Deguchi: The first thing customers look at is the speakers, and it’s also the speakers that bring the experience to life, so we thought that if the control box, the conductor in the shadows, so to speak, was too big, it would detract from the experience. And then above all, there is how it fits with the TV. We decided on the visual characteristics while considering not only the size, but also the color and surface texture of the control box when it is put together with a TV. We decided that this is an indispensable condition for the control box and asked for the design team to help us achieve it.
Horiuchi: We actually brought over a black box of the same size and were told over and over again, “You see? This would be too big.”
Suzuki (Masaki): in the end, after seeing that something the size of an AV receiver has been reduced to such a small size, maybe embarrassing to say, but I realized that some things really are possible if you put in the work. (laughs)
Suzuki (Takashi): We had a very hard time figuring out how to dissipate the heat generated inside the control box. We identified the source of the heat generation, and the mechanism and framework for dissipating the heat were simulated many times to make sure they were compatible with the wireless configuration. It was particularly difficult to improve wireless performance and downsize without compromising heat dissipation efficiency.
Ninomiya: As with the speakers, we were really particular about hiding the screw holes on HT-A9. Strictly speaking, only one on the back is slightly visible, but all the others, including the one on the bottom, are hidden from view. In many cases, there is an exposed silver metal plate on the bottom of products like this, but HT-A9 has an additional cover component to cover this plate.
Deguchi: I think of it as a consensus among not only the design team but also the development team. We mentioned earlier about considering how HT-A9 would look when placed with a TV. Adding on to that, if HT-A9 is placed in a higher position, not only would screw holes become visible, but a metal plate on the bottom would become visible as well. In order to prevent this from happening, we didn’t cut corners and hid what needed to be hidden so that it can fully blend into an interior.
Deguchi:We’re flattered you think so. If we were to go into detail, we also put a bit of thought into the shape of the slit on the sides used to dissipate heat. By making the slit diagonal, you can’t see the circuit boards and other interior components from the front.
Sakai: The HT-A9 speaker units are 2-way speakers with both a tweeter and woofer driver. The woofer utilizes the X-Balanced Speaker Unit to deliver clean sound with minimal distortion. Another key aspect is that we made the woofer a low-profile unit with a shallow diaphragm. Making it a low-profile unit made it possible to further extend the directivity of the sound. For the same reason, we cut the left and right edges of the body at an angle to prevent diffraction (sound waves bending around corners) and allow it to distribute sound in a full spherical shape.
Ninomiya: We cut not only the left and right edges of the body at an angle, but also the top edge for the same reason, even though it’s hard to tell because it’s hidden by the speaker grill. There needs to be a frame to hold the grill in place here, so there was quite a bit of trial and error on things like how broad or thick it should be.
Sakai: That’s right. For 360SSM, the position of the sound source is defined as a point, and measurements are made based on the assumption that spherical sound waves are emitted from this point, so our goal was to create an acoustic mechanism as close as possible to that for the speakers. The cone of the speaker unit is made of foamed mica, a material that has been used in Sony products in recent years. There are characteristics of foamed mica, such as being lightweight yet firm with just enough impedance, that make it an excellent material to use for the diaphragm. These characteristics enable the diaphragm to produce everything from low to high-pitched sounds in high quality, but in the case of HT-A9, the strength of the foamed mica also allows for the diaphragm to be thinner. Strong magnetic circuit magnets are also used, which are powerful enough to allow the diaphragm to provide a strong bass sound on its own.
The cabinet opening near the front of the speaker unit is a flared shape to ensure that the sound emitted from the up-firing speakers is not heard directly by the listener, but is rather distributed upward in a precise manner so that it is reflected off a surface. In order to develop the appropriate flare shape, a considerable amount of time was spent repeatedly conducting simulations, taking measurements, then using these results to create a more appropriate shape.
Deguchi: HT-A9 is capable of playing high-resolution audio, but in order to produce that sound, if the grille is made of metal, the grille holes would need to be around this big. If you look closer, you’ll be able to see that the grille holes in the front and the back are a different size.
Deguchi: We had to make the holes bigger to make the up-firing speakers to perform at their best. As a design team, we wanted to make the holes as small as possible, but there needs to be a balance between performance requirements and appearance.
Horiuchi: We had a lot of discussions about how to come to the best middle ground with the different contradicting specifications that are required for the top and front grilles. We tried out various combinations not only in the size of the holes and hole density but also grille thickness.
Sakai: As mentioned earlier, there are high sound power speaker units in the speakers’ woofers. This, however, can have an adverse effect on units like these, causing the speaker enclosures to be prone to vibration. Excessive shaking of the enclosure can destroy the sound image and adversely affect the tweeter and up-firingspeakers. To counteract this, we have a thick bridge-shaped component on the back of the speaker unit to provide a sturdy structure that can support it from behind.
Ninomiya:I remember really vividly how the first prototype was so overpowered by the speakers, the body was just vibrating all over the place. To prevent this, in addition to adding the bridge on the back of the speaker unit, we also took many other countermeasures. Not only did we add many ribs (reinforcement) in the fundamental places, but we also added beams to secure and stiffen the front and back of the body.
The ribbing has a diagonal wave shape, which also serves the purpose of eliminating unwanted standing waves inside the speaker.
Suzuki (Takashi): In terms of electrical design, in order to make the most of all the ingenuity we put in and maximize sound quality despite the size constraints, we developed and put in a newly designed power amplifier and a powerful power supply made especially for HT-A9.
Suzuki (Takashi): We’re using high-audio-quality electrolytic capacitors, such as those used in AV receivers, for both the amplifier and the power supply. For the power amplifier, we are using S-Master HX for both high outputs and to downsize the circuit board. We are using this S-Master HX as a base for the electrical characteristics necessary to achieve the high fidelity sound reproduction suited to HT-A9. We also went through a process of choosing components that would provide the best sound quality while listening to the actual sound that is played with each option until we arrived at the final product. On top of this, in order to achieve high sound quality even with a small circuit board, we optimized the placement of each component so that the copper patterning can be as straight and short as possible. We also designed for the patterning width to be as wide as possible while meeting the safety standards. It is innovations like these that make the sound feel more independent of the speakers, and facilitate the expansive sound field expression possible with HT-A9.
Suzuki (Masaki): We have a wireless subwoofer available as an option to enhance the HT-A9 sound experience. Of course, the speakers were made to provide great bass sound on their own, but we’d also like you to try them with the wireless subwoofer if you want even more powerful bass sound. There are two types to choose from depending on the size of your room and the sound experience you are looking for.
Sakai: With an additional subwoofer, the bass will feel like it’s coming from the ground. I’d recommend adding a subwoofer if you're looking for a cinema-like experience where it feels like the air is vibrating around you. For music, you should be able to feel the difference, especially with synthesized music like EDM that is packed with all kinds of sounds within the audible range.
Suzuki (Masaki): Another advantage to connecting a subwoofer is that you can leave the bass sound reproduction to the subwoofer and allow the speakers to focus on the rest of the sound range. This makes it possible to reproduce a sense of silence as well as different ambiences with greater precision.
Suzuki (Masaki): When pairing with external devices, if you’re using a Sony BRAVIA TV, you can use a feature called Acoustic Center Sync to further step up your sound experience.
Suzuki (Masaki): BRAVIA models released in the last few years, like the OLED models, support Acoustic Surface Audio+, an original acoustic technology that emits sound from the screen itself. Acoustic Center Sync links this acoustic technology with HT-A9. While getting a surround sound feel you can only get from this unit, the dialogue of the characters on the screen are played from the BRAVIA, creating a sense of unity between image and sound and providing a more natural sound experience.
Horiuchi: To achieve this, the TV and audio departments worked extra closely together. OLED TV (Acoustic Surface Audio Plus) and LCD TV (Acoustic Multi-Audio) acoustic technology are completely different from each other. On top of this, there are also specific differences between each product. To work around this, our engineers exchanged ideas and fine-tuned the feature so that optimal sound can be enjoyed on each one of the products.
Horiuchi: No, there’s no need. When the control box is connected to the TV with an HDMI cable, the control box automatically identifies the model and links with the TV under the optimal settings.
Suzuki (Masaki): When it is connected to a BRAVIA TV, HT-A9 functions can be controlled on a graphical user interface that can be operated with the BRAVIA remote control. I think people who already have a coffee table filled with remote controls will also be happy with this feature.
Deguchi: We used the “Omnidirectional Block” concept in the design of a group of audio products called the “A Series”, which includes HT-A9. Units are designed to go with the optional devices, such as subwoofers, that are connected to them and this harmony in their appearance emphasizes their effectiveness as a series. The design of HT-A9, however, actually takes advantage of the unit’s originality to signify the brand-new sound experience it offers.
With that said, it’s not like we tried to make the design too unnecessarily new. In a sense, a speaker is like a musical instrument, and when you fine-tune its characteristics, the optimal shape for the speaker naturally comes into being. So what we did this time is that we sought to make those characteristics more evident and visible.
Deguchi: That’s right. And so it became this cylindrical shape. Earlier, Sakai and Ninomiya mentioned that the edges of the body were cut diagonally to help with the sound dispersion. By making it this shape, we were able to make bold cuts to the interior. This shape also makes the unit look smaller than a square speaker of the same size, and it looks natural no matter how you position it. As a result, 360SSM sound characteristics are conveyed in a straightforward manner. We also cut away a part piece of the back to make the flat surface signify the wall so it’s easier to see the area the sound will cover and how to place the unit. This also made it easier to put it against or hang on a wall.
In addition to these features on the back of the unit, there is also a hidden hook that can be used for hanging the unit on the wall and a hidden screw hole for attaching the unit to a stand. The terminal for connecting the power cable is also located inside a hollow on the bottom of the unit so that the strain relief portion of the cable is not visible when the unit is placed as normal on a surface or when it is mounted on a wall or stand. Also, all the buttons that are not usually used are hidden on the bottom.
Deguchi: That’s right. The color of the main unit is also light gray for this reason so that it can match any interior. This light gray is not just a plain gray. We had fine black and white beads mixed into the paint and sprayed it on so that the black and white appear evenly scattered across the surface. The result is a texture that gives a sense of depth even though it is only one color. The black beads emphasize the white beads in dark places, and the white beads emphasize the black in well-lit places. We did this with the intention of creating a finish that is both beautiful and complementary to any space. By the way, the power cable is also exclusively made in light gray to match the main body color.
Horiuchi: HT-A9 is a home theater system that uses new stereophonic technology to provide an unprecedented spatial sound experience, so we were both excited and worried about what film audio professionals would think when they heard the sound reproduction on this system. We had the opportunity to have sound engineers from Sony Pictures Entertainment in the U.S. to try out HT-A9, and it gave us a lot of confidence to hear very positive reactions and comments from people in actual movie production saying that the sound is exactly as they intended. We hope the readers of this article will also watch the video of this interview. We hope many people will enjoy this brand-new sound experience with HT-A9.
Suzuki (Masaki): As Horiuchi said, HT-A9 will give you an experience completely different from anything you’ve experienced before. 360SSM is a new technology that creates a sound experience that gives you the sensation of hearing sound coming from a place beyond the walls of your living room, an experience that has never been possible before. Combined with the increasingly large screens and high-definition images on TVs, this product will make you feel as if you are right in the middle of the action taking place on your screen. This product also removes the barrier of the complicated settings and setting techniques that used to required as the “standard” to enjoy good sound. On top of being a great product that can be easily enjoyed by the whole family, it will also give you the best sound experience available. We hope you’ll visit a Sony retailer near you to experience the sound for yourself.
Sakai: People tend to think of home theater systems as something for avid movie fans, but I’d really like to see HT-A9 be a good choice for people who are newly developing an interest in a home theater experience. Not only will it go with rich movie content, but it will also bring out the best sound experience for content like TV shows and YouTube videos.
Suzuki (Takashi): For HT-A9, the automatic Sound Field Optimization function is a very important feature for enjoying 360SSM. Even if you have a slightly irregularly shaped living room that makes it difficult to accommodate the ideal speaker arrangement, this product will properly counterbalance this, so I would like people who have given up on a surround sound environment for reasons like this to give it a try.
Ninomiya: It’s fine even if you have a tricky setup where the right speakers are placed next to the TV, and the left speakers are wall-mounted. There is no need to change the layout of your room around the TV to install this product. It can be positioned in any way to match the different lifestyles of different people. We’ve also made it very compact, so installation should be relatively effortless.
Deguchi: As Suzuki (Takashi) and Ninomiya said, we designed this product with our top priority being that customers will be able to place and use it wherever they want. Also, I think for this product, the contrast between how it looks and its actual performance is pretty satisfying. We hope as many people as possible will get to experience this feeling of surprise when the product gives you a sound intensity and expansive spatial sound experience that you wouldn’t expect from its compact, interior-conscious appearance.