The AV receiver — undoubtedly the centrepiece of a home theatre.
Creating a microcosm within a limited space, using finely honed skills, can be seen as something of a Japanese tradition.
Individual parts that highlight and enhance the harmony of the whole, this represents the ultimate accomplishment.
Kano:"An AV receiver is usually thought of as simply an audio component that performs various advanced functions. But I feel that in essence it actually comes pretty close to representing an authentic aspect of Japanese culture."
— This somewhat surprising comment comes from a young engineer as an afterthought at one point during the long interview, while explaining the configuration of the latest model that he helped design. Masaya Kano is a sound design expert who has worked on numerous Yamaha AV receivers. Rock, Jazz, Classical and Latin music — his musical interests span a wide range of genres, but one would not normally assume him to be very keen on traditional culture. Yet, in the course of his work, he says he came to be more and more convinced of some underlying similarities.
Kano:"Since early times, we Japanese have had a knack for representing a likeness of the universe within a limited space. Think, for example, of the aesthetic concepts realized in traditional Japanese gardens or in bonsai trees, or think of the kaiseki cuisine with its numerous courses of exquisitely presented small dishes. It takes a special skill to carefully select materials and arrange them to be part of a harmonious whole, while still retaining their distinctive flavour. Receiver design could be seen as pursuing a similar goal."
— In fact, the functions demanded of an audiovisual receiver get more complex every year. It has to decode the multi-channel audio signals from Blu-ray discs and DVDs as well as digital broadcasts and other sources, properly assign these to multiple surround speakers, and offer video signal processing as well. If one likens the home theatre to an orchestra with a configuration of various instruments, the receiver is the conductor who brings it all together. The ability of the conductor will greatly affect the musical experience of the listener. The engineers whose task it is to design the receiver therefore carry quite a responsibility.
Of course, latest surround audio formats must be supported, and the constant version improvements of HDMI and other digital interfaces need to be accommodated quickly. As Mr Kano puts it, "Within the AV sector, receivers are an ever-changing target, and the competition is fierce." Mr Izumi Ozeki in charge of overall development management, points out that AV receiver design requires "an excellent sense of balance".
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Ozeki:"For example, unlike a stereo amplifier where the designer can simply pursue optimum sound quality, an AV receiver must combine various elements on an equally high level. In recent years, 7.1 channel surround sound has become the norm, leading to an increase in the number of speakers. Music sources have diversified with the addition of new formats, such as iPod playback and streaming of music from a computer over a network. Of course,incorporating a larger number of functions requires more circuits, which have to be accommodated within a limited space, while making sure that Yamaha's high standards with regard to sound quality are fully met. And going beyond that, there is the individual character of the product that is to be nurtured and refined. The tasks that the engineers are faced with are on a par with solving a complex simultaneous equation."
— The models RX-A3000, RX-A2000, and RX-A1000 released in the autumn of 2010 represent Yamaha's latest answer to the puzzle. While inheriting the design philosophy of the widely acclaimed flagship model RX-Z11, they implement latest audio and video technology at a very affordable price. Each of these high-class receivers is truly a "microcosm in a box".
— All too often, AV components are updated by simply tacking various new functions onto the previous model. But when formulating the concept of the V67 series, Mr Ozeki took a different tack. Putting technical legacy aside temporarily, the decision was made to re-examine the design from the ground up, beginning with chassis construction and basic parts layout.
Ozeki:"Renovating and expanding an old house in order to improve living comfort sooner or later will hit a limit. Similarly, when attempting to keep a good balance between sound quality and upgraded functionality, a point will be reached where the house has to be rebuilt from its very foundations. This evidently is a formidable task, but the opportunity to completely redesign and optimise the layout of circuit boards and parts also presents a great chance to take overall sound quality to the next level."
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— After having been selected to participate in the design team, Mr Kano got together with the other experts in charge of various fields including video and software. The first objective of the passionate discussions was to work out the direction in which they would be heading. The topic was explored through frank exchange of opinions and the presentation of the team members' respective vantage points. But the final conclusion turned out to be deceptively simple: "Create an AV amplifier that sounds great in the actual environment of the customer and that is easy to use."
Kano:"To increase sonic purity, we first need a solid chassis that is not affected by vibrations. Even the most precise audio circuits cannot perform well if they are put into a flimsy enclosure. Therefore it seemed best to adopt the chassis design policy of the RX-Z11 as much as possible, as the flagship model is renowned for its sound quality. Of course, the top-ranked model has a larger budget, and assembly procedures are also different. But while being aware of these differences, we still decided to use it as a starting point for development. We thought that the frame or backbone, namely the chassis, was the crucial factor that would decide whether the new series was going to become a well ordered microcosm or just a jumble of functions."
— As in the RX-Z11, the most massive part, namely the power transformer, is situated in the centre of the receiver, with a symmetrical structure built around it. This was done to ensure stability. Various other measures such as two reinforcing beams on the chassis bottom are evidence of the efforts to achieve ideal weight balance and rigidity within the budget restraints of the series. The fact that the heat sinks of the power amplifier stage are also separated into a left and right section is another important characteristic. This improves L/R separation of the front and surround speakers and provides a notably wider sound stage.
The maximum extended channel configuration supported by the three models, starting with the highest-ranked one is 11.2 channels, 9.2 channels and 7.1 channels respectively. After finalizing the construction principles and creating a common platform for the three models, variations according to price class could be implemented more easily. A good example is the D/A converter, which has a decisive influence on the sound quality of sources using the digital inputs. The top-ranked RX-A3000 model, similar to the RX-Z11, features a high-performance Burr-Brown converter. The other two models also have converters from the same manufacturer, in a somewhat lower price range. Care was taken to ensure uniform sound characteristics for all models, on a level that far surpasses what is often considered "normal" for the respective class.
Kano:"Creating a sound profile really consists of down-to-earth tests and verification steps, repeated many times over. By changing conditions little by little and judging the results by ear, we gradually attained the sound we were looking for. Since the aim of the current project was to eliminate superfluous aspects, and since we had a common platform to work from, we could concentrate even more than usual on audio quality . In the end, this enabled us to achieve high-end sound at a very affordable price. AV receivers are by nature obliged to keep evolving in terms of functionality, which carries the dilemma that the price tends to increase but audio quality stays at the same level. The Vx067 series breaks through this impasse. I am proud to say that these models provide sound that is several notches above what would be expected at their price.
The completely revised construction has enabled us to take this significant leap forward. That said, I already have a mental list of functions that I want to implement and further improvements to pursue in coming models, so I am also looking forward to what the future will bring."
?Evolved Auto Adjustment
Even the most accomplished DSP feature is meaningless if it does not sound natural in the actual living environment of the user. Therefore, Yamaha AV receivers have incorporated a function called Yamaha Parametric Room Acoustic Optimizer (YPAO) from an early stage, aimed at creating the ideal home theatre environment through automatic adjustment. The RX-A3000 and RX-A2000 models incorporate an additional feature called YPAO-R.S.C.(Reflected Sound Control) designed to control early reflections in the room. By using sound field compensation technology to control irregular early reflections from walls and the floor, the acoustics of the room are balanced out to ensure a favourable environment for viewing/listening.
Ohashi:"When enjoying playback in a home theatre, direct sound from the speakers is not the only sound reaching the ears. So-called early reflections, i.e. sound bouncing off the walls, the ceiling and the floor, as well as other objects in the room also need to be considered. On a time axis, the direct sound arrives first, followed after a certain interval by the delayed reflections. Reflections that are delayed by about 30 milliseconds or more are known as reverberation and usually are experienced as a pleasant phenomenon. By contrast, early reflections that reach the ear only a tiny interval later than the direct sound tend to overlap it and have a negative effect, resulting in muddiness and lack of focus. By removing reflections in this early time bracket, the sound becomes clearer and better defined."
There are not many manufacturers who take not only speaker placement and settings but also the reproduction space into consideration. The use of sophisticated sound field compensation technology developed entirely in-house and paired with advanced DSP techniques results in a synergy effect that makes Yamaha quite unique in this field.
?Evolved User Interface
An AV receiver must deliver good sound, be flexible enough to fit various usage patterns, and provide effective control over playback of sources with different quality levels. The user interface is therefore an important consideration. It determines whether the receiver can really develop its potential in the hands of the user. The Yamaha AV receiver RX-Z9 was the first in the world to incorporate a Graphical User Interface (GUI). Subsequent further improvements include the SCENE function for single-button operation and a System Memory.
Ozeki:"The discussions during the model development stage led to the conclusion that we should build an AV amplifier that would not only sound great but would also be completely intuitive to use. We knew that this was going to be no easy task, but we wanted to reconsider the entire concept."
The Vx067 series represents one answer to this quest, with the completion of two new features, namely the "Icon Operated GUI" and SCENE PLUS.
Kano:"The user interface, in essence, is a response to a series of questions, such as who wants to do what and in which way? The optimum answers will differ in various scenarios. An AV receiver is used by a wide range of people under various circumstances. To harmonize the different requirements is a creative task that is at least as difficult as designing good sound. During GUI development, the software engineers presented a concept including things they had been wanting to create but had not been able to do so far. In close cooperation with the hardware engineers developing the GUI engine, solutions were then implemented that show the value of true team work.
With regard to one-touch operation, the aim was to have experts program optimum settings for various scenarios, allowing users without technical knowledge to easily get the best performance. Through a series of trial and error sessions, the System Memory function incorporated in earlier mid-range and high-range models was further expanded and made easier to use. The result is SCENE PLUS."
The new GUI is streamlined for seamless operation and does not obstruct the whole screen, similar to the popup menus of Blu-ray discs. It not only looks good but also allows direct access to functions such as selection of iPod and network content when inputs are switched. Whether from the remote control or the GUI, SCENE PLUS enables optimum content playback with a single operation. It makes multi-functionality truly accessible.
If the AV receiver is the conductor of the home theatre orchestra, the user interface can be seen as the baton that makes it all happen.
Sound, image and functions are the players of the orchestra, and the conductor inspires and leads them into a great performance. The Vx067 series represents this Yamaha philosophy at its best.
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— Another brilliant aspect of Yamaha AV receivers, in addition to their excellent sound, is CINEMA DSP technology. Normally, DSP stands for "Digital Signal Processing" and refers to a single chip, but with Yamaha, it actually means "Digital Sound Field Processing". This refers to the technology of faithfully recreating the acoustic ambience of many different venues such as a theatre, concert hall, or cinema in the living room of the user.
Ozeki:"In the mid-nineteen-eighties, when home theatre first came onto the scene, there were only two-channel analogue sources to work with, but Yamaha already started to develop its own DSP techniques. We kept refining and perfecting that approach, and we now have a store of technological knowledge that is second to none."
— Mr Ozeki who has been deeply involved in the history of AV receivers for more than 20 years, knows what he is talking about. The biggest difference to run-of-the-mill DSP implementations lies in the fact that Yamaha's approach is entirely based on actual sound field data.
Ozeki:"As you know, Yamaha is originally an instrument manufacturer. Going beyond this, the company has also been involved in the design of concert halls since the 1970s. This resulted in extensive experience with acoustic measurements and a great store of raw data. In 1986, the company introduced the model DSP-1 which for the first time offered sound field creation capability for home use. Its functions were based on actual measurement data from famous venues, including concert halls, opera houses, churches, and auditoriums. Since then, Yamaha has been steadily pursuing the question of how best to create a natural sound field in the home. This dedicated and intensive research is reflected also in our latest AV receivers."
— The measured acoustic data comprises information about numerous reverberation components arising from the sound being reflected at various angles by the walls, ceiling, and floor of the venue. The volume of data is much too large to be contained on a single chip in an AV receiver. The data therefore must be carefully adjusted and reduced in size while maintaining the character of the original as much as possible. Mr Noriyuki Ohashi is an expert in this highly specialized and complex task. He has visited numerous concert halls and other famous venues in many countries to perform detailed measurements. Currently, he is in charge of DSP technology for the entire range of Yamaha AV equipment.
Ohashi:"DSP at Yamaha can be divided largely into two categories. The first is the concept of "HiFi DSP", aimed at enhancing the ambient characteristics during music playback by faithfully recreating the acoustics of famous venues all over the world. The second category aims at creating an acoustic space that does not exist in reality but that greatly enhances the enjoyment of watching movies, playing games etc. We refer to this concept as "CINEMA DSP". The user can select various modes such as "Spectacle", "Sci-Fi", and "Adventure" to match the type of movie being watched and to match personal preferences. Therefore, developing sound solutions for DSP is never a "one size fits all" kind of proposition. A slight tweak of the data can result in a drastic change in the acoustic impression that is created. The engineers' sensibilities therefore play a significant role with regard to the outcome."
— For example, when reducing the data size for HiFi DSP, simply decimating data according to an automatic pattern may end up destroying the original ambience. Although some of the sounds involved are so weak as to be almost inaudible to the human ear, the approach of simply cutting them off below a certain threshold is unacceptable. It is necessary to use human experience and discrimination when deciding which data to keep and which to discard.
Ohashi:"Obvioulsy, someone who was there when the measurement was made and who has actually experienced the acoustics of the venue will be better equipped to make such decisions. The image will serve as guideline later, during the extended listening sessions that are necessary when editing data in such a way that the original sound remains present as much as possible. Even though the data may seem somewhat irregular and mere mathematics may point in another direction, the question of whether the sound is authentic or not often calls for this kind of personal approach. For Yamaha, the fact that there are many staff members who know the actual venues is clearly an important asset."
— Unlike a sound field created through simulation, the raw data of an actual sound field is not always well formed. Random patterns which cannot be reproduced through algorithms are often what make a sound pleasing to the human ear. To keep this natural, random aspect that characterizes a venue while making the overall set of data more compact is the real target of DSP development. Mr Ohashi likens this complex process to painting a life-like portrait from a photograph.
Ohashi:"If you take a digital image for example, sometimes making the colours a little more intense can bring the image closer to the recollection of a scene in real life. Similarly, with DSP we aim to recreate a natural phenomenon within the limitations of the hardware, therefore we must identify the essential elements and sometimes slightly alter these to achieve the desired effect. Of course data should be logically correct, but the subjective human impression is really important to us."
— Mr Kano pursues sound quality from the construction angle, while Mr Ohashi is concerned with DSP programming. In fact, these two engineers in charge of hardware and software aspects of the V67 series play music together in a band in their spare time. An avid keyboard player, Mr Kano belonged to a brass band in high school and took part in musical productions. During his university days, he joined a social dancing club. Mr Ohashi who started working at Yamaha at the same time as Mr Kano and who invited him to join the band, started playing percussion in his teens and still enjoys playing across many musical genres.
Kano:"There are many people at Yamaha who play instruments, like we do. This involvement with music on a daily basis may account for the fact that in general, I think Yamaha favours natural, realistic sound with plenty of ambience rather than an analytic, monitor-like sound. When we encounter a problem during sound tuning, we often consult other band members. It also is pretty common for people to come up with new technical ideas that arose out of their musical hobby."
— The DSP 3D mode featured in the new V67 series was originally the brainchild of engineers Kano and Ohashi. This mode which is currently attracting a lot of interest adds a height dimension to regular CINEMA DSP, thereby creating a virtual surround space of amazing spatial impact. It is based on the DSP HD3 mode which appeared for the first time three years ago in the flagship model RX-Z11.
Previously, Yamaha had proposed a 9.2 channel CINEMA DSP mode whereby two small presence speakers are mounted above the front left and right speakers. The floor-standing front speakers accurately reproduce the multi-channel audio signal, while the presence speakers above them only add a special component generated by the DSP. This creates a more spacious ambience by improving the impression of height and depth. As a further evolution of this approach, Mr Kano designed the "11.2ch CINEMA DSP" mode of the RX-Z11. A 7.2 channel surround system is augmented by two pairs of presence speakers positioned at the front and at the rear.
Ohashi:"The data that originally formed the basis of CINEMA DSP contained complete three-dimensional position information. But initially, because we thought that the number of output targets would not be sufficient for separate output of source and effect components, we converted the data into two-dimensional form. We believed that this would allow cleaner playback of the multi-channel source and therefore result in better sound quality. However, when Mr Kano proposed an 11.2 channel mode, I looked at the speaker positioning diagram and noticed that the speakers would create a cuboid space. Imaginary lines linking the speakers form a box that encloses the viewer/listener, which should allow the effect sound to be placed within a three-dimensional space. I had been thinking that we should try something like this, and therefore counter-proposed the idea to Mr Kano."
— With the addition of the 3D mode, CINEMA DSP gained dramatically in the capability to express spatial information. Take for example a scene in an opera house. In addition to the reverberation descending from the ceiling, as in conventional reproduction, height information about reverberation from the walls is also reproduced, giving a highly realistic impression of the sound as emanating from the entire building. The fear that having different sound output components share the same speaker would degrade sound quality proved to be unfounded, as the upper and lower, left and right, and front and rear speakers together produced a more seamless and transparent sonic image. In addition, the V67 series also offers the newly developed VPS (Virtual Presence Speaker) function. This makes it possible to enjoy the 3D sensation also with a regular 7.1 or 5.1 channel speaker configuration.
— Latest technology enables us to experience a highly convincing sense of "being there", experiencing sound that is so realistic that one feels almost able to reach out and touch it. This is natural sound reproduction at its best. Engineers developing recent home entertainment systems are working hard to make this experience ever more real.
To meet the needs of the modern age, an AV receiver must house a variety of signal processing circuits within a single enclosure. How to reconcile diverse elements that have a tendency to conflict is a never-ending challenge for technical designers. "But it also is an opportunity to ask myself what is really important, to clarify my priorities" says Mr Kano with a delighted air.
Kano:"Because the challenge is so complex, the possibilities are also endless. While fighting with all sorts of contradictions in the pursuit of any particular aim, we are creating new realities. Working as an audio engineer is a bit like arranging the pieces of a challenging and compelling puzzle. The game remains interesting because it is never quite finished, and we may even gain new insights as we go along."
— Thanks to these efforts, the microcosm that is an AV receiver will keep developing towards performance on an ever higher plane.
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