What is DSP?

Even the best surround technology doesn't take into account one very important factor affecting the sound you hear. That's the fact that your cozy living room has nothing in common, acoustically speaking, with cavernous theaters and concert halls, or any other locations where real movie or musical performances take

place.Yamaha's musical heritage includes extensive research into the way sound behaves in venues such as these. And we've developed some very sophisticated techniques for reproducing that behavior in your home, using proprietary microchips designed and fabricated in our own facilities.

We call this DSP. And it's short for Digital Sound Field Processing. It can make a few home speakers reproduce the seamless curtain of sound created by multiple-speaker arrays in your local theater. It can recreate the ambiance of a stadium, a concert hall or an intimate club. And when combined with Dolby Digital and Dolby Surround Pro Logic, it can even expand the apparent dimensions of your room--letting you experience the spaciousness of a large theater, while hearing every sound coming from exactly where the director intended.

Yamaha’s Digital Sound Field Processing Creates the Ultimate Home Theater Experience

Digital Sound Field Processing (DSP) is a Yamaha innovation that has opened a new chapter in the history of audio. Instead of having to go to a performance venue to experience the actual acoustic environment, you can now stay home and hear the same or even better sound. This is an entirely new listening experience that only Yamaha can bring you. Using special single-point quad microphones to measure acoustic data, Yamaha engineers have been able develop the world’s first sound field processor with the ability to store digital data on the acoustic conditions of concert halls, cathedrals, movie palaces, and other environments and reproduce these conditions in ordinary listening rooms.

Dolby Stereo used in large movie theaters was the basis for Yamaha's next technological breakthrough in home theater sound. Dolby Surround Pro Logic produces a surround sound environment by projecting dialogue straight from the front while

music and sound effects come from the back and sides of the listening area. By combining this Dolby technique with its own DSP technology, Yamaha was able to achieve a further breakthrough that we call Cinema DSP. This new technology achieved what was long believed to be impossible: an enveloping surround sound that brought the ambience of a movie theater to an ordinary listening room.

Tri-Field Cinema DSP offers the most accurately realistic listening experience ever attained by a home theater system. An advanced new digital technology called Dolby Surround AC-3 uses 5.1 channels ( 5 channels plus a bass-only channel) to provide

accurate localization, high-channel separation and clear music and effects. Using this Dolby AC-3 technology and utilizing a new technique in acoustic properties called Tri-Field DSP Processing has resulted in Tri-Field Cinema DSP, the ultimate home theater experience.

Yamaha takes cinema digital with our Cinema DSP Digital concept.

Yamaha is a leader in acoustic research and technology, and in developing and producing sophisticated audio microprocessors. We were also one of the first companies to embrace digital technology, and have helped to make digital audio as popular as it is today. Combining this acoustic, audio and digital expertise led to the development of our innovative, high performance home theater systems. Suddenly, it became possible to experience movies at home with all the dramatic sound impact that the director intended to convey.

And now we're going even further with Cinema DSP Digital. We'll be releasing new technologies and products that will give you a more exciting, realistic experience no matter where you watch movies: on a home theater system, in a movie theater, or on a computer. Cinema DSP Digital : a new era of movie sound and video.

Question: How is Yamaha PlayXchange different from all other 5-disc changers that allow you to change discs while a disc remains playing?

Answer: Transport design. Yamaha makes the only 5-disc CD Changer that combines the convenience of a changer with the performance of a single disc player. And the story of the development of PlayXchange begins here....

A few years ago during a product meeting with Yamaha Audio engineers, the subject of carousel changers came up. These meetings, held annually, are intended to discuss and design the products of the future. At this particular meeting, 5-disc CD changers were new on the market, and Yamaha didn’t make one yet. Well, our competitors did, and they were gaining market share in this category. So the topic of changers was red hot! Unfortunately, the engineers didn’t share the same enthusiasm for 5-disc changers as the sales and marketing staff. In fact, the engineers were steadfast in their opinion that the 5-disc carousel changer was the worst thing to happen to the compact disc since its development! The reason was simple: A CD carousel changer has a large tray or drawer that slides in and out to hold all 5 compact discs. It is also subject to a lot of resonance and vibration that seriously degrades the performance of the player. Although not identical, the problem is similar to acoustic feedback in a phonograph player.

Well, it seems that the product meeting ended with no hope of a CD carousel changer in the near future. The sales and marketing staff and the engineering staff were at an impasse. But it turns out that the engineers took the request seriously and immediately went to work on designing a CD changer that had the convenience of a changer with the audio performance and specs of a single disc player. The result: Yamaha PlayXchange.

At first, everyone thought that the most important feature was the ability to change four discs while the fifth disc plays. And most people think that all changers that have this feature are the same. But when you dig a little deeper you learn that PlayXchange is a by-product of a more important feature—the isolation of the playing disc. When you examine a Yamaha CD Changer more closely you discover that the superior isolation characteristics of the PlayXchange design make it perform like a top notch single player with the specs to prove it. The key difference between the Yamaha design and others is the way that the playing disc is isolated from the tray and drawer. In the Yamaha design the CD transport is mechanically separated from the rest of the chassis so that vibration and resonance do not affect playback. The playing disc is lifted off of the tray with a magnetic clamp, literally suspended while playing. In fact, the transport is so isolated from the rest of the chassis as to be almost a separate component. In other designs, the transport is connected directly to the drawer and subject to the slightest vibration. This is also why many changers can only change two or three discs while in play mode, not four.

The Yamaha PlayXchange design is so unique that a patent has been granted for the design.

So, the real benefit is hidden from view. It says PlayXchange on the front panel, but it's really a high performance single disc player.

Head Related Transfer Function , or HRTF has 2 main components:

The TRANSFER FUNCTION refers to the transmission of sound to the ears, and between the ears and the brain.

The HEAD RELATED refers to the method of measuring transfer functions by placing tiny clinical probe microphones in the ear channels of people in anechoic chambers (specially designed acoustically flat rooms), and recording measurements at many positions around their heads.

Using these "HRTF maps", Yamaha engineers were able to direct sound into the ears via headphones that accurately reproduces speaker sound from various directions. This is briefly how Yamaha's unique Silent Cinema works

It has been over a decade since the introduction of the compact disc player, and during that time various digital to analog conversion systems like Yamaha Super Hi-Bit and S-Bit Plus have delivered improved sound quality.

However, while there were improvements made in compact disc players, there have been few changes in the CDs themselves--compact discs are recorded in 16 bits and sampled at 44.1 kHz. Professional recording, on the other hand, has made major advances in these areas--most notably in the introduction of the 20-bit recording format. The major advantage of the 20-bit format over 16-bit is less quantization noise in the A/D conversion, which results in significantly better sound quality or low signal levels. Simply put, the signal resolution is 16 times higher at 20-bit than at 16-bit. But because CD software is limited to 16-bits, consumers have not been able to benefit from these advances. Yamaha, with their strong background in music and digital technology, has devised a new digital-to-digital translation system called Pro-Bit that can successfully recover full 20-bit data from 16-bit CD software.

The Pro-Bit translator system begins by reading the digital data from a regular 16-bit compact disc sampled at 44.1kHz. It also reads the data before and after the data being heard at that moment and sends the information to a Line Pattern Decoder. From these separate readings the translator recognizes the changing pattern of the music and has developed over 20,000 music patterns (or mathematical algorithms) and stores them in memory. These patterns were derived from a data base containing over 200 million possible patterns. Based on these patterns the 16-bit data is adjusted as if it were resting on a much smoother 20-bit curve. By resting on a 20-bit curve, each data point contains more information about the music, or has a higher resolution. The result is a more natural, smooth, musical sound that is much closer to the original analog wave. See below.

Yamaha’s Pro-Bit was achieved through the cooperation of engineers from the Professional Audio Division and scientists from the Applied Research Facility. After years of analyzing the differences between acoustic music, 16-bit signals and 20-bit signals, this group developed the musical algorithms that are the heart of Pro-Bit Technology. The easiest way to appreciate Pro-Bit is to listen to a Yamaha CD Player with Pro-Bit technology. The easiest way to understand signal resolution is to use a photograph as an analogy.

The two photographs of the Yamaha musical instruments are identical except that one photo has sixteen times more resolution, the identical difference between a 16-bit and 20-bit audio signal. It’s not hard to see how much difference you can hear.

The photograph above has 16 times more resolution than the photo below. This represents the difference that Pro-Bit technology provides when it translates a 16-bit audio signal to a 20-bit audio signal. You can even recognize the brand name on the 20-bit photograph.

Most innovative product developments begin with a question. It may be, "How can we build a better product" or, "How can this be improved?" Yamaha Servo Technology (YST) began the same way.

This time, however, Yamaha engineers asked, "How can we build a better sound reproduction system?"

The key word in that question is system. Although many significant advances have been made in the design of both amplifiers and loudspeakers, there have been few engineers that have recognized that amplifiers and speakers must be designed as a system. The reason is because amplifiers and speakers interact with one another and each has a considerable effect on the performance of the other. It is commonplace to hear an audiophile say, "This amp sounds best on these speakers," or vice versa. This is because amps and speakers have different performance characteristics. Mixing and matching amps and speakers will clearly show the differences. Yamaha engineers recognized that in order to achieve better sound quality, they had to look at amps and speakers as a system, and not individually. Their work began by looking at the design of a typical amplifier. Most good amplifiers will perform flawlessly when tested in the conventional manner. Generally, amplifier testing consists of driving a "dummy load" (a resistor with a fixed value) while sitting on a technician’s test bench, instead of driving a pair of loudspeakers. This is unfortunate because it does not tell us how the amp will perform in the real world, connected to a pair of speakers, playing real music. Once connected to a pair of speakers, an amplifier’s performance can change drastically.

As you may know, an amplifier must be able to accurately control the motion of the loudspeaker drivers. This is called Damping Factor. You may also know that many amplifiers don’t do this very well, which causes a tremendous loss in the potential performance of both amplifiers and speakers. So, Yamaha engineers conducted extensive research on amplifiers and speakers with the objective of designing a system that would balance the performance of both. Their research led to the development of Yamaha Servo Technology (YST), which represents a significant advancement in music reproduction and enjoyment both for full range loudspeakers and subwoofers. Several innovative products using YST have been designed and many more are in development. As a direct result of the research and development that led to the YST system, Yamaha has applied for 37 international patents.

Yamaha Servo Technology Simplified
The YST system has significant benefits for music lovers and audiophiles, such as:

1. Incredible bass from a small cabinet. The Yamaha line of subwoofers, mini systems and shelf systems are good examples.

2. Easy and convenient placement because of smaller size.

3. Better imaging - imagine sitting in the front row of an orchestral performance - close your eyes and try to visualize the placement of the members of the orchestra. The ability to do this is known as imaging; and imaging improves with smaller speakers. YST speakers are small enough to have excellent imaging characteristics and yet they can reproduce tones from the very low bass of a pipe organ to the highs of a triangle or cymbals.

YST can be explained and understood in many ways, but the simple explanation is probably best. As mentioned before, YST is a system; that is, the amplifier and speakers work together to produce the resulting sound. Understanding it involves some basic knowledge of what typically happens between amplifiers and speakers.

Loudspeakers have voice coils, which consist of copper wire wrapped in the shape of a coil around a magnet. The signal, or electricity, coming from an amplifier causes the coil of wire and the magnet to interact resulting in the speaker’s cone moving in and out thus producing sound. In addition, all wire (copper or otherwise) has a property known as resistance. This resistance tends to resist the flow of electricity through the wire. This can be demonstrated with a garden hose. Turn on the water and then crimp the hose. The crimp in the hose resists the flow of water. Electricity through a wire behaves the same way. The resistance prevents the speaker from doing exactly what the amplifier tells it to.

This results in some inaccuracy in sound reproduction because the speaker is not moving precisely as instructed by the amp. This results in a very low Damping Factor, and this undesirable trait is most noticeable in bass response. Bass that is undefined or unclear is the result. So, how can this resistance be eliminated? Well, it can’t! Any wire, no matter how short or long will have some resistance. The resistance can’t be eliminated, but it can be compensated for. Think back to the garden hose analogy for a moment. If the garden hose is crimped, which slows the flow of water, how is the blockage compensated for? Simple, just turn up the water pressure. Walk over to the faucet and turn it up.

In fact, that’s exactly what YST does. It’s called a Negative Impedance Circuit. In effect, it compensates for the resistance that the wire in the voice coil creates in the same way that turning up the water faucet compensates for the drop in water pressure when the hose is crimped or blocked. The obvious difference is that the YST amplifier compensates for the electrical resistance by sending additional electricity (certainly not water!) to the YST loudspeaker. Essentially, this compensates for the electrical resistance of the voice coil. By now you’re probably thinking, "so what, just because the amplifier compensates for the electrical resistance of the voice coil, how does it make Yamaha subwoofers or full range speakers put out that kind of bass?"

The Negative Impedance Circuit is only half of the story. The other half is the cabinet design and construction. In many ways the YST speaker cabinet design is just as important as the YST circuitry. The interesting part is how much bass is output from the port. The reason is directly related to the Negative Impedance Circuit. In a typical bass reflex or vented speaker enclosure, the port is supposed to reinforce the bass coming from the cone, but in reality, most of it comes from the cone itself. That’s why most bass reflex speakers traditionally use larger cones (10",12", or 15" in diameter). But why does this happen? When a bass signal enters the speaker, it is supposed to cause the cone to excite (or resonate) the air in the enclosure. This excited air is then supposed to escape through the port as bass . Unfortunately, what really happens is that the bass escapes through the cone itself, not through the port. This is because most amplifiers cannot control the speaker cone very well because of the voice coil resistance. The cone is not rigid enough to contain the excited air and force it out of the port. So, it escapes through the cone and not the port. That’s why speakers with a lot of bass are usually pretty big.

But, with YST, you’ll remember that the job of the Negative Impedance Converter is to maintain better damping control of the speaker cone by compensating for the speaker’s voice coil resistance. So, when a bass note enters the YST speaker, the air in the cabinet resonates (just like a regular bass reflex speaker), but because the amplifier has better control of the cone, the bass doesn’t escape through the cone, but comes out of the port as bass (and a lot of it!) It is interesting to note that all bass reflex speakers SHOULD behave the way a YST speaker does, but because of the voice coil resistance that exists in all loudspeakers and the fact that standard amplifiers don’t compensate for this resistance, bass reflex speakers don’t produce as much deep, solid bass. Surprisingly, the bass reflex loudspeaker system (also known as a Helmholtz resonator) was invented almost 100 years ago, and only now does it work the way it was designed to work.