What is HIFI, the industry does not currently have a particularly unified statement, according to popular understanding, HIFI English original word is High Fidelity, referred to as HIFI, meaning high fidelity. High fidelity means that the audio recording and playback system or device has the ability to faithfully reflect the original appearance of the sound signal, as well as the realistic level of the sound image position and its movement when the device specifically modifies, processes, and reproduces the sound signal. But in the eyes of the players, HIFI is divided into two factions, one is seeking truth, and the other is seeking beauty. Everyone's perception of beauty is different. For the simplest example, for beauty, some people think that the big buttocks are more important than the face, and then some people think that the white skin will make people more fascinated. . In HIFI, from a technical point of view, some people want to pursue something that is free of sound, the sound is as straightforward as possible, and true, while some people want to have a special taste, such as The high-frequency bulge feels the female voice enchanting, the low-frequency bulge feels full of sound and so on. This thing is understandable, personal taste, but if it is to be a standard, personally think, true, or better than the United States, more in line with the definition of HIFI.
But there is a big problem. The design and production of hardware is always a yin and yang process. Whether it is the production of the unit or the tuning of the later stage, the means are limited and there will be a loss of one. According to the ideal situation, a HIFI earphone or speaker needs a straight frequency response curve, a flat impedance curve, a smooth phase curve, an appropriate decay time, and a full frequency band as small as possible. Distortion curve. Of course, this thing is impossible to achieve according to the current technology. On the high-end headphones and speakers, these parameters can be done, but still flawed. On the low-end headphones and speakers, these things can only meet one or two parameters.
With the development of digital audio technology, more and more hardware functions have been replaced by software. The development of digital audio algorithms has actually reached a very horrible situation. Let me give you an example. In the impression that the EQ of the software is added, the sound is easy to falsify and divergent, but I have used an EQ like a tube. The CPU is very scary. After an old Core I7 hangs two or three, the DAW will flash directly. But this sound is almost the same as the hardware sound of his tens of thousands of dollars. No matter how it is screwed, the sound is strong, good, and high density. Existing audio software technologies have been able to mimic the hardware sound of a particular console or the sound of a particular tape drive through convolution operations. These things are more common in the studio, but in the HIFI circle, you may not notice too many of these friends. Maybe there are a lot of friends in the HIFI circle, and there are still a lot of people staying in the software. The sound of the software is the concept of hard and cold thorns. In fact, almost every 100% of the music on the market has passed the audio soft processor. Processing, the world has changed for many years, and the difference between audio technologies is also very large, definitely not the kind of rough algorithm and the sound field that only BBE, SRS.
The Dirac HD Sound technology to be talked about today is very different from the traditional sound effects. First, the biggest goal of traditional sound effects is to make the sounds sound, and the goal of Dirac HD is to fix the shortcomings of the hardware with software. This idea is available in many places, such as photo-processing of photos that have been smeared through algorithms to synthesize clear photos, etc., but in the audio industry, this is still a relatively new thing.
In fact, many friends already know the easiest way to fix hardware defects with software, which is EQ. One of the simplest audio systems, a player, and a headset. When the earphone's auditory frequency response has a large pit, or a large peak, adjusting the corresponding position with EQ can have a certain effect. But now the situation is that the current EQ on the market is basically a 5- or 7-segment graphic equalizer. The Q value, that is, the width of the affected frequency is also fixed, and can only be a very rough adjustment. The way Dirac HD is used, and EQ is not a single path. The traditional EQ uses the principle of filtering, and the principle of Dirac HD is to use the mathematical principle to construct a function relationship of the F(x) of the original frequency response curve of the earphone and the frequency response curve of the target. The operation can achieve the target frequency response. It's a bit complicated to say this. Let's give you a simple example. There are two sets of numbers, one is 2, 5, 8, and 9; the other is 4, 10, 16, and 18. The first group is equivalent to the original sound of the headphones, and the second group is equivalent to the sound that the target is to achieve. The relationship between the two is that the original number is multiplied by 2 to get the number of goals. Then, if the original value of a piece of music is 1024, the value of the target sound can be 2048 by this algorithm. The principle is probably like this, but this function is the core of Dirac, and it is indeed a brainstorming game. Of course, I thought this was a complicated EQ, because the official claims that there are thousands of points to fine-tune. In fact, if you say so, this number is infinite because the algorithm is continuous, which is equivalent to simulation. And even if it is tens of thousands of points of EQ, it is not continuous, it is discrete. Therefore, this algorithm is much more elaborate than EQ. Of course, this precision is theoretically infinite, but if it is used on the mobile phone, it is necessary to use a simplified algorithm, such as counting only 16 decimal places after the decimal point, although there is no PC 32-bit or 64-bit high. In fact, it is basically enough.
Dirac HD Sound frequency response before and after comparison
In addition to the technical advantages of frequency response, in fact, there are several more important points in the Dirac HD technology, the most important is the phase adjustment. This phase involves several directions. First, the traditional EQ will inevitably cause phase drift. The more adjustment, the greater the phase change. What is the phase? In the simplest terms, the sound playback time, for example, a 200hz and a 2Khz sound, is broadcast at the same time, and when 200hz is processed with EQ, the two sounds that should have been simultaneously emitted, It will not be issued at the same time, it may be issued after 200hz first issued 2Khz, or it may be issued after 200hz, 2Khz is issued first, this thing has a relationship with each algorithm, and it is related to the degree of gain or attenuation, one sentence in total It is the sound that should have been emitted at the same time, and it has become different. What is the result of this? I don't have much to say about the complexity. Basically, the sound will be eclipsed and the sound field will be irregular. The frequency response of Dirac HD is in principle higher than the ordinary EQ. Then there is another important point. Every earphone is also a good speaker, and its phase is not static. It belongs to its own phase characteristics, and these phase characteristics will cause the sounds of different frequencies that should be emitted at the same time not to be emitted at the same time, which will cause the sound just mentioned to be fainted. The Dirac HD technology can adjust the phase shift of the headphones themselves, making the phase response of the system more natural and realistic. The phase characteristics are also an unavoidable defect in the speaker and earphone system. Dirac's technology can also be used to fix this one bit. It is quite powerful.
Phase corrected by Dirac HD technology
In addition to the frequency response and phase fixes, Dirac HD technology has a nice feature that adjusts the attenuation characteristics of the headphones. What is the attenuation characteristic? Let me give you an example. You can knock on a big clock. When the sound does not end immediately, there must be a certain extension of time. The sound gradually becomes smaller. The characteristic that this extension does not have is the attenuation characteristic. In the earphone, this attenuation characteristic also exists. Of course, the attenuation characteristics of different headphones are naturally different. Why do people think that the speed of moving iron is fast and the speed of moving coil is slow? A large part is the difference in attenuation characteristics. The most black technology part of Dirac HD I personally feel is this, you can change the attenuation characteristics of the headphones through software. In theory, you can even use the dynamic circle to make the moving iron sound, but now it is not so high precision. The algorithm and the amount of computing, it is estimated that to wait for this to wait for the development of technology. I ventured to guess the principle, perhaps by testing out the attenuation principle of a particular earphone, and then generating an attenuated inverse sound wave inside the software, and superimposing the two, the part of the attenuated sound can be offset. Of course, this is what I guess. Maybe Dirac has more NB technology, which is the core secret of others.
Whether it's frequency, phase, or attenuation, the gap between each particular headset or speaker is very different, so what's the result now? Dirac HD technology must target specific headsets and systems. To make the simplest assumption, the low frequency of the noodles is very high, the low frequency phase is on the front, and the decay time is very long. How will the Dirac engineers deal with it, first attenuate the low frequency of the earphone, then adjust the phase of the low frequency backwards, and decay the time. Shorten. When all the parameters are fixed, it is labeled as a Dirac HD FOR noodle headset (I guess). If it is ER4P, the lack of low frequency, high frequency phase front, and especially fast attenuation, then Dirac engineers will increase the low frequency, shift the high frequency phase back, add a little attenuation, and then pack these parameters, the name Call Dirac HD FOR ER4. At this time, everyone will find that the adjustment parameters of FOR noodles and FOR ER4 are completely different. If you plug the noodle headphones into the DISR HD preset of FOR ER4, you can imagine a bigger low frequency and then a slower low frequency. Speed ​​plus a greater attenuation, Mom, I can't imagine it, this sound can't be heard completely, anyway. Of course, because I have not participated in the research and development of Dirac, these things are also assumed by me, but the principle is not wrong, so the technology of Dirac HD must be specific to the earphones, can not be inserted, which is the biggest difference from the traditional sound effects. local.
Having said that, is there any flaw in Dirac HD technology? Of course not. First of all, in mobile phone applications, because of the CPU occupancy and power consumption, Dirac can not use the most sophisticated algorithm, because that power can not stand, certainly use a simplified algorithm, and simplify The consequence of the algorithm is that the accuracy will drop a bit. Don't squat on the street first. If you have used the BBE at the studio level on the computer and the BBE at the general consumer digital level, you will know that BBE has a lot of pitfalls in consumer digital. What is the result of this? On the low-end headphones, the problem of frequency response and phase attenuation is the main problem. After using Dirac HD to make a specific fix, you can fix many problems of the headphones themselves, even if The accuracy is not high enough, and the effect of the repair is very obvious, so at the low end, using Dirac is a very good solution. On the high-end headphones, the problems of the headphones themselves will be smaller, the repair efficiency will be higher, but because the problems of the headphones themselves are less, the improvement is not obvious enough. Of course, I am talking about mobile phones and mobile phones. If it is a PC or a workstation, Dirac HD can make the sound of high-end headphones even better, because the direction is right, and the rest is the means.
All in all, Dirac HD audio processing technology is a targeted repair technology. It is also a kind of sound effect, but it is very different from traditional sound effects, so the official is not willing to define him as sound effect. It is audio fidelity technology, but if you understand the principle, it doesn't matter. It can be said that Dirac has created a new technology and new ideas for implementing HIFI with software, which is still worth recommending.
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