本帖最后由 znd06 于 2021-11-28 06:15 编辑
HiFi电声的要害——驱动变形失真
长期以来，电声界一直误认为低失真功放推动低失真喇叭就应得到低失真电声，于是大家极力提升二者指标，降低已知各项失真，功放总失真已能做到百分之0.00后。所谓HiFi高保真似乎已经实现了！
其实事情并非如此。个中存在原理性必然失真，结论令人瞠目，即便是0失真功放推0失真喇叭，得到的仍是有特殊变形失真的电声。此变形不能用连续正弦波解读，它发生在具有音头音尾变化状态时。拎出来如音叉、击鼓声等（这个变形指声波包络线形状相对原声形状之改变），实际音乐或自然界声响基本都是由强弱变化的声波组合而成。
高指标功放推喇叭将造成音尾萎缩，听感干、紧、硬，不自然顺畅。因此就有HiFi声不一定好听，没音乐味一说。殊不知这本来就不HiFi，根本谈不上高保真，而是属于基因缺陷的残疾性失真。造成这个失真的祸首即是被忽略的扬声器反电势（耳机耳放也同理）。其机理是反电势抵消了部分驱动电流（连续正弦波时可以达成平衡，如果是在音量减弱时，抵消会强化递减，所以造成音尾收缩）。
鉴于这个所谓HIFi声音不尽人意，大家不得不采取各种措施加以改善，常见的方法主要有两种，一是放松法，二是是渲染法，再就是双管齐下放松加渲染。放松法是减低功放阻尼系数，让喇叭有一定的自由余震，使听感不那么紧绷。渲染法则是附加一定谐波成分，效果类似卡拉OK加混响，既有一定延音作用，听起来还丰满些。典型的是那些够味胆机，还有利用号角喇叭反射衍射制造伪泛音带来听感愉悦。有一种说法叫前级控声后级出力，也是对应驱动失真的招术，靠前级软化和添加谐波，补偿后级声损。总而言之，传统产品调声无外乎靠某些失真修饰驱动失真，结果会变化多多，莫衷一是。所谓调声基于主观喜好完成，实际得到的是不同组合失真电声。由于存在原理缺陷，市面产品从来未曾做到真正的物理高保真（HiFi），尽管很多都标榜HiFi。HiFi高保真本意即是低失真，传统调声有悖高保真宗旨，声音当然也不可能正确。
对于一般性工作放音这点变形无关紧要，不影响可懂度，HiFi则另当别论，应精益求精有错必纠，传统做法不HiFi，且没出路，只能在各种失真怪圈转悠。
The Key of HiFi Electroacoustics-Driving Distortion Author Zhu Naidong （China）
For a long time, the electroacoustic circle has always mistakenly believed that low-distortion power amplifier should get low-distortion electroacoustic when it drives low-distortion speakers, so we try our best to improve the specifications of both and reduce the known distortions, and the total distortion of power amplifier can reach 0.00%. The so-called HiFi high fidelity seems to have been realized!
Actually, this is not the case. There is inevitable distortion in principle, and the conclusion is eye-popping. Even if the zero distortion amplifier drives the zero distortionspeakers, it still gets electroacoustic with special deformation distortion. This deformation can't be shown by sine wave, it occurs when there is a change state of the head and tail of the sound. Take for instance, th sund of tuning fork, drumming, etc. (this deformation refers to the change of the envelope shape of sound wave relative to the original sound shape), and the actual music or natural sound is basically composed of sound waves with varying intensity, driving the speaker with high specification power amplifier will cause the tail of the sound to shrink, and the sense of hearing will be dry, tight and hard, which will be not natural or smooth. Therefore, as the sayig goes, HiFi sound is not necessarily pleasant to listen to, and lacks musicality. Nevertheless this is not HiFi at all, not high fidelity at all, but disability distortion due to genetic defects.
The culprit of this distortion is the neglected speaker back EMF (the same is true for headphone amp). The mechanism is that the back EMF counteracts part of the driving current (balance can be achieved when the sine wave is continuous, and if the volume is reduced, the counteraction will intensify the decrease, thus causing the sound tail contraction). In view of the unsatisfactory sound of this so-called HIFi, we have to take various measures to improve it. There are two common methods, one is relaxation, the other is coloration, and still the other is both relaxation and coloration. The relaxation method is to reduce the damping coefficient of the power amplifier, so that the speaker has a certain free aftershock, and the listening feeling will not be so tight. Whereas, the coloration adds certain harmonic components, and the effect is similar to karaoke's reverberation, which not only has a certain delay effect, but also sounds fuller. Typical ones are those flavor-oriented tube amps, and those that use horn reflection diffraction to create pseudo overtones to bring pleasure to hearing. There is a saying that the pre-amp controls the tune while power amps provide the force, which is also a trick to del with the driving distortion. The pre-amp softens and adds harmonics to compensate the sound loss of the power amp.
All in all, the traditional tuning is nothing more than modifying driving distortion by some other distortion , and there can be countless different results. The so-called tuning is based on subjective preference, and what is actually obtained is different combinations of distorted electroacoustic. Due to the defects in principle, the products on the market have never achieved true physical high fidelity (HiFi), although many flaunt themselves HiFi. HiFi originally meant low distortion, and traditional tone adjustment was contrary to the purpose of hi-fi, so it is certainly impossible for the sound to be correct. For general work playback, such minor deformation does not matter much in terms of intelligibility, while HiFi is another matter, and it is necessary to strive for perfection and correct mistakes. The traditional way is not HiFi, and has no way out, people can only wander around in various distortion circles. 刘镭修订版 The Key of HiFi Electroacoustics - Drive Distortion Author: Naidong Zhu（China) For a long time, the electroacoustic circle has always mistakenly believed that low-distortion power amplifier should get low-distortion electroacoustic when it drives low-distortion speakers, so we try our best to improve the specifications of both and reduce the known distortions, and the total distortion of power amplifier can reach 0.00%. The so-called HiFi high fidelity seems to have been realized! This is not the case. There is inevitable distortion in principle, and the conclusion is eye-popping. Even if the zero-distortion amplifier drives the zero distortion speakers, it still gets electroacoustic with special deformation distortion. This deformation can't be shown by sine wave, it occurs when there is a change state of the head and tail of the sound. Take for instance, the sound of tuning fork, drumming, etc. (this deformation refers to the change of the envelope shape of sound wave relative to the original sound shape), and the actual music or natural sound is basically composed of sound waves with varying intensity, driving the speaker with high specification power amplifier will cause the tail of the sound to shrink, and the sense of hearing will be dry, tight and hard, which will be not natural or smooth. Therefore, as the saying goes, HiFi sound is not necessarily pleasant to listen to, and lacks musicality. Nevertheless, this is not HiFi at all, not high fidelity at all, but disability distortion due to genetic defects. The culprit of this distortion is the neglected speaker back EMF (the same is true for headphone amp). The mechanism is that the back EMF counteracts part of the driving current (balance can be achieved when the sine wave is continuous, and if the volume is reduced, the counteraction will intensify the decrease, thus causing the sound tail contraction). In view of the unsatisfactory sound of this so-called HiFi, we must take various measures to improve it. There are two common methods, one is relaxation, the other is coloration, and still the other is both relaxation and coloration. The relaxation method is to reduce the damping coefficient of the power amplifier, so that the speaker has a certain free aftershock, and the listening feeling will not be so tight. Whereas, the coloration adds certain harmonic components, and the effect is like karaoke's reverberation, which not only has a certain delay effect, but also sounds fuller. Typical ones are those flavor-oriented tube amps, and those that use horn reflection diffraction to create pseudo-overtones to bring pleasure to hearing. There is a saying that the pre-amp controls the tune while power amps provide the force, which is also a trick to deal with the drive distortion. The pre-amp softens and adds harmonics to compensate the sound loss of the power amp. All in all, the traditional tuning is nothing more than modifying driving distortion by some other distortion, and there can be countless different results. The so-called tuning is based on subjective preference, and what is obtained is different combinations of distorted electroacoustic. Due to the defects in principle, the products on the market have never achieved true physical high fidelity (HiFi), although many flaunt themselves HiFi. HiFi originally meant low distortion, and traditional tone adjustment was contrary to the purpose of HiFi, so it is certainly impossible for the sound to be correct. For general work playback, this distortion is not important and does not affect the intelligibility. HiFi is another matter, and it is necessary to strive for perfection and correct errors. The traditional way is not HiFi, and has no way out, you can only wander around in various distortion circles.
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发表于 2022-8-17 09:10
