关于输出抗阻与耳机抗阻匹配问题的文章

孤岛飞鹰

原文链接在此：http://nwavguy.blogspot.com/2011/02/headphone-amp-impedance.html
有一定的参考意义，最近总有人说参数党和听感党，我认为二者相依，参数不能代表绝对听感，因为有个体差异存在，
但是参数能够代表大致走向，就酱。
Headphone & Amp Impedance耳机 & Amp

INTRO: The output Impedance of headphone sources is one of the most common reasons the same headphones can sound different depending on what they’re plugged into. This important parameter is rarely specified by manufactures but can make a huge difference in sound quality and headphone compatibility.

简介: 耳机来源的输出阻抗是一个最常见的原因，因为同样的耳机可以根据它们插入的东西听起来不同。这个重要的参数很少被制造商指定，但可以在声音质量和耳机兼容性方面产生巨大的差异。

HEADPHONE IMPEDANCE MOVED: This article used to be about both output impedance and headphone impedance. But, in the interest of shorter articles, I’ve split them. So if you’re looking for info headphones, please see:

耳机阻抗移动: 这篇文章曾经是关于输出阻抗和耳机阻抗。但是，为了更短的文章，我把它们分开了。因此，如果你正在寻找信息耳机，请看:

• Headphone Impedance Explained 耳机阻抗解释
  

THE SHORT VERSION: All you really need to know is most headphones work best when the output impedance is less than 1/8th the headphone impedance. So, for example, with 32 ohm Grados the output impedance can be, at most, 32/8 = 4 ohms. The Etymotic HF5s are 16 ohms so the max output impedance is 16/8 = 2 ohms. If you want to be assured a source will work well with just about any headphone, simply make sure the output impedance is under 2 ohms.

简言之: 你真正需要知道的是，大多数耳机工作最好的时候，输出阻抗/耳机的阻抗小于1/8。所以，举个例子，32欧姆的 Grados 输出阻抗最多可以是32/8 = 4欧姆。的 hf5是16欧姆，所以最大的输出阻抗是16/8 = 2欧姆。如果你想确保一个来源将工作得很好，几乎任何耳机，只要确保输出阻抗是2欧姆以下。

WHY DOES OUTPUT IMPEDANCE MATTER? It matters for at least three reasons:

为什么输出阻抗很重要? 至少有三个原因:

• The greater the output impedance the greater the voltage drop with lower impedance loads. This drop can be large to enough to prevent driving low impedance headphones to sufficiently loud levels. A real world example is the 输出阻抗越大，阻抗负载越低的电压降越大。这个下降可以足够大，以防止驾驶低阻抗耳机足够大的水平。一个现实世界的例子是Behringer UCA202 百灵达 UCA202 with a 50 ohm output impedance. It struggles with some 16 - 32 ohm headphones. 50欧姆的输出阻抗，16-32欧姆的耳机
• Headphone impedance changes with frequency. If the output impedance is much above zero this means the voltage delivered to the headphones will also change with frequency. 耳机阻抗随频率变化。如果输出阻抗远高于零，这意味着传递给耳机的电压也会随着频率而变化The greater the output impedance, the greater the frequency response deviations 输出阻抗越大，频率响应偏差越大. Different headphones will interact in different, and typically unpredictable, ways with the source. Sometimes these variations can be large and plainly audible. .不同的耳机将以不同的，典型的不可预知的方式与信号源进行交互。有时，这些变化可以大而清晰地听到
• As output impedance increases 随着输出阻抗的增加electrical damping 电阻尼 is reduced. The bass performance of the headphones, as designed by the manufacture, may be audibly compromised if there’s insufficient damping. The bass might become more “boomy” and less controlled. The transient response becomes worse and the deep bass performance is compromised (the headphones will roll off sooner at low frequencies). A few, such as those who like a very warm “tube like” sound, might enjoy this sort of under damped bass. But it’s almost always less accurate compared to using a low impedance source. 减少。低音性能的耳机，作为设计的制造商，可能是可听的妥协，如果有不足的阻尼。低音可能会变得更“牛气哄哄”，更不受控制。暂态响应变得更糟糕，低音的性能是妥协的(耳机将滚动更快在低频)。一些人，比如那些喜欢非常温暖的“管状”声音的人，可能会喜欢这种低阻尼的低音。但与使用低阻抗源相比，它几乎总是不够精确
  

THE 1/8th RULE: To minimize all three of the above problems, it’s only necessary to keep the output impedance less than 1/8th the headphone impedance. Or, put another way, just divide the headphone impedance by 8 to get the maximum output impedance without potential audible degradation.

八分之一原则: 为了最小化以上三个问题，只需要保证输出阻抗的耳机阻抗小于八分之一。或者，换句话说，只需要将耳机阻抗除以8，就可以得到最大输出阻抗，而不会造成潜在的声音衰减。

IS THERE A STANDARD FOR OUTPUT IMPEDANCE? The only standard I’m aware of is IEC 61938 from 1996. It specifies an output impedance of 120 ohms. There are numerous reasons why this is standard is way out of data and a really bad idea. In a Stereophile article about headphones, they said of the 120 ohm standard:

输出阻抗有标准吗？我所知道的唯一标准是1996年的 IEC 61938。它指定输出阻抗为120欧姆。有很多原因可以解释为什么这是一个标准的数据，是一个非常糟糕的想法。在一篇关于耳机的 Stereophile 文章中，他们提到120欧姆标准:

“Whoever wrote that must live in a fantasy world.”

“不管是谁写的，他一定活在一个幻想的世界里。”

I have to agree with Stereophile. The 120 ohm standard might have been (barely!) tolerable before the iPod and other portable music sources became immensely popular, but it’s not any more. Most headphones are designed very differently today.

我不得不同意 Stereophile 的观点。120欧姆的标准可能是(勉强!)在 iPod 和其他便携式音乐资源变得非常流行之前，它还能忍受，但现在已经不行了。今天大多数耳机的设计都非常不同。

PSUEDO STANDARDS: A lot of professional gear has a 20 – 50 ohm headphone output impedance. I’m not aware of any that follows the 120 ohm IEC standard. Consumer gear tends to be in the range of 0 – 20 ohms and, with the exception of tube and certain other esoteric designs, most high-end audiophile headphone sources are well under 2 ohms.

标准: 许多专业设备都有一个20-50欧姆的耳机输出阻抗。我不知道任何遵循120欧姆 IEC 标准。消费齿轮往往是在0-20欧姆的范围内，除了管和某些其他深奥的设计，大多数高端高保真耳机源远低于2欧姆。

THE iPOD INFLUENCE: Since the 120 ohm standard was published in 1996, music players advanced from lo-fi cassette tape and skipping portable CD players to the massive iPod craze. Apple helped take high quality audio portable and there are at least half a billion portable digital players in circulation not including phones. Nearly all portable music/media players now run from a single cell Li-Ion battery. These batteries only produce a bit over 3 volts which means you typically get less than 1 volt RMS of audio output driving typical headphones (sometimes much less). If you add 120 ohms to the output, and use typical portable headphones (nearly all of which are in the range of 16 –32 ohms) the headphones usually won’t play loud enough. And most of the battery power is wasted as heat in the 120 ohm resistor. Only a small fraction of the power makes it to the headphones. That’s a big problem in portable audio where getting the best battery life from ever smaller devices is critical. It’s much more efficient to deliver all the power to headphones.

影响: 自从120欧姆标准在1996年出版以来，音乐播放器从低保真盒式磁带和跳过便携式 CD 播放器发展到大规模的 iPOD 热潮。苹果公司帮助采购了高质量的便携式音频播放器，目前市面上至少有5亿个便携式数字播放器，不包括手机。现在几乎所有的便携式音乐/媒体播放器都使用单芯锂离子电池。这些电池只产生超过3伏的电压，这意味着你通常得到不到1伏的 RMS 音频输出驱动典型耳机(有时要少得多)。如果你增加120欧姆的输出，并使用典型的便携式耳机(几乎所有的都在16-32欧姆的范围内) ，耳机通常不会播放足够大的声音。而且大部分的电池功率都浪费在120欧姆电阻的热量上。只有一小部分的能量被传送到耳机上。这是便携式音频的一个大问题，因为从更小的设备中获得最好的电池寿命是至关重要的。将所有的电力传输给耳机要有效得多。

HEADPHONE DESIGN: So what output impedance do headphone manufactures design for? As of 2009 well over 220 million iPods had been sold. The iPod, and similar portable players, are the 800 pound gorillas in the headphone market. So, not surprisingly, most manufactures started designing many or all of their headphones to work well with the iPod. That means they’re designed to work with an output impedance under 10 ohms. And higher-end full size cans are most often designed for sources that follow the 1/8th Rule or have a near zero output impedance. I’m not aware of any current audiophile headphones intended for home use designed to the ancient 120 ohm standard.

耳机设计: 那么耳机制造商的设计输出阻抗是什么？截至2009年，ipod 的销量已经超过2.2亿台。以及类似的便携式播放器，是耳机市场上800磅重的大猩猩。因此，毫不奇怪，大多数制造商开始设计他们的许多或全部耳机，以便与 iPod 很好地配合。这意味着他们的设计工作输出阻抗低于10欧姆。而高端的全尺寸罐通常是为遵循1/8法则或输出阻抗接近于零的来源设计的。我不知道任何现行的高保真耳机为家庭使用设计的古老的120欧姆标准。

THE BEST HEADPHONES ARE DESIGNED FOR THE BEST SOURCES: If you do a quick survey of the most well reviewed high-end headphone amps and DACs, they nearly all have very low output impedances. Examples are products from Grace Designs, Benchmark Media, HeadAmp, HeadRoom, Violectric, etc. It only stands to reason that most high-end headphones are designed to be at their best with similar products. Some of the most highly regarded headphones have relatively low impedances including several models from Denon, AKG, Etymotic, Ultimate Ears, Westone, HiFiMAN and Audeze. All of these, as far as I know, were designed to be used with low (ideally near zero) impedance sources. I’ve also had a Sennheiser representative tell me they design their audiophile and portable headphones for zero ohm sources.

最好的耳机是为最好的来源而设计的: 如果你做一个快速的调查，最好的审查高端耳机放大器和数字音频接收器，它们几乎都有非常低的输出阻抗。例如 Grace Designs、 Benchmark Media、 HeadAmp、 HeadRoom、 Violectric 等产品。这只能说明，大多数高端耳机的设计都是为了在同类产品上达到最佳状态。一些最受推崇的耳机具有相对较低的阻抗，包括来自 Denon、 AKG、 Etymotic、 Ultimate Ears、 Westone、 HiFiMAN 和 Audeze 的几个型号。所有这些，据我所知，被设计用于低(理想接近零)阻抗源。我还有一个森海塞尔的代表告诉我，他们设计他们的音响和便携式耳机零欧姆来源。

THE FREQUENCY RESPONSE PROBLEM: If the output impedance is more more than 1/8th the headphone impedance there will be variations in the frequency response. With some headphones, especially balanced armature or multi driver designs, these variations can be rather extreme. Here’s what 43 ohms of output impedance does to the Ultimate Ears SuperFi 5’s frequency response—a total, and very audible, variation of 12 dB:

频率响应问题: 如果输出阻抗超过耳机阻抗的八分之一，那么频率响应就会发生变化。有些耳机，特别是平衡电枢或多驱动设计，这些变化可以相当极端。以下是43欧姆的输出阻抗对 Ultimate Ears SuperFi 5的频率响应---- 总的，非常可听的，12分贝的变化:

10 OHM OUTPUT IMPEDANCE: Some might look at the above example and think it’s extreme with a 43 ohm source. But plenty of sources have around a 10 ohm output impedance. Here’s the same headphones with a 10 ohm source—there’s still a very audible 6 dB of variation. This sort of curve creates weaker bass, a “glaring” midrange emphasis, muted high frequencies, and odd phase characteristics due to the sharp “notch” at 10 khz that can alter spatial perceptions:

10 OHM 输出阻抗: 有些人可能看到上面的例子，认为它是极端的43欧姆源。但是很多电源的输出阻抗都在10欧姆左右。这是同一款10欧姆声源的耳机ーー仍然可以听到6分贝的变化。这种曲线会产生较弱的低音，“耀眼”的中音强调，低沉的高频率，以及由于10千赫处锐利的“缺口”可以改变空间感知的奇怪的相位特征:

FULL SIZE SENNHEISERS: Here are the full size, higher impedance, Sennheiser HD590 cans with the same 10 ohm output impedance. Now the variation is only a bit over 1 dB above 20 hz. While 1 dB isn’t that much, it’s right in the most “boomy” bass region which is the last place most want any sort of emphasis:

全尺寸 SENNHEISERS: 这里是全尺寸，高阻抗，senheiser HD590罐与相同的10欧姆输出阻抗。现在的变化只有一点超过1分贝以上20赫兹。虽然1分贝不是很多，但它正好处于最“牛气哄哄”的低音区，这是最不需要任何强调的地方:

DAMPING EXPLAINED: Any dynamic driver, in a speaker or headphone, moves back and forth with the music. That’s how it creates sound and they all have moving mass. The laws of physics say an object in motion tends to stay in motion. Damping is used to help avoid unwanted motion. Without going into too many details, if a speaker is under-damped, it keeps moving after it should have stopped. And if it’s over-damped (rare) its ability to accurately follow the signal is compromised—imagine a speaker trying to operate submersed in maple syrup. There are only two ways to damp a driver—mechanically and electrically.

解释阻尼: 任何动态驱动，在扬声器或耳机，移动来回与音乐。这就是它如何产生声音，它们都有移动的质量。物理学定律说，运动中的物体倾向于保持运动。阻尼是用来帮助避免不必要的运动。不需要太多细节，如果一个扬声器是低阻尼，它继续移动后，它应该停止。如果它的阻尼过大(罕见) ，它准确跟踪信号的能力就会受到影响——想象一下一个扬声器试图把自己浸在枫糖浆中操作。只有两种方法来阻尼司机——机械的和电动的。

BOUNCING CARS: Mechanical damping is much like the shock absorbers on a car. They add resistance so when you hit a bump the car doesn’t keep bouncing up and down long after the bump. But they also add harshness because they reduce the suspension’s ability to accurately follow the road. They’re a compromise—soft shocks give a softer but more bouncy ride and stiff shocks control the bouncing better but make the ride harsher. Mechanical damping is always a compromise.

机械阻尼很像汽车的减震器。它们增加了阻力，所以当你碰到颠簸时，车子不会在颠簸之后继续上下颠簸很长时间。但他们也增加了严厉，因为他们减少了悬架的能力，准确地跟随道路。它们是一种妥协ーー柔软的冲击可以带来更柔和但更有弹性的乘坐感，而刚性的冲击可以更好地控制弹性，但会使乘坐感更加严酷。机械阻尼总是一种折衷。

ELECTRICAL IS BETTER: There’s a better option to control unwanted motion of headphone drivers and it’s called electrical damping. The voice coil and magnet of the driver work with the amplifier to control the motion of the driver. This kind of damping has fewer negative side effects and allows headphone designers to create headphones with less distortion and better sound. Just like a car suspension that can better follow the road, an optimally damped headphone driver can better follow the audio signal. But, and this is the critical part, electrical damping is only effective when the output impedance of the amplifier is much lower than the impedance of the headphones. If you plug 16 ohm headphones into an amp with a 50 ohm output impedance, there will be almost no electrical damping. That means when the driver is supposed to stop moving it might not. The headphone is more like a car with worn shock absorbers. If the 1/8th Rule is followed, however, there will be sufficient electrical damping.

电气更好: 有一个更好的选择，以控制不必要的运动耳机驱动器，这是所谓的电气阻尼。驱动器的音圈和磁铁与放大器一起工作，控制驱动器的运动。这种阻尼有较少的负面影响，并允许耳机设计师创造耳机少失真和更好的声音。就像汽车悬架可以更好地跟随道路，一个最佳阻尼耳机司机可以更好地跟随音频信号。但是，这是关键的部分，电阻尼只有在放大器的输出阻抗远低于耳机的阻抗时才有效。如果你把16欧姆的耳机插入一个50欧姆的输出阻抗放大器，几乎不会有电阻尼。这意味着，当司机应该停止移动，它可能不会。耳机更像是一辆磨损了减震器的汽车。然而，如果遵循1/8法则，就会有足够的电阻尼。

A SPEAKER ANALOGY: Back in the day, before my time, speakers were mostly driven by amplifiers that used tubes instead of transistors. Tubes are high impedance devices that operate at high voltages so nearly all tube amps use output transformers. Without going into all the details, tube amps had widely varying output impedances that were often significant and violated the 1/8th Rule. Speaker manufactures couldn’t rely on amplifiers having a low enough impedance to provide much electrical damping. This compromised speaker design much like headphone design is compromised today if a headphone designer can’t rely on a low impedance source for proper electrical damping.

一个演讲者类比: 在我那个时代之前，演讲者主要由管子而不是晶体管的放大器驱动。管是高阻抗设备，在高电压下工作，所以几乎所有管放大器都使用输出变压器。没有进入所有的细节，电子管放大器具有广泛变化的输出阻抗，往往是显着的，并违反了1/8规则。扬声器制造商不能依靠具有足够低阻抗的放大器来提供大量电阻尼。这种妥协的扬声器设计很像耳机设计是妥协今天如果耳机设计师不能依靠一个低阻源适当的电阻尼。

ACOUSTIC SUSPENSION: In the 1970’s the situation changed as solid state amplifiers became popular. Almost all solid state amps easily pass the 1/8th Rule. In fact, most pass a 1/50th Rule—their output impedance is generally below about 0.16 ohms—known as a damping factor of 50. Suddenly speaker manufactures were free to design better speakers that could take advantage of these much lower output impedances. And the first really good acoustic suspension sealed box speakers like the original AR's, Large Advents, etc. were developed. They had deeper and better bass than any of their tube-powered predecessors could manage from a similar box size. It was a big milestone in "hi-fi" to rely on lots of electrical damping from the amplifier. It’s too bad many headphone sources are 40+ years behind.

声学悬挂: 在20世纪70年代，随着固态放大器的流行，情况发生了变化。几乎所有的固态电流放大器都能轻松通过第八定律。事实上，大多数都通过了1/50法则---- 它们的输出阻抗通常低于0.16欧姆---- 被称为50的阻尼因子。突然，扬声器制造商可以自由设计更好的扬声器，可以利用这些低得多的输出阻抗的优势。第一个真正好的声学悬挂密封箱扬声器像原来的 AR 的，大的研发等。他们有更深和更好的低音比他们的任何管动力的前任可以管从类似的盒子大小。这是一个巨大的里程碑，在“高保真”，以依靠大量的电阻尼从放大器。很遗憾，许多耳机的来源已经落后了40多年。

WHAT OUTPUT IMPEDANCE DOES MY SOURCE HAVE? Some manufactures make it clear they strive for a low output impedance (such as Benchmark), while others specify the actual output impedance of their products (such as Behringer does with the UCA202 at 50 ohms). And most, sadly, keep it a total mystery. Some product reviews, such as the ones on this blog, include measurements of the output impedance as it’s critical to the sound of the device with various different headphones.

我的消息来源有什么输出阻抗？一些制造商明确表示，他们力求低输出阻抗(比如 Benchmark) ，而另一些制造商则详细说明他们产品的实际输出阻抗(比如百灵达对 UCA202的定价为50欧姆)。可悲的是，大多数情况下，这一切都是个谜。一些产品评论，比如这篇博客上的评论，包括了输出阻抗的测量数据，因为这些数据对于不同耳机的设备声音至关重要。

WHY DO SO MANY SOURCES HAVE A HIGHER OUTPUT IMPEDANCE? The most common reasons are:

为什么这么多资源有更高的输出阻抗? 最常见的原因是:

• Headphone Protection - 耳机保护 -More powerful sources with a low output impedance might be capable of delivering too much power into low impedance headphones. To help protect such headphones, some designers raise the output impedance. 更强大的低输出阻抗源可能会给低阻抗耳机提供过多的功率。为了保护这种耳机，一些设计师提高了输出阻抗This is a compromise to try and have the amp adapt to the load used. But it comes at a big price with many headphones 这是一个折衷的尝试，并有放大器适应负荷使用。但是它的价格很高，而且有很多耳机. A better solution is offering two gain options The low gain setting can lower the maximum output voltage when using low impedance headphones. And, in addition, active current limiting can be used so the source will automatically restrict the maximum output into lower impedance headphones even if the wrong gain setting is used.  一个更好的解决方案是提供两个增益选项低增益设置可以降低最大输出电压时使用低阻抗耳机。此外，有源电流限制可以使用，所以源将自动限制最大输出到低阻抗耳机，即使错误的增益设置使用
• To Be Different - 与众不同Some manufactures raise the output impedance on purpose claiming it makes their source sound better. Sometimes “different sells” as it’s a way to differentiate the sound of their product from their competitors. But, in this case, 一些制造商故意举起输出阻抗，声称这样可以使他们的声源听起来更好。有时“不同的销售”，因为这是一种方式来区分他们的产品声音从他们的竞争对手。但是在这种情况下,the particular “different sound” you get is entirely dependent on which headphones are used 你听到的“不同的声音”完全取决于使用哪种耳机. With some it might be an improvement and with others it’s more likely a big step backwards. The odds greatly favor degrading the sound. .对于一些人来说，这可能是一种进步，而对于另一些人来说，这更像是一种倒退。降低声音的可能性很大
• It’s Cheap 很便宜 – A higher output impedance is a band-aid for many inexpensive headphone sources. It’s a cheap way to achieve stability, a crude form of short circuit protection, and it can allow using an otherwise substandard op amp or output device that would be unable to drive 16 or even 32 ohm headphones directly. By adding some series resistance to the output all these things get “fixed” with a $0.01 part. But 高输出阻抗是许多便宜耳机来源的创可贴。这是一种实现稳定性的廉价方式，一种粗糙的短路保护形式，它可以允许使用不合格的运算放大器或输出设备，不能直接驱动16或甚至32欧姆耳机。通过对输出增加一些系列阻力，所有这些问题都得到了“修复”，部件为0.01美元。但是the cheap “fix” comes at a substantial price in the sound quality with many headphones. 便宜的“修复”来在音质的许多耳机的实质性的价格
  

EXCEPTIONS TO THE RULE: There are a few headphones supposedly designed for significantly higher output impedances. I do wonder if this might be more myth than reality these days in terms of audiophile and consumer headphones as I’m not aware for any specific examples. But it’s certainly possible. If so, using these headphones on a low impedance source might cause under-damped bass performance and a different frequency response than the manufacture intended. This might explain some of the “synergy” claims when certain headphones are mated with a certain source. But those “synergies” are entirely subjective—one man’s “bright and detailed” is another man’s “harsh”. The only way to get consistent performance is to use a low impedance source and follow the 1/8th Rule.

例外的规则: 有一些耳机设计的显着更高的输出阻抗。我确实想知道，就音响发烧友和消费者耳机而言，这可能是更多的神话而不是现实，因为我没有意识到任何具体的例子。但是这当然是可能的。如果是这样，使用这些耳机在低阻抗源可能会导致低阻尼低音性能和不同的频率响应制造的意图。这也许可以解释一些“协同效应”的说法，当某些耳机与某些来源交配时。但这些“协同效应”完全是主观的——一个人的“聪明而细致”是另一个人的“苛刻”。获得一致性能的唯一方法是使用低阻源，并遵循1/8规则。

A CHEAP TEST: If you’re wondering if your current source is compromising the sound quality because of an unknown output impedance, consider buying the $19 FiiO E5 amp. It has a near zero ohm output impedance and has enough output for most many headphones under 100 ohms. If it obviously improves the sound, it’s likely your source has an output impedance that’s too high.

一个便宜的测试: 如果你想知道你现在的信号源是否因为一个未知的输出阻抗而影响了音质，考虑购买19美元的 FiiO E5安培。它有一个接近零欧姆的输出阻抗，并有足够的输出大多数耳机低于100欧姆。如果它明显地改善了声音，那么很可能你的声源有一个过高的输出阻抗。

BOTTOM LINE: Unless you know your particular headphones sound better with a specific higher output impedance, it’s best to always use a source with an output impedance no higher than 1/8th the impedance of your headphones. Or, to make it even simpler, an output impedance of 2 ohms or less.

底线: 除非你知道你的特定的耳机声音更好地与特定的更高的输出阻抗，最好始终使用一个来源的输出阻抗不高于1/8的阻抗你的耳机。或者，让它更简单一点，一个2欧姆或更少的输出阻抗。

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TECH SECTION:技术部分:

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阻抗与阻力: 这两个术语可以互换使用，但是在技术上有一些重要的区别。电阻由字母“ r”表示，在所有频率上具有相同的值。阻抗更加复杂，它的值通常会随着频率而变化。它由字母“ z”代表。为了本文的目的，两者的计量单位都是欧姆。

see Wikipedia Voltage Divider.

输出阻抗图: 下面的图表显示了输出阻抗的影响。上图左侧的蓝色圆圈代表“完美源”，中间的蓝色电阻器(锯齿形线)代表输出阻抗。右边的电阻表示负载阻抗(耳机)。如果输出阻抗不为零，当负载连接时，电源产生的电压将降低。输出阻抗越高，负载电压下降越大。这个下降是由公式给出的: 负载电压 = 源电压 * (Zload/(Zload + Zout))。有关更多信息，请参见 Wikipedia 电压分配器。

电压和电流: 了解电压和电流对于理解阻抗和本文很重要。电压类似于水压(即 PSI) ，而电流类似于水的体积(即每分钟加仑)。如果你让水流出你的花园软管末端没有连接你得到了很多流量(电流) ，可以填补一个桶很快，但在软管末端的压力是接近零。如果你把一个小喷嘴的软管压力(电压)是高得多，但水的体积减少(需要更长的时间来填补同一桶)。这两者通常是相反的。高压通常意味着低流量，反之亦然。电压和电流也是如此。电压、电流和电阻之间的关系(为了本文的目的，阻抗)是由欧姆定律定义的。代替 z 代替 r。

第1/8条规则从何而来？大多数人能听到的最小的声音差异大约是1分贝。对于创建一个 -1 dB 变化的输出阻抗，您有一个 antilog (- 1/20) = 0.89。使用上面的分配公式，当输出阻抗为负载阻抗的1/8时，你可以得到0.89或1分贝的降幅。耳机阻抗可以变化的一个因素10或更多的音频频带。5的额定功率为21欧姆，但是从10欧姆到90欧姆不等。所以1/8法则给出的最大输出阻抗为2.6欧姆。假设我们得到了1伏的电压源:

• Headphone Voltage at 21 Ohm Nominal Impedance = 21 (21+2.6) = 0.89 volts 耳机电压21欧姆额定阻抗 = 21(21 + 2.6) = 0.89伏
• Headphone Voltage at 10 Ohm Minimal Impedance = 10 (10+2.6) = 0.79 volts 耳机电压10欧姆最小阻抗 = 10(10 + 2.6) = 0.79伏
• Headphone Voltage at 90 Ohm Maximum Impedance = 90 (90+2.6) = 0.97 volts 耳机电压90欧姆最大阻抗 = 90(90 + 2.6) = 0.97伏
• Frequency Response Variation = 20*LOG(.97/.89) = 0.75 dB (under the 1 dB goal) 频率响应变化 = 20 * LOG (. 97/. 89) = 0.75 dB (低于1db 的目标)
  

测量输出阻抗: 如上图所示，输出电阻形成了一个分压器。通过测量空载和已知负载下的输出电压，你可以计算出输出阻抗。这个在线计算器使它变得简单。空载电压是“输入电压”，R2是已知的负载电阻(不要使用耳机) ，输出电压是负载电压。点击 Compute，r 1就是计算出来的输出阻抗。这可以通过使用一个60赫兹的正弦波文件(Audacity 可以创建这样的文件)、一个数字万用表(DMM)和一个15-33欧姆的电阻器来实现。大多数数字多用表只能精确到60赫兹左右。播放60赫兹的正弦波文件，将音量调整为0.5伏。然后接上电阻器，注意新的电压。例如，0.5伏的空载电压和0.38伏的33欧姆负载电压给出的输出阻抗约为10欧姆。数学公式是: Zout = (Rload * (Vnoload-Vload))/Vload

反应性负载: 很少有耳机代表一个纯粹的电阻负载，在音频频带上是恒定的。相反，它们是反应性负载，代表一个复杂的阻抗。由于耳机中的电容和电感元件，它们的阻抗随频率而变化。例如，这里是超级 Fi 5的阻抗(黄色)和相(白色)。阻抗只有21欧姆以下约200赫兹。在200赫兹以上，它在1200赫兹爬升到接近90欧姆，然后在10千赫下降到10欧姆以下:

全尺寸罐: 有些人不感兴趣的 IEMs，如超级 Fi 5的，所以这里的阻抗和阶段为流行的森海塞尔 HD590。它仍然从大约95欧姆到近200欧姆不等，范围为2倍:

数学: 早些时候展示了一个图表，显示了约12分贝的频率响应变化的 SuperFi 5的驱动从43欧姆的来源。如果我们把他们的额定阻抗为21欧姆作为参考电平，并假设1伏源，耳机上的电压将由以下方式给出:

• Reference Level: 21 / (43 + 21) = 0.33 V and we’ll call that 0 dB. 参考电平: 21/(43 + 21) = 0.33 v，我们称之为0分贝
• At their minimum impedance of about 9 ohms it’s 9 / (9 + 43) = 0.17 V = – 5.6 dB 在他们的最小阻抗约9欧姆，它的9/(9 + 43) = 0.17 v =-5.6分贝
• At their maximum impedance of 90 ohms it’s 90 / (90 + 43) = 0.68 V = +6.2 dB 在它们的最大阻抗为90欧姆时，它们的阻抗为90/(90 + 43) = 0.68 v = + 6.2 dB
• Total Variation = 6.2 + 5.6 = 11.8 dB 总变差 = 6.2 + 5.6 = 11.8分贝
  

阻尼水平: 耳机驱动器的阻尼，如前所述，要么是完全机械阻尼(Qms) ，要么是电阻尼(Qes)和机械阻尼的组合。总阻尼称为 Qts。这些参数是如何相互作用的低频率被解释为泰勒小模型。阻尼可以归纳为三类:

• 严格阻尼(Qts = 0.7)-这被广泛认为是理想的，因为它提供了最深的低音扩展没有任何频率响应变化或过度“振铃”(无控制的驱动器运动)。低音从一个严重阻尼司机往往被描述为“紧”，“快速”，和“干净”。0.7给出了大多数人认为的理想暂态响应
• 过阻尼(Qts < 0.7)-这使得对驱动程序的控制更加严格，但是代价是低沉的低音(响应速度更快)。因此，制造商很少故意过度打湿自己的产品
• 这个交易了一些低低音延伸为高低音频率的峰值。该驱动程序也不再是良好的控制和展品过度“铃声”(即它不会很快停止时，音频信号停止)。低阻尼产生的频率响应变化，较少 deep 深的bass,  低音，低音暂态响应和高低音峰。低阻尼是一种廉价的方式，以牺牲低音的质量为代价，提供更多的低音错觉。它经常用在廉价的耳机和扬声器，以提供“假低音”。低阻尼耳机/扬声器经常被描述为“牛气哄哄”或“邋遢邋遢”的低音damped bass 如果你的耳机是为电阻尼而设计的，并且你使用的源阻抗大于其阻抗的八分之一，你就会得到低阻尼的低音.
  

阻尼类型: 阻尼驱动器和控制共振有三种方法:

• 电力阻尼 –  这是众所周知的是 Qes 和它的东西再生制动上的混合动力或电动汽车。当你踩下刹车时，电动马达就会变成一个发电机，把能量送回电池，从而使汽车减速。戴着耳机(或扬声器)的司机也可以做同样的事情。但是随着放大器输出阻抗的增加，制动效果大大减弱---- 这就是第八定律
• 机械阻尼 正如前面解释的，它更像是汽车上的减震器。当你添加机械阻尼到一个驱动程序，它抗拒的音乐信号驱动它，变得更加非线性。这增加了失真和降低了声音质量
• 外壳可以提供阻尼，但这通常需要一个密封的外壳，一个有调谐端口，或一个有控制的限制。然而，许多最好的耳机通常是开放式的。这在很大程度上消除了耳机设计师的选择，使用附件提供阻尼，因为是与扬声器
  

耳罩加载: 对于形成一个相当一致的密封耳机，这样一个完全电路的耳机耳罩耳机，适合贴近头部，设计师可以有点依赖“外壳”形成的耳罩，可能提供一些阻尼。但是头部的形状，耳朵，头发的类型，耳机的位置，眼镜和其他因素使它高度变化。这个选项是不可用的所有超音响(在耳朵)耳机。下面是两张森海塞尔 HD650阻抗图。注意，露天低音共振峰值约530欧姆，但下降到500欧姆的模拟头部。这是由于耳杯外壳和耳垫提供的阻尼。

最后一句话: 希望我已经说得很清楚了，要在耳机和它们的来源之间获得一致的性能，唯一的方法就是遵循1/8法则。虽然有些人可能喜欢使用更高的输出阻抗，这是非常具体的每个特定耳机，特定的输出阻抗，和人自己的主观口味。理想情况下，一个新的标准应该开发和制造商应该鼓励设计耳机来源的输出阻抗低于2欧姆。

孤岛飞鹰

最后几张图删除不掉，麻烦管理帮忙删除一下    以前卖的耳机图，误操作传上来了   好有历史感