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这小东西大家聊 [复制链接]

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91#

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92#

4个字:“因为好听”
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93#

科研级旗舰 在 2006-5-31 18:26:35 发表的内容
felixcat 在 2006-5-31 9:30:46 发表的内容
Dr kuang 在 2006-5-31 0:25:05 发表的内容
非常复杂的调试带来的问题是机器之间的误差,几乎所有使用过开盘磁带的录音师都强调,开盘带要用原来录制它那台机子重播声音才好。两台相同的机子,单是压带的松紧不同声音就会有非常大的差异。
而且磁带最要命的是保存和使用问题,不提磁粉脱落和自然退磁,单是复制效应就使磁带的声音严重退化了。所以唱片公司才急于开发新的技术来代替目前的磁带保存技术。




关于LP直刻好还是磁带录音好,各大开盘带论坛里早就是老生常谈。这个问题有机构作过实验的,用最好的直刻LP设备和用最好的开盘带设备去录同一个现场,最后测试分别录制的效果,结果无疑是开盘带远远胜出——它从始至终在20kHz一下的频段内频响曲线误差不超过0.5分贝。关于该实验的细节假如有人有兴趣我可以私下提供有关人士的email供询问。


这个有兴趣。据我所知,早期的母带频响其实并不好,录音的黄金年代时期用电影胶片做录音介质的声音效果甚至要更出色,VANGUARD,MERCURY等都是这么做的


早期的母带频响其实并不好,不完全是磁带机的原因,麦克风不平坦而且高频上不去其实也是重要因素。由于麦克风的频率响应不够平坦,录音时使用均衡器就可以进行“补偿”;后来也把均衡器用于音色的调较了。
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94#

谈到这里又要感慨一声,录音设备/放音设备都在进步,为什么那么多人怀念那种老派声音?  
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技术并不等同艺术
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95#

关于失真的衡量问题我实在无能为力了,动态压缩是失真,瞬态反应延时也是失真,频响曲线扭曲是失真,奇次谐波是失真,偶次谐波也是失真,相位失真也是失真,射频,电磁,振动,供电干扰又带来一大堆外加的失真,还有器材的内部噪声。而仪器测到失真大的器材,到实际聆听时又未必比指标更好的器材听感失真大。这一点,你在比较开盘母带和CD唱片时必然会有所觉察,希望你能更准确地分析出不同失真方式对声音听感的影响?
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96#

Dr kuang 在 2006-6-2 14:46:59 发表的内容

你关于磁带松紧对声音影响的贴子就在几页之前,你确实没有说没有影响,只说过你听不出来,而且提出盲听测试而已,如果你觉得十分窘迫,我保证以后就不再提了。
关于摩改带来的动态提升问题,我觉得您可能忽略了一些细节:把50dB讯噪比的机器摩改一下就可以提升20dB,这个不难理解,是否70dB的器材也摩改一下就可以做到80甚至90dB?每个有过摩改器材经验的网友都知道结果,我现在的唱头放大讯噪比才80多dB,看来也摩改一下,应该有机会冲击“黑手指”95dBMC放大的要求?


磁带松紧我是听得出来的,但我的感觉是“不巨大”,我也在原文里写了这是我的感觉。并且盲听测试不意味着只能测试“是否有区别”,比如说对同一产品的多台样品进行试听,就不只是为了“是否有区别”这个目的了。
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97#

讨论到这里我觉得已经没有必要了。
60年代的电子管录音机和磁带只能提供50dB甚至更低的讯噪比,而你心知肚明这一点,但你的试验却测到70dB的动态。
我对开盘带的了解多数是来自曾经长期使用这些机器的国内录音师们,还有当年负责维修和调试录音器材的技术人员,是道听途说,但我并不认为你对开盘机和磁带的知识和经验比他们丰富和准确,而且他们提供资料时会比你的态度要中肯一些,至少不会说磁带的松紧对声音没有影响,不会说60年代的电子管录音机可以录出动态70dB甚至更高动态的磁带。
关于偏心对声音的影响,我记得说出的前提条件是1MM,而你就列出了一个莫名其妙的图来说明1Hz低频对声音的影响,列出例子的是开心果网友,他的结论是在长的持续音时才会在内圈听出抖晃导致的走音。现在说导致“拆声”是最近发现部分偏心唱片,内圈会出现这个问题,因为手头的偏心和拆声唱片很少,我现在甚至无法确定是否普遍现象,所以才说“部分”。
最后一个问题的我之前已经回答过一次,达到比磁带优胜的动态和讯噪比是直刻LP,原始记录的是磁带还叫直刻吗?而且你如何确定没有唱片公司保存了父盘和母盘?
这是个开放的论坛,谁有疑问谁都可以参与讨论,这里是你要求我找出你提供错误数据和事实的例子,有多少这样的情况你自己比我当然更清楚,说到威胁好像太夸张了些,如果你不希望我或者其它网友发现你的错误,就请不要先保证自己的绝对正确。我非常欢迎你和其它网友善意地指出我的错误,只要我确定自己是错的,我会乐于承认和修正。
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98#

JWang 在 2006-6-3 7:06:13 发表的内容
在我关于LP的高频测试的贴子中,felixcat一看到是我写的,就迫不急待跳出来,大讲半速刻制什么什么。实际上他跟本不懂什么叫半速刻制。他多次被我指出他的错误百出之处。故每次我的贴,他总要胡搅蛮缠一气,结果总是搬起石头砸自己的脚。看看前面他关于频响曲线的讲法,连基本常识都没了。好,现在他改变战术,还要在那个屁股后面跟一个贴,讲明不答,不应在我的ID下的贴。呵呵,认输了还是什么?够蠢的。

英语中有句话,If you can’t stand heat, get out of the kitchen!用中文来讲,如果你不能忍受热量,滚出厨房!网上也一样,只要我开口,我不怕任何人来加以批评。我也不怕任何没头没脑的人的骂街。相反地,我从不会邀请felixcat来评论,但felixcat只要有这个胆量来针对我来讲,我必答无疑。你如果受不了,你可以闭嘴不讲。尽管你的知识面很狭窄,分析问题的能力又很差,但不用人家来教你如何闭上嘴吧!

下面是半速刻制的创始人Stan Ricker讲半速刻制的LP可以在音质上超越母带。我没有功夫把全部翻成中文,而是挑些关键字句翻。这是enjoymusic.com对Stan Ricker的一个采访。补充一句,引用Stan Ricker的讲法并不代表我的观点。只是给大家一个参考。

Dave:    You've told me that some of the things that you like about the sound of half speed is that it has lower distortion and better transient response and improved high end, and that one of the big benefits is that when you drop the frequency band by an octave it requires only one fourth the amplifier power to cut the record.
  
Stan:    Yeah.  You drop it by an octave and you also double the length of time it takes to put the signal on the record.  So you've got the two factors of two there.
  
Dave:    So how is it possible for a lacquer, which is cut at half speed, to sound better than the master tape from which it was made? (如何可能一片从母带制成的黑胶比母带声音更好?) At first blush that sounds like a bit of a conundrum, but I understand that it is really not.
  
Stan:    Quite a condom, you say?  (Laughs)  You've got to realize that it sounds better played at real time than the analog tape does, played at real time.  One of the primary reasons for doing the half speed analog recording is that more tape playback problems are solved by playing the tape back at half speed.  (其主要的原因之一是母带在以半速播放时可以克服母带在全速播放时的很多毛病)Hysteresis problems in the playback head, the slew rate problems in the tape head preamplifier; the resonance peak of the playback head circuitry is a fixed resonant peak, so in terms of the music you're transcribing, it's moved up an octave and is way out of the audible range of any of those high frequency resonance circuits.  So when you consider all of this, therefore, the signal is cleaner as it passes through the system, especially anything that involves cymbal crashes, brass instruments [trumpets, trombones, etc.] other high frequency type tone bursts.  At half speed they go through the system quite easily and are not apt to cause any kind of power supply or slew rate distortion, or TIM, or any of this stuff.  So if you can cut a disk that way and you have a really pristine disk playback system like many audiophile folks do, then you get to enjoy the advantage of a record that was cut from a tape in a way that you get away from a lot of these tape playback anomalies.  The tape record and playback anomalies are part of why Doug Sax did all those marvelous direct-to-disk sessions.  (Dong Sax的那些直刻盘其部分原因就是因为录音带及重放中的毛病)The tape machine itself is a huge stumbling block in the transparency of the audio, of the music, of the sound.  The transient response isn't there and with tape, as with practically every recording medium, it's easy to get the signal recorded; it's harder to recover it.  So, if you recover it at half speed, transfer onto another medium, and you have a really good playback of that other medium, the phonograph record, then when you compare the analog tape played at real time versus the lacquer played at real time, the signal off of the lacquer has managed to come out without all the problems inherent in real-time tape playback.  So what you're really hearing is the signal with problems and then the signal without the problems.  That, to me, is why half speed mastering was such a phenomenal process.  I used to think that this was because of the lower amount of power required at half speed.  But I'm convinced now that it's about a 70/30 situation.  That seventy percent of the improvement is due to scanning the tape at reduced velocity, and not driving those tape head preamplifiers into gross distortion.  We just hear people say, "Oh yeah, that's just analog tape overloading, or whatever."  Whereas, in reality, we recover it without those problems.  That's why it's been such a tremendous treat to find some of the really good stuff buried on some of that old Scotch 111.  It really is quite possible that the disks, under those conditions, can sound better than the master tape played at real time.  It's amazing to listen to a good analog tape at half speed, one that's truly wide range, low distortion.  I mean, it just blooms in front of you.  It's just unbelievable.  I think of the experience I had listening to a MoFi re-release recording of Russian music, with the Russlan and Ludmilla Overture in D Major [MFSL 1-517].  I mean it's full orchestra, the orchestra's just going a mile a minute, just lickety split.  At half speed the recorded sound just opens up and wow!  And it was not a Dolby tape, and that was important.  It was pre-Dolby for Decca.  Just such a wide open spaciousness.  When you played it at real time it tended to get congested.  But the record didn't come out that way.  The record has the spaciousness of the original tape, which you could only really perceive in the half speed mode.  There's a lot to be said for half speed transcription.  I tend to like, right now, this two thirds speed thing because the bass frequencies seem to be better integrated with the mid range and treble.  It didn't always happen at half speed.


支持!
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