彙整 | 五月, 2007

揚聲器之唯快不破

31 五月

上一篇旺記談到揚聲器的速度,玩了hifi廿幾年,旺記始終是個速度主義者。也許有人認為 hifi 有許多 perspective ,不同的 figures of merit,但個人認為,不論如何拆解,hifi可以稱得上 fidelity,就是 能夠高度還原,"還原" 本身就是一個追踪的過程,沒有速度,談不上追踪,追踪不了,資訉便會流失或變形。這個 concept ,可以應用在整個音樂傳輸通道上。

例如 Phono recording,MC (理論上) 優於 MM,質量輕,速度快,這是物理。

小訉號放大器我們講 slew rate,slew rate 就是追從率,也是速度。

power amp ,不用說,power supply 最重要,又是速度。胆機好聲,好多人唔信邪,SE不說,Tube PP 隨時好聲過石機 PP,兩者都有 even harmonic cancellation ,你點解釋胆機多 even harmonics ? 旺記同你講,two things ,first,胆機用高壓低電流,速度自然高;second ,胆的 electrons 在真空中按電塲強度游走,忠實反映,毫無阻力,石機嘛,在 silicon裡游走,速度慢好多。

又是 a matter of speed 。

到揚聲器了。

Mechanical device ,唔駛講,由電轉聲,由 drift velocity 轉為 mechanical propagation, 速度一定慢,資訊一定會流失,所以揚聲器是 bottleneck,絕對是越快越好。

拾人牙慧,姑且引一段 Decware 的 Steve Deckert 的文章 :

A) If your speakers are fast, and your amplifier is fast, and your preamp is fast, you would find that the average $500.00 CD player becomes unlistable. Reason being the electronics and speakers can now reveal the shortcomings of the source. Result: Fatiguing and non musical

B) In the same system, a slow preamp is installed in place of the fast one. Now the grainy top end is gone, the digital sound seems smoother more analogue and the end result is pleasing non-fatiquing sound. The reason being the preamp has masked the shortcomings of the source.

Masking, or altering the sound is often the side effect of complex circuits that use lots of parts. The less parts in the signal path, the faster the circuit typically becomes. Other factors that influence the speed of audio circuit are the speed of the power supply and coupling caps.

Now suppose in the examples above that the source was a world class turntable and cartridge instead of a $500.00 CD player. In that situation both A and B would be musical, however A would sound far superior with greater dynamics, loads more detail, and far better clarity.

非常認同最後一句 “greater dynamics, loads more detail, and far better clarity."

許多音響器材的評論不談資訉量,速度,一味講有幾 musical ,其實可能暗示 ….


廣告

怎樣的揚聲器好聲

15 五月

TSM300 是 tonal balance 非常好的揚聲器,單獨聆聽真的相當不錯,人人當它是 giant killer ,side by side comparison 最殘皓,TSM300 速度唔掂,用 low damping factor 的 amp 推即露底,(難為了許多人仲以為佢最夾單端機)TSM300仔全靠高頻號角取分。

所以,tonal balance 不是大唒,是入門,要聲音好聽需要 反應快,decay 適中,phase accurate, 才可以 catch up 輸入的訊號。過去旺記介紹的單元像 Saba ,Coral 等等,都是紙盤輕反應快的單元,至於NXT的 transducer本來非常好,但一大片傳度快又輕盈又廉價的振板 market 上不會有,所以 NXT 無法進入HiEnd之門。

許多時我們用頻率響應(其實即 tonal balance 也),相位,同步等等去 describe 揚聲器的優劣,不過,有一個 perspective,甚少有人提過的,就是揚聲器的追重性。揚聲器是 transducer,我們的耳朵中的耳膜也是傳動機器,揚聲器的傳動反應快如耳膜或超越它,聲音就會好聽,因為我們聽覺的極限就是耳膜的傳動速度,與它同速,就是 fidelity。High Fidelity 還是 Ultra-Fi 已經不再重要,因為要接收的資訊已 100% 被傳遞。