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[#1] To 行內人, power requirement calculation    
I read your post contains some interesting calculations for matching speaker with amp, it involves some dB to W convertion.
i.e. if speaker's power handling is 250W
then equal to 10 x log(250) = 23.9dB

Then the matching should have around 23.9dBW.......(Correct me if I missed anything so far)

For the sake of discussion, here are the assumptions I assumed you have made for your calculation.

a. You need full power from power amp all the time.
b. The music you listen most contains full dynamic range all the time.

How true are above assumptions in reality?

kcm
203.xxx.xxx.24
2001-10-19 22:43
[#2] To 行內人, power requirement calculation    
kcm

若有最高承受必v-(是連續不是瞬間),就可以計算出該喇叭的動態(dynamic range)及最大聲壓值(SPL).

點解說明書上沒有標明該喇叭的dynamic range,該數據實在好重要,但為免自曝其短,喇叭與擴音機中夠膽寫清楚的真係絕無僅有,標明最大SPL數值喇叭,不及百份一,ATC PASSIVE 10 與 PMC某型號屬小數,因為當你知最大聲壓值就可輕易計算到全部,以我記憶當中祇有CD/DVD機之類有標明.

當晚,我將數計出來是(針對一對喇叭)的數值,去配合一部能發揮盡該喇叭的擴音機,而所有外來數值不計算在內,就祇是一部擴音機及一對喇叭的配搭!





















行內人
個人訊息 會員
202.xxx.xxx.27
2001-10-19 23:17
[#3] To 行內人, power requirement calculation    
行內人
I know you are based on a particular speaker, but according you said, why we need to do complicate calculation? Why can't we just simply say you need 250W power amp because the speaker (A) power handling is 250W?

And let say another speaker B power handling is 120W, i.e. equals to 20dB, and if I got a 20dBW power amp, then if your logic is hold, I should get the same dynamic range no matter which speaker (A or B) to pair with my amp, I only got 20dB dynamic range both cases, correct?

Then, should I give up my amp simply because it cannot fully explore speaker A's dynamic range? Why I need more power simply because my speaker can handle more, not require more?

kcm
203.xxx.xxx.24
2001-10-19 23:26
[#4] To 行內人, power requirement calculation    
kcm

1)如果我想出售一型號喇叭最大承受必v為50W-1000W,我跟著對他說要用1000W才推得好,他會相信嗎?他一定轉頭就走,無可能說實話!

2)你覺得找一部能發揮盡喇叭的"有限動態"擴音機有問題嗎?(我個人覺得合理)

3)你當然可以用一部輸出比喇叭承受必v較大的擴音機去配合,因為你唔會用peak power去聽,(日常工作中、我很多時會用3-500W power amp去推動一對承受必v1-150W喇叭,當然太大damping 的power amp會令它過於受制),我個人覺得反而用一部小必vpower amp去推動低效率及低零敏度喇叭更危險!
行內人
個人訊息 會員
202.xxx.xxx.15
2001-10-20 00:39
[#5] To 行內人, power requirement calculation    
1. This is the question, you shouldn't say 'you require 1000W to perform their best', you should say 'the speaker requires min 50W only, but the speaker can handle up to 1000W for full loudness 121dB, if necessary. other speaker can't achieve this loudness even feed it with 1000W because.......' something like that. This is
the spec should be intepreted.

2. If cost is not an issue, it is definitely no problem to get a amp as large as possible. Say 5000cc car should better than 3000cc, right? But do we really need 5000cc if we there is traffic jam all the time. Besides, is 5000cc the only factor we should consider? Should we consider other features, luxaries, comfort etc?
Same logic to amp, with certain amount of budget, should we get as much power as possible, regardless quality? How about similar price Bryston vs Pass?

3. I disagree using small power to lower sensitivity too, I know distoration is the most dangerous thing to spk. I'm just talking about how many watt do we really need.
kcm
203.xxx.xxx.1
2001-10-20 09:09
[#6] To 行內人, power requirement calculation    
TEric, for hifi discussion, why don't come out here? This forum is getting bore and bore without real hifi discussion.....

Certainly some energy are lost in crossover, coil, etc. But it is already stated in the efficiency rating, otherwise speaker will have 100% efficiency. But it is not related to the subject.

kcm
203.xxx.xxx.1
2001-10-20 09:25
[#7] To 行內人, power requirement calculation    
kcm and hifi insider, besides, rms, current, ohm ,i think the 5-50000 is better than 20-20000, the amp has 5-50000hz 100W is much better than 20-20000hz, 100W , it may be have more dynamic and details normally ensure that the figure is accurate, expensive amp has better and higher range !!
hifi oldman
個人訊息 會員
210.xxx.xxx.151
2001-10-20 10:37
[#8] To 行內人, power requirement calculation    
kcm and hifi insider, besides, rms, current, ohm ,i think the 5-50000 is better than 20-20000, the amp has 5-50000hz 100W is much better than 20-20000hz, 100W , it may be have more dynamic and details normally ensure that the figure is accurate, expensive amp has better and higher range !!
hifi oldman
個人訊息 會員
210.xxx.xxx.157
2001-10-20 10:37
[#9] To 行內人, power requirement calculation    
hifi oldman,
I don't quite agree that 5-50khz must be better than 20-20khz.

yes, 5-50khz is more extended in both extreme, but it doesn't tell you how is the quality within more important 20-20khz range. If all of us only look at this figures, manfacturers can easily achieve high bandwidth by incresing NFB.

Typical example is tube preamp, if manfacuturer just want to have better figures, they can just use more NFB, but the result is frequency is extended but doesn't sound good.
kcm
203.xxx.xxx.1
2001-10-20 10:46
[#10] To 行內人, power requirement calculation    
kcm, what i point out and is a normal case about the dynamic, and details, compare within the same design , of course , different brand, different price, different grade of parts and design may also greatly affect the sound quality. spec. base on wrong measurement and misleading information are sure incorrect, but wide 5-50000hz compare 20-20000hz in the same above factors, sure better, i am trying to explain the dynamic related to these factors.
hifi oldman
個人訊息 會員
210.xxx.xxx.154
2001-10-20 11:47
[#11] To 行內人, power requirement calculation    
hifi oldman,
Well, frequency response shouldn't be confused with dynamic range.

Freq response is referring how low and how high freq the amp can reproduce.

Dynamic range is referring the difference range between quietness and loudness, something related to sound ampitude not frequency.
kcm
203.xxx.xxx.1
2001-10-20 11:55
[#12] To 行內人, power requirement calculation    
kcm, the things listen to your ears and are related in too many factors, in the wordings , they are difficult to separately consider, eg, a very strong power supply play and important role in dynamic and details in the amp performance , although they are part of it, it don't think a weak power supply amp can produce good sound except some very econmonic and high efficient amp eg . qual 405 ! therefore normally every part are related,eg, the transitors, or mosfet, as result, use the ear and price for judgement may be better, in wording explaination may be only partially, have you remember the topic bi amp, a VERY BIG AND WIDE TOPIC, the content is too big and not easily to discuss with good conclusion therefore i didn't say too much !!
hifi oldman
個人訊息 會員
210.xxx.xxx.154
2001-10-20 12:07
[#13] To 行內人, power requirement calculation    
kcm,

我諗行內人想講出一點,
動態表現越好, 樂器的質感表現就越好,
音質表現就會較好. 音質同音色唔同, 不過
好多人都混淆了.

由CDP 一般都有100db 動態範圍去到
喇叭(就算在full power output) 時
可能得番20-30db, 已經衰減三份之二有多,
如果連呢個有限動態都表現不足,
咁音質又再降底.

至於最大聲壓問題又是另一回事,
因現在祇談論必v放大器與喇叭之關係,
空間能受幾大的聲壓並不在討論之中.

因要趕往銀行, 祇能討論到呢度,
呢個係一個十分之好的話題,
我相信如能正面地討論,
大家會得益不少.
TEric
個人訊息 會員
210.xxx.xxx.120
2001-10-20 12:10
[#14] To 行內人, power requirement calculation    
TEric
From cdp 100dB to speaker 20-30dB(?), this is exactly I'm skeptical about the dynamic range calculation method.

By definition, dynamic range is the difference between the quietness and loudness, in dB. So, if a speaker can achieve 120dB, and the quietness we can hear, say 40dB-50dB (40-50dB because it is the general background noise level in "silent" area), then dynamic range should be
120dB-40dB=80dB!

Again, it shows that dynamic range is related to environment, depends on how quiet your room is. And it is also why spk manufacturer can't show it at the spec.

All above are only my educated guess, any comment/correction is welcomed.
kcm
203.xxx.xxx.1
2001-10-20 12:38
[#15] To 行內人, power requirement calculation    
One more point to add, even your speaker and amp can output 120dB, it doesn't mean your room can withstand this level without distortion.
kcm
203.xxx.xxx.1
2001-10-20 12:48
[#16] To 行內人, power requirement calculation    
I think the problem is we shouldn't take sensitivity as zero point for calculating dyanmic range.

Because for sensitivity 87dB, 1W, then
when 0.5W input, we got 87-3=84dB (-3dB)
0.25W input, we got 81dB (-6dB)
0.125W input, we got 78dB (-9dB)

and so on until we cannot hear anything, then we got background noise only, around 40-50dB.


kcm
203.xxx.xxx.1
2001-10-20 13:46
[#18] To 行內人, power requirement calculation    
kcm

1)多謝朋友指導,但我真沒有膽量對人客說一對power handling 50-1000W喇叭,最小用50W就能用,想更好就改用1000W推動的說話,想必總公司的投訴電話就馬上響起,一時間用50W,一時間又話1000W,有點像氣弄客人之意思(起碼對方會有這樣想法).

當然,實話實說是對,但生意好可能會跑掉,問題就好似一對四路電子分音喇叭一樣,買它,請同時買8部Mono block or 4部stereo power amp,容易賣嗎?依我愚見,提議配一部500W又如何?(500logx10=27dB,1000logx10=30dB),27跟30好似近一點吧,500跟1000W差一倍,犧牲3dB可行嗎?另外,相同品牌中的擴音機500W跟1000W輸出,無論價錢、體積都一定相差得很遠,對嗎?我做得成生意的機會高一點嗎?

2)又是一個兩難問題,3000cc與5000cc的車在塞車時效率是相差不遠(常理),但同時要跑一轉舊山頂道,相信一部較有寬餘度的車在斜坡上行走會較輕鬆吧!

我時常指出hifi綜合性係好重要,器材配搭得好,比找一位知心人伴侶更難,但針對性選擇可縮小購買範圍,你行進店內大大小小擴音機,你會怎選擇?

多謝指教!
行內人
個人訊息 會員
202.xxx.xxx.107
2001-10-21 01:08
[#19] To 行內人, power requirement calculation    
行內人
Oh don't use the word 指教, I learnt from you!

BTW, any comment on the following:
For sensitivity 87dB, 1W spk, then
when 0.5W input, we got 87-3=84dB (-3dB)
0.25W input, we got 81dB (-6dB)
0.125W input, we got 78dB (-9dB)

Seems it is not so correct to use 87dB as reference point for calculating dynamic range because below 1W, we still have 0.5, 0.25, 0.125W....

kcm
203.xxx.xxx.3
2001-10-21 10:21
[#20] To 行內人, power requirement calculation    
Kcm
靈敏度287dB,它的含義是向Spk輸入1W pink Noise,在離音箱正前方1M處所接受到的音壓值是87dB.這個定義測試方法是IEC的方法.需要說明靈敏度的測試方法,不同廠家,不同國家都可能不同.所以不同廠家的音箱靈敏度,他的含義不盡相同,還要看一下它的定義與測試方法.
這是大部份廠家的測試方法,有必要考慮1M或1/2,1/4米內之測試值嗎?這埵陪虓妝擊搎〝,音箱所標靈敏度是正前方1M處,實際聆聽位,常常大於1M,而且不在正前方,這時所聽到的靈敏度就會下降,也就是在實際聆聽位要聽到相同的靈敏度,輸入必v就要增加,再有就是,輸入必v和音壓值是對數關係,也就是音壓值每增加3 dB(也就是聲音響度增加一倍),輸入必v要增加10倍.
當然,87dB絕對不是一個參考值,有些比它更低例如Chord 5/12A=81.5dB,Chord 5/12B=83dB,Celestion 600…..或更多.
多謝指教!
行內人
個人訊息 會員
202.xxx.xxx.79
2001-10-21 13:13
[#21] To 行內人, power requirement calculation    
Dynamic range can be adjusted by using different power cord?
aheung
個人訊息 會員
219.xxx.xxx.2
2018-09-15 09:22
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