BBC LS3/5A 筆記

 一個小小的傳奇 ----   A Little Legend  BBC LS3/5A

 引用

http://musicalsound.com.tw/club/%E6%A8%82%E5%8F%8B%E5%B0%88%E6%AC%84/LS%2035a.htm

http://musicalsound.com.tw/club/ls-3-5a.htm

原載於HiFi News & Record Review，1990年3月號

作者： Trevor Butler   翻譯： 阿蜜  排版：abrams 

只這裏只引用我有興趣的部份為作筆記 ，完整的文章請上原址觀看

 很難找到任何一個方盒子，如同BBC LS3/5A一般，能勾起如此多的情緒反應，或是製造出這麼多的迷思與誤解。光是它的名字，就引起了困惑，而實際上它只是單純的遵循了BBC的器材編碼方式。依循此一方式，音箱cabinets最前面的兩個字母以CT代表，分音器filters為FL，而喇叭loudspeakers則為LS。編碼中的3表示此一設計主要是供外製轉播(outside broadcast-OB)所用。如果此一編碼為5，則代表供錄音室廣播用，如LS5/9即是。在斜線後的5則是型號。LS3/5即取代較早的OB喇叭如LS3/1。所以我們可以理解LS3/5是當初開始製造時的編號。編號最後的A則是後來加上去的，用以表明第一次也是唯一一次的設計修正。如果有後續的修改的話，則會以B來標示，但那從未發生，也不太像會發生，其原因後文將述明。

There can hardly be another single box which as provoked as much emotive comment，or given rise to so many myths and misunderstandings，as the BBC LS3/5A。The very name has caused confusion，but in fact it simply follows the BBC's coded equipment format。In this，cabinets have the prefix 'CT'，filters 'FL'，and loudspeakers 'LS'，hence the first two letters。The figure '3' in the code indicates that the design is primarily for outside broadcast (OB) use。A figure '5' would mean studio broadcasting，as LS5/9。The number '5' after the stroke is the model number，the LS3/5 supplanting previous

當時是以1/8比例的模型，並在1/8的波長(也就是8倍高的頻率)下錄音，某些音響技術的優缺點就可以被評估出來，而不必花大錢建構1：1的環境。當然，正因為如此，這也暗示了整個模型的再生過程所使用的器材，從放音機，喇叭，麥克風到錄音機，都要能在極高的水準下運作，其所處理的頻寬為400Hz到100kHz，以便能正確模仿一般頻寬的40Hz到15kHz。

By using one-eighth scale models，and one-eighth wavelengths (IE，8-times frequencies)，recordings can be made by which the merits of particular acoustic techniques can be assessed without the expense of a life-size environment。

Naturally，though，this implies that the entire model reproduction chain，of tape player，loudspeaker，microphone and recorder，must be capable of operating at very high quality with a frequency range of 400Hz to 100kHz，in order to be able to model accurately a typical bandwidth of，say，40Hz to 15kHz。

BBC自行製作了一小批這種喇叭，使用在電視轉播車的控制室中，並提供了令人滿意的效果。而後BBC終於面臨一種狀況：需要邀請外面的廠家在認證許可下製造LS3/5。實際上，Rogers在1974年2月19日發出了一則新聞稿，驕傲的宣稱將在該年4月的SONEX ’74大展中展示這種新喇叭。他們附上了一張照片與一組臨時的規格：25瓦的輸入功率，頻率響應80-20，000Hz +/-3db，或是60-20，000Hz +/-4db。分頻點設在3k Hz，低音單體為110m Plastiflex doped Bextrene 音盆，高音單體為27mm半球型Mylar振膜。定價為一只52英鎊外加營業稅!

A small number of these units where made in house by the BBC and used in television mobile-control-rooms where they gave satisfactory service。The BBC got to the stage of inviting applications to make the LS3/5 under license by outside manufacturers。Indeed，Rogers issued a press release on 19th February 1974 which proudly announced that they would be exhibiting the new design at SONEX '74，an exhibition to be held that April。They offered a photograph and a provisional specification：25W power handling with +/-3dB 80-20，000Hz and +/-4dB 60-20，000kHz。Crossover frequency was quoted at 3kHz and the units were a 110mm bass driver with a Plastiflex doped Bextrene cone and a 27mm Mylar dome tweeter。The price，&52 each plus VAT!

儘管如此，當時也出現了一些早期的問題。雖然BBC對KEF生產的B110低音單體有信心，但當他們隨後需要一批供內部使用的LS3/5時，發現低音與高音單體已經歷經重大的改變，必須要重新設計才能接續生產。因此，這款喇叭就被交給當時在大波特蘭街的BBC設計部門，要求將它修改到合適。

Alas，though，there were to be early problems。Although the BBC had confidence in the KEF B110 bass unit at the time，when a subsequent batch of in-house LS3/5s was needed it was found that the low and high frequency units had undergone significant changes and a re-design of the speaker would be required before production could resume。

Accordingly，the speaker was passed on to the BBC's Designs Department，then located in Great Portland Street，with a request to modify it so that it would once again be suitable。

當時的問題來自三方面：被改變後的B110單體，以不同於前的方式刺激箱體，導致染色的產生。這染色不僅來自低音單體，也來自音箱; 高音單體則產生出明顯的’唇齒’音(lipsy)。

The trouble was in three areas; the B110 had changed，exciting the cabinet in a different way，producing a coloration both from the LF unit and the cabinet; and the HF unit had developed a pronounced 'lipsy' quality。

為了確保音箱的共振不會引起問題，兩面側板都以瀝青墊增加其阻尼，上下箱板也做相同的處理，但更鋪上兩層。此外，一種PVC邊料被加在低音單體的框架上，其作用是將低音單體與前障板隔離(de-couple)，並使接縫密封。為降低箱內空氣共振，所有的箱內壁都再鋪上聚亞胺脂發泡材料。箱體並加以密封，以防止在高音壓時空氣滲漏產生雜音—實際上甚至連螺絲孔也被做成不透氣的。箱體的問題也與軟木材巴拉那松木製的肋條有關，這些肋條連結前障板與背板，但因為不夠硬無法有效支撐，改以櫸木代替。而背板的規格也重新制定，由原本的雲杉木三夾板改為多層的樺木夾板，如此可避免雲杉木常有的空隙。修改後的音箱被稱為CT4/11A。

In an attempt to ensure that cabinet resonance would not cause problems，the side panels had each been damped with a bituminized pad，and the top and bottom panels likewise，except that two layers were required here。In addition，a PVC edging was applied to the chassis of the LF unit and to de-couple it from the front panel and seal the join。In order to damp the air modes of resonance inside，all internal surfaces were lined with polyurethane foam。The cabinet was sealed to prevent air leaks，which might produce extraneous sounds from the high pressures produced - indeed even the screw holes were made airtight。The cabinet problems were associated with the softwood parana pine fillets which connected the back panel to the front; these had an insufficient impedance and were therefore replaced with beech。The back panel was re-specified from the precious sandwich of spruce to multi-ply birch，thus obviating the voids often associated with spruce。This then became the CT4/11A。

藉著此一修正機會，高音單體的高頻唇齒音也被加以處理。當時認為這個裸露的KEF T27 SP 1032高音單體很容易在工作場所打包綑綁時受到損害，故決定加上一層保護金屬格柵，並在Celestion HF2000單體上找到一個，稍事修改後即可適用。另外T27高音單體的振膜很小，其擴散方向近乎無指向性，故其外圍以一圈固定在前障板上的厚毛氈條加以圍繞，意在防止音箱突起的邊緣干擾造成聲音不連貫(acoustic discontinuity)。而前面網的效果也在設計中被考慮進來，因此聆聽時必須要裝上面網，以避免高音域的不平順。

The opportunity was also taken to sort out the treble lisp of the tweeter。It was felt that this unit，the KEF T27 SP1032，was vulnerable because it was exposed and could easily be damaged during rigging at a venue。It was decided to incorporate a protection grille and a suitable one was found，with some modification，from a Celestion HF2000。The tweeter is surrounded by a thick felt-strip mounted on the baffle in order to prevent acoustic discontinuity presented by the edge of the cabinet setting up an interference pattern，since the T27 radiating surface is small and the radiator nearly Omni-directional。The addition of the protection grille was wholly beneficial as it raised the output at higher frequencies and help cure the lisp。The effect of the Tygan cover on the front was taken into account in the design，and the loudspeaker should always be used with the grille on，to avoid discontinuities in the upper presence region。 

在做了這許多修正之後，分音器也必須要調整，因此以FL6/23取代原來的FL6/16。經過所有這些變動，LS3/5的第一個修正版於焉誕生---LS3/5A。這最後加上的’A’有其必要，因為儘管LS3/5A的聲音近似於LS3/5，其差異卻大到無法各取一只配對做立體聲聆聽。既然只有少量的LS3/5曾被製造，這一改款並未造成太大的問題，只有約20只LS3/5必須停用。

Having carried out these changes，the crossover had to be adjusted to compensate and the new type，FL6/23 replaced the original FL6/16。Sporting these alterations the first variant of the LS3/5 was born - the LS3/5A。The 'A; suffix was necessitated because although the LS3/5A sounded similar to the LS3/5，the differences were significant enough for it not to be possible to use a mixed pair for stereo listening。Since only small quantities of the LS3/5 had been built，this did not present much of a problem and only 20 units had to be considered obsolete。 

在1977年產生了一些明顯的問題，而幾乎每個夏天，製造者的不良率都會稍稍提高。80年代初期做了一個修正，當時單體懸邊的凹陷(surround-dip)似乎稍微被更動了。解決之道為將負責控制它的分頻共振器(crossover resonator)調整到一較低頻率並更改制振電阻(damping resistor)。任何一個這類的修正都由BBC發佈給當時的製造廠家並併入執照中。當時並對高音單體並聯電容(coupling capacitor)的數值做了一些修正，這是整個平衡調整的一部分。當高音單體的材質更動時，它的’Q’值也跟著變動，並在頻率響應上產生一個輕微的偏斜(tippling)。此一並聯電容影響電路的型態並決定其制振為過度或不足(under or over damped)。為調整高音域的平衡，對FL6/23上一個tapped transformer的輸出做了調整，並且改變並聯電容以維持其分頻點。

There were a few noted difficulties in 1977，and almost every Summer saw the reject rate at the manufacturers rise slightly。The early 1980s saw a change when the surround-dip was seen to have moved slightly。This was resolved when the crossover resonator controlling it was tuned to a lower frequency and the damping resistor changed。Any alteration like this is issued by the BBC to the current manufacturers and is incorporated into their license。There have been also some adjustments to the value of the tweeter coupling capacitor; these are part of the relative balance adjustment。As the material of the tweeter alters，the 'Q' changes and there is a mild 'tippling' of the response。This coupling capacitor affects the shape of the network and decides whether it is under or over damped。To adjust the treble balance，an output from a tapped transformer on the FL6/23 is adjusted，and the coupling capacitor changed to maintain the crossover frequency。

1987年的重大修改已經在專門雜誌中被廣泛報導過了，而這次的變動主要卻來自於製造廠商的要求。經過這許多年以後，授權廠商之一Rogers的Richard Ross解釋道，雖然當時製造LS3/5A使其聽起來與測量起來均符合規格是可行的，且可以被接受;但單體符合容許誤差的良率卻有變動，尤其是低音單體。因為LS3/5A的特殊設計，雖然B110單體符合KEF的規格，剛好卻有一種特點，那就是在這種喇叭設計上最關鍵的部分，此一單體的誤差卻最不穩定。在炎熱的夏天，低音單體的不良率可以從10%到85%。從授權廠商的經濟觀點而言，這是無法被接受的。

The major re-assessment of 1987 was widely reported in the specialist press; but this time the alterations had been requested primarily by the manufacturers。As one of the licensees，Richard Ross of Rogers，explained，over the years，whilst it had been possible to make an LS3/5A which sounded and measured within spec，and which was acceptable，the number of units，in particular the woofers which were within tolerance varied。Because of the particular design of the LS3/5A，the B100s，although being to KEF's standards，happened to have the point where their tolerance was most variable occurring at the most critical point in the speakers design。In hot summers the reject rate of the bass units could be anything from 10 to 85 per cent，and，for the licensees，this was not satisfactory from an economic standpoint。

在授權廠商發現難以製造品質劃一的單元的同時，BBC也有他們自己的問題。在1987年年底，成品品質似乎朝向能被接受的底限飄移。確切的說，它們被發現在1k Hz附近的八度有2db的隆起，而這正是影響聲音平衡的關鍵地帶。之前的LS3/5A在這一頻率通常也稍微隆起，但現在它隆起的程度卻開始使人不悅。必須要強調的是，它仍然可以在Grade II監聽喇叭的要求中運作，但以Grade I的標準而言，就無法被接受。

At the same time as the licensees were finding it difficult to make consistent units，the BBC was encountering their own problems。At the end of 1987 it was noticed that the units were tending to drift towards the limit of acceptability。

Specifically，they were found to be about 2dB up at a octave around 1kHz，a particularly critical area for balance。There had always been a slight lift on the LS3/5A here，but now it started to become objectionable。It should be stressed that the units were still operating within limit for a Grade II monitor，but would have been unacceptable in a Grade I。

這件事的關鍵又發生在懸邊導致的頻率凹陷上(surround-dip)，它的確切頻率隨著時間而有數百Hz的飄移。而這又與箱體共振產生牽連，到了必須採取行動的地步。非得做一些變動，使這種喇叭能被製造得可讓BBC接受，且品質劃一，符合他們所需。

The crux of the matter was again the 'surround-dip'，the precise frequency of which varies by a few hundred Hertz over time。This had become interactive with the box resonance to the extent that action was needed。A change had to be brought about so that speakers could be manufactured which the BBC would find acceptable，to provide them with a consistent loudspeaker they designed，and wanted

BBC將這件事知會KEF，而KEF派其”特殊產品部門”(Special Products Division)來做因應。此一問題被追本溯源，發現SP1003 B110所使用的二稀橡膠Neoprene缺乏一致性，為此，一款新的B110因應LS3/5A而設計出來。這次使用一種PVC的懸邊，其材質一致性較高，且對溫度變化較穩定，但是順服度較低。因此一個種新的蛛網狀音圈(spider voice-coil)構造就被用來使這種新單體保持與舊單體一樣的靈敏度，以獲致相同的低頻表現。這就是B110 SP1228單體。分頻器設計通常是一個爭論不休的領域，這當然也發生在LS3/5A上。幾經修改，正如報導所言，但這種喇叭的主要規格與整體聲音平衡卻維持不變。

The BBC referred the matter to KEF，who set their Special Products Division to work。The problem was traced to variations in the consistency of the Neoprene used in the making of the SP1003 B110 and so a new B110 was specifically designed for the LS3/5A。This uses a PVC surround，more consistent and temperature stable than the Neoprene but less compliant。A new spider voice-coil assembly was therefore required to give the new drive the same sensitivity as the older one，in order to achieve the bass performance。This is the B110 SP1228。Crossover design is always a source of great debate and this has certainly been the case with the LS3/5A。Changes have been made，as reported，but the main specification and overall sound balance of the speaker have remained the same。                                                                                                               

分頻器 Crossover

關於這個主題，與LS3/5A有關的事足以寫成一本書。它的複雜性顯現在它的電路圖中。L1與R1被用來等化軸線上的響應突起與低音單體的頻率特性。而C5，L2與R2這組則用來補償另一個響應凹陷。針對高音單體，L3的作用為一分流指示器(shunt inductor)與自耦變壓器(autotransformer)，以便區別靈敏度的等級。C2是用以調整保持分頻點的衡定，而R3則用來避免鈴振(ringing)，併同R4與C6以調整高頻端的頻率響應。

A book could be written on this subject as far as the LS3/5A is concerned。The complexity is indicated in the circuit diagram。L1 and R1 are employed to equalize the rising axial response and frequency characteristic of the bass unit，while the group C5，L2，and R2 compensate for a hump in this characteristic。For the tweeter，L3 acts as a shunt inductor and as an autotransformer to allow for differing levels of sensitivity。C2 is adjusted to keep the crossover frequency constant and R3 is there to prevent ringing，with R4 and C6 to adjust the frequency response at the upper end。

SP1228低音單體較先前的B110有著較平順的響應，也因此需要較溫和的分頻等化。於是當時決定：分頻器不能單只是重新設計，以補償驅動單體的改變，而應將新技術也整合進來。基本上這個等化裝置(equalization)與先前相當近似，其線路看起來也差不多。之前的設計使用前面提及的自耦變壓器作為高通濾波器的一部分，且用來以1db為單位調整高音單體的音壓。但是當高音單體的靈敏度越來越穩定(誤差在0。5db以內)時，設計者發現可以改用一個較簡單的衡定阻抗衰減器(constant impedance resistive attenuator)，在+/-1db的範圍內以每段0。5db的方式作調整。這個較簡單的等化器(equalization)所帶來的效應之一，就是整體阻抗由原來的正常15歐姆變為現在的11歐姆。

The SP1228 has a considerably smoother response than the older-type B110，and hence needs gentler crossover equalization。It was decided therefore that the crossover could not only be re-designed to compensate for the change to the drive unit，but could also incorporate new technology。In essence the equalization is very much the same with a similar looking circuit。The earlier design used the already mentioned taped auto-transformer as part of the high-pass filter and to adjust the level of the tweeter in 1dB steps，but it was noticed that as the tweeter sensitivity was becoming increasingly consistent (to within 0。5dB)，a simpler constant impedance resistive attenuator could be used to give the +/-1dB of adjustment in 0。5dB steps。One consequence of the simpler equalization is that the overall impedance has been reduced from the previous 15ohm nominal to now 11ohm nominal。

KEF從整個響應頻段分析了組件的誤差值後，發現在最關鍵的一些地方縮小誤差的容許值，可以改進其一致性。先前的喇叭單元相互間可能有2db的差異。舉例而言，如果分頻網路在關鍵頻段為+1db，與之組合的喇叭單體也是+1db，二者就會加成為+2db。KEF於是決定採用電腦輔助配對，以利在一般情況下選取組件，使得若分頻網路為+1db時，喇叭單體為-1db，最終得到0db的整體效果。這一新的分頻器為FL6/38，SP2128/。

KEF analyzed the effect of component tolerances on the overall response and found that by tightening these in the most critical areas an improvement in consistency could be achieved。In previous units it had been possible to obtain a 2dB variation。For example，if the network was +1dB in the critical area and the accompanying drive unit was also +1dB the two compounded。KEF decided that by opting for computer-aided matching，it was possible to nominally select components so that if the network was +1dB a drive unit with a -1DB figure would be chosen to give 0dB overall change。The new crossover is the FL6/38，SP2128/

因此，KEF得以提供配對的組件給製造廠家，雖然該公司自己並不完整組裝這種喇叭。目前所有三家授權廠家都使用KEF的配對組件。歸根結底，我們必須要說KEF做得實在很好!BBC交付給他們一只1975年製造的LS3/5A參考標準單元No。6，而他們在1988年製造出的組件與之聽起來如此接近，甚至符合Grade 1的標準，且能在品質更為穩定的狀況下生產。因此LS3/5A的編號就被保留下來。

Therefore KEF was able to offer matched components to the manufacturing licensees even though the company does not manufacture the speaker in its entirety themselves。It so happens that all three current licensees use the KEF matched parts。At the end of a day it has to be said that KEF did a superb job。They were issued with a BBC LS3/5A reference unit (no。6) of 1975 vintage and produced a set of 1988 parts which sounded so similar that they were within Grade I limits，and could be made much more consistently。Hence LS3/5A remains。

Spendor過去都完全自行製造分頻器組件，他們表示如果情況需要，同樣能自行生產。他們現在使用鐵粉電感(勿與純鐵ferrite搞混)，且被准許不使用先前的矽-鐵E & I繞線電感(E & I transformer winding)。E & I繞線(laminates)較為昂貴，因此他們也沒放過向KEF購買配對組件的機會。

Spendor used to make their own complete crossover units and say that they could start again if they situation called for it。

They have now adopted the iron-dust inductors，not to be confused with ferrite，and have dispensed with their previous silicon-iron E & I transformer winding。The E & I laminates tend to be more costly，and the opportunity to buy the matched KEF sets was taken。

Rogers多年來都使用各種純鐵與鐵粉電感，因為他們的研究顯示：鑒於在變換器(transformers)中微小的縫隙卻有著高磁場束，而在純鐵(ferrite)中有較大的空隙與許多磁性物質，因此與無線金屬(radio metal)或單向結晶鋼條(grain-orientated strip steel)比起來，這麼做較經濟，且有較佳的磁飽和品質。雖然繞徑較多，且直流阻抗稍微增加，磁飽和的特性卻相當的增強了。Rogers認為以現代的分頻技術，與其製造一個有縫隙的無線金屬扼流圈(radio metal choke)，不如較單純的製造一個有2%至3%誤差的鐵粉磁心電感。部分原因是因為這一設計很複雜，而任何可以使事情簡化的機會都不容錯過。

Rogers had for years used various ferrite and iron-dust cores，because their research showed that they were more economical and gave superior saturation qualities compared with the radio metal or grain-orientated strip steel，given that in the transformers there are quite small gaps with quite high fluxes，whereas in the ferrite’s there are big air gaps and a lot of magnetic material。Although there are probably a few more turns and the DC resistance rises slightly，the saturation properties are considerably enhanced。Rogers decided that with modern crossover techniques，it was simpler to make a 2 or 3% tolerance iron-dust core inductors than to make a gapped radio metal choke。This is partly because the design is complicated and any opportunity to make things less so should not be avoided。

在修改之後，阻抗稍微的有改變 --這可以由圖中的模式看出來，它反映出Rogers的兩種標準模式。當原本的阻抗為正常值15歐姆，新型號的正常值則接近11歐姆。檢視列線圖表(nomograph)，我們可以看到舊款的阻抗在15歐姆，它使用了舊的等化器與舊的低音單體，這單體的阻抗大約是7歐姆。新的低音單體有較低的直流阻抗，但是在配上新的等化器後，二者的曲線形狀非常相近，儘管現在的平均數值較接近11歐姆。這仍舊意味著LS3/5A是由電壓而非電流所驅動，因此擴大機要能有撼動電壓的勁道(swing volts)，並且有適當的輸出功率，但不能是低輸出阻抗者。

The impedance has altered slightly post modifications - this can be seen by the modulus shown，reflecting the Rogers' two standard models。Whereas the original was a nominal 15ohms the newer model is nearer to a nominal 11ohms。Looking at the nomograph，we can see the original as 15ohms，using the old equalizer and with the old bass unit which had about a 7ohm resistance。The new bass unit has a lower DC resistance but，with the new equalizer，the curves are very similar in shape，although the average level is now more like 11ohms。This still means that the LS3/5A is voltage rather than current driven and needs an amplifier that will swing volts and produces reasonable power levels，but not into low impedances。

因此，1977/78年製造的LS3/5A，將不在任何方面比1983年或現在生產的較好或較差。多數對平衡有所瞭解的人，認為這個系統與先前一樣，而且在聲音特性上提供與前相同的品質。

So an LS3/5A circa1977/78 will not in any particular way be better or worse than one from 1983 or now。The consensus of opinion from those who understand balance，is that the system is the same and offers the same qualities as it always has in terms of its tonal characteristics。

進一步說，近期的製品可說更為平順，因為高音的不平坦已經被去除掉了;而在使用新的懸邊之後，染色也被稍為減低，卻還不至於影響音調的平衡，因為對某一特定頻段染色的察覺，其實關係到整個喇叭系統的平衡與等化。因此，比如說在1k Hz附近的音調染色若被減低到某一可查覺的程度，可能會因而強調出其他頻段的染色。

In detail，the latest models are now marginally smoother because irregularities of the high treble have been sorted out，and the coloration has been reduced by a small degree with the new surround，but not so as to affect the tonal balance，because the perception of localized coloration is all part of the balance of the loudspeaker system and its equalization。So if the tonal coloration was reduced to an extent in，say，the 1kHz region where it was noticeable，it could highlight colorations elsewhere。

從發出第一張執照至今，據估計總共約有六萬對LS3/5A被製造出來，所以它能贏得舉世注目倒也並不奇怪。在BBC這種喇叭備用來作各種用途，從一個人的OB，到幾年前在Promenade演奏會中的實驗性四軌傳送中用來做控制與平衡，或在BBC的地方電台提供主要的小房間監聽。即使如此，此一設計也有它的缺點，例如它的分頻器中要用到既被動又複雜的等化線路，以補償因箱體與振膜太小所導致的低頻損失。

The total number of LS3/5As made since the first license was granted is estimated to be around 60，000 pairs so it is not surprising that a huge interest has been generated around the world。In the BBC the speaker has found many uses from the one-man OB to the control and balance of experimental quadraphonic transmissions from the Promenade Concerts several years ago and in BBC Local Radio Stations，the design provides the main cubicle monitoring。Even so，the design has its fallbacks like the passive and complicated equalizer in the crossover to restore the loss of low frequency caused by the cabinet size and limited cone area。 

授權廠家 Licensees

執照收費被用來補貼當初開發的花費，而非僅是一種以大量生產降低單位成本的手段，而該筆款項由工程部(Director of Engineering)而非BBC企業接收，因為BBC企業有其他由出版與錄音等所得的商業收益。目前有四家廠商有生產執照，但實際上只有兩家在生產。當初任職於BBC研究部門，且參與LS3/5A規劃的H。D。Harwood所創辦的Harbeth，與Rogers，Spendor，Goodmans等廠家都獲權製造。Goodmans實際上已經停止製造，且未在合約到期時重新申請，而Harbeth則尚未開始製造。

The license fee is a means of recouping the original development cost，not purely a way of cutting unit costs by mass-production，and the money is recovered by the Director of Engineering and not BBC Enterprises，the commercial arm of 'Auntie' which has taken over other money making areas like publications and records。Recently as many as four companies had licenses although in essence only two actually had a production line at that time。This situation came about when Harbeth，formed by HD Harwoodd who was working on the LS3/5A at BBC Research Department，was granted a license while Rogers。Spendor and Goodmans were also permitted to manufacture。Goodmans in fact had ceased production and did not re-apply for their license when the renewal time came，and Harbeth had yet to start making any。

另一家授權廠商Spendor，由晚年的Spencer Hughes與當初同在BBC工作的Dudley Harwood合組。他們最初並未申請執照。當時該公司處在工作滿檔的狀況，但是在後續出現生產空檔時，他們也加入申請，因為實際上Mr。Hughes非常瞭解這個設計與要注意的所有相關事項。

Another licensee manufacturer，Spendor，founded by the late Spencer Hughes who had worked with Dudley Harwood at the BBC，did not apply for a license at the first opportunity。The company was then already working to full capacity，but when a 'vacancy' next arose it did apply，encouraged by the fact that Mr。Hughes knew the design and all that would be entailed by association with it。

Rogers幾乎從一開始就參與，並且目前擁有Chartwell品牌。Chartwell當初也是被授權製造LS3/5A的廠家之一。Rogers的母公司Swisstone在1975與Rogers合併之後，在1978年又併購了Chartwell這家先前的競爭品牌。Rogers隨著大量市場需求而生產，在1979年宣告他們賣出了第一萬對LS3/5A，並且宣稱這是世界上最成功的小喇叭。而到目前為止，Rogers共賣出了33，534對。

Rogers were involved almost from the start and now own the Chartwell brand，a company who also previously licensed to make the LS3/5As。The parent company，Swisstone，acquired the defunct Chartwell，a previous competitor，in 1978 having merged with Rogers in 1975。Manufacturing to quantity demands，in 1979 Rogers announced that it had sold its ten thousandth pair and proclaimed LS3/5A the worlds most successful small loudspeaker。With the Rogers total to date standing at 33，534 pairs。

Harbeth是最後獲得授權的廠家，目前由Alan Shaw經營。在所製造的第一批樣品通過BBC驗證後，目前已可合格的正式生產。他們所生產的是經過電腦輔助測試的版本。

每家廠商都要通過開始製造時的抽樣程序，使BBC確保喇叭的製造正確無誤。授權廠商由最初製品中挑選出兩只送交BBC。其中一只由BBC保存以做為該廠家之工作參考標準，另一只則被調校到符合BBC自己的參考標準，該參考標準喇叭出自BBC最初自行製造的一批。這第二只喇叭將會送還給製造廠，變成該廠隨後所有製品的參考比較標準。

The latest company to be permitted to manufacture is Harbeth，now under the control of Alan Shaw。They had samples from their first batch passed by the BBC and are now eligible for full production; all are of the computer-optimized type。

This initial sampling process，a condition of all licensees，is to assure the BBC that their speakers are being made correctly。The licensee selects two units from the initial batch to send to the BBC。One of these is kept by the Corporation as that licensee's working reference，while the other is tweaked so that it matches the BBC's own reference，a unit from the very first in-house batch。This second speaker is then returned to the licensee and becomes the reference for all their subsequent units to be compared

像Audiomaster這種品牌，在1976年4月開始他們的生產，只維持了短短的時間;而RAM牌的則從未面市：它們都在生產線完成前破產了。幫Goodmans製造分音器的Falcon，曾為情況不妙的RAM製造了一批，卻發現他們得自負盈虧，因為RAM根本沒有立場付他們錢。JPW也曾有過一些動作，但從未具體化。

BBC對授權廠商產品的檢驗持續進行，而一些”見不得人的事”(nasties)也被發掘出來。其中一個例個子是：一只送來檢驗的喇叭有著比正常為厚的金屬罩材質，造成了兩個八度音程有1 1/2db的響應凹陷。不用說這只喇叭很快就被退還了!

Names like Audiomaster，who launched their models in April 1976，had a rather short lived license span while RAM never got any units out on the street：they went bankrupt before the production line got underway。Falcon，who were making crossovers for Goodmans，made a batch for ailing RAM company and then found themselves having to distribute the boards directly because RAM were not in any position to pay for them。A flurry of activity was seen from JPW but no quantities to speak of ever materialized。Constant checking of the licensees production is carried out，and there are some tales of 'nasties' being found。There's the case of a unit coming in for evaluation with a thicker than usual grille material causing a two-octave 1 1/2dB dip。Needless to say it was swiftly returned。

在目前的三家製造廠商中，Spendor表示雖然部分賣到英國，卻有80%的產量是供外銷用的，主要是歐洲，美國與遠東地區，包括日本與台灣。Rogers也外銷到日本，歐洲，北美，香港與新加坡，而他們賣到日本的數量甚至超過英國;在英國當地，除了一部分提供給BBC，經由hi-fi零售店賣出的也不少。儘管其他設計有著許多優點，LS3/5A在它的等級中始終維持著參考標準揚聲器的地位。

Of the three current manufacturers，Spendor says that although a percentage of their production line ends up in the UK，80% of their sales are to the export trade，the areas being mainly Europe，the USA，and the Far East，including Japan and Taiwan。Rogers also export to Japan，Europe，North America，Hong Kong and Singapore，with more sales to Japan than to the United Kingdom even，where，while a quantity go to the BBC，the hi-fi retail outlets get through a fair volume too。Despite the advances of other designs，the LS3/5A remains a reference standard loudspeaker in its class。

結論:

由上述可知

1、單體本身的特性會影響聲音的走向。此外，KEF的T27還有分自用跟外銷的版本。

2、B110單體本身的不良率會影響聲音改變走向。

3、保護金屬格柵(厚度會影響聲音的走向)。

4、T27高音單體的振膜很小，其擴散方向近乎無指向性，需要以一圈固定在前障板上的厚毛氈條限制指向性。

5、箱體強化及本身的材質。(強化的材質 例如瀝清 及內容物 羊毛)會影響聲音。本身的材質影響到也就是為何香港有一批酸枝木的箱體會作到很像真的LS3/5A。

6、分音器的調整會影響聲音。

也就是說，目前市面上復刻的LS3/5A，沒有作到以上6點就算不上是復刻。因為基本上T27跟B110都沒辦法復刻，如果有找到單體，其他幾點也要相近才會得到相近的聲音。

光是「取得」認証「LS3/5A」是沒有意義的。這也就是為何復刻版的聲音就是跟原版LS3/5A的聲音跟本不是同一回事的原因。有的復刻版連「厚毛氈條」這樣的外觀都沒有也叫「LS3/5A」，已經到沒什麼關連性了。