EMI 350 style combination speakers, Single Point Source Monitors

Aufrufe 6 Mal bewertet mit „Gefällt mir” Kommentare Kommentar
Mag ich anklicken, wenn dieser Ratgeber hilfreich war

EMI 350 is what the manufacturer called a "combination speaker", in the USA a mere coaxial, the elliptical cone 'combines' the sound of 8 inch and 13 inch round drivers, giving a smoother so more detailed reproduction of recorded material.  The tweeter mounted across the bass driver gives a Single Point Source meaning music travels as a single waveform, phase accuracy is higher than Tannoy Dual Concentric or Altec Duplex due to their long throat concentric tweeter horns.
The various coaxial EMI speakers are the 630, 650, 319, 350, 450 and 92390BN series.  There's the broadcast 92390PB that exists in Japan but is very strictly confined to the Japanese elite.  It would have been possible at one time to have copied many interesting models from sites but as soon as their secrecy is in question, they're blocked from search engines.  The 950, 901 and Club are similarly scarce.  The reasons why such folks remain so secretive is anybody's guess.  The 92390PF has a white coaxial tweeter that goes to 30KHz, it's probably a gold foil electrostatic type as the 'magnet' is molded white plastic, but the similar PB has an EMI 319 tweeter behind the white plastic grille.  Why did the British send these only to Japan?  According to the Japanese elite site, they didn't but in the USA and other places, they were only for the global elites.

>>>The EMI RLS 10 & 11 'White Elephants' seen with 'The Beatles' in photos, one with a large round bass unit featuring what looks to be a white dome, is likely to be an early aluminum presence dome, 12 inch, the American Altec Lansing 600B Dia-cone with British GEC tweeters crossing where it expired at 4KHz as in the REDD.36, that extended to only 13KHz but with a more compact Marconi-EMI 13 x 8 basket and Plessey alnico cube magnet.  The Coles super tweeter later used with BBC Celestion versions had aimed above 11-15KHz.  Production tolerance varied +/- 2KHz in the GEC 1853 meaning some reached 15KHz and others only 11KHz (as the EMI Lo-Fi 13 x 8 twin cone).  Parmeko copies right of the Altec-Lansing Duplex, aimed at very close manufactured tolerances of F.R. and so were the only speaker said to be used by 'The Beatles' at Abbey Road Studios, used firstly to ensure the best mono sound, the close tolerance production wasn't about similar stereo pairs but consistent sound quality over time with other reproducers able to offer a better F.R.  The Altec Lansing 419-8B Bi-flex likely influenced the naming of the later issue EMI 319 speaker but the 319 wasn't a bi-flex, a speaker type that didn't need tweeters as going to 15KHz.  However such recordings needed re-engineered after digital sound to help deliver higher frequency fidelity.  Baffle mounted tweeters also once covered the same frequencies handled by some main units but had offered better effects.  Note that out of the cabinet a twin cone appears to have a better high frequency treble than it retains when the bass appears too within a cabinet.  Youtube adverts often played even Triaxials out of cabinets to suggest this was their treble quality, the treble is greatly reduced in a cabinet and the bass much increased, but quality depends on inputs and cables.  The Duplex with its tube harmonics, high sensitivity, large diameter efficiency for tube amplifiers used AlNiCo magnets, not the later, vintage ceramic magnets for the more powerful 1970s Audio Research D79 tube amplifier.  Little is known about BBC LSU/10 Parmeko speakers, sometimes described but not in very knowledgeable ways, it's likely they used a 1945 year model Duplex with 16KHz but the BBC had fitted a Lorenz plastic cone tweeter so it could be covered over with a piece of cardboard and taped around, a bit of handiwork not easily achieved with the Duplex concentric tweeter that was simply bypassed because at this time in television sound monitoring, nobody wanted to hear the 405 line scan frequency at 13KHz, nor a lot of hiss and noise that was carried by the Lorenz tweeter when not monitoring the desired high frequencies from FM radio broadcasts.  The 20 watt 350 is rare on eBay, the 20 watt 319 preferred by classic tube amplifier collectors also rare.  350 were for Solid State power supplies, giving a tighter bass over the 319 for tube rectifier amplifiers.  The BBC LSU/10 studio speaker worked with a German Nazi era Lorenz LPH65 tweeter, it had a clear plastic cone, real similar to the black or white PVC ones in the Lo-Fi EMI speakers.  The Lorenz LP 312 coaxial uses two of the LPH65 in the manner of EMI 92390FY, similar to the later American Bozak B-200Y, wartime origins of this know how isn't discussed anywhere on the internet at present.
Because the 319 used cone tweeters, it's outdated as a modern sound source.  Single tweeter dispersion is poor and in cone tweeters the tiny voice coil formers give more distortion.  Better dispersion was given by the GEC BC1853 ring radiator that had a larger voice coil than many dome tweeters giving very low distortion.  Cone tweeters and whizzers may use bulb dispersion lenses like the George Sioles one above left, added in front of the cone tweeter and must be mounted rigid and fashioned out of resin.  The Peerless cone tweeter above is horn loaded, modern tube speakers put a dome tweeter in the center.  Right EMI STD 400 series preamplifier is clearly based on the QUAD 22 and the STD logo at the top right hand corner may seem not what was meant to be there.  Right various envelope sizes of the KT 66, the Marconi M.O.V. being the best for audio.  The origin or purpose of the QUAD II beside its use for High Fidelity, is mysterious, they were made for other uses that nobody in the audio press wants to mention, a post war utility explaining the large numbers produced but not the most prestigious of products.  Metal strips above the STD/400 preamplifier suggest mounting in radiograms but the build quality is remarkable to say the least.
Left the 10 watt per channel Orthotone STD/381 EL 84 power amplifier was Hi-Fi stereo, 0.1% Distortion, 30Hz-20KHz, +/- 1dB.  Right a Hi-Fi EL 84 audio amplifier, the EMI STD 381.  Note the steel shielding under the irons to prevent stray interference reaching other radio equipment, possibly located underneath.  The amplifier has -80dB noise, 4dB better than the EL34 STD/383 with 20Hz-20Khz and 25 watts per channel, a 10dB improvement over the 1952 QUAD II.  A photo for the Specto Avionics Head Up display - for the Harrier Jump Jet shows Air Marshal Sir Douglas Morris KCB CBE DSO DFC of the Royal Air Force with Major Clarke and Alec Smith who developed the EMI DLS-1 speaker and sold it to Herbert Weisberg, President of Scope Electronics USA.  <<<Left the 92390EA shows a 'whizzer' in the center, named from the noises it makes by itself with the bigger cone removed.  These whizzers appear in hi-End speakers like Lowther and Redheko besides the lo-End, they aren't damaged by record scratches and tape hiss like the tweeter.   It's likely that the large number of EMI units were produced for the British Empire, in decline after Suez.  Civil war in Zaire soon ended AlNiCo magnets but they were fragile, never exceed their watt rating or they'll discharge.  Specto made a whole load of weird air force stuff, some even back-engineered by the USA, EMI was a mysterious company then and much of their involvement still seems secret now.  But after Smith died suddenly in 1972, the EMI audio group came to an end just as old Empire ways began to change.
Right in the gray scale photo is seen the STD 400 series control amplifier in a console at the bottom right hand corner.  In the center of shot are the Capitol Records EMI speakers, a QUAD ESL-57 to the left.
hi-End audio experts prefer modern speakers for their vintage hi-End tube amplifiers but the 319 remains truly exceptional in recreating whatever was recorded at the stereo microphone and in its 1970s version is a great achievement that few modern speakers could match. The extremely small 'sweet spot' is a result of listening to the stock issue speaker and to unlock the 'single driver' effects easily obtainable from a 319 or 630, needs key knowledge confined to a few, elite customers.
Left the EMI 450 for the STD 400 series above has famed twin hard PVC plastic tweeters, the rarest 350 speakers (for the STD 300 series) also have twin 2.5 inch tweeters only made of paper like the American Bozak B-200Y tweeter pair.  The twin tweeter EMI 350 in 15 or 20 watt powers are never seen on eBay.  (Right the KLH Research X).  Twin tweeter 350 speakers are not needed, the problem of sound being too directional with single tweeters doesn't apply with a coaxial working as it ought to.  Ribbon tweeters and electrostatic speakers suffer from 'car headlamp-like beam sound' and use lenses and horns to widen the sweet spot at the listening chair.  Twin tweeters widen the sweet spot making the rare, twin tweeter 350 speakers exceptionally valuable on eBay but the reversible fix for 319/ 350 treble dispersion, giving surround sound and eliminating a sweet spot, takes only a few minutes to obtain but isn't shared with the lower social classes.  Denying the key to any but the intended customers is just like awarding a medal only to a deserving few.
>>>92390BN are a series later known by the masses as 'the 550'.  The speaker here is the late 1960s BN (III) but the chassis stamp only says 92390BN.  However the 550 was only the 5 ohm 92390CR by EMI thinking.  In any case the 92390BN is a 450 with alloy portion, not a 350 style speaker and was excluded from this guide until ebay trader ballsgallery(191) claimed on Nov 4th it was 'the rarest EMI for tube speakers' as if it was a paper twin tweeter 350 with a PVC edge.  550 is remarkable despite a paper suspension edge.  92390BN have the smaller magnet of the standard Broadcast studio monitor, (92390PB), frequency response is 40Hz - 13KHz, better than a 450 but only a 450 with an alloy portion, same x.o., not the rarest but rarely seen.  For 92390BN we need its own (or a similar) British tube Lo-Fi amplifier from the set, a 13KHz limit, specially engineered, partners well with FM stereo and cassette decks.  92390PB has a different tweeter (to 30KHz), x.o. and the thick alloy portion of the  91230M.  Left below the Isophon squawker is between the tweeters as with the alloy portion of the elliptical 92390BN right.  Note that it's best firstly to use vintage tube analog FM tuners with these speakers as optimized at transmission for 30-15KHz, some Hi-Fi tuners make 18Hz-22KHz, but the actual F.R. depends on broadcast conditions.  The Stereo tube tuner version of the QUAD FM2 is very good but it will need an early QUAD 303 of the black top silver smoothing can vintage, and 20 watt EMI 350.  However other combinations of vintage equipment will depend a lot on the quality of everything involved.
Back e.m.f. is an unwanted small amount of power fed back from speakers, the way a microphone sends power to an amplifier.  1970s 3-way speakers likely send three sets of back e.m.f., one from each ferrite magnet driver, less if AlNiCo drivers.  The amplifier and speakers are best of similar vintage designed to cope.  (Right a Marconi 13 x 8").  1990s speakers are "Bi-wired" to help reduce back e.m.f. problems developing since AlNiCo magnet production ceased with Civil War in Zaire.  1960s speakers were to be connected to tube amplifiers with Output Irons, the x-over in EMI combination speakers were designed for Leak Output Iron behavior.  Note how the Sansui speaker below copies Isophon's horn squawker between the two tweeters left that use reflection to improve dispersal.  Sansui has mounted a horn tweeter between cone squawkers and added a horn Super-Tweeter at the top.  In the 92390BN and FY there may be some German influence at work in the double tweeters or it may be an American Bozak influence.  Output Irons are much affected by back e.m.f. compared to modern amplifiers,  the AlNiCo magnet was inherently resistant to back emf.  Ferrite magnet tube speakers were carefully designed to cope with vintage back emf behavior but ferrite magnets after the year 1980 aren't made with tube amplifier output irons in mind.  Many 1970s Sansui speakers have AlNiCo magnet drivers and sound best with tube amplifiers although their brand match catalog range are Solid State.  Owners of the 'Audiokamaloka' web thread variety, puzzle over the mediocre result of own brand Sansui vintage amplifier and speaker matches not knowing about their design for low back emf.  These Sansui speakers were listened to at the factory with Japanese 'Circlotron' tube amplifiers instead of the Solid State products they'd be heard with at home.  'Audiokamaloka' web threads think they know it all, dismissing such claims as 'utter rubbish' and 'bad advice to give people', but it was a fault of marketing pointed out by the British industry, care to partner speakers with the very amplifiers they'd be used with in the best bang for the buck 'separates' market.  B&O, SONY and REALISTIC all paid close attention to partnering the amplifier and speaker sound quality.  The Japanese at Sansui preferred tube amplifiers for auditioning, believing Solid State to be inferior, their amplifiers manage to sound better on other brand speakers so folks assume that all do, it isn't so, all own brand vintage often matters.
Right above Sansui speakers voiced on Mr Shimada's CSPP patent amplifiers of 1952.  Cross Shunt Push Pull Topology is recognized as the thinking behind the evolution of modern amplifiers and the demise of the Output Transformer in tube amplifiers.  This 'cutting edge' Japanese technology was never real popular with the British Imperialists.  Right the Decca Decola had only an FM radio, no A.M. or L.W.  We need to be real careful in partnering equipment of Japanese origin, that the speakers chosen are meant for a particular vintage of amplifier - or poor sound results.  Folks then say they had Japanese stuff and it sounded so so.  The British audio industry have long rejected outside influences in pursuit of their own perfection.  Mocked Oriental speakers are actually quite remarkable if correctly matched.  Web threads like 'Audiokamaloka' forget that it's not the piece of audio equipment that necessarily sounds bad, so much as the decision making on the part of the audio buyer, matching up the wrong vintage and type of equipment, often on what is available at a bargain price. Left a dispersal lens like the George Sioles one above as seen on the German Isophon full range 12 x 5 inch elliptical speaker, from the front looked like a concentric horn.  EMI used a similar strip upon which was mounted a tweeter.  Isophon initially used a tweeter on the baffle with this speaker, but had another 12 x 5 coaxial as did Saba.

The 'Circlotron' sound Sansui speaker engineers wanted to hear.

Left Decca Decola Aristocrat radiogram below with EL34, KT77 output tubes, puts the power supply low down in the cabinet to avoid hum, the power amplifiers and Output Irons are in separate modules to keep speaker wires short, for example to allow solid silver strand speaker wire, the stereo preamplifier is on one side of the cabinet.  Right German Saba and far right Isophon coaxial ellipticals.
Listen before buying?  The eBay bidder and stereo buyer doesn't need to hear before buying if an expert audition panel is agreed a set works best together.  The problem with most magazine reviews and 'Audiokamaloka' web threads is the sets they heard are all different.  Some magazine reviews offer the test audition set but for only one source, say Compact Disc with a speaker and amplifier.  For that reason the audio press in the early 1980s were telling buyers to set their system up for a main source - listened to most of the time, that made life easier for magazine reviewers.  However the B&O, REALISTIC and to a lesser extent due to their real poor reliability, SONY systems, take great care with speaker and amplifier matching, the amplifier and its speaker are a pair.  Partnering audio equipment needs either 'own brand' chosen sets or recommended partnering of separates.  Matching the EL34 tube Output Iron to the best loudspeaker is what folks were paying for in the DECCA Decola Aristocrat.  Dynaco ST-70 is real popular US EL34 output tube amplifier and is often matched with Sansui speakers of the AlNiCo magnet type.
Left EMI Vortexion CBL6 Stereo 1/4 inch tape reel to reel tape heads.

2008 book "Built like a Battleship", by Terry Martini

"A history of the Ferrograph Company 1920 - 1983, has a well known and respected collector and expert in sound recording techniques and equipment, capture a complete history, taking you on a chronological journey through the events and products of a company, which survived the decimation of the British manufacturing industry whilst continuing to use the highest mechanical and electronic standards without compromise.
Right another picture of the Stereo EMI Vortexion CBL6 with the 1960s battleship build of the 1960s mono Ferrographs Series 4, 4a, 5 and 6 ... "the very special and thoroughly British company, that from its earliest inception helped shape the public interest in wireless - the newest form of entertainment in the early 20th Century, targeting its products within the home construction market and making the proposition of building and operating a quality receiver, a reality.  Through diversity of business, war time research work and capitalization of the post war public interest in high fidelity sound recording and reproduction, it grew from very modest roots to a company respected world wide for broadcast quality equipment”  - Mike Barker.
"Tung Sol"left and below was a brand claiming unusually high linearity in tubes of the mid-1950s, based in the state of New Jersey in the USA, a place with a battleship named after it.  The company had supplied the U.S. Navy and Army in WW2.
KT 77, EL34 above is surely one of the most memorable tubes, partly from the kind of folks who owned these hi-end tube amplifiers, their quiet confidence in the equipment.  Back then we thought that in 20 years the sound quality would be ubiquitous but it wasn't to be, instead folks strive to preserve the greatness of those times.  The battleship sums it up.
<<Left an advert showing EMI, like its cohort DECCA, were heavily involved in hi-tech military projects.  EMI also made the electronics for the ill fated TSR.2 jet.  The development of OTL, CSPP and the Electrovoice 'Circlotron' likely affected their withdrawal from audio.  But for Output Iron vintage tube sound, EMI are still useful.
Early Solid State amplifier Output Irons work with real expensive obsolete germanium transistors that are unreliable in suffering serious overheating called 'thermal runaway' - sounding better and more wonderful the closer they approach failure temperatures.   These amplifiers also suffered from a loud hiss caused by high distortion devices and were Lo-Fi relative to tubes in the STD 300 series.  Constantly blowing fuses using only their own, very high sensitivity AlNiCo magnet easy to drive, low power speakers.  The silicon transistor was sold on its claimed "freedom from thermal runaway" but (in fact) lacked the awesome germanium transistor sound and was above all cheaper to make and sell.  Right Germanium transistors  were far more expensive than even hi-End tubes.  Amplifiers like the QUAD 50E and 303 tried to simulate tube sound, the early 303 sounding best of all but in later years silicon transistor amplifiers came to make their own 'best sound' with specially matched speakers the vintage EMI speakers obviously don't equal.  Newer Solid State sounds best with only the original prototype test matching speakers of the factory, catalog or long term owners.


10 Watt 319 (tube rectifier) pleated edge left and 350 (Solid State rectifier) roll edge, long throw above

The 92390FT 319 has the single solid cap of the 450 with which it also shares the ten watt L coil, but the 350 has two such solid caps behind the tag board.  Note black PVC ring on the tweeters above, it covers a foam, preventing any 'memory ringing' in the paper tweeter's pleated edge, also note the tweeter rivets in the 350 and slot head screws on the 319, these are clues that few would ever notice.  Each has a ten watt x-over L coil similar to the plastic tweeter EMI 450.
Left EMI Vortexion CBL6 control panel
The larger 15 watt 350 magnet for roll edge Long Throw, as the cone travels further, is continued in the 92390FT leftabove.  Bass in the 350 and 750 Long Throw series was thought 'overblown' in 1968, a much stronger bass sound than the more natural EMI 319.  10 watt rating is quite high compared to the 6 watt Wharfedale Super 8 RS.DD but forget modern Home Theater receiver power, these speakers should only be connected to same vintage equipment.  The price of quality today in Home Theater electronics is cheap compared with tubes of yesteryear, they're different systems.

No voice coil wires on the 10w tweeter cone as absent in the 15w 92390KE versions


Leak Stereo 30 is a pure germanium transistor amplifier, if getting solder renewed stay away from the transistors!  Replacing the resistors and capacitors supporting them is suggested.  Rated at 0.1% THD for 8 watts output, with full output -66dB noise figure, it's a fair amplifier to try the 'germanium' sound with 10 watt EMI 350.  But later with the Leak Stereo 30 Plus, engineers tried increasing the output power and silicon transistors are likely to replace the Germanium, not many owners care to give such details.

Leak Mini Sandwich speakersleft have an elliptical driver, described in their circa 1966 adverts as thoroughbreds - to appeal to the echelon of British society who went to watch horse racing.  A story suggests elliptical speakers radiate sound more at their narrower side and avoid sideways interference in stereo speakers.  Hi-End audio designers claim a mono single speaker source sounds more natural but with EMI's Alan Blumlein, the founder of stereo sound, the EMI elliptical drive unit gets past the concerns of two speaker source interference.  Many Leak speakers were built quirky - appearing real time consuming to make and unusual.  Right the dark slate grey basket, EMI 350 KE8 15 watt inductor beside the older green basket 15 watt.  These dark units were apparently sold by EMI as to be identified as replacement units.

B&O Beomaster 900, 2 x 5 watts at 4 ohm only, for 10 watt, 4 ohm EMI 350 etc.  Don't use 4 ohm speakers with amplifiers giving more distortion at the 4 ohm load, use amplifiers like B&O designed to run 'undistorted' at 4 ohm impedance!  Some people are not too strong on these points so some amplifiers need a 15 ohm loudspeaker to run 'undistorted' and have 4-15 ohms printed on the rear plate, this kind of amplifier has higher power at the lower impedance but the distortion penalty paid is disregarded!  Distortion of such amplifiers can be 3 x higher at the low impedance, this will spoil audio results, the greater low impedance power is not needed if using instead a more sensitive speaker.  <<<Left the 15 watt EMI 350 92390KE, 8ohm, 310 - 315uH air cored inductor/ coil, 0.3% tolerance and 2.2 uF solid capacitor, wired as a second order simple high pass crossover.  Most modern speakers are not sensitive enough for 1960s Solid State or tube amplifiers.  Peter J Walker of QUAD likened the volume control to the focus wheel on a camera and this should give the novice an idea of what these 'window on the performance' amplifiers are all about.  Not about being loud or powerful, the aim is to capture a true stereo effect that comes up like a phantom when the distortion and power is low enough.  Volume should never be turned up without fear of too much distortion and blurring of the images, a stern discipline taught the previous generation by using germanium transistor amplifiers.  The silicon transistor has become a different pursuit of poorer quality power that many people today don't know to be a truly 'second class' Solid State sound quality.

Armstrong 521, Another germanium transistor amplifier, with the recommendation to replace stock output AL102 devices with Mullard OC 28 to avoid failure of devices under bass extension.  The germanium transistor had a sound encouraging power limit, loud playing with bass, a lesser but reliable Silicon output amplifier is the Onkyo A-33, suited to the Shure M75EJII cartridge - possible UK eBay site find.  Below Russian Germanium AL102 equivalents have real good sound quality, blowing of circuit fuses is due to modern music bass extension, being a remarkable effect folks just can't resist playing with.


£76 UK, $122.82, pair of 92390KE coaxial, there's a single baffle tweeter version of this 350 bass unit



15 watt chassis L coil 1970s EMI 350  Note the difference between the ten watt bronze basket L coil and 15 watt below.EMI 15 watt L coil

The EMI 92390CM chassis above was a bass/mid 13 x 8 speaker built into cabinets as shown below and powered by tube amplifiers.  The x-over is the same but the tweeter is up on the baffle in 2-way box style, although not as good as the combination speaker as not a 'point source' they were an EMI design that caught the popular market.

Right the late production run, 15 watt 350, has a chassis mount 'L only' coil x.o., its most interesting feature in the tweeter above being the smallest possible tweeter dust cap, apparently of a natural material, the aluminum bass center cone was treated with a special natural base lacquer as natural materials are reputed to sound better.  Full 3 tags on the wiring board, the tweeter has a shorter length voice coil former and may not even be a paper one!  The type of on-board chassis coil is seen on the Goodmans Trebax bass unit, a cast chassis, also in green hammer tone.  (The Trebax is another revered vintage driver).  A capacitor is mounted behind the wiring board possibly a red 'metaxial' type around which was wound the older 350 15 watt L.C. x.over.  Many people couldn't care less what a capacitor looks like but others delight in original product details. These late production run EMI  92390 KE8 15 watt tweeters are interesting as lacking any voice coil wires on the cone and lacking the PVC covering over the tweeter foam covered pleated edge as seen in the late 1960s 10 watt EMI 350.  The silver bars with slot head screws are unusual as is the green -ve pole tweeter wire.  The green wire seems to take place of the red wire at the top tag with the black wire (above) replaced by a red wire!  See how slack the tweeter wires are and the way they don't fit through the chassis in the older more time consuming fashion suggesting falling standards of manufacture and cost cutting.
Right the 350 style x.over, here on a 15 ohm 92390DD. (A speech domed cone tweeter grey PVC edge 319 combination speaker). This x.o. first appeared on the 92390PB in the early 1960s and clearly uses a larger inductor under the cloth jacket with a smaller solid capacitor in its L.C. network.

An EMI SQ was a unit offered to decode 4 channel quadraphonic stereo, that between the early and late 1970s had been adopted as a fad by the British elites on both sides of the pond.  The EMI unit is for EMI cut records and isn't usually listed among the recognized units of the day.  They were expensive systems needing more speakers and amplifiers of equally high quality and were usually seen with phonograph records of classical music or jazz.  The early 1970s EMI SQ system used a speaker called the LE.3ss, (surround sound) that adopted an old EMI 1950s voice coil winding practice, in the bass unit where there was wire on both sides of the voice coil former.  Note that the particular reasons for it are known only to the British elite of the time, but may have offered a deeper, sharper image.  So little is known about EMI items because they were only offered to the upper classes and unknown to the masses.  SONY, Realistic, Marantz, Lafayette, Fosgate/ Tate and Tesla offered mass market systems.

1968 EMI 350 15 watt chassis, LC x over & 1960s QUAD 303

1968 EMI 350, 15 watt, 25 / 30 Hz - 20KHz, 11,000 Gauss high flux magnet.

Left below the EMI 350 red 'metaxial' capacitor in the orange sleeve, as seen in the EMI 650 for Solid State rectifier, germanium transistor amplifiers.
Leak tube amplifier rebuild services claim to improve Vintage Classics but do they?  Trouble with flashy audio mods is lost original sound quality and lost Euphonic Distortion of original parts!  New Rhodium plated phono sockets sound real good on the shelf but put them in and you might wish you'd left them out!  Re-wiring with 99.99% pure silver wire, insulated with PTFE and silver soldered on all joints, sounds just like a $200 lunch!  But don't buy it - as silver wire increases current and will affect sound quality, you'll hear more treble, but Classic components work together to reproduce a total effect!  Add an Alps pot (volume knob) and quality switches and distortion is cut right down but do 'Idiot Techs' also modify the original Negative Feedback loop?  - No, they don't mention any clever stuff at all, Idiot techs perform probably stupid swap-out mods on Leak amplifiers originally engineered by genius teams these techs could never match!  Tube amplifier rebuild services can be just like one old lady who thought she could improve on a worn away painting in her local church, like Tony Hancock in his movie "The Rebel" she didn't really know a whole lot about the subject.
Left a QUAD 410 made from a kit conversion of a 405 and relegated to the loft afterwards, rusting through disappointment in the resulting sound quality.   'Idiot' Techs are often army radio technicians with no Hi-Fi knowledge.  They just fit a new component upon the can or jacket value of the one removed.  They're good at repairing sets and after the set is working again, it's best to fit the ideal components in your own free time, specially selected parts based on their audio quality.  Right a black basket EMI 350 with 10 watt x.o. and 15 watt magnet in a what may be a middle-range horn made by the Kettering firm, Ben Ford Hi-Fi cabinets Ltd.  Overall size is 31.5 inches x 12 x 12 inches.  Top the EMI DY15 speaker below left has a 10 watt magnet,.  Adding a back wave horn to a 350 is slightly suspect, both 319 and 350 needing no such enhancement with amplifiers like the harman kardon A 402, based on the A 300 and A 500 tube amplifiers, spectacular bass depth and definition are delivered from a bookshelf size closed box in small rooms.  Lowther lack bass being Hi-Fi twin cones using folded horns to increase bass.  Tannoy Westminster and GRF use bass horns in larger rooms.  Room sizes affect results, bass horns are most often seen in halls and in public address.

7591A tubes in the Fisher 500c are better for EMI 319 as of British speaker voice while the Jazzy 7591 are for American speakers.

If techs could measure the sonic signature of a Leak 12.1 and recreate it, why don't they?  Perhaps Bob Carver owns the only patent capable of it.  So maybe 'idiot techs' need to form an association to get their standards of restoration up to original Vintage Classic sonic specifications?  All too often we're seeing 'idiot ideas' like improving current being improving Power from I x V, but more power is not important with originally matched 'sonic signature' speakers.  Leak Stereo 50 below has less power (2 x 25w) than a Leak Stereo 60 <<(2 x 30w) left, a more powerful design but with compromised sound quality at any volume setting.  Their main hope is driving ESL-57 speakers (but in vain).  Getting an 'Idiot Tech' to increase the power output from a Leak Stereo 50, is just not real clever!  More power is more distortion.  Instead you need the best speakers to work with the Leak Stereo 50, these 'best speakers' are the ones Leak himself would have had hooked up at the factory in the 1960s, not the 'best speakers' for modern amplifiers.  Left 20 watt EMI 319 just to prove they exist but ever getting a pair anywhere, is unlikely.  The 20 watt 319 is for an amplifier like the Leak TL 25 used by the BBC.


Leak TL/25 Plus, 32 watts per channel, 450 volts on EL 34, Class B / Push Pull.

Leak Stereo 50, right, 1958 year, (a mouse had been living on this one at one time) 25 watts per channel, 380 volts on EL 34, Class B / Push Pull stereo symmetry layout metal chassis with Shorter-Wigan preferred tag board solid core hook-up wire circuits but C-R-C power supply filtering, single 5AR4 (GZ34) rectifier tube supplies both channels.  3925 Output Transformers with 50% screen taps for preferred triode sound.  Problems, failing cathode resistors seen above chassis.
Leak Stereo 60, below 1962 year, 35 watts max, 25 watts @ 0.1% distortion, 420 volts on EL 34 Class B / Push Pull with C-L-C power supply filtering.  8615 Output Transformers with 25% screen taps for more power.


Original EMI 319 'black and tan' cone, £330 each Japan, 'Lowther-like Jazz sound'

Tubes for EMI 319: 6L6, KT66, 7591A, these have a natural sound compared to the Jazzy 7591, hence USA EMI 319 are seen amplified by the New York origin Fisher Radio Corp. 500c and 800c with the 7591A output stage, these have a Solid State power supply not the old, higher quality choke tube amplifier supply, this Solid State supply is thought to give them their deep tight bass.  EMI speakers were popular in the New England and New York areas due to the location of Scope EMI Electronics and Benjamin EMI Sound Corp.  The 7591 has a different tube sound and EMI 350 is aimed at the different sounding KT 77 tube amplifier, today KT 77 is usually replaced with EL 34 / 6CA7, its bass extension suited to EMI 350.  Left <<<the early 319 on-board LC x-over with the biggest capacitor and least inductor wound under the orange sleeve, below is the next 319 type x.o. with what appears to be more inductor wound around a smaller value bipolar electrolytic>>>.  The EMI 319, 8 ohm, mid 1960s 'black and tan' cones look sprayed to disguise the aluminum center cone, they're found in the Scope EMI 319 and Benjamin Model 92, they may not be sprayed but cardboard layering.  Early black and tan cone have a bare cork gasket and in the above photo, the later blackened cork gasket.  One 92390BP 319 speaker version has a blue tint black cone and tweeter partnered with the Fisher 500c or McIntosh MC225.  EMI sound slightly more entertaining than many older speakers, as if, given a choice of speakers, EMI is the one you'd end up choosing.  EMI 319/350 are N.F.M. like the Yamaha NS1000 but do suit larger rooms, they have a lot of sound volume for not much power, but the amplifier is critical, just don't assume yours will ever be okay with other than your usual speakers.  Left impressive craftsman built EMI 350, H.93cm x W.39cm x D.22cm, thick plywood rear baffle mounted, sealed box, braced halfway between where the lower chassis ends and the base of the cabinet.  Screwed lap joint timber side panels with finished ribbon ply red mahogany veneer, rear panel.  Baffle is unpainted bare ply except around the edges of the black grille fit, held in place with Velcro strips.  Grille cloth appears transparent.

Here the Heathkit AA-100 has the Jazzy 7591 U.S. speaker voice tone


Leak TL12.1, 0.1% distortion, KT66 tube mono block, Class B / Push Pull.

Leak TL12 Plus, EL 84 tube, Class B / Push Pull.

QUAD II, KT66, 15 watts mono (GZ32 rectifier) 0.02% distortion, Class B / Push Pull.
Left compare the jagged 1960s Celestion CX2012 F.R. with the smooth EMI 650 below, this is why EMI sound 3D compared to others. Right in 1969 the J.E. Sugden C51 and A51 were used with the EMI 650 by the Gloucestershire elite, whom had also closely followed Heathkit equipment.  These early Solid State amplifiers had 20 watts output power at 8 or 15 ohms.  Jim Sugden had stipulated using the amplifier up to only to 1 watt of power and the farm cat appears to have approved.  F.R. at 1 watt was 30Hz-20KHz +/- 0.5dB and 0.01% T.H.D.  Note at +/- 0.5dB, 30-20 and 1 watt appear much louder than 1 watt with poor F.R. amplifiers and speakers.  The input F.R. also needs to be as accurate.  These are elite sets for discerning individuals as from the order of St John.

EMI 630 chassis with Rogers EL84 Junior and Heathkit AA111 EL 84 amplifiers

'The cone' is the cone-shape bit of a speaker and it can be felt to vibrate when playing, the EMI 630>>> aluminum cone is real light, absolutely rigid yet freely suspended, following the audio signal with great accuracy, providing better transient response, better attack and recovery characteristics.

<<<EMI 650, 93879EH is a later version of the 630>>>.  Black capacitor on the 630 above right differs from red metaxial/ orange sleeve on the green back 650 above left spotted in an EMI 621.  Larger EMI 319 style orange sleeve x-over is seen on the early 630.  Single 630 make for slow sellers in the USA.
<<Left, Solid State EMI 650 and below valve Leak Stereo 20, (2 x 10w), EL 84 tubes for the EMI 630.  Note the large output irons.
EMI 650 are 8 watts RMS in power, the 630 only 5 watts continuous or 10 watts American i.e. 'Peak'!  Check wiring in a speaker and if it's solid conductor, fit similar.  Sellers who chop through solid conductor audio cables could be throwing away what today costs £2000 for two six foot lengths.  Be real careful to preserve the wire lengths including any connectors, increasing the vintage value as modern wire may not compete on sound quality, old wire may well be thin and crumbling away but often that unique speaker wire is making a sound impossible to upgrade.  This audio tip is called Euphonic Distortion.

Rogers Junior through speakers best suited to precious tube watts

Scope EMI 630 enclosure has a 1960s EMI 630 chassis, a studio monitor, Japanese enthusiasts claim has no deep bass and its Leak TL12 Plus, the EL84 push pull tube amplifier as tested by the manufacturer, have soft muted bass but EMI speaker Frequency Response (F.R.) is boosted for such tubes and a cheap, possibly Solid State amplifier mismatch will make the poor bass the Japanese enthusiast has complained of.  As Leak TL12 Plus, sell over $2000US, some enthusiasts use cheaper wrong match amplifiers.  EICO HF81 has EL84 tubes but 2 x EZ81 rectifiers and despite suggestions it isn't Lo-Fi as a C-R-C amplifier with 10Hz-100KHz +/- 0.5dB, THD is not very good at between 1 and 2% 20-20.  Although reviews claim the HF81 as one the finest of all, noise is not real great and it's strange the figure for a tuner is -57dB while that for aux is a claimed -75dB, it's just dubious.  The quoted damping factor has a specified F.R. of 20-15 betraying Lo-Fi character.  It's suggested any of the EMI baffle (Hard PVC) twin tweeter Lo-Fi speakers are tried, a 10 x 6 pleated edge right.
"Befuddlement ...  How could this unassuming little integrated tube amp from 1959 make my painstakingly assembled cast of modern separates sound like they were emitting a sonic connect-o-dot drawing of the musical event?"

Left - Long throw pleated rubberized-cloth edge EMI 6/1/2 driver was likely an early version of the roll edge EMI 812 speaker sold in one convex and one concave Long Throw PVC roll surround pair for some obscure typical EMI reason.  Real interesting long paper voice coil former, sold fast on eBay USA as with so many EMI speaker listings, they're here today gone tomorrow.

"OK, perhaps I am exaggerating a bit, but I would be lying if I didn't admit this amplifier could embarrass many well known sub-$2000 solid state amps (as well as more than a few tube compatriots)."


Audition opinion needs similar quality vintage equipment.  The Scope EMI 630 might be compared with the B&W D.M.1 not the Lo-Fi version of the EMI 630, its Lo-Fi appearance is eye-popping weird but gets it no bids as real specially made for Lo-Fi amplifiers, yes the $1000US EICO HF81 is Lo-Fi and its Lo-Fi speaker has a white hard PVC tweeter, fixed like a diamond in the center on two strips of steel, its grey corrugated bass unit edge, is like two inches wide and just fascinating to look at, the cone and its wide suspension are one piece but Lo-Fi is a whole different branch of tube audio, so don't get things mixed up.  That hard PVC tweeter goes only to 13KHz.  EICO "Classic Series 2036" above left have a screened off control zone to keep stray hum away from the knobs and has the same Lo-Fi output transformers as the HF81, a single GZ34 takes the place of 2 x EZ81 in the HF81, both are EMI 93670HS speaker suited, Lo-Fi C-R-C power supplies, on first appearance real similar to the 1958 year Hashimoto-made Australian Encel X1212, left, also with Lo-Fi hum bucker and GZ34 tube rectifier.  Right 93870HS, Lo-Fi version of EMI 650, long throw super-bass cone, specially optimized for Lo-Fi amplifiers with Solid State rectifiers. Encel's later 1960s 'motional feedback' C.S.M. 40 M.F.B. amplifier, above, has itself a C-L-C Hi-Fi power supply with no hum and with Solid State rectifier suits the Hi-Fi EMI 650.  The Lo-Fi Encel and EICO may look real similar to inexperienced eBay bidders but the Hi-Fi Encel above right has a C-L-C choke bottom left.  Amplifiers are valued on power supply quality, the platform on which amplified quality stands or stumbles.
Left the EMI STD/381 EL84 amplifier with GZ34 removed, it had no choke but with better noise than most previous choke power supply amplifiers was a real curious design that received good reviews in the press and was made by Clarke & Smith at their Walington factory.  B&W, BTH and others in the BREMA Audio Group adopted EMI developed prototype models.  Bowers & Wilkins were just a couple of shop owners.  Lowther speakers were in the BREMA group and their complicated speaker cabinets help explain the genius of EMI radiogram cabinets at this time as with the many speaker cabinet designs Clarke & Smith created for claimed School use, where in fact these schools would have been makeshift BBC studios in the event of a nuclear war.  The Lowther speaker was liked for high sensitivity but its cone travel is only +/- 1mm, so it has to have the large heavy plywood horn.  Recent examples use a mains driven field coil magnet because the alnico is very fragile with higher power amplifiers.  Today many Hi-Fi owners are much more careless than in the 1960s.  Vintage tube amplifiers are prone to arcing and other mysterious conditions, although mostly reliable if treated with great care, they should be regarded as potentially troublesome if not treated with care.  Using a 4 ohm speaker on a 15 ohm tap is to be avoided.

Rogers Junior playing through speakers only for modern Solid State


The B&W B14/7W chassis has a double diaphragm or twin cone to eliminate cross over network distortion and e.m.f. found in 2-way speakers with a crossover, the whizzer acts as the single point tweeter with low phase error.  B14/7W were not used by B&W as single drivers, but as bass / mid drivers with the B&W B14/8W mid bass in the other of the speaker pair and in what were 2-way baffle speaker systems.  Some transistor amplifiers of this vintage suited 2-way speakers.  The hi-End EMI 13 x 8 B14/7W twin cone seems to be an experimental driver being used up.  Whizzers are real complicated devices and this 13 x 8 is likely to have been developed early in the 1960s for the QUAD II.  The silver finish alloy portion was a B&W preference for synthetic materials so the usual alcohol based natural lacquer wasn't used.  The EMI B14/7W whizzer lacks Lowther and Richard Allan whizzer cone 'dispursment' plugs, fashion playing an important role in High Fidelity sales.  Single Point source is only now finding favor again in U.S. studio monitors.  If customers are looking for tweeters in speakers, old whizzers, no matter how good with expensive tube watts, will not sell.  A mid woofer in one speaker and a whizzer cone in its stereo opposite don't make a stereo pair.  Such differences in unseen x.overs hidden inside even the BBC LS3/5A, shows manufacturers cheating their too-trusting customers.

QUAD II tubes with Hi-End EMI whizzer cone speaker
The original M.O. (Marconi Osram) KT 66 issued with the QUAD II are rarely seen as claimed the best KT66 tube ever made and with short, 1 year lives at full power they last longer in low powered 1950s QUAD II, albeit by the year 1980, often troublesome and replaced, best with GEC Gold Lion, then around $200 each.  Right DECCA Decola speakers with pairs of open baffle AlNiCo ELAC squawker and AlNiCo EMI 98890B tweeters using AlNiCo EMI 13 x 8 mid/bass low range for unrivaled speed and definition, they'd used the QUAD II or Leak RS141 studio amplifiers.  The later EMI 13 x 8 Hi-Fi speakers had improved lower bass over the 1950s AlNiCo models but weren't as accurate in upper bass as the sought after cube AlNiCo 13 x 8, the array ideas were continued in single boxes of the 1960s, only none have yet appeared on eBay.  It's likely array speakers like the 1973 year Hacker L.S.1500, remain in private collections of the elite.  Where the KT66 are not Gold Lion it suggests the owner was not an enthusiast and repairs have been done by someone not most interested in the sound.  Many QUAD II sets worked in practical roles, some so specialist they need rebuilt as audio amplifiers, most fetch remarkable prices on eBay especially in the USA.  The Long Plate Mullard EF 86 has a totally different sound from the Short Plate Mullard EF 86 but the particular sound of the older Long Plate may well suit the EMI 319 13 x 8 speaker better.  The Short Plate Mullard EF86 sounds far more detailed on some more modern 3-way speakers; and with single driver speakers like the B&W B14 / 7W, the Short Plate EF 86 may well be found more suitable.  Telefunken Diamond gray and silver plate EF 86 are used with the EL 34 tube and to fit a Telefunken EF 86 in a QUAD II or where Mullard are usually seen is not recommended as the tubes can have different specifications.  However the EF 86 in QUAD II need to be a matched pair, the different Mullard EF 86 pair seen here suggest they are not a matched pair.  Left an EMI 950 of the British elite is unlikely to change hands on eBay, they were hidden from the lower social classes.  Collectors should not play about with the tube sets in QUAD II by buying from eBay, such tube amplifiers have to be carefully matched by a radio tech expert, occasionally with elements below the chassis having been changed.  The tube line-up positions of any tubes removed, should be carefully marked and the same tubes refitted after careful packing for transit.  This may be done with a diagram showing where each tube of a set belongs, drawing out the amplifier on a piece of paper as a rectangle with squares for the transformer irons and small circles for the tube sockets.

EMI 319 and early 630 chassis have large orange sleeved L.C. x.o.

Main 319 difference with 350 is wide corrugated PVC edge or 1960s bronze hammer tone basket with green label, however 1970s 319 with a green basket were still made for the QUAD II.  The 350 cone sits further back near the spider, an orange color voice coil suspension, than in the 319 as the 350 is a Long Throw and in general Long Throw speakers suffer many more distortions.  As a Long Throw however, the 350 bass in organ notes is probably not going to make the 319 sound better but remember the 319 was made specially for 'loose bass' tube rectifier amplifiers like the QUAD II.  A paper spot on EMI 319 or dimple in the ceramic magnet of 92390BP appears to indicate the wiring side of the speaker.  EMI 350 lacks these reassuring labels and the green EMI plastic labels dry up and come off, EMI 319 magnet did have a green label.  Only older EMI 350 have the wiring hidden in carefully placed black plastic sheaths like the 319.
Ferrograph Series 6. Mono
Last of the Wearite decks.

Ferrograph Series 4a Mono
1959 year.

Ferrograph Series 5. Mono.
5A 40-10,000Hz +/- 3dB, 3/3/4 i.p.s.
5A 40-15,000Hz +/- 3dB, 7/1/2 i.p.s.
QUAD 22 / Single II amplifier, Goodmans Axiette monitor.
Marconi (Mimco) Ferrograph Model 5A OAK is drawer mounted for use on ships and liners in 1963.

Ferrograph Series 6. (633 photo)
1966 year 631T Mono, 632T 2-track Stereo, 633T Mono, 634T 4-track. T series have teak sides for Hi-Fi systems.

Ferrograph series 7. Stereo.
7HD 1973 year.

Right, Ferrograph F-307 amplifier Mk.2 for the series 7 stereo tape recorder above, the Mk.1 version is suggested for 8 ohm 20 watt and 15 ohm 15 watt EMI 350 speakers.  Noise is not too great at -65dB AUX and -60dB phonograph but the transformer mains iron is enclosed in a screening wall and the underside iron has steel shielding like the EMI Orthotone STD/381 tube amplifier with which it shares the separate stereo power amplifier fashion seen in the early QUAD 405.  But the STD/381 has -80dB noise and at the time of design, tube amplifiers were still better than Solid State in noise.  Build is similar to other EMI Solid State equipment.  0.25% THD is equivalent to the REALISTIC STA-2000, that with the best speaker is capable beyond many better specified amplifiers.  F.R. is 20Hz-25KHz +/- 1dB.  The tone control of +/- 17dB at 50Hz (as there's no Loudness Button) and +/- 13dB at 15KHz is probably what most impresses people about the apparent quality of these amplifiers.  Only the the Mk.1 amplifier with its obsolete 39285 output devices is best for the EMI 350. 
Left Metro Sound (EMI) ST40 (2 x 20 watts)
The old tube era Bass Boost and Treble Cut are obviously related to the F.R. of the ancient reproduced reel to reel Ferrograph tape playback.  Although the F-307 are highly regarded by owners, appearance and brand probably affect attitudes.  There's a capacitor output like the QUAD 303.  The hidden door allows filters to be switched as a means of controlling tape or FM radio hiss and are today somewhat obsolete or specialist.  Although prices of the F-307 are climbing on eBay, there's no real clue as to why, although the ancient build is likely to make a real smooth, mellow sound, the PCB boards aren't fiber glass but basic Bakelite.  Build suggests EMI, QUAD and Dynatron engineering influence.  Above right a rare internal view of the EMI 1515, the green smoothing can strapped to the chassis by the same means as the electrolytic on EMI Hi-Fi speakers.  The transformer isn't large and the output devices are obviously meant to be run at low power, under 1 watt.  The stereo symmetry circuit board is large with few components suggesting advanced circuitry design for best valve-like sound quality.
Below the EMI 1515 amplifier is similar in build to the U.K. A&R A60 that for many years was a prestige audio component of considerable power in order to drive awkward speakers like the Rogers Studio 1.  The reason so many EMI 1515 are not working and being sold as 'spares and repair' is because these amplifiers were made for EMI's 15 watt speakers like their 8 ohm 350 where the volume would always be low down.  Unlike the A&R 60 and Spendor D40, there's no rugged heat-sink at the rear to ensure staying power with the hard to power 1970s BBC loudspeakers.  The DIN plugs - that were better for sound quality than many other types back then were for very low power, B&O used them, the original QUAD 405 and the Metro Sound ST20 (2 x 10 watts) left.  The wood wrap on the A&R 60 was to give better sound quality than a steel case and the EMI 1515 will offer good service with the EMI 350 and Keesonic Kubs at moderate power, as claimed superb with Keesonic speakers but no sellers of the 1515 etc ever offer a 'lid off' view, describing the interior as unimpressive.  The Metro Sound does sport an expensive style of control knob unlikely to be found on an inferior amplifier.  The inside of an A&R 60 does look 'unimpressive' particularly if we don't know about a fiber glass board etc and early British Solid State amplifiers have elderly Solid State circuit designs - sounding far better than they look, only EMI built Solid State, 'suffers' from silver solder, making repairs expensive or difficult but vastly improving sound quality and solder life.  The 1515 should be treated as a serious amplifier for EMI and Keesonic speakers but not one to rebuild, since amplifiers of this kind were wide tolerance and modern technicians would need to do a meter test in trial and error of many components, identical in appearance and specifications - a task few would attempt.  Often rebuilt tube equipment suffers from tolerance mismatched components, stemming from supposedly 'higher specification' parts being substituted instead.  Unfortunately tube/ valve radio is different from Solid State as their circuit stages are combined in more advanced designs with deceptively few but real critical component values.  So the best rebuild tube valve sets have the most components and are actually the cheapest designs, it's just that the many components of the cheap design has fewer electrical tasks on each component.  So replacing even one component in wide tolerance advanced sets is not recommended, a specialist 'large component' engineer must to do all the work.  <<<Left and below, the EMI 600 amplifier is certainly strange as it appears to be the first Hi-Fi amplifier to use toroidal transformers and in octagonal pots, apparently of cast aluminum to eliminate all 'E.M.I.' - electromagnetic interference.  The 600 used the 556 preamplifier bearing the Royal Household coat of arms.  The specification of the 600 amplifier was not particularly impressive but 10Hz-30KHz +/- 0.5dB, 30 watts per channel continuous, 0.1% T.H.D. and 80dB S/N ratio.  Most round transformers appeared after the late 1970s when many thought a British company called I.L.P. had claimed to have invented them!  The early 1960s 600 amplifier wasn't more widely copied.  The Solid State rectifier may be seen point to point soldered to the new small replacement smoothing cans.  In being confined to an entirely separate elite world, it's possible that nobody else saw an EMI 600, pictures of them weren't reproduced in publications patronized by the general public.  Note the cathode ray tube in the <<<556 is from EMI military origin and the round transformer in its octagonal can was probably called, Ex-W.D. or former War Department.  The eight sides on the irons probably relate to the Illuminati symbol of perfection that is 8 or infinity and real esoteric know how.

Möchten Sie Ihr Wissen weitergeben? Erstellen Sie Ihren eigenen Ratgeber… Verfassen Sie einen Ratgeber