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Nightingale, Italian Transmission Line, KEF woofer, Peerless mid and Isophon tweeter.
...Anglo-American company produced the now legendary IMF Monitor.[4] In 1975 the English and US
divisions of IMF were split, the trademark FRIED thenceforth seen on all
of Bud's items. New designs were based upon the same principles that
created the IMF
Monitor in addition to better know-how as it became available. FRIED
benchmarks include the Model H System, Model M (1977), the SUPER
Monitor, and B satellite series (1976 to 1979). Left a Canadian, Calgary Oil State Radford Studio S90, Export T-Line. "Bud Fried was
advised by Decca to look into transmission lines and sent him to Radford who were
working on them. 'Bud' intended to import them to the US but Year after year Radford postponed production. One year Bud announced the transmission
line speakers after Radford promised to deliver - they didn't so with John Wright plum decided they'd no choice but to up and produce their own. A KEF Concerto kit was built into a transmission line with more
work on drivers and x-over, that evolved into the original IMF Monitor."
Below mass-market TDL T-Line... ...speakers retain the deep gloss and weight of early, elite designs but differ from EMI in a relatively poor Frequency Response. To get an audition of these 1989 speakers in a store, required the showing of something like a Harrods Gold card, the seller looking for creditworthiness. Note the parquet flooring and reflected posh circular wooden foot of a long sofa. Mass market speakers like this TDL are about a powerful leading-edge giving an exciting bite. 3D sound of 1960s EMI and similar 1970s Japanese speakers beggars belief, their very accurate Frequency Response at low input power is today favored by Bruce C. Edgar. The powerful speakers right suited the younger buyer of their day. A white arc is seen in both drivers due to over-excursion from beat music driven by some very capable powerhouse like a Threshold or Citation XX.
Mass market speakers have available cores where vintage don't. Replacing EMI with similar cores
would prove impossible. a.png)
Left, a curious picture shows a QED British Shoe-box amplifier atop a 1969 year upper middle class Radford FMT3 tuner and matching amplifier from a record collector's estate sale. The QED amplifier was one of the most tuneful of the 1980s shoe-boxes as from a 1960s speaker cable maker of famous 49 and 79-strand, so widely faked that QED took the unusual step of advising buyers they'd only ever see brown sleeved genuine QED but they'd later made a white sleeve just like the fakes, old QED speaker cable is a good online auction buy. The photo suggests the shoe-box was preferred to the Radford amplifier set. A look inside the QED shoe-box reveals a high standard of components. Below, Monitor Audio MA7, Cambridge University buyers..jpg)
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Left, the 4075 woofer grey rubber on the rear betrays that EMI spray painted the cone and later roll surround and to be the Keesonic Elf Major woofer's black basket. What of differences between the 2875 and 4075? The mid/woofer appears to have a shorter excursion not as deep in tone and the roughened tweeter baffle that some refurbishing tinkers have mistakenly painted, accidentally destroying anti-reflective properties, has to be unvarnished again to restore its 3D sound stage effect. Below the curious MA7 ferrous core inductors in the x-over are hard-wired but simply screwed to the cabinet with no damping foam underneath. Capacitors are a solid EMI type.
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>>What does the lack of damping foam under the x-over tell us about the MA7 engineers? Well, it may be that the components used hadn't been affected by vibrations and it may mean that sound could be improved using a foam underlay but Wharfedale used a thicker, tougher foam for x-over underlay, than simply being screwed into acoustic wadding. It was more like Hornby Model railroad track underlay..jpg)
<<RS was a U.K. electronics supplier from before the internet that sent out catalogs to engineers. Their six and a half inch twin cone speaker has a gap flux of 7500 gauss aimed at amplifiers of 10 watts R.M.S, of 33,000 Maxwells and brown paper voice coil former diameter of 1 inch. Free Air Reasonance is 60Hz, F.R.: 70Hz-16KHz. Impedance at 400Hz is 8-ohms. The black roll surround likely comes from an early inability to make it in a color other than grey but may indicate a faster cone reaction speed or voice. The Omar Skinner mid/woofer version below likely gives a slightly deeper note nearer 50Hz but needs a tweeter and x-over. These EMI 6.5 inch full range single cone fetch US$176 each (at auction) used as desk studio monitors, presumably by British elite 'New Venetians'.
<<Rare possibly unique, 1974 year Omar Skinner Model 'S' a cut down basket (as below for cabinet volume), not circular as above, late production black roll surround with ubiquitous Peerless MT20 AlNiCo paper cone tweeter, aimed at Bang & Olufsen's germanium or ECL 85 output tube receivers, infinite baffle, no port or hard dome tweeter Omar, a lower middle class market pitch, baffle of low density chipboard not in the same bracket as EMI Sirocco but a surplus source EMI mid-woofer. The early 1970s British Empire EMI was thought world's best tape recording company, ahead of Philips and Revox, their surplus drivers capable of splendid results, but vintage Studer design full range speakers were better known and so as highly prized in the USA, although today less vaunted.
Left, full range version of the above mid-woofer? a cut-down 6.5 inch long excursion full range of 70Hz-15KHz F.R., an old world squawker using a compact ceramic magnet, such squawkers once sported huge, heavy AlNiCo magnet motors, dual purpose sellers as squawkers or mid/woofers but the argument raged compromised in either role, prices in the late 1970s therefore very reasonable, today just never seen, if they were to appear on an auction site, prices commanded would start very high, based on appearances but getting speakers to perform as intended by original designers is a different story, germanium more difficult for constructors than simple tubes, depending on Output Transformers. EMI speakers of the 14A series occupy the later part of the 1960s High Fidelity Audio scene, exclusive to the British upper class. Some passed to Bowers & Wilkins, B&W.
We might wonder today what all the fuss was about. It was the future in Audio, long excursion and hard dome tweeters, ten years before mass-market designs of cheap and profitable manufacturing. A space saving speaker capable of low frequencies using the relatively new long excursion woofer, voice coil travel optimized in the gap flux by a British Empire military research company, EMI that would deliver the goods. The later tweeter dome baffle is rough to prevent reflections, the earlier versions left were smooth.
Irving 'Bud' Fried attended Harvard University,[2] meeting Professors Hunt and Pierce who, under a Western Electric research grant, conducted monumental research into high fidelity phono reproduction.[3] 'Bud' received his undergraduate degree from Harvard University, thereafter serving as an officer in the US Navy during World War II. Among his assignments, he'd posted as liaison officer to the Free French Air Force and after the war attended and graduated from Harvard Law School.
Left a TDL woofer version of the KEF B139 in the later IMF Reference Mk.VII has a paper cone.
Based on the advice of Victor Brociner, co-founder of the
Philharmonic Radio Co., Bud became official importer of Lowther
corner horns, creations of P.G.A.H. Voight.[4] A year later, he'd expanded offerings and began importing the revolutionary Quad electrostatic, the ESL-57.
EMI 630 right, in a unique photo of a T-slot design RadioShack called a Transmission Line in their Optimus T-70 using a 30-watt REALISTIC STA-111 receiver, with two SANYO STK modules for slimline looks and before harman/kardon led the preference for discrete circuitry. Technics used them in the A900S Reference as late as 1995, a celebrated, albeit tongue-in-cheek elite styled controller/ power amplifier set.
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Below mass-market TDL T-Line... ...speakers retain the deep gloss and weight of early, elite designs but differ from EMI in a relatively poor Frequency Response. To get an audition of these 1989 speakers in a store, required the showing of something like a Harrods Gold card, the seller looking for creditworthiness. Note the parquet flooring and reflected posh circular wooden foot of a long sofa. Mass market speakers like this TDL are about a powerful leading-edge giving an exciting bite. 3D sound of 1960s EMI and similar 1970s Japanese speakers beggars belief, their very accurate Frequency Response at low input power is today favored by Bruce C. Edgar. The powerful speakers right suited the younger buyer of their day. A white arc is seen in both drivers due to over-excursion from beat music driven by some very capable powerhouse like a Threshold or Citation XX.
Mass market speakers have available cores where vintage don't. Replacing EMI with similar cores
would prove impossible. a.png)
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Right, a black surround EMI 4075 version woofer of the early grey roll surround, late 1960s 2875 in the Cambridge University elite community speaker called the EMI Sirocco, of Limited Production, not known to the lower society, named after a 62mph yachting wind. The seldom seen semi-spherical dome EMI 14A/1720 tweeter is thought to be clear plastic with the suspension visible on the rear, a hard dome in the late 1960s, nearly a decade before the upper peasantry Wharfedale Glendale XP2. Surplus 14A/1720 was used in the Monitor Audio MA7 from 1977 with the far eastern imported Essex own brand woofer that proved disappointing compared to the long excursion, EMI 2875, elite only model from the old Cambridge-based factory.
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Right although the Polydax HD100D25A is very similar to the EMI 14A/1720A, and known in England as a KEF SP1068, it's an Audax and downmarket version, that is, not an elite EMI. The reason for the asbestos resin on the rear of the EMI above as compared to the cheaper steel baffle in the Polydax, likely has a price impact on sound quality. Odd Frequency Response in the MA7 14A/1720 tweeter is similar to the rare Rank Domus.
Above, a 1975 year Audax HD17 B25 bears a white cone surround and is found in the IMF Compact 2. <<Australian Richard Allan RA-82 with HP8B low-frequency speaker very similar to the IMF Compact 2. Fane was by repute connected with Richard Allan and the similarity in build suggests a common origin although these woofer baskets look Richard Allan the Bextrene cones and surround is atypical. Richard Allan built Transmission Line speakers with KEF units including the B139 woofer. The DT20 dome tweeter appears to be a Rank Organization, Rola-Celestion that would explain the same 1975 year Celestion 'UL series' cones of this appearance. Richard Allan Minette was a 1960s Hi-Fi mini monitor before the mass-market LS3/5A (that had only 80Hz in low frequency as had the Rola UL6). UL8 had 70Hz, +/- 3dB.
Rogers LS3/5A near right is a lower social class speaker developed from the KEF BBC LS3/5 far right. Although KEF made early LS3/5A woofers, most are from the Far East. The IMF Compact 2 right above better resemble BBC LS3/5.
In Leak speakers, the cloth edge appears left and rubber edge right. The cloth edge on the black baffle is later with a Leak 250, the older Leak 200 tweeter>> these alnico purple tweeters are 90dB SPL replacing Wharfedale Melton.
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>>an Alnico motor of a DECCA purple tweeter below from Rank-Leak Sandwich speakers of the tube amplifier age, needing best sensitivity (SPL) its alnico motor carried on by maker Joe Ackroyd in his early Royd speakers after DECCA were sold to Racal nautical radar systems, DECCA lending air support during the Vietnam War via U.S.A.F systems from the former British imperialist Empire military machinery.
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<<Note the white foam damping glued behind the diaphragm and carried on to the 8-ohm version below.
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...no fixing lugs resembling the IMF Compact 2 Audax. Origin of the cast basket on these isn't Celestion or Leak, the cones may be 'sandwich speakers' with a paper finish unlike the later plastic coned Rank Celestion UL6 and 8. The flat edge LTP rubber surround may not have suited most mass-market amplifiers at the time.
Victorian British gentry marble fireplace, the one below, being the modern mass-market equivalent. An ordinary fireplace.
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Mitsubishi is popular in the United States, their Music Centres right styled like SONY HMK77B are mostly unknown.
Left news reached England that IMF was making this special STUDIO model for export to the United States. Demand for something similar in the United Kingdom led to a lesser mockup model with no KEF-style external crossover and a cutout where it had been! Down-home England's 'Export STUDIO Monitor' as seen below. Frequency Response seems very jagged compared with 1960s EMI and so may not be a later fiber-glass cone EMI squawker albeit pictured in the lab test and seen in the IMF TLS50 down the page, it just might be a 'smooth cone' ELAC! A split baffle STUDIO cabinet limits the bass to suit 25-60 watt Hi-Fi tube amplifiers as Output Transformers had a bass problem. Not elite only EMI but mass-market, using a special version of an ordinary KEF bass unit - the speaker is a compact version of the IMF TLS80 with polystyrene coned B139.IMF 8/28BR ELAC LF & MF. MSP IMF 6/30R
IMF was multinational and the amusing lower social classes 'Export Studio Monitor' is what lower England got. Smooth cone ELAC right is a foam edge squawker, not the original rough coned ELAC copy (of the fiberglass doped coned EMI left) - a copy rated 'utterly astonishing' by listeners but impossible to obtain secondhand or new as elite only. The Studio model split baffle cut low frequencies as powered at... 
...only 25 tube watts, with no F.R. peaks, unlike the above plot. Later IMF TLS50 right below has a long baffle for Solid State amplifiers with low frequencies.
and simulated tube sound built to follow the Criterion LA-280. Mitsubishi, Lo-D above, and SONY below are tube sound with deep bass. The best known simulated tube sound Solid State amplifier is the British QUAD 303 in many versions aimed at reducing prices. Later QUAD 303 help Japanese competition. SONY V-FET TA-N7 below is unreliable needing totally rebuilt. Hitachi's Lo-D and Mitsubishi are better but expensive and less known. TLS50 still has the EMI squawker and doesn't use much power. Lo-D HS-1400WA has the small baffle of the IMF Studio with alnico magnet squawker similar to Criterion 3X up page, Allied had a Lo-D relationship. Hidden inside is a ceramic magnet woofer with grey paper pleated edge stuck on, for low Damping Factor.
Left Australian IMF TLS50 with MSP's Dutch IMF market version of the old, London based Tannoy girdacoustic cone woofer (Manufacturer's Special Products, Marconi-Telefunken, AWA) on a veneered 'long baffle'. A British Rank Rola Celestion tweeter and British ELAC squawker. Robert William Ludovic Lindsay OBE (18 August 1905 – 6 September 2000) English-born Australian politician. From Norwich, England, educated at Eton College and Royal Military College, Sandhurst. An officer of the British Grenadier Guards, fluently spoke Arabic, stationed throughout Persia from 1925–37 with the Transjordan Frontier Force, regimented nearly 2000 enlisted Nepalese Gurkha Troops. In 1939–52, part of Whitehall Defences. In 1954 elected to the Australian House of Representatives. The Liberal member for Flinders, until 1966. Order of the British Empire 1971.
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Right OEM 35Hz Peerless foam edge woofer with its own squawker and no glass fiber plastic covering. The strange foam edge is a flat type, not the slightly older and more sound distorting roll style. Danes used clamps but IMF screwed through the foam. The Peerless foam edge, squawker is also seen as the 'pistonic edge' flat foam type developed by the elite Bakers Selhurst company near London and seen in the 1950s as adopted by Gilbert Briggs of old, lower-middle-class Wharfedale. Replacing with a 'roll' edge above probably suits less capable equipment.
Left, a re-foamed doped Peerless woofer in an IMF Studio (the short baffle reduced low frequencies that drained tube amplifier power). EMI squawker, KEF T-15, and black- painted baffle Coles Super-Tweeter. 
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Right, the Hafler DH-220 was built as a kit by the lower peasantry and appears in a number of curious ... home built ... inside finishes that nevertheless resemble the Crimson Elektrik or QUAD 405 only with a bigger heat-sink and is a wide-band, 6-60000Hz with 120 watts, around twice the power of the Crimson and slightly more powerful than a 405 but lacking its 'Class A' stage. Basically without looking too deep into circuitry the Hafler has more space for a higher current power supply and many of these 1970s Hi-Fi amplifiers could have more power if more current was available in a beefier power supply. The Hafler was popular in the US and in Britain but like some kit amplifiers it didn't flatter lower quality inputs used by lower income buyers and was more of a kit builder's area of interest. The Hafler amplifiers had serious credibility back in their day but enjoy more of a cult following.
HAMLET.
Ah, ha! — Come, some music! Come, the recorders! —
For if the king like not the comedy,
Why then, belike he likes it not...
Right IMF ALS40Mk.2
with ELAC version of EMI squawker and SABA basket LTP edge woofer of unknown origin. The tweeter is an original Audax HD 12 x 8 D25 that gives it's oft-seen square felt strip border detail to the Rogers LS3/5A,
different dome finishes imply quality issues. It's interesting the
German SABA basket fits into the KEF cutout, as elite only versions might use the same cabinets. Below Rola Celestion made British IMF Super Compact II with ELAC squawkers. The model on the left is earlier vintage and higher in social class than that on the right. A 'white belly' (from the doped center), KEF woofer is difficult to date without removing some are more recent.
TC Smout, "the No.1 most snobbish university".
<<Early 1970s Celestion made British IMF Super Compact with original fiberglass cone EMI squawker and Peerless tweeter. 'White belly' KEF woofer doesn't quite fit the cutout, suggesting a
SABA woofer may fit. Below, the Isophon KK10 used with no mid range driver in the Orchester 2000 12 inch woofer that H.C. Bennet-Clark B.Sc, Ph.D (Oxford Univ., England) gives in his 1969 year Practical Wireless article Pg.98 as flat to 800Hz and in the article is working with improving bass resonance frequency in the university's early 1950s Goodmans 12 inch speakers by improving the cone surround material and so maximum permissible excursion.
TC Smout, "the No.1 most snobbish university".
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It seems likely that the SCW is the Super Compact coming before the Super Compact II bringing the Bextrene unit and what IMF described as an in-line x-over network developed as a no compromise filter for the KEF bass unit, although the original SCW had bass to 25Hz and sold very well, the x-over doesn't look no compromise nor does the baffle thickness. Peerless woofers in the original were a special design not readily available as an off-the-shelf replacement and this probably gives the SCW its appeal. Below Fried Model speakers used Series XOs, apparently no mystery but in truth, x-overs are very difficult for mere mortals.
Left an elite only BBC Lockwood enclosure for the EMI 550 Merciless speaker system.
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Two plastic ducts above weren't of the usual 1980s Helmholtz resonator by DuKane in the 1960s but an elite only system operating below audibility to prevent 'closed-in' sound in amplifier mismatching. Marketed by IMF in the United States as their Styrene Pressure Loudspeaker based on research by Lectronics and Rola Celestion, subsequently, Rola made IMF Super Compact in England. Although a problem with Leak and other vintage Styrene speakers is poor efficiency, the EMI 14A series didn't give better and increased amplifier power was needed. Reduced size of speakers gave wider domestic appeal.
In an early elite version Celestion 15 speaker left aimed at the QUAD II, note a thick, bare plywood baffle and foam that the elite only EMI duct system sought to avoid. Early Celestion 120 and later 'Ditton 15 Studio' aimed at the upper-middle class. So many versions of Ditton 15 exist, this one serial number 4812, later versions reduce the cost of materials and improve sound with lower-cost equipment. Black baffle Ditton 15 aims at the lower-middle-class buyer with final working-class Ditton 15 XR in a wooden veneered baffle to persuade those swayed by looks. Made by Rank with steel basket mass-market drivers and a mesh-covered dome tweeter, they have many friends, early Ditton need pricier equipment.
The lower-middle-class Celestion UL8 below and working-class SP15. 15XR right has rare HF1001, replaced by KEF1068/ Audax HD100D25.
These polystyrene auxiliary bass radiator speakers made by Rola of the United States were all the rage in the 1970s and widely adopted by leading manufacturers like B&W and Revox. However, they don't make a 3D sound heard from all sides. The Home Theater system 7.1 etc places satellite speakers around the ceilings of rooms to obtain effects nearer the 3D of only two EMI speakers in stereo. Goodmans Magnum K has a very level Frequency Response but the smaller diameter woofer is faster with a punchy quality. Magister had a 15-inch woofer and Mezzo a ten-inch. The larger diameter is about 'feeling the bass' even with a baffle cut-off frequency meaning we don't actually hear below it.
Above the problem with this polystyrene, woofer speakers compared to EMI may be seen in their Frequency Response plots, the upmarket IMF version above. This is why they don't have a 3D sound and helps explain the rise in popularity of the stereographic equalizers below. In the lower-middle-class black baffle Ditton, 15 left is seen the BBC ring radiator tweeter that's very accurate but extends to only 15KHz. Listening to, recording and playing back FM stereo broadcasts the black baffle Ditton 15 was used by the upper peasantry aimed at powerful Japanese Solid State amplifiers as were Tannoy HPD385 of that time and later made in Scotland when sensitivity increased to 94dB but had only 22Hz F.R. 
Below left British BBC Atkinson TL Studio Monitor with time aligned KEF T-27 tweeter and right a lesser, mass-market
equivalent doing without wide dispersion twin Rola HF 1300. The flat
KEF B139 driver originally a cheaper to make a version of EMI elliptical speakers used polystyrene and downmarket amplifiers with a 4-8 ohm load capability, dropping to 2 ohms on peaks. 
Below left Ferrograph S1 and brown KEF MK.2 6171 version of B139 differs markedly from an SP1082 BD138B KEF basket in the Lentek speaker below. Many different versions are not interchangeable as in the Model T Ford days. Bargain demon internet reviewers write:"...and I never heard a good Goodmans dome tweeter..."
Left a number of such dome versions, heavy Axtent 100 and lightweight, plastic-bodied clones, great with EL34, awful even with 'tube sound' Solid State like QUAD 405-2.
Right, Lentek branded Transmission Line based on the US Fried Model R, some red stuffing appealed to Australians and not in the UK model. Rank Celestion's take on a Coles super-tweeter and KEF designed mass-market drivers were likely shipped from a far eastern source, in the 1960s made briefly by KEF in the UK. The matching Lentek amplifier was middle class, mass market, an average 60 watt styled after British 'shoebox' items of the 1980s -such as the NAIM below with loud hum in the speakers, a whine in its mains transformer, hum noisy mains power wires led physically around and over-sensitive input switches. NAIM was advertised - even in the US as 'the best buy in Hi-Fi', audition of 'British shoebox' amplifiers had salespeople knowing no better, the loud hum from speakers vanished when music played but smoothing cans mounted on the rectifier module board below are the cheapest of designs.
Below the harman/kardon 730 shows the 1977 year idea of power cans on a small circuit board separate from the output board. The reason NAIM above is thought better is due to a mismatch of speaker vintage. 730 have both channels on a single heat-sink as in the NAIM above were bolted to the metal case in British tradition rather than a pricey aluminum heat-sink.
Right when the Akai SW-180 appeared it had an American style cloth edge and not the white rubber one of an elite only, L.T.P. edge EMI it had been advertised with. Below a bare chipboard baffle Ditton 15 aimed at valve amplifiers, makes do with mass-market Solid State instead, the sound not very good but with more expensive equipment would have a much better result.
Left, EMI 300 C and T had the 300 tube rectifier woofer capable of 10Hz lowest note. The 315, 14A/780 above was the Solid State rectifier version, aimed at a special version of a color TV line scan tube known as the PL509. The Audio version tube is out there but only bespoke dealers could have identified it. The 315 speaker cabinet was very large with an effortless, low note very useful for beat dance music. No Disco speaker could compete.
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