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Left, Crimson Elektrik grew out of DECCA in the early 1970s arriving in time to compete with the very similar QUAD 405, Crimson was a marketing move omitting the 405's RCA 'Class A' stage, giving just the 405's more powerful Toshiba device 'Class AB' output and using similar speakers by Castle and Spendor.  Crimson is of the 'British Shoe Box' build style fashioned after older Californian minimalist build amplifiers but at a low price aimed at downmarket speakers.  The later QUAD 405-2 doesn't use Toshiba devices but RCA, wholly designed to match the new custom fit Spendor SP 1, although used by Bargain Demons with many other offers. 

Right, Boothroyd-Stuart or Meridian is another British Shoe Box styled amplifier like Crimson above and competing with Technics below for a British lower middle class following.  Early Meridian used a shallow depth active speaker visually resembling a REALISTIC Optimus-27, none such specialist brands ever acknowledging the substantial value of Tandy or Radio Shack products.  A look at drivers in Meridian's active speaker and inner electronics suggest they're cobbled-together using more expensive components than Radio Shack was allowed, so giving an audibly improved performance albeit at much higher retail prices. 

Right, and above Technics new class A, the 1980 year SU-V8 that was very similar in construction to the 1982 SU-Z2 but with one potted power iron for each stereo channel.  The thing that no seller ever understood was the difference between old Class A of the Single-Ended tube era and the new Technics system designed to reduce x-over distortion in the Output Stage.

Left and below, the  NEC  Active Drive is a similar system with smoothing filter cans mounted on the power output board between the stereo heat-sinks, Aurex Clean Drive and Yamaha Natural Sound, were others.

Right the Single-Ended, Class A, EMI Model 544 below from the mid-1960s was only bought by the British Elite but had found its way into University Physics lectures where the principle of mounting transformers at right angles was actually believed to cancel some of the usual hum found in Hi-Fi amplifiers.  The 544 amplifier had used the tube rectifier EZ81.

Left, 2-way speakers for Single-Ended low power like the Model 544, a three port drone in a Live plywood baffle.  Tweeters are Al-Ni-Co Plessey, often viewed as the best available and the full-range speakers are Goodmans Al-Ni-Co, generally viewed as 2 watt and need run as the 'Class A' Single-Ended volume allows, very loud with well under 1 watt.

Right, the 4 + 4 watts of the Model 544 was aimed at Al-Ni-Co motor speakers consisting of a single driver and no tweeter.  The Grundig gold foil tweeter seen in many British Single-Ended speakers doesn't need any x-over, capacitor nor overwind and therefore compliments the zero x-over distortion of the very hot single output tube.  In the 1950s the British Elite feared that a QUAD II couldn't be Hi-Fi because it wasn't 'Class A' and EMI speakers meant for 'Class B biased for Class A' were dubbed Lo-Fi and did a very good job of coping with 'push-pull amplifiers' with severe x-over distortion.
 

Right the EMI 95130 series is one the best EMI Single-Ended speakers from the 1950s and is here fitted with what is sometimes called a network-free tweeter using a solid die-electric capacitor.  However few vintage Single-Ended amplifiers will work well with such an arrangement and it is aimed at a more expensive higher Damping Factor design.  The lowest Damping Factor Single-Ended tube amplifiers need certain ancient speakers to sound good.  Cones with a whizzer are 1960s vintage and triple or twin single cone types like Baker's Selhurst are 1950s.

 

Left, a Single-Ended Tripletone with the 5AR4 tube rectifier powering the controller and power stage, separate controller amplifier has two quality Output Transformers but the brand had its own whizzer-coned speakers suggesting low Damping Factor that wouldn't use a tweeter as above.  Below the Al-Ni-Co motor Single-Ended loudspeaker aperture is cut slightly above the center of a large sounding board baffle, no tweeter or woofer.

Right, Al-Ni-Co motor loudspeaker of 8 x 5 inch size meant for 'Live Box' cabinets popular in the mid-1960s as large televisions, and in particular portable record players with an opening lid, so ingenious by artifice that few amateur carpenters could create their like. Below in the video the Japanese are seen to reuse old cardboard from boxes for easy-buit 'Live boxes' the speaker sides make a hum, others use thin 6MM ply or chipboard.

Right, US CTS elliptical loudspeaker mounted on a hardboard baffle for the necessary 'Live Box' humming accompaniment with speakers engineered for television sets, or portable record and reel to reel players but used in early box-type enclosures.  Mouse Click on image.  Magnavox tube amplifiers were often reused by enthusiasts in the US, London and Australia, the sound of these and early Solid State needing matching speaker systems of dead or alive enclosure type won't sound best with the wrong choices.  When choosing a Magnavox console amplifier, try to check how original speakers are housed, taking care to keep any dispersion devices seen.

Right, Magnavox branded CTS ported reflex 2-way speaker with Al-Ni-Co magnet system needs an amplifier of good sound without acoustic batting and simple network-free capacitor.  Modern amplifiers used will lack in low frequencies whilst the best vintage amplifier match appear better than any modern amplifiers with their ideal speakers!  Low amplifier Damping Factor works best with these and adding wadding won't help.  Amplifier or receiver has vintage high quality low power sold in the 1960s and in their day, very expensive.  Sellers often describe ideal amplifiers as surprisingly defined and powerful at low volume, speakers more efficient then.

Left, Infinite Baffle CTS speaker has wadding to mute back waves and needs tubby or powerful low frequencies from amplifiers.  1960s designers used a more efficient woofer and we see the larger magnet cup with a cast basket.  But modern I.B. speakers need more power and also, amplifiers intended to work with them.  Twin tweeters used to widen dispersion before dome tweeters were invented or wide-dispersion tweeters were cheaply available.  Some old tube or Single-Ended amplifiers don't work well with tweeters as the crossover distortion is more obvious and have single-point-source drivers instead.

Above, the most fabulous type of Single-Ended EL84 stereo amplifier uses an Al-Ni-Co speaker that differs markedly from the one built for the UL, or PL designation tubes.  Some such receivers on an asbestos resin, 'pcb' or printed circuit board base are good enough but a chassis is even better.  The EL84 tube loudspeaker seen left differs from the UL84 construction below.  The Al-Ni-Co motor and voice coil diameter are smaller suggesting that EL84 had less power.

 Right, a Mullard Stereo 44 from the year 1958 is a 3 - 3 design for A.M. radio, Frequency Response is 200Hz-4KHz and power from EL 84 is 4 watts per channel, Single-Ended.

EL84 in its application not only had less power but used the rectifier EZ81 as seen in the chassis above.  The UL84 tube has a much better circuit for Single-Ended operation with a cleaner power stage using UY85 for less switching noise.  The voice coil diameter is halved in size as EZ81 is supplying two channels.  Home constructors will be able to build their own Single-Ended equipment using two UY85 tubes and no chassis power iron, the above chassis one has elsewhere.

Left, a battery operated Technics controller sought to eliminate power supply switching noise from the early stages, amplifying up a purer signal source, and now very pricey in used auctions.

Right and below, Dynatron radiogram power amplifier with Single-Ended KT66 of the metal envelope type used during WWII as a radio Beam transmission tube.  Rare and used today with Single-End loudspeakers like the hand-made EMI 95130, very delicate loudspeakers compared to modern items.  With modern amplifiers 95130 sound quiet and very dated but need correct vintage equipment.

Left, EMI 97542 is a smaller size of Al-Ni-Co motor loudspeaker for Single-Ended EL84 and used in stereo radiograms on smaller baffles.  Such speakers do rather better as a small aperture cutout on a large plywood baffle and are of the 'dead box' cabinet type.  It should be noted that loudspeakers of the 'live box' Al-Ni-Co type won't sound at all better in a 'dead box'.  For many years enthusiasts struggled with the expensive Japanese High Fidelity speakers of light build wondering if they were 'Live' or 'Dead' box.  -Well, if we stiffen the box of a 'Live' type it'll sound inferior compared to what it had been.  Many 1980s Japanese speakers of light build improve if their 'Live' boxes are deadened.  It depends on the drivers used.

Right, 97542 above the 95130 make astounding Single-Ended loudspeakers using A.M. radio amplifiers like Mullard Stereo 44 up page and Heathkit S-33 down page, producing a low drum note heard outside the house if high volume is applied but need heavy plywood not the lighter blockboard for the enclosure and baffle.
 

Right, British Dynatron elite stereo amplifier with Single-Ended N78, the Marconi Osram Valve (M.O.V.) small envelope tube similar to EL84 but reckoned to be superior in Single-Ended use.  It was hardly more powerful, higher in distortion but for some reason, and possibly snobbery, highly valued by the British and American upper class.

Left, American stereo V.O.M., Voice Of Music Single-Ended amplifier with virtually no capacitors is seen below and this gives a superior tone that is it fills the room with detailed sound.   Like the N78, the tubes are Beams, very hot but the Output Irons are larger than the Dynatron hidden beneath the chassis.

Below, the Air Motion Transformer (AMT) horn driven by a type of electroacoustic transducer as invented by noted physicist and scientist Dr. Oskar Heil (1908–1994).  These were elite CerwinVega speakers designed by Gene Czerwinski and used with single-ended triode tube amplifiers, note the dated narrow dispersion, rear baffle mounting.  Little was shared about Cerwin Vega speakers back in the day, they were a well kept secret and from a similar market to Tannoy Dual Concentric, presumably upper-class.  After the year 1990, the brand was seen as Home Disco or domestic Karaoke but they were a mystery.

Left, Heathkit of England (funded by the United States) S33, was a Single-Ended Mullard 3-3 that has a 33H version for the red-bodied ElectroVoice brand, High Output crystal pickup.  Use Goodmans Al-Ni-Co, 3 or 15 ohm, ten inch, or 10 x 6 Single-Ended loudspeaker and replace circuit elements.

Above, Tannoy Buckingham used push-pull LEAK Stereo 20 with 1940s Jazz above, until in 1985 sold in Brixton, London, for reggae music with the black MARANTZ PM 94 right in "Quarter A" operation, a term denoting pure Class A until power output was nearly a quarter of its rated value.

 Right, the 1985 year Marantz LS-17A for original black finish PM94 above was banned in many cities as antisocial, the most notorious domestic neighbor and street disturbing speakers of their day and related to the similar LS-20A about which little is known as so rare.  'Banned speakers' were listed by local government and seized by authorities at loud home disco events.  The in-car entertainment sub-woofer let the effects travel around neighborhoods in the early-1990s.  The PM-94 had been used instead with Tannoy, the PM-84 with Wharfedale Efficiency Series, E-70 and E90, that went quite loud in large city rooms.

Left, 1980 year Technics SU-V2A 'New Class A' amplifier system came before Sansui's SUPERCOMPO of 1981 and dates to the older 1970s Technics era when their rack systems were most expensive in lists.  The SU-Z2 (10Hz-50KHz F.R.) system and SU-V2 (5Hz-100KHz) are wide-band amplifiers and unusually the speakers used with both were the competent SB-3050 below of 42Hz-20KHz and 89.5 S.P.L. at 1 watt and 1 meter.

These Technics brand wide-band amplifiers are very good for listening at low levels when suitably rebuilt.  The SB-3050 offers an affordable match but wasn't available in all markets and the Lo-D Hitachi sourced RadioShack REALISTIC Optimus X-100 is recommended, capable of a deep low frequency extension without Loudness and tone knobs at flat, it also gives a remarkable sound stage.  Below the Technics SU-V1 was a 35 watt discrete output version of the SU-V2 both made in only one model year (1980) with a hefty black anodized aluminum finned heat-sink, to the steel of the hybrid output SU-Z2 that uses the SL-D1 turntable and later, an LED tuning meter resembling the radio tuner above.

'Real' upmarket Technics SU-8088 were rack systems, factory made to work as a one brand system and downmarket hybrid amplifier sets like the one left weren't sold separately for that reason, until the Sansui SUPERCOMPO of 1981.  SU-Z Technics amplifiers work today with other speakers although in the hybrid Sansui A-710 below, the original speakers sourced in auctions and tricked-out, are better than similarly specified aftermarket replacements.

Right, High Sensitivity Series Technics SB-440, for the SU-Z2, a better match than SB-3050 albeit style or catalog placement, back in those far distant days, hadn't seduced many buyers, before even hearing its hefty price tag, it looked more like a plastic, portable ghetto blaster speaker, albeit a 10 inch woofer and a larger box for the lucky few able to accommodate it, 93db SPL won't disappoint with wide-band SU-V2, SU-Z2 or SU-Z1 systems.  In the 1970s Technics brand customers were superior and had mattered more, the 1990s brand became a status symbol of the working-class nobody.

Left, the 91.5 SPL 1 watt 1 meter, ten inch woofer  NEC  speaker for the A.H.S.S.T. or 'Active Drive System, A-520E amplifier, a wide-band 3-differential stage amplifier that sounded strange with the wrong speakers but better with others.  In the speaker above the tweeter is a cone type, in retrograde rear mounted fashion behind a dispersion grating, left a horn tweeter and such different speakers have effects depending on the own brand partnering amplifier, the wrong combination used to suggest the speaker was inferior where in fact, it was just the wrong choice of speaker and amplifier.  Note  NEC  speakers are rarer than hen's teeth.  Below, the Brahms Manufacturing Co. of England, a tiny ferrous motor resembles the 8 watt EMI 13 x 8.  Right below S69.75 =  $693,95 in 2022.

 

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Left, powerful Sansui, a brand mostly preferred for 1970s Rock music and below the loudspeakers that were banned in many cities but used in large, middle-class studio rooms.  These people might have been aristocracy because they had time to party and enjoy listening to music.  At 100dB for 1 watt they were Disco speakers but often had very lightweight magnet motors, some were Al-Ni-Co and the x-over at 1000Hz suggests that SP-X9700 were too.  If so the amplifiers will need Al-Ni-Co motor woofers.

Right, Sansui (San-soo-ay or in Broad Scots:  San-Syou) SP-X9700 from the year 1979, Karaoke Home Disco speakers with 100dB at 1w and 1m, 22Hz-23KHz.  8 ohms, 280 watts peak.  Grille hand carved Kumiko fretwork.  4-way, seven speaker system.  432MM woofer, x-over at 1000Hz.  208MM squawker cone, x-over at 7KHz.  2 x 171 x 59MM presence horns, x-over at 15KHz.  3 x 49MM brilliance tweeters.  Size 470 x 688 x 270MM and weigh 20Kg each.  The Brahms speaker above and Home Disco speakers from Sansui had very small magnet motors that were supported by matching electronics.  Many amateurs prefer larger magnets that however demand much more from amplifiers to sound as good.

Left, sales people in England thought Japanese speakers inferior to British ones albeit actually toned to match the sets they were sold with, the curious appearance so often sounded disappointing, maybe a little harsh and when the networks or inside of the speaker boxes were investigated, hadn't been well put together begging the question were these maybe 'Live' toned boxes, meant to have vibrating panels?  The problem was partly a lot of large apertures cut in a thin baffle weakening it so that it vibrated and poor treatment inside the cabinet when compared to similar drivers in upmarket Technics or SONY.

 Right, how about the Sansui SP-Z9II for a bookshelf speaker?  Well ... below the video proves that the loudspeaker can be made to deliver.  The hooked up receiver is a Sansui 7070 and an online check says it's not a wide-band, has 20Hz-30KHz, Damping Factor 45 and power of 65 watts per channel, 8-ohms both channels driven.  Maybe the audition speaker has been tricked out inside, strengthening, sound deadening felt, baffle strut added and other care.

Left, Sansui's 16.5 inch SP-Z9II woofer, a 6-ohm with overall impedance at 8 ohms may mean a fixed 2-ohm resistor in the network.  Looking at inside details of speakers before you buy helps asses quality and access to improve the specifications.  Below the much acclaimed Yamaha NS-1000 made by SANYO, has a self-damping baffle, a thin layer of plywood glued to the usual chipboard and yellow fiberglass loading the enclosure as seen.
 

 

Below, an EMI 319 box features a rear magnet strut that in the style of H. J. Leak, supports the rear of the speaker instead of using a front to back baffle strut in many upmarket Japanese speakers, these make the box much stronger and help the baffles stay rigid and quieter, thereby improving the clarity of reproduced program material.  The type of acoustic insulation used alters the sound available from the enclosure but at the design stage the kinds used and how to fit them is usually specified.  White fiberglass batting differs in tone from yellow, green or red.  In tricking out vintage speakers, a number of batting types are tried for the best effects.  The inside wiring of British enclosures was often twisted together to cancel audible stray field effects.

Below, a KEF Concerto supports the woofer with a small hardwood dowel instead of the large softwood one left.  Many speakers are complex on the inside whether the experimenter realizes it or not, it's better to follow a published plan than waste time in trial and error.  The KEF midrange and tweeter occupy a separately loaded enclosure and the two braces seen support acoustic wadding behind the KEF B139 flat diaphragm woofer, braces stiffened the two long side panels and rear baffle to make an acoustically 'dead box'.  KEF used a cast aluminum resonator tube on the large floor standing enclosures to prevent any spurious noise from the usual cardboard vibration.

Below, H.J. Leak's sandwich speakers with the wood blocks used as support.  The Al-Ni-Co motor on the right had been changed to ferrous on the left, here giving a British measure of relative Al-Ni-Co magnet to ceramic magnet size.  The loss of the Al-Ni-Co accompanied loss of Empire although the Empire types have descended en masse upon the British town of St Andrews where their ilk might be readily found.  There is no real sonic advantage in the Al-Ni-Co motor, they're used with Germanium and tube amplifiers for high sensitivity and need less power but successful Audio is more difficult.  The elite do seem to cling to Al-Ni-Co but their reasons are likely to do with what was traditional.  

Note the twisted wiring on the speakers to cancel audible effects in single wires was a British Radio practice, something like finding a Cheese on a yacht deck, a neatly laid single coil of rope.  The practice is seen in the US but rare.  Click on image for a better view.

 

Above the Goodmans Module 80 and right its large smoothing cans replaced with small ones similar to an early NAD 3020.  Note these solid copper wires have to be tested for heating effect with the load current or could get red hot but solid wire is tidier than stranded cable.  The smoothing caps in these wore out quick with most replaced but sound quality had kept them around.

Right, Goodmans Axiom 401, 301 and 201 were a bunch of speakers used by (what might only be described as) private school people.  The 401 was 40 watts Max at 8 ohms nominal, American or Peak and we might say it was 20 watts R.M.S. like the NAD 3020 and ... a Module 80 may very well have been used but these speakers were around money whereas the NAD brand was at least, marketed lower in society.  401 had 30Hz-12KHz and here a Trebax horn is present plus the Goodmans port device (very expensive back in the day).  Nobody ever shared what amplifiers they'd actually used with 401, 301 or 201 but they're still very popular in the United States.

 

Left, LEAK TL50/PLUS is a likely 401 amplifier, this one made after 1963 is fitted with KT88 and an even rarer 'glass shouldered envelope' 5AR4 as made by Cossor apparently to improve electron flow.  The rare silver TL50 was seen in elite possession with a solid, effortless low frequency delivery.  The idea that a pair of TL12 sound better is academic and you know uncertain. 

Right, although the elite never shared what amplifiers they'd used with Goodmans 401, it's likely that they'd tried the wide-band 15 watt QUAD II and the LEAK TL12, Point One that had Beams and not the Pentode TL 12 Plus, even although their sound is very similar.  What did the elite use with Goodmans 401?  Well ... good question.  The Damping Factor of a QUAD II is only 11 and it so happens that the 401 is a twin cone cutting out the need for a separate midrange and so not spoiling the Damping Factor.  There are a great many QUAD II sets that are available and in the improved 22 watt Dunlop Concordant rebuild, power was over the highest rating of the 401.  This is done by the ECC83 that boosts the signal and the double triode is disliked compared to ECC82, for the absolute pursuit of fidelity.  As for the particular TT or CD player chosen for this rack set, it maybe just another mystery they've taken to the grave.

Right, another Concordant rebuild by Doug Dunlop is the 30 watt Exultant QUAD II A appearing to use two triodes and two EL34 that might be replaced by KT77 for a Kinkless Tetrode sound.  We know little of the quality or stability and power seems the main guiding light in redesign, a tube rectifier is retained to help eliminate the Damping Factor problem speaker protection relay.

Right, LEAK STEREO 30 does have 30 tube watts equivalent to the Concord Exultant QUAD II A but servicing these sets isn't recommended,  there's loads of problems not least the condition of the mains transformer, that burns up if there's any grounding issue, even rebuilt, if it's not silent, don't use it, post off to refurbishing engineering services.
 

Left, before concluding solid wire linked electrolytic caps in old Module 80 receivers is a bad sign, the x-over on this Yamaha NS-1000 uses the same idea, there is some sound quality reason besides the size of a single larger capacitor why technicians do what you see but it may take amateurs many years to discover just what the reasons are.  The Goodmans x-over above uses a box as the components are pressure sensitive whereas the world acclaimed NS-1000 left, has no box.  Note the grey wadding and the photo up page with the yellow fiberglass batting added.  Note the red batting above differs from white or yellow seen left.

Right, harman/kardon Citation 19, a New York designed amplifier for ceramic magnet woofer motors seen in the 401 above right, they were made in Japan by Hitachi/Lo-D.  The harman/kardon A 402 is for Al-Ni-Co woofers in the JBL Century L100 that need to be recharged in many vintage examples.  Below, Goodmans 301 enclosure with Trebax horn and a type of 1950s batting.

   What amplifier?  Probably QUAD 303 or 50, but they'd suffered from switch-on-thump, and modern refurbished versions could have added speaker protection relays, running from your power supply, that protects your speakers but can affect sound quality, ideally some other amplifier might suit better and a LEAK STEREO 20 tube amplifier inherently protects the speaker by only allowing speakers to be powered after they've slowly warmed up.  The real problem with tube amplifiers is the lower and upper registers, needing tinkered with by adding more sensitive tweeters.  The problem with tubes is always going to be the 'quick fix' sub-woofer, this or that and ultimately causes a room full of equipment that doesn't attain perfection. 

"There has been an increasing resurgence of interest in tube amplifiers in recent times.  Most commercial high-power, Hi-Fi examples occupy a giddy altitude with prices going up to the equivalent of a house - well not a Manor House, but certainly one of the Council Housing Estate description".  Above and below United Kingdom Kit Firm Maplin in 1980 offered affordable 25 watt MOSFET amplifiers followed up by a tube amplifier below using easy-build microchip circuits.

 

 Left, EMI 92390DE, 3-ohm, smooth, shiny, lightweight cone for tubes.  8 watt, push-pull ECL86.  These are for Hi-Fi amplifiers engineered for single-point source speakers and in 1960s elite parlance referred to as 'Lo-Fi', it relates to low power and low Damping Factor and will suit some modern Class A or Single-Ended but won't suit so well you know, the Technics New Class A.

Left, EMI 92390DF, 15-ohm, 8 watt, High Quality.  15-ohm is really a tube amplifier impedance and used to be the British Hi-Fi standard impedance but for amplifiers seeming to come alive with no x-over and tweeter in your loudspeaker.  They're mainly aimed at push-pull ECL86 but a QUAD II will give an easy guide to sound quality.  EMI 92390DW

 

 

 

Left, EMI 92390DG, first of the green baskets, made at a later time than bronze baskets, EMI continued to churn out versions of the older codes but unlike the 92390FY, the DG has a long-fiber pulp paper cone like the 10 watt 450, but an 8 watt motor as a matter of two watts amounted to a vast difference in those days.

Left, EMI 92390FL, 8-ohm, smooth, shiny, lightweight cone for Solid State.  10 watt.  These as 8-ohm suggest early Solid State, and low Damping Factor, simply won't sound good with a modern amplifier output designed for complex x-overs.

Left, EMI 92390FL, 3-ohm, long fiber pulp cone for tubes.  10 watt.  Damping Factor 5 Hi-Fi amplifiers, need the stiffer surround.  Don't use your modern Damping Factor 60 amplifiers or you'll perceive a poor quality of low frequency.  Use a long baffle (pioneered by EMI in the 1950s) to enjoy deep bass but you will need a 15 watt EL84 push-pull Hi-Fi tube amplifier or QUAD II. 

Left, EMI 92390FA, 3-ohm, 10 watt.  3.2-ohm is the Japanese standard Hi-Fi impedance, even today JBL offer it in their High End.  Surprising white transparent cone version of the black Lorenz style hard PVC cone.  Curious 1965 year layered voice coil for doubling sensitivity in the small gap flux motor.  Begin with a Damping Factor 5 tube amplifier but QUAD II were used.

 

 

Left, EMI 92390FY, 8 watt, smooth cone, not Karad paper but something similar.  Tiny ceramic Magnadure II with high efficiency motor suited to Armstrong potted Output Irons with push-pull ECL86.  Note the pleated surround details hint at the best amplifier Damping Factor.

Left, EMI 92390PE, 3-ohm, 15 watt, professional series.  Belgian and British elite owned.  Very curious, scarce and difficult to obtain, might be seen as still of exclusive wealth group ownership.  The exotic burr walnut cabinets aren't broadcast on the internet.  The CROFT Series 3 is widely hailed as OTL, and below a double mono Hi-Fi germanium amplifier is OTL but not OCL these with a sound also suited...

...to their own vintage of loudspeakers, not to just any speaker hooked up because we liked its looks.   Left, EMI 92390BN have an alloy portion and paper pleated surround like the EMI 550 but use the Hard P.V.C. Al-Ni-Co motor plastic cone tweeter and 10 watt, Magnadure II ceramic magnet.  The BN is of the 550 series 13 x 8 that are very seldom seen today.  

Left, EMI 92390EH, smooth cone, 8 watt motor, 8-ohms.  Cabinet construction below of thin plywood baffle, not chipboard or blockboard.  Cabinet sides veneered plywood, back is finished.  Hard to cut aperture, Bitumen painted after a vintage elite fashion.  Pleated edge pattern suggests a germanium Solid State amplifier as the one seen above, not using a modern Damping Factor 60 amplifier
 

Left, unlike MAPLIN above CROFT were ready built commercial amplifiers used by the British elite of the independent school fraternity, the Series 4SA improving on the other '4' and '4S' models, 4SA low frequency sounds remarkably solid, not the usual woolly but fast and tuneful with satisfactory bass extension. Mid-range delivers a full and generous sound, very clear and detailed at most levels, albeit revealing a compressed quality with mild glare towards full power. The treble has a touch of `zing' and sibilance, (British words) but overall the rating was still good, strikingly well focused, wide and deep stereo images with dynamics conveyed.

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Left, British Dynatron ECL86 Output, improves upon Bang & Olufsen ECL85 and Philips MiniWatt ECL82 but Output Transformers seen might suggest otherwise.  Tarred mains iron and steel chassis cut to the bone, at the rear, a 5AR4 rectifier means business.  Tiny power output of stunning quality dubbed 'the poor man's QUAD II'.

Right, critically assembled ECL86 and with high quality Output Transformers.  Photo Picclick UK

Left, the British Empire 4 ohm EMI 92390AL cabinet is plywood unlike the U.S. DLS529X equivalent but is circa 1963 year with a cloth grille instead of the American metal one.  It was what's called a twin box, braced at the top under the tweeters, the mid/woofer occupies its own enclosure, the baffle not weakened by the tweeter apertures and so giving a deeper low frequency note.  Below, white wadding of the British 92390AL differs from yellow fiberglass in EMI DLS 529X.

Below, cabinets for the British issue of the U.S. EMI DLS 529X.  92390AL was the early double letter 13 x 8 series with a small diameter voice coil former and somewhat dated looks compared to the later models.

92390AL is a 15 watt with pepper pot dust cap.