It was in 1924 that Chester Rice and Edward Kellog patented the direct radiator moving-coil loudspeaker drive unit. While other technologies have attempted to muscle in on the action with varying degrees of success, the drive units found in the vast majority of loudspeakers on the market today are still based on the very same technology the pair outlined 90 years ago. Of course, materials have grown more high-tech, driver shapes and sizes have changed and computers have aided designers in attaining the sort of performance that Rice and Kellog could only have dreamed of. But the basic principle remains the same.
HUGE RANGE
One result of these many decades
of development is that there is a
huge range of loudspeakers of all
shapes and sizes to consider when
assembling a vintage system. For the
purposes of this feature, however,
the story really begins in the 1960s
when the increasing adoption of
stereo led to the development of
freestanding loudspeakers.
Many audiophiles of the
pre-stereo era purchased drive
units which they then housed in
radiogram-style cabinets, sideboards
and even the walls of rooms
where convenience was the sole
determining factor. But the move to
two channels necessitated optimal loudspeaker positioning, which was much easier with freestanding enclosures. Of course, fine designs of this type existed previously, such as Voigt's Domestic Corner Horn and Quad's Ribbon loudspeaker, but the fact that these models were developed and sold when mono was the only option means that finding pairs of such examples on the secondhand market today can be very difficult. As for matched pairs, this can be nigh on impossible.
TOP TANNOYS
One of the most successful
companies to bridge the gap
between individual drive units and
complete loudspeaker assemblies
was Tannoy. Its Dual Concentric
drive unit was developed in 1946
by engineer Ronnie Rackham and
the 15in Monitor Black was the first
model to hit the market. This was
duly developed into a bewildering
range of Monitor Red, Silver and
Cold models of many different sizes,
but in the mid 1960s the company
released the Lancaster free-standing
cabinet and the York corner cabinet,
which both used the 15in Monitor
Red drive unit. The flagship Monitor
Cold came a little later, with its
natural home being the mighty
Autograph cabinet.
Tannoy loudspeakers have a huge following among vintage audio enthusiasts and it is not difficult to understand why when you hear a pair in good working order. They have a sound all of their own, with excellent imagery being just one of their strengths. Most original speakers are serviceable by specialist companies and replacement surrounds and cones for many models are available, making them a viable secondhand proposition. Prices tend to be high for original models in good condition but there are plenty about, so choice is not an issue. Back on the other side of the Atlantic, developments in loudspeaker cabinet design
were also underway during hi-fi's formative years and one of the most notable resulted in the Acoustic Suspension loudspeaker, developed by Henry Kloss and Edgar Villchur at Acoustic Research. This type of loudspeaker meant that smaller cabinets could be used that would also deliver good bass response. The result was the AR-1, released in the mid 1950s, followed by the AR-3 in 1958, which employed the AR-1's 12in bass driver in conjunction with the first commercially available dome midrange driver and tweeter. The AR-3 was regarded as one of the finest loudspeakers of its era and, thanks to its groundbreaking design, can more than hold its own today. The drivers are generally robust provided they are not overdriven and a pair in good condition can sound superb when suitably partnered.
MIGHTY MAXIM
The acoustic suspension design
became very popular in the 1960s
and 1970s and spawned many
successful models. Perhaps one of
the most important back in the UK
was the original Goodmans Maxim of
1965, which can be regarded as the
first mini-monitor to bring true high
fidelity performance to a cabinet
that could be sat on an upturned
hand (but only just - they're
surprisingly heavy!). Even the BBC
evaluated an early pair and judged
the performance to be 'adequate for
a number of applications in which
high sound levels are unnecessary'.
While it's true the speaker lacks
any meaningful amount of deep
bass and requires more than a modicum of power to perform at its best, the original Maxim is a remarkable loudspeaker even by modern standards and prices continue to rise. Its driver surrounds are not made of foam so have good longevity, but the plastic edging of the tweeter cone has a tendency to come unstuck from the chassis, so check this carefully if you're considering buying a pair.
LEAK SANDWICH
At this time, work was continuing
not only on cabinet design but also
on the materials
from which drive
units were made.
Paper had always
been popular due
to its cheapness,
lightness and
relatively benign
break-up behaviour
but 1961 saw a breakthrough when
Leak introduced its 'Sandwich'
loudspeaker cone, developed by
Don Barlow. This saw a layer of
polystyrene sandwiched between
BEFORE YOU BUY...
The biggest killer of old
loudspeakers is 'foam rot' - the
breaking down of the foam ring
that supports the cone at its
periphery. Replacement rings
are available from many sources
at very reasonable prices and
fitting them is not difficult,
although several companies
will do the job for you if you
prefer. Note that continuing to
use a loudspeaker with a rotten
surround is likely to damage the
voice coil so beware of 'they
still sound fine' when buyingl
Also remember that
component and wire quality
has improved greatly since
the 1960s and benefits may
be wrought by re-wiring and
replacing crossover components
in old loudspeakers, particularly
the capacitors.
to hear a good pair of 3090s is a cabinet magnificent experience and possibly the ultimate expression of the teak vastness of 1970s loudspeakers! Sadly, relatively few pairs were made and they are quite rare. However, their predecessor, the Leak 2075, is very similar, more common and can be bought more cheaply. These also perform well but their Mylar dome tweeter is an altogether less civilised proposition. Using modern capacitors in the crossover does bring noticeable improvements in this area, however. As mentioned, over the years a number of other technologies have tried to rob the moving-coil drive unit of its crown and one of the most successful has been the electrostatic loudspeaker. The Quad Electrostatic Loudspeaker of 1957 (subsequently known as the ESL-57)
was the first successful model and this was replaced by the ESL-63 in the early 1980s. While the original ESL is a fine performer, it does have limitations when it comes to power handling and bass output due to the use of different panels to cover different areas of the frequency range
THINK DIFFERENT
The ESL-63 takes a different
approach, using multiple concentric
rings through which the audio
signal passes from inner to outer,
with suitable delays applied
electronically. The net result is that
the loudspeaker generates an image
with similar properties to that of
a point-source located behind the
panel. This in turn gives a phasecoherent
signal and an absence of
treble 'beaming' due to the large
area involved. Further improvements
mean that the ESL-63 is also more
tolerant of being overdriven, thanks
to a better protection circuit.
Despite this, the ESL-63 has
a tendency to be overlooked in
favour of its
more famous
predecessor, or
the even more
technologically
advanced models
like the ESL-
989 that came
after. As a result,
prices are not as high as might be
expected, especially for the quality
of sound on offer.
Quad still offers full service
facilities for this model, so there
is very little reason not to snap
up a pair of ESL-63s if you fancy
experiencing the sound of an
electrostatic loudspeaker.
Other panel loudspeakers have also met with considerable success over the years and one of the most interesting was the planar loudspeaker developed by Jim Winey of Magnepan in 1969. This design took the form of a large number of thin conductive wires on a Mylar panel suspended in a magnetic field arising from a vertical array of magnets. The whole sheet moves in a similar manner to that of a conventional loudspeaker unit but the wires are directly attached to the radiating surface and the loudspeaker behaves as a dipole. In other words, like an electrostatic but without the need for the high voltages.
RIBBON TWEETERS
The company's first loudspeaker of
this type was the MG-1 of 1976 and
development has continued to the
present day. The benefits of such
designs are similar to those of
electrostatics, namely superb
imagery and coherence, but
Magnepan also added ribbon
tweeters to many of its later models
to improve treble response. Deep
bass can also be an issue due to
the sheer size of panel needed if this is to be achieved. Despite this, original MG-ls can perform very well indeed and have a dedicated following. Tweeter fuses can blow giving rise to a dullness in sound and the exposed aluminium wires on the drive panel can corrode and break. These can be repaired, however, albeit with patience and a steady pair of hands.
CELESTION'S STAR
As the industry moved into the
1980s, cabinets shrank once
more and designers continued tc
experiment with driver construction
and cabinet configuration.
The likes of the Epos ES14, with
its plastic-coned bass/midrange
driver and metal dome tweeter,
provided a recipe that would endure
throughout the 'flat-earth' years of
the decade. However, the speaker
that stood head and shoulders
above the rest was
made by Celestion
and called the SL6.
This speaker
marked the first
major use of laser
interferometry
to analyse drive
unit behaviour
and was also the first loudspeaker
to feature a copper metal dome
tweeter. This was followed by the
SL600 with its 'honeycomb' cabinet
made of Aerolam. The result were
loudspeakers with outstanding
clarity and class-leading dynamics.
Unfortunately, both designs were difficult to drive, had no deep bass to speak of and a surprising lack of crispness at the top end, treble rolling off quite early due to the weight of the copper tweeter dome. Later variants of both models saw aluminium used for the tweeter dome, which alleviated the treble issues while the superb dipole SL6000 subwoofer was introduced to add extra bass. The latter remains a much sought-after classic in its own right (it works well with Quad ESL-63s, tool) but, despite their advanced design, sonically the SL6 and SL600 remain truly 'Marmite' loudspeakers: you'll either love them or hate theml
GOING ACTIVE
A final mention should be given
to active loudspeakers. Although
companies like ARC, JPW and Linn
marketed versions of their models in
the early 1980s that could be driven
by amplifiers equipped with suitable
electronic crossovers, the only
companies to dedicate themselves
fully to active operation were
Meridian and Bang & Olufsen.
The former's M1 loudspeaker of
1978 was an undoubted statement
of intent and was followed by
smaller designs such as the M2
and M3, plus even more impressive
flagships such as the Ml 00.
Reliability of all these models is
excellent and they still sound superb
today. Only rarity and price conspire
against the keen buyer.
ALSO CONSIDER... BBC LS3/5A: Famous mini broadcast monitor made by many manufacturers including Rogers, KEF and Goodmans. Has a unique blend of strengths, some of which remain unsurpassed even today. IMF Professional Monitor: A big 1970s bruiser with a KEF B139 bass driver in a transmission line. Super bass and a big, relaxed presentation. Apogee Scintilla: Fine-sounding full-size ribbon panel design but dubbed the 'amp killer' by many due to its lohm minimum electrical load. Make sure your amplifier is up to the task.
B&W 801: One of the best passive studio monitoring speakers ever [pictured above], Discontinued during the company's last upgrade of the 800 series to 'Diamond' status. Greatly missed! TDL Reference Standard: Produced some of the lowest and finest bass to be heard from any domestic loudspeaker. Very big and very rare. Mission 767: Unassuming looks hide first-class design giving a fabulous sound. Make sure they come with their Cyrus 2-based 'LFAU' bass tuning/amp unit. Monitor Audio R352: Affordable 1980s large standmount. Matching stands not the best sonically but they just don't look right sat on anything elsel Goodmans Maxim 2: Budget '80s bookshelf design that is absurdly good for something that originally cost £70.
