Loudspeaker design isn’t the black art its practitioners often claim. Speakers aren’t above and beyond the laws of physics; indeed, it is precisely these that determine the sound of any given product. Put simply, there’s the cabinets to get right, the drive units, and the interplay between the two. This done, any given box will have a fighting chance of making music. For this reason, a loudspeaker is only as good as its drive units. The success (or lack thereof) of these is critical to the finished product…
Each generation of loudspeakers tends to use similar, or the same, drivers. Even the units are bespoke ones made by the speaker manufacturer itself, it’s fair to say that similar philosophies, materials and production processes are used. This is precisely why, generally speaking, nineteen seventies speakers tend to sound very different to those from two decades on, for example. Sometimes, however, a ‘speaker arrives that rewrites the rule book in some respect, and produces a sound is quite different from those that came before – and Spendor’s BC1 was such a product.
For several decades, the BBC was a force behind loudspeaker design, and back in the sixties, it had spent considerable time and money investigating alternative cone materials to the then ubiquitous paper pulp bass units. Plastics were the obvious answer, and eventually a new drive unit material, Bextrene, appeared in the BBC LS5/5 studio monitor. As a laboratory technician, Spencer Hughes was intricately involved in the process of plastics research and development.
Hughes duly decided to make a drive unit “in the home environment”. In his journals, he reveals how, “with the aid of an electric fire, a compressor working in reverse and an old iron bedstead, the first vacuum former was built.” An eight inch drive unit was eventually produced, “which turned out to be the first commercial eight inch Bextrene driver, and still arguably one of the best”.
The very first pair of BC1s was made with these very drivers, plus the respected Celestion HF1300 tweeters. Hughes wrote that the cabinets were smaller than “the now famous commercial product”. However, the initial listening tests indicated that the performance could be improved by an increase in size, and development continued. Spencer Hughes found that this was beginning to impinge on the terms of his BBC contract, so the BC1 had to be offered to them. However, “fortunately the ‘pop’ era had just started and the main request was for more power, so the BC1 was turned down”.
Still, the Beeb was looking for a pair of speakers about the size of the BC1s, and so Spencer Hughes began work in “an official version”, the LS3/6. This was eventually offered Rogers, then under the control of Jim Rogers. Soon after, the BC1’s were fitted with an amplifier mounted in the back panel and the 4001G super tweeter added. This addition brought improved dispersion characteristics and, “from the broadcasting angle, it made the detection of any 625 line breakthrough more easily detected”(!) Spendor was born, and the company began production of the BC1 in 1969, offering a royalty to the BBC in recognition of the work Hughes had done on the loudspeaker whilst still employed by the Beeb.
The speaker became a huge commercial success, at least as far as high end designs were concerned, and was nothing less than a sea change in nineteen seventies loudspeaker design. It gave hitherto unheard levels of clarity, and freedom from distortion. Of course, by today’s standards, Bextrene leaves something to be desired, but it was so successful against generic nineteen sixties paper cones (which many manufacturers used right through the seventies and even eighties) that it started a wholesale move to plastic drive units.
In absolute terms, plastic cones are relatively heavy – which makes for poor attack transients – and prone to a curious ‘quacky’ tonality. This is obviously audible against modern drive units, but against the old generation of paper cones, their obviously lower colouration and distortion proved a real civilising influence, giving a very even, couth and finessed sound (you can see why the Beeb liked them!). The BC1 was the first, and arguably the best exponent of Bextrene, although there followed a number of accomplished designs, from the BBC LS3/5a and Linn Kan to the KEF 104ab and Linn Isobarik. All of these were characterised by a smooth, even tonality, low distortion, plus relatively ‘sedate’ transient ability and middling efficiency; all of which were distinctive characteristics of plastic drive unit cones.
The days, Spendor BC1s are enduring favourites with their owners; they appear for sale surprisingly rarely, as those who use them love them. They’re accomplished for those wanting an expansive, neutral ‘monitor’ sound, best attuned to classical music, and a big, open, fulsome bass.
The Spendor ‘Bextrene Cone 1’ loudspeaker is essentially a three-way system with crossover points at 3kHz and 13 kHz. The 8” mid-bass driver uses an inverted rubber surround similar to the KEF B200 or SP1039. Above 3kHz, the Celestion HF1300 tweeter takes over right up to13kHz, where it hands over to a three-quarter inch plastic dome Coles 4001 supertweeter. The cabinet measures 300x300x637mm, with an internal volume of 38.5 litres. The front baffle and rear panel is 12.3mm Baltic birch, while the side panels are 10.5mm Baltic Birch with 10mm lightweight bitumen impregnated masonite damping pads. 30mm thick polyester foam is used on all internal panels except the front baffle. The port is tuned at 28Hz.
Despite the understandable popularity of the BC1s, and their long production run, they remain relatively scarce on the secondhand market due to the fact that their owners often struggle to find something that comprehensively outclasses them – unless truly big money is available. However, they do crop up from time to time, at prices from £200 to £600 depending on condition. Even at the top of this range, they represent superb value for money, at least if you put openness, neutrality and scale above pace, rhythm and timing.