As commercial recording studio technology exploded in the late 1970s, the leading edge of the BBC was narrowed significantly. At the dawn of the 1980s the BBC invested heavily in updating their studios and as a result of its longstanding relationship with KEF the BBC fully supported KEF’s development of the KM1I – a fully active (and powerful) studio monitor.
Each KM1 enclosure included four 12” B300 LF drivers (woofer) each housed in an individual reflex box, and a MF/HF module positioned in the center of the four LF drivers. The MF/HF module consisted of a pair of B110 mid-range drivers that were coupled with large aluminum rods acting as heat sinks to draw heat away from the voice coils (these speakers played LOUD!), and an enormous T52 HF driver (tweeter) that was a very early ferro-fluid cooled driver.
Placed in the center of each cabinet was a Quad 405 amplifier module that when operated in bridged mode reached a stunning 350 Watts RMS. All of that power generated a lot of heat which was vented through grilles on the top of the enclosure. BBC policy restricted the use of cooling fans so the amps and MF/HF modules were mounted on rails for easy servicing – overheating was an ongoing problem at the volume levels these units were played at.
Stark differences between the professional side of things (the BBC demanded the enclosures perform as well units with 15 inch woofers and stacked horns) while KEF’s engineers following the protocols of the consumer side of things couldn’t understand who would possibly play music at such extreme volumes for such extended periods. The BBC’s demands were mostly from a perspective of operational headroom – these monitors would be expected run at fairly decent volumes seven days a week for many hours at a time. Although most engineers listen at moderate levels the BBC installed a red warning lamp in each studio that would light when sound levels exceeded 95dB; of course there were plenty of engineers who took it as a personal challenge to keep that red light permanently lit. For those of you ready to try this out for yourselves, 95dB is the sound of a New York City subway train at two hundred feet; permanent hearing loss begins after only 17 minutes or so at that volume.
KEF’s KM1 monitors were used throughout the 1980s until they were surpassed by the next generation of studio monitors, but even though only a few were produced the KM1 is considered by many to be a groundbreaking advancement in studio speaker technology. KEF’s heralded LS50W and Blade are just two examples of our cutting edge development in a quest for the perfect musical experience in your own home.
