The most famous BBC-designed speaker is undoubtedly the little LS3/5A. Arguably the first proper high-quality mini-monitor, this little box design from 1975 has long achieved legend status among a section of the hi-fi community.
It is a two-way design, barely bigger than a typical shoebox. Given the tiny 5-litre internal volume and modest 11cm mid/bass unit, don’t expect much in the way of bass extension or ultimate loudness capability.
Yet, listen to the LS3/5A with vocal-based recordings or small-scale classical, and they can still sound magical. They render voices and acoustic instruments with the kind of palpability, warmth and body most modern alternatives barely hint at.
True, the best of the current breed, KEF’s own LS50 Meta or PMC’s Prodigy 1, are notably more revealing and dynamic. However, there is no denying that the LS3/5A’s music-making abilities remain captivating.
The BBC is a broadcaster rather than a manufacturer, so its speakers were made under licence by outside suppliers. A range of companies, including Rogers, Spendor, Harbeth and KEF, signed the dotted line.
Our limited edition mid-90s KEF LS3/5A samples come straight from the company’s museum. They are specified as having a miserly 82.5 dB/W/m sensitivity and power handling of just 30 watts.
That gives a maximum output level in the mid-90dB range, which is fair – but hardly party levels. This is a low-sensitivity speaker that can’t be driven hard to compensate.
But that didn’t matter to the BBC, as the LS3/5A was intended to work in nearfield conditions, in cramped studios and outside broadcast vans. It was designated a ‘Grade II’ design, used to monitor general speech and overall balance, rather than for critical evaluation.
To do that job, the BBC ended up designing something bigger and more ambitious. Enter the LS5/9.
The 28-litre LS5/9 was introduced in 1983, eight years after its more famous sibling. Its job was to let sound engineers optimise every aspect of the broadcast/recording, from microphone placement to overall sonic balance.
The LS5/9’s home was any studio where the company’s huge full-range monitor speakers wouldn’t fit. Graham Audio is responsible for our beautifully built samples.
Both the LS3/5A and LS5/9 designs were based on decades of research done by the BBC’s engineering department. That research covered every aspect of speaker design, from cabinet construction to drive-unit materials, and was far better resourced than anything a commercial speaker manufacturer would or could ever do.
The research led to some unusual conclusions. Thin, heavily damped cabinet panels were considered a better option than the thick-walled, ultra-rigid approach so favoured today.
The slight ‘give’ thin panels provide pushes any resonances away from the midrange, where our ears are so sensitive, into the bass region, where they are not. The LS3/5A’s enclosure panels use 12mm birch ply, while the LS5/9’s are thinner at 9mm.
Most speakers of the day used paper diaphragms in their drive units, which were prone to unwanted colourations and distortions. The BBC's solution was to use new-fangled plastics instead.
The LS3/5A's KEF-sourced B110 mid/bass featured a Bextrene cone to avoid any such issues. This was partnered with a 19mm Mylar-dome tweeter, linked, as in the LS5/9, with a complex crossover that prioritised tonal evenness, seamless integration and consistent dispersion characteristics.
The LS5/9 is a front-ported design rather than a sealed box. Its more modern 20cm mid/bass switches to polypropylene on performance grounds, and is mated to an unusually large Audax 34mm soft-dome tweeter.
The large dome size helps with power handling and integration but restricts treble extension to just 16kHz (+/- 3dB), whereas the LS3/5A is claimed to reach closer to 20kHz (+/-3dB).
Both speakers have protective metal grilles fixed in front of their tweeters to avoid accidental damage.
The LS5/9 is a more electrically sensitive design than its older sibling. It has a quoted sensitivity of 87dB/W/m, so it is notably louder for any given input signal. Maximum loudness capability is up too, at more than 100dB, a big gain over its relative.
Given the shared engineering foundations of these two speakers, I thought it would be interesting to compare their sound. Before we start, you should know that our samples differ greatly in age.
The KEF LS3/5A is around 30 years old. While it is in great working order, those years are likely to have taken some toll on its drivers, crossover components and enclosure. On the other hand, the Graham Audio LS5/9 is the company’s current demo pair.
It is easy to understand why so many people still love what the LS3/5A does. It offers a smooth, easy-going listen. The midrange sounds surprisingly full-bodied, giving voices and acoustic instruments a natural warmth and fluidity that is hugely appealing.
Position the speakers on solid stands, close to a rear wall, and they deliver a decent impression of bass weight for their size. This is down to a low-frequency hump deliberately introduced to highlight any hum or buzz in the original signal.
Remember, the BBC designed this for monitoring broadcasts and recordings, and such unwanted noises would be common issues.
The relatively smooth higher frequencies aren’t particularly insightful by current standards, though the integration with the midrange is seamless. There is no doubt that the better current £1000-£1500 standmounters deliver greater dynamic reach, stronger rhythmic drive and better overall transparency.
That’s 50 years of engineering progress. Still, there remains something quite wonderful about the way these BBC monitors make small-scale and intimate music sound.
In contrast, the LS5/9 are much more like a modern speaker. Stravinsky’s The Rite Of Spring holds no fear, even at high volume levels. These are detailed and articulate performers that can challenge the best at their price (£3839 / $5999 / AU$9749).
They are notably more transparent than the LS3/5A, revealing flaws in recordings and partnering equipment far more readily. That Audax tweeter isn’t shy about sounding harsh or edgy, if provoked.
Tonally, the LS5/9 sound more neutral, trading the smooth, slightly rich balance of their older siblings for a more upfront and direct approach. Their midrange still has a lovely sense of naturalness, delivered with a fluidity that most equivalent designs would struggle to better.
Both BBC monitors image superbly. The LS3/5A disappears more successfully into the soundstage, but even the bigger speakers render impressively stable and focused results.
The LS5/9 age starts to show only when it comes to delivering large-scale dynamic shifts and rhythmic drive. Current class leaders communicate the energy and authority of a recording better.
Even so, I’m astonished by just how appealing both these speakers sound. The LS3/5A is the more forgiving choice. It has a smoother balance, a truly lovely midrange and superb stereo imaging. However, it excels at being soothing rather than exciting.
The LS5/9 is the better all-rounder, though fussier about the partnering system and recording quality. It was designed as a critical monitor, and that shows. Ultimately, it is the one I would like to live with, even though the LS3/5A manages to sound more magical with certain recordings.
Whichever one you lean towards, both designs are solid testaments to the excellence of the BBC’s engineering department all those years ago.
MORE:
Read our Graham Audio LS5/9 review
The BBC’s 50-year-old LS3/5A mini monitor shows the uneven progress of modern speaker design
A tale of three speakers: mini monitor legends from Acoustic Energy, BBC and KEF
