The Rogers return

LS3/5A production resumes

Veteran UK speaker manufacturers Rogers have just restarted production of the legendary LS3/5A, alongside that of its bigger brother, the LS5/9 (pictured below). As well as making Classic models (built to the exacting specifications of the originals), both speakers will also be available in SE (Studio Edition) versions, which are fitted with Panzerholz (a hardwood/resin compound) baffles and upgraded crossovers, for the most demanding of studio applications .

The revival is being headed by Andy Whittle, who was Rogers Technical Director back in the 90s, when the company were still making the original LS3/5A. To find out what makes that speakers design so special (and why second-hand models are still so highly sought after), well let SOS speaker guru Phil Wards fascinating history lesson (originally published in SOS June 2016) do the talking...

History Of The LS3/5A

The LS3/5A originated in the mid-'70s, at a time when the BBC designed a fair proportion of their own broadcast and studio equipment. The whole idea of state-owned broadcasters designing and building their own kit is all but unthinkable now, but right up until relatively recently, if the BBC found themselves needing a specific tool that wasn't available commercially, their Kingswood Warren research labs were tasked to come up with the goods.

The genesis of the LS3/5A was not as straightforward, however, as the Kingswood Warren boffins simply being asked to design a compact monitor and dutifully delivering. Although there was a need at the BBC for a Grade II' compact monitor for use in outside broadcast trucks, the development of the speaker that became the LS3/5A didn't kick off in direct response to such a request. In fact the progenitor was a speaker designed for one-eighth-scale acoustic modelling of concert halls...

Long before virtual' computer-based acoustic modelling of performance spaces was possible, such work was done using literal modelling techniques. A physical scale model of the space would be built and miniature speakers and microphones placed appropriately within it to analyse its internal acoustic characteristics.

Now, there is no record (well, not in any document I've found) of who the engineer was to whom it first occurred that the acoustic modelling speaker used at Kingswood Warren actually sounded pretty good and might form the basis of a compact monitor. But whoever it was, I'd wager they had no idea at the time how significant a lightbulb moment they'd had.

In the early 1970s, when our story begins, speakers, whether for domestic or professional applications, were on the whole pretty big. Stereo hadn't really been around all that long, and neither had powerful transistor amplifiers, so a single, large speaker was still the norm. Now, even if it's on the large side, positioning one speaker is far easier than positioning a pair, as is required to create a stereo image, so the physical size of the speaker wasn't so much of an issue. With stereo, however, came the problem of speaker positioning, and with that not only came the need for speakers to be smaller, but also for pairs of speakers to be closely matched in terms of performance.

It hardly seems believable now, but back then, there were very few commercially available small speakers that would satisfy the BBC's needs. One of those few speakers that was available to the BBC was the original Goodmans Maxim, and a 1965 internal Kingswood Warren report describes its performance and assesses its potential. The report was written by Dudley Harwood, who went on to found Harbeth Audio (the company name being a conjunction of Harwood's name and that of his wife, Elizabeth). The Goodmans Maxim itself was designed by a young Laurie Fincham, who went on to become Technical Director of KEF, manufacturers of the drive units eventually used in the LS3/5A. There's none of that six degrees of separation' stuff in the British loudspeaker business; one or two degrees will usually suffice.

Harwood's Maxim report, which can be found at http://downloads.bbc.co.uk/rd/pu..., makes interesting reading (well, it does if, like me, you're irrationally interested in the history of speaker design). Even without converting the archaic imperial measurements of the test results, it's obvious that the Maxim, by today's standards, was inefficient, had restricted bandwidth at both ends of the spectrum, and displayed precious little power handling. However, those shortcomings weren't issues that Harwood expressed much concern over; in fact he was generally satisfied with the Maxim's performance. The issue that was of most concern to Harwood was sample consistency.

Along with the basic requirement for a small speaker that performed adequately for broadcast quality monitoring, the BBC needed the speaker to be consistent from sample to sample. If, say, a single speaker in an OB truck failed, it would be decidedly inconvenient if the pair had to be replaced, and equally unsatisfactory if the second pair didn't sound the same as the first. So each individual speaker was required to perform within response limits that, even today, are a challenge. If the Goodmans Maxim report revealed one thing, it was that this degree of consistency would not likely be found in an existing commercial speaker. So, with a concept on the table for a design inspired by the acoustic modelling speaker, the Kingswood Warren engineers turned to KEF Electronics for help.

KEF got the call partly because, now under Laurie Fincham's engineering leadership, the company were by some distance the most technologically advanced in the field, and partly because there was already an established relationship with the BBC. An earlier research project at Kingswood Warren into thermoplastic diaphrag

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