BBC LS3/5a loudspeaker 1989 Rogers version
It is unusual for a loudspeaker to remain in production for more than three years. It is rare for one to still be sold five years after its introduction. It is virtually unknown for a speaker to be still available, virtually unchanged, 14 years after that date. Such is the case, however, with the $650/pair LS3/5a design, which is still popular well into its teenage. (Only a number of horn speakers from Tannoy and Klipsch have been around as long.)
Its genesis was a little unusual, however, and goes some of the way toward explaining its longevity. Back in the early '70s, the BBC needed a physically unobtrusive, nearfield monitor loudspeaker for use in outside-broadcast trucks. Accordingly, they instructed their design department, which at that time featured such luminaries as Dudley Harwood (the "father" of polypropylene) and the late Spencer Hughes (who went on to produce the classic Spendor designs) to produce such a model. The result, the LS3/5a, was then licensed to commercial speaker companies for production. Thus not only was what was then probably the finest collection of British speaker design talent involved in its development, there were no commercial constraints placed on the design. The only limitations were intended to be those arising from the necessarily small enclosure and the absence of the need for a wide dynamic range under close monitoring conditions.
Is it so surprising, then, that the design has proved to be a stayer, outliving many would-be rivals?
Rogers was the first licensee, I understand, and still keeps the LS3/5a in production, but a number of other manufacturers have been licensed at one time or another to produce the speaker, including the now defunct Audiomaster, Chartwell, and RAM (UK) companies. In addition to Rogers, Spendor, Harbeth, and Goodmans all currently produce versions which, while differing in such details as connectors and wood finishes, are intended to sound identical both to each other and to the original standard.
The reason for this classic's inclusion in this review—you might think it's a bit like Consumer Reports comparing a '73 Toronado with an '89 Taurus (footnote 1)—was twofold. First, I listened last summer to a system owned by friends, Jan and Ric Mancuso, in which Vandersteen 2Cs had been successfully replaced by a pair of '3/5as.
Second, a recent report by Martin Colloms (footnote 2) indicated that the BBC had consented to a revision of the design, not so much to "improve" it but to ensure that current production was still on target. One of the continuing problems, apparently, was that the KEF woofer specified by the BBC actually lay to one side of the bell curve of production parameters, resulting in a large drive-unit rejection rate. KEF was persuaded to undertake a program aimed at improving drive-unit and crossover consistency, even to see if the speaker's performance could be improved, although an overriding dictate from the BBC was that any changes were not to alter frequency or tonal balances. A preliminary result of this program was that KEF now supplies matched kits of drivers and crossovers to the companies manufacturing the LS3/5a, even to Rogers, I am informed, who for a while stuck with assembling their own crossovers.
As it happens, I have been using a pair of 1978-vintage LS3/5as for some years, mainly as location monitors, but I also get them out every now and again to use as part of a particular system. I used these bewhiskered samples for the review auditioning; though I had requested a pair representative of Rogers' 1988 production from the current importers, Audio Influx, these got lost in shipping and comparisons were not possible before the review deadline. A follow-up is planned.
The cabinet is one of the keys to the LS3/5a. Constructed from real wood—birch—veneered with wood (apart from the front and rear), braced with solid beech strips, and heavily damped, this alone costs the manufacturer the same as the retail price of a typical massmarket speaker. (This is from experience: when Martin Colloms designed a small DIY speaker for HFN/RR in 1985, he persuaded me that we should specify that home constructors use the LS3/5a cabinet to ensure consistency of performance. When I found out what the cabinets were going to cost our readers, I almost fainted.) The recessed nature of the front baffle reveals the age of the design—once upon a time, all box speakers looked like this—and the woofer/midrange unit is mounted from the rear of the cutout. This is a KEF B110, the classic 4.5", doped-Bextrene-cone unit.
Whereas the original driver had a Neoprene surround, the latest version uses a different synthetic material said to give a better termination to traveling waves in the cone, the result being better clarity in the midrange (footnote 3). The tweeter is the 19mm, Mylar-dome T27 from KEF, fitted with a perforated cover. Possessing an extended HF response, this driver has also been used as a supertweeter in some designs.
Owing to the recessed baffle, the designers found it essential to add some form of diffraction control in the tweeter's acoustic environment, this consisting of thick felt strips to minimize the effect of reflections from the edges of the side, top, and bottom panels. The grille is acoustically transparent and is intended to be left on. (It can also be disturbing to see the quite large excursions the B110 cone makes on bass transients.) The crossover, carried on a large printed circuit board attached to the rear wall, is the heart of the LS3/5a, and is complex, consisting of 13 elements. It can be individually tuned to compensate for variations in drive-unit behavior.
Used on Chicago 24" stands well out in the room, the characteristic LS3/5a sound was immediately identifiable. Low bass was missing in action, while the upper bass was underdamped, leading to a lack of clarity and a slight degree of congestion in the lower midband. (It was the English writer Chris Rogers, I believe, who once referred to the '3/5a's as having a "boomy midrange" compared with a typical reflex design's boomy bass.) Cello became too gruff, and male speaking voice a little chesty.
Footnote 1: No contest, right?
Footnote 2: HFN/RR, August 1988.
Footnote 3: For a full discussion of the design's evolution and the improvements featured by the latest version, see the excellent article by Trevor Butler in the January 1989 issue of HFN/RR.