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Volume 3 No. 3
Oh No, Not Another LS3/5a...
The BBC-licensed LS3/5A help make Rogers into a global brand. Its current Far East owners have worked with the UK designers an manufacturers to create this BBC-licensed 11 Ohm 'revival'.
We won't labour the LS3/5a story, which began in the BBC in early 1970s, as this was covered in depth in Vol1 No3 (May-June 2007). The fit and finish of this official £1499/pair Rogers revival was excellent. It certainly looks the part with its fine matched rosewood veneer, though the repro Tygan grille material might be a little softer and more open than the original. As expected, these speakers use a 5-inch (138mm) polymer cone bass/mid drive unit partnered by a nominally 19mm dome tweeter, mounted in a sealed-box enclosure. Build detail includes thick felt absorption around the tweeter, to ameliorate reflection effects from the integral grille frame. (The LS3/5a is meant to be used with its grille in place.)
This new example has a glued on back, as were most LS3/5as. The bass/mid driver has a 110mm pressed steel chassis with a flared, talc-filled polypropylene cone, powered by a double-wound voice-coil (the windings series connected), and a large ferrite magnet. A fine 19mm tweeter with recessed soft dome and sophisticated rear loading is fitted, while that unnecessary perforated metal cover completes the original look. Built of birch plywood according to the original recipe, the panels are well damped by traditional bitumen loaded pads, and the interior is lined with thick, absorbent polyurethane foam. This model is bi-wired (unlike the original) with average quality gold plate brass binding posts and brass link pins (preferably replaced by copper wire on installation). The crossover is built on the usual epoxy glass reinforced PCB, securely bolted to the panel area around the tweeter. It uses normal film capacitors, ferrite core inductors, and an array of resistors forming a calibrated attenuator to achieve the essential close tolerance matching of mid and treble levels. (The original 15ohm model used mu-metal cored transformer inductors and ratio matching of driver sensitivity levels.)
Sound
Quality
With references assembled, and memory not too dimmed from the pleasant experience of that other,
Derek Hughes guided 11 Ohm LS3/5a for Stirling Broadcast (Vol1 No3), I set to. Location as ever, was
free space with little toe-in, and copper links fitted to the terminals.
From the very start that genuine LS3/5a magic was there, though inevitably at modest loudness levels. Shut your eyes and coloration is really low, and the soundstage is spacious, deep and focused. The natural timbre and the elegant, surprisingly deep image perspective reminds one of much larger and more costly designs. If a listener doesn't demand higher volume levels or need cracking dynamics, it might not be necessary to go further than this in the quest for genuine high fidelity.
In my opinion this is the best of the modern LS3/5a clones I've heard to date. It has quite good coloration
in the low midrange -- a weakness of many -- though it is a little 'boxier' than the best
15 Ohm examples. It is also a little 'sweet', not quite as crisp and open as is possible, though one would not want it as bright
as some later original Rogers 15 Ohm examples. This new contender is self-effacing, clean, even, smooth
and well balanced, with a particularly seamless transition from midrange to treble, albeit a tad
dynamically reticent in the piano's middle register. Spacious, transparent and detailed, if a touch
'darker' (and therefore not quite a dynamic, expressive, transparent or 'powerful', this new version of that
old trouper just sounds bigger than the original, with a touch more realism.
This new Rogers certainly has a good percentage of the better drive and timing of the earliest models. We should remember that middle period 15 Ohm models often sounded hard and forward in the midband, only just meeting the BBC spec. This new version actually bests a huge number of the less good 15 Ohm models, never mind the more boring 11ohm examples and most of the 3/5 clones (which were never proper 3/5as anyway). In reality this Rogers is quite close to the standard, comparing well with the equally well mannered and similarly neutral Stirling Broadcast version. I think that it may be just a little livelier musically than the Stirling Broadcast, but reckon you would have to do an A/B to find out.
Measurement
The spec says 83dB/W/m sensitivity, some 1.5dB higher than the original 15ohm model, and truthful.
Frequency responses were very tidy, and with superb pair matching. The on-axis frequency response gives
70Hz to 29kHz +/-3dB, with -6dB points at 60Hz and 30kHz. Partnering stands should not be too
high because the response dips sharply by 10dB at 10 degrees below the axis in the crossover zone, around
3.3kHz, while remaining perfect at 10 degrees above. The speaker should therefore be sited at or a little
below seated ear level. The off-axis lateral results were good too, but that noted dip was beginning to show
itself in the 45 and 60 degree off-axis results. The small tweeter keeps the output going nicely up to
11kHz off-axis, so it should stay open and clear. The bass is understandably limited with some characteristic
'plumpness' 80 to 150Hz, though this is part of the 'voice' of this little box. The in-room averaged
response (not shown) is very good: it's typical for the size, with good overall power integration and with
in-room bass down to about 50Hz.
The impedance graph shows an average value of about 7 Ohms. It's easy to drive, with a minimum
of 5ohms and moderate variation. The box bass resonance is seen at 91Hz. The waterfall response is
quite tidy, well integrated in the early response, with only moderate decay
clutter thereafter. Enclosure coloration is low thanks to the good construction
and small acoustic footprint.
Conclusions
This LS3/5a contender can be recommended. It's beautifully made with great care and fine finish, and
while I still await the equal of my ancient Robin Marshall made BBC originals perhaps it simply
cannot be done, as some of the materials used to make that speaker are no longer available.
Contact
RoyalHiFi
Tel: +44 01628 820134
e-mail royalhifi@aol.com
Price: £1499/pair
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