BBC LS3/5a loudspeaker 1977 BBC Version part 2

We were not able to determine how far out the high end goes, because our oscillator's upper limit is 20kHz, but the smoothness and the ability to reproduce hard transient information (triangles, castanets, etc.) suggested that 27kHz might not be a bad guess for the upper rolloff point (footnote 3). Overall, the monitors have an extraordinary feeling of depth and breadth to their sound. Inner details were excellently rendered, and there were no audible vowel-like colorations that we could detect. The only thing we could fault the Monitors on (other than the low-end range) was a subtle tendency to lighten or "stretch upward" the vowel structure of some instrumental sounds. The effect could be likened to the difference between the lower range of an oboe and the upper range of an English horn, although the extent of the difference was less.

Our comments about the sound of these speakers have thus far been based on its performance with what we feel (as of this writing) to be the best available power amplifier: the Audio Research D-150. (The new Audio Research equipment has just been announced, but will not have been auditioned by the time we return our Monitors.) We freely acknowledge the idiocy of driving a $430 pair of speakers with a $2700 power amplifier, but we can report that these Rogers/BBC speakers did just as well (if not slightly better in one one respect: a less "hot" high end) when driven by a Dual 76A. It is both a tribute to, and a liability of, these speakers that the lesser their driving equipment, the worse they sound. They reproduce the high-end roughness of solid-state amplifiers mercilessly, and most such amplifiers tend also to dry up their bass end a bit so that they lose some of their nice bottom fatness. (Placing them nearer to room boundaries then helps to compensate).

As for room placement: Except for the possible detrimental effects of standing waves, these are refreshingly uncritical of room placement. They are, as we said, best used on stands, and any carpenter can make up a pair. The speakers should be about 6' apart and 10-12' from the listening area, and each should be toed inwards, by about 5 degrees.

Optimally placed, and driven by suitably high-quality electronics and signal sources, these are a perfect way of getting sound that is comparable to that from Quad electrostatics, at far lower cost and with added bonuses of slightly smoother high end, better stereo imaging, a broader listening area, and considerably greater apparent (that is, audible) size. Their low-end output is, in most rooms, deeper and fuller than that of the Quads, but like the Quads, their major weaknesses are limited sound output and lack of extreme bottom. Above 60Hz, the Rogers BBC minimonitors outperform the vast majority of systems costing upwards of $500 per channel. And with the addition of subwoofering, via M&Ks or Janises, these could provide perfoorance comparable to that of some of the best systems com mercially available, regardless of cost.

The only real handicap that we can see to owning a pair of these is that your tin-eared friends won't be as impressed as they would be if your speakers took up the whole East Wall of your living room.

Footnote 3: Stereophile's subjective frequency response curves show how the transducer under test sounded to us, rather than how it measured. The vertical scale on each curve is the same, and is scaled so that a barely perceptible audible deviation from flat frequency response is reflected in a barely perceptible visual deviation of the response curve.

Fig.1 Rogers LS3/5a, "subjective" frequency response.

A Followup appeared in December 1977 (Vol.4 No.1):

Subsequent experience with these remarkable little speakers has strengthened our feeling that that they should not be used with solid-state power amplifiers. The speakers need a slight high-end softening, and are more likely to overload (the woofers bottom, making an alarmingly loud bang) from the average solid-state amp. An Audio Research Dual 51A is ideal (with a solid-state amplifier for the woofers if you choose to bi-amp), while an upgraded Dynaco Stereo 70 does very well. The Audio Research D76A is fine but has more power (and a higher price) than is necessary.

Output level is limited to around 85dB with a high-powered, wideband solidstate amp, 95dB with tubed electronics and no subwoofer. With a subwoofer and the Rogers rolled off below 70 or 100Hz, listening levels of over 100dB can be obtained without stress.

If you missed our full report on these in the last issue, a summation: Superbly balanced sound overall; very subtly nasal in some rooms; slightly rising (above 5kHz) but very smooth and extended high end; no deep bass but deficiency not noticeable on most program material; very good detail; extremely large apparent soundsource; very good stereo imaging; limited output level.—J. Gordon Holt

edgrr's picture

Is it worth trying to use my amazing old 15 ohm monitors with a new Panasonic SC-PMX70 (3 ohm) or should I just stick to the speakers provided?
I moved to Peru and will hold off on buying a "proper" audio setup til I go back to the First World...

David Rapalyea's picture

Someone should to put these components into a bigger box with a passive radiator and recreate the KEF 104.

I have both the 104 and the 104ab. I prefer the 104 on my solid state Marantz 1060 and the single ended Reisong A10 on the 104ab.