The LS5/9 Itself
The LS5/9 is a small speaker—the enclosure is just over one cubic foot (that of the LS3/6 is two cubic feet). The BBC brief for the LS5/9 was to get as close as possible to the sound of the really large LS5/8, but in a much smaller box. I have not heard the LS5/8, but according to reports at the time, the LS5/9 filled the bill, except, of course, for less bass extension.
As such, the LS5/9 was and is a true monitor in the BBC sense—the LS5 category being the designation, as I understand the system, for monitors suitable for all types of program material and under the most demanding circumstances. (The numbers after the slash are chronological—later designs have higher numbers.)
As monitor speakers are supposed to, the LS5/9 was specified to have flat response in its original version. In the present “reissue,” this remains true. As it happens, the original mid/bass driver is no longer available so a new custom design is used, produced by Volt under the supervision of designer Derek Hughes. The Audax tweeter of the original survives to this day, in revised form. The tweeter, with a diameter of 34mm, is somewhat larger than is customary today. This has the virtue of reducing the “tweeter flare” effect and bouncing less sound off sidewalls compared to a smaller tweeter with the same crossover—and a most convincing virtue it is. Among other things, this speaker images exceptionally well, with startling focus.
The limitation of the larger tweeter is that the top end extension is slightly reduced. Since extension at the very top is mostly a matter of air and texture, this is perhaps a reasonable trade. (If one wants the top end to go way on out beyond 20kHz, one can of course add a super-tweeter, those being quite abundant nowadays.)
The LS5/9s have a rise in the bass, with the 50-to-100Hz octave up a few dB, and a gradual slope down to level above 100Hz, the down-slope ending around 300Hz. From 300Hz to 900Hz the speaker is essentially flat but slightly down in level compared to the overall lower treble level. (This is presumably a “monitor balance,” with the slight recession backing the sound away a bit since nearfield listening was anticipated, while the slight lift in the lower treble would give insight into problems in the material in this crucial region.) At around 1.25kHz there is a fairly narrow bump up in response, then a touch of the traditional 3kHz BBC dip. From 4kHz on up, the treble maintains level response up to around 10kHz, above which there is a small amount of droop. These response deviations above 100Hz are all small as speakers go. The speaker really is quite flat. (The rise in the 50 to 100Hz octave is actually useful, giving the speaker a sense of weight, which keeps it from sounding “small” even though its output drops quite rapidly below 50Hz.)
One of the advantages of a small stand-mounted speaker of this type is that it will actually deliver in a listening room its essentially neutral response. Visual fashion has made the high-end audio industry move into floorstanders. But the real truth is that very few floorstanders come out anywhere close to as flat in room as they are anechoically (or as one hopes they are, anyway). Stand-mounted speakers offer greater flexibility in position relative to room boundaries, and it is thus easier to get the in-room response to be reasonable. I suppose everyone has looked at the in-room response of typical floorstanders that are published around and about. The typical one has a boom at around 70Hz (from the floor to ceiling mode) followed by a hole between 100 and 300Hz, a midrange prominence, and a roll-off above. This last is actually something that ought to happen—in-room response needs to relax a bit in the upper frequencies. But the results below that hardly qualify as high fidelity. (When one works with room-correction systems one soon finds out how much that big floor-dip hole matters—it matters a lot.)
By contrast, even my initial, relatively casual placement of the LS5/9s produced a quite smooth in-room response, with only a rather narrow dip around 125Hz. Tweaking the position smoothed things out even more. (BBC-style stand-mounted speakers make possible really neutral in-room behavior. This is aided by the slight rise of the speaker in the range between 100 and 300Hz, where, with floorstanders, a hole typically develops. And if you get into room correction, it is of course much more desirable to have a bit too much energy in the sub-300Hz area, where room effects are most prominent, than too little, since cutting is always a much better thing to do than boosting with EQ.)
So far, so good on general balance questions. But as one might expect, among the BBC-oriented group, which if not a cult in any negative sense is surely a dedicated bunch with shared interests, there is a difference of view on the question of such small differences as exist among the various BBC heritage speakers. In particular, the Harbeth speakers, themselves outstanding examples of the survival of BBC ideas, tend to have a bit of extra energy in the 400 to 800Hz region, even the ones that are officially monitors, like the M30.1s and M40.1s. (The original M40s are an exception, being flat in this region.) You can see this for example on the (all but infallible) NRC measurements of the Harbeth M30, published on soundstage.com.
Enthusiasts of Harbeth have expressed dismay at any sign of midrange recession. This kind of controversy over things that seem small to the outside world is what happens when one gets really interested in some specialized matter. (Ask people who really care about pitch or temperament of scales!) Personally, I am somewhere in the middle—I liked to push up the 400 to 800Hz octave of the LS5/9 very slightly and push down 1.25kHz a bit. But on the Harbeth M30.1, I liked to pull down the 400 to 800Hz region. I am not at all fond of midrange projection. Recession of the mids can be a problem too, but the effect with the LS5/9s is small and mostly just moves the image back a bit.
I also reduced the 4-to-8kHz octave of the LS5/9 slightly. With these small adjustments, the LS5/9 could be brought into what I perceived as an almost completely neutral tonal balance. On its own, it is already fairly flat and neutral sounding, but as John Dunlavy used to remark, once you are flat within a dB or two, getting even flatter and more neutral becomes of really great interest.
After this digression, let me turn now to what the LS5/9 actually sounds like on music.
First of all, it really does sound quite close to truly neutral, even if one skips the EQ tweaking. But it sounds neutral in a way that perhaps might come as a bit of a surprise to those who think of the BBC sound as being a bit slow and heavy and recessed. Now it is, indeed, a little heavy in the bass as indicated (before it rolls off below 50Hz). But the sound overall is very precise and abundantly present. The BBC dip is only a hint here compared to some other designs, and the kind of droop from 4kHz to 8kHz, say, that some speakers use to make female vocals sound “nice” or “beautiful” is not really in the picture. In fact, rather the other way around. As one of my friends who knows music, but reacts to audio only intuitively, said, “It sounds as if the musicians are right there in front of you.” And so it does.
This is what a monitor is supposed to do—if that is the way the recording is—and that is what the LS5/9 does, especially with the small adjustments indicated. This is not shorthand for super-aggressiveness. Rather, it is just a matter of telling the truth about the recordings. But the truth here is not tempering the wind to the shorn lamb, and without the EQ touchup the LS5/9 is doing something of a monitor thing in the lower treble (except for the BBC dip). For reasons that are unclear to me technically, the effect seemed smaller with the Quad Artera stereo amplifier than with the Benchmark AHB2.
Incidentally, a couple of practical notes: Best sound is on an axis just below the tweeter. Avoid sitting above the tweeter axis; this means either a low seat or high stands! Second, leave the grilles on. They are part of the design—or so it seemed to me. There is a tweeter control on the front panel, via a jumper. This was part of the design, too, to accommodate variations among the tweeters. On my samples, it was set in the middle, which means you could cut the tweeter by a dB if you wanted to. (I doubt you would want to raise it, if you are a real accuracy person.) I left it where it was for review purposes. I did experiment briefly with a jumper from 0dB to –1dB position, which cuts the tweeter level a bit more than 1dB. While this was nominally a little flatter in the 4-to-8kHz range, I actually preferred the setting the manufacturer provided.
It is interesting to note that so habituated is everyone to absurdly aggressive treble nowadays, that reviews elsewhere have emphasized how smooth and non-toppy the speaker is, in spite of the 4-8kHz elevation noted above. We live in an odd world nowadays, where the overabundance of top-end energy of so many speakers can make a speaker that is only very slightly hot still seem a blessed relief.