JBL L112 Bookshelf speakers
The JBL range of professional studio monitor loud speakers has secured a special position in the market worldwide, even though they are generally characterized as possessing the "West Coast" sound. This description, if it means anything, refers to a certain forward presence of sound, with tight bass and an ability to handle transients and high level signals without flinching. When JBL make more modest loudspeakers aimed at the well-heeled end of the domestic market, something of this characteristic sound remains. I have noticed, however, that the big JBL monitors in their latest range-the 4430 and 4435-achieve a smoother and more universally acceptable total sound: their domestic loudspeakers are following a similar trend.
The JBL L112, which is the subject of this review, retain s traces of hardness but has a number of real virtues which will appeal to many keen home listeners. The JBL literature calls this a "bookshelf' loudspeaker but an extremely strong shelf would be needed as each L112 weighs 25kg (55Ib). The three drive units each contribute a fair bit to this weight, being built to JBL's usual high power/high efficiency standards. The 300mm bass driver alone has a 4.7kg magnetic assembly and, like the other units, a massive cast frame. Its unusually large 75mm edge-wound voice-coil produces high efficiency and crisp transient response. The 130mm mid-range unit has its own isolated acoustic chamber, a stiff cone and 22mm voice-coil. The 25mm tweeter has a light phenolic dome coated with aluminium for strength and rigidity.
The crossover network is mounted on a heavy-duty printed circuit board and operates at 1.1 kHz and 3.7kHz. Both the mid-range and tweeter circuits include adjustable level controls, which are mounted on the front panel. There is a "0" setting corresponding to flat response in an anechoic chamber, with calibrated markings from + 3dB down to -12dB and " infinity". These controls enable the sound balance to be altered quite drastically to suit particular room conditions or personal taste. Of course the y operate in a different fashion than normal amplifier tone controls, and actually raise or lower the output over the whole operating range of the associated driver, i.e. 1.1-3.7kHz for the mid-range and 3.7kHz upwards for the tweeter. Combined use of the speaker and amplifier controls should solve most problems of balance.
The drive units are asymmetrically arranged on the baffle-board and so the loudspeakers are sold as a mirror-image matched pair. The beautifully produced instruction manual illustrates how best to mount the speakers for optimum stereo, and shows that they can either be used vertically or laid on their sides. All sides are finished in attractive American black walnut, treated with oil/wax and hand rubbed. The removable grille is made of acoustically transparent brown cloth stretched over a shaped frame which fits by dowel-pins on to the baffle. All panels are cut from 19mm high-density particle board and strongly braced. The enclosure is a bass reflex type, with the circular vent opening in the front baffle-board. Connections are made via twist-to-secure bare wire terminals recessed at the centre of the back panel.
How they performed
Having unpacked the pair of L112 speakers from their robust cartons (green markings for 'left' and red for 'right'), and set them at a suitable 3-metre spacing for stereo listening, I was in no doubt that they were built like battleships. Rapping my knuckles on the panels confirmed that interior bracing and absorbent lining had effectively minimized structural resonances. I then connected the speakers via suitable low-resistance cables to a Quad 405 stereo amplifier and checked the response to very high level signals.
Sensitivity was above average, as might be expected from the combination of high-power driver s and the bass reflex enclosure design. Quite low amplifier power outputs were therefore sufficient to produce loud acoustic levels in a fairly large room. Winding up the volume steadily increased the loudness, but without the least trace of discomfiture in the system. JBL suggest that an amplifier rated at 300 watts per channel would be optimum as giving "the reserve power necessary for accurate reproduction of transients". I quite believe that this loudspeaker could handle peaks of this order of magnitude, so that any clipping distortion heard should be blamed on the amplifier rather than the speakers. Signals remained clean during all my tests, even when the windows started rattling.
Searching with sine-waves and pink noise, I found that the true bass response is unusually extended and consistent to below 40Hz. Subjectively, however, the bass sounds tight rather than boomy and ears accustomed to a false resonant bass might experience some initial disappointment. Longer, more critical, listening will show that the lowest frequencies are all there right enough. Measurements of middle and high frequency response again showed a remarkable smoothness, though a tendency to hardness on most types of music led me to experiment with the two level controls. To my ears, the most acceptable tonal balance required settings of about -1.5dB on the mid-range and -1dB on the tweeter. This still left percussion and string tone, for example, very clearly delineated yet allowed exceptionally loud reproduction without harshness. Directivity was acceptably wide at high frequencies and stereo performance excellent.
The JBL L112 is not the loudspeaker for everyone. At around £700 per pair it will appeal most to people with large rooms or a taste for high volume sound, or both. They will not be disappointed. This is an easy-to-drive loudspeaker, compact enough to fit in anywhere and, with proper use of its level controls, adaptable to different situations.
