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JBL LT-1 Mini-Monitors

Article from Home & Studio Recording, March 1986

A speaker suitable for car, snowmobile or studio... Ben Duncan investigates.

Consistent with its North American origins, JBL's LT-1 is designed 'for use in cars, trucks, speedboats and snow-mobiles,' but is no less at home in the studio.

The enclosure's shape and size invites comparison with the Bose 101, Fostex SP8, and Yamaha's S20X, but unlike any of these models, it's driver complement is 2-way. The 4½" bass driver features JBL's characteristic grey-coloured pulp cone, with a foam surround for a long, linear excursion at the low bass end. The magnet is bigger than average, which signifies high sensitivity, albeit at the expense of the deep bass.

The tweeter is of the domestic dome variety, 1" in diameter, and the adjacent baffle is gently bevelled. Thus the two surfaces come together gently, to alleviate diffraction, which would otherwise debase the power of point-source imaging. Again, the magnet's dimensions are above average, in fact higher than it needs to be, to partner the LF driver. However, in padding it down, with a series resistor (Figure 1), the excess sensitivity has been translated into reserve power handling capacity.

Packaging is well thought out: the enclosure itself is stone-dead, ⅛th" diecast alloy, with a tough epoxy finish, which doesn't chip or scratch, even with moderate abuse.

Figure 1. LT-1 Crossover Specification

The LT-1's come complete with a swivel mounting bracket, held in place with 'handwheel' adjusters. A rubber gasket prevents slippage, once the angle of attack is set, while the bracket comes with three slotted fixing holes, and a bag of screws and wingnuts. Construction is up to macho Rock 'n' Roll standards. The drivers are held in place by tightly fastened pozidrive machine screws, while the electrical connections inside are on tight fitting Lucar spades. Connection to the music is with spring-loaded terminals, which grip like a dog's teeth, and accept wires up to 0.75mm2, that's 6 Amp cable.

Specs and Sound

The LT-1 is rated at '50W continuous, 100W peak'. In practice, this means we'd be safe using anything up to 200 watts, provided we're respectful, but if overload is mandatory, then we'd do better to stick to an amp rated at 50W or less. Sensitivity is precisely average for this size of unit, at 87dB SPL at 1W at 1m.

The LT-1's rated impedance is 4 ohms. In practice, we can anticipate dips below this, especially around the crossover point, in the upper, nor is any impedance curve given in the instruction 'booklet' (a folded A4 sheet). We didn't actually encounter any problems, or tell-tale signs (such as harshness on particular vocals), when driving with a Quad 405/11, but an amplifier not rated to drive down to 4 ohms can't be recommended, for best results, though no actual harm may result. Even if rated at 4 ohms, we must assume in the absence of any evidence to the contrary, that the reactive characteristics of the LT-1 may upset some amplifiers whose 4 ohm rating means precisely that (and not a milli-ohm less). Older domestic hi-fi amps are an example of this class, like the Mk 1 Quad 405.

Figure 2: Horizontal Mounting Options

Figure 3: Horizontal Mounting Options


Unlike mini-monitors with just a single driver, or two identical drive-units, the LT-1's ideally have to be set up in the vertical plane with the tweeter at the top. However, JBL give some hard practical advice in the booklet, in recognition that in real life, monitors do sometimes have to be mounted horizontally. In this mode, Figure 2 shows the correct positioning, when the units are spread 4' or more apart, such as they would be when placed across a console. But if or whenever a pair are mounted close up, Figure 3 depicts the correct method, where the bass drivers are brought closest.

After a solid two weeks of production and mixdown on the LT-1's, Duncan Bridgeman and Andy Dransfield emerged from the Chapel Studio with glowing reports, having gone in with some reservations about JBL speakers.

Compared alongside the Yamaha S20X,the LT-1s were warmer, less 'toppy' (at about 8kHz), and also less woolly in the mid-bass. Duncan felt the S20X were truer, in the ultimate sense, yet the LT-1s provided the vital 'other side to the picture' (an equally valid dimension in the sound, akin to domestic hi-fi sound). Andy found this contrast particularly valuable for mixdown, describing it as a 'synergistic combination'. Also noticeable was the added low-end definition, and the LT-1s undoubted 'balls' when driven hard.

Shortform specification
Nominal frequency response: 100Hz to 19kHz
Dimensions: 9⅝ x 6¼ x 5" (244 x 159 127mm)
Bracket width: 10" (254mm)

The RRP for a pair of LT-1s is £365 including VAT.

For further information, contact Harman UK, (Contact Details).

Also featuring gear in this article

Previous Article in this issue

Readers' Tapes

Next article in this issue

SMPTE Uncovered

Publisher: Home & Studio Recording - Music Maker Publications (UK), Future Publishing.

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Home & Studio Recording - Mar 1986

Donated & scanned by: Mike Gorman

Gear in this article:

Monitors/Speakers > JBL > LT-1

Review by Ben Duncan

Previous article in this issue:

> Readers' Tapes

Next article in this issue:

> SMPTE Uncovered

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