SLS (Superior Line Source) is an American loudspeaker manufacturer that has just arrived in our country through the also fairly new distributor AudioGestion. Unknown to me (or perhaps it slipped by me amid so many brands), I have now discovered its RLA series, yet another acronym, this one standing for Ribbon Line Arrays. The last two English words are well known to many: the current craze for hanging everything. What is new and distinctive about this series is, among many other things we will see shortly, the use of the PRD1000 ribbon, or, more down to earth, a transducer that departs from the traditional concept of a high-frequency driver or tweeter. Its rectangular shape is itself an energy radiator, which delivers a coherent waveform ideal for maintaining and creating the linear propagation you want in an “array” system. Another advantage of this type of high-frequency driver is that, since it does not depend on any inductive component, its impedance stays linear across its entire range (in this case, 8 ohms).
A 9-kilo little box
The photographs that will surely accompany this article won’t do any justice to the cabinet’s real dimensions. Named the RLA-3, it is the smallest in the series, and its dimensions are 184.2x356x234 mm (surely the smallest flyable cabinet on the market). That keeps its weight to just 9 kg, which makes a cluster of four cabinets entirely manageable (there are conventional closed-box speakers that weigh considerably more). Compact, tremendously compact, and light, lightweight. Advantages? Many. First, it is something rigging crews will appreciate, especially their precious backs; the load requirements on vehicles are reduced; the cabinets are far more manageable and can even be flown without complex aluminum structures: even with a 120 kg VMB we could hang 8 cabinets in an “array.”
I’m sure the advantages of an “array” configuration are already well known to our readers. It has become fashionable, although this revolutionary system has been well known to engineers for years. The concept is nothing new, but the advantages offered by the new waves of cabinet design and performance are. An “array” lets you control the drop in SPL (sound pressure level) with distance and maintain control of dispersion, above all in the vertical plane. In return, the first step must be executed with mastery. I’m referring to the always more complex process of designing and applying the system. Tackling that subject would take a whole article, and it is not the goal of these lines anyway.
Let’s get to our guests, called the RLA-3 or LS6500. Besides the aforementioned 5" ribbon for the highs, it includes a 6.5" midrange driver capable of handling up to 100 W RMS. Its frequency response runs from 80 to 20,000 kHz and its horizontal coverage is a far from negligible 110 degrees. According to the distributor, all the accessories for mounting or “rigging” are included as standard.
I ran the test at AudioGestion’s own facilities, a warehouse of pleasant size but not very suitable for the event. We used a mono configuration made up of four RLA-3 cabinets arranged in a vertical column, complemented by a subwoofer from the same SLS brand, although any other transducer and cabinet can be used as desired (as an option there is the RLA-2LF, also flyable, with a 15" driver capable of handling up to 600 W RMS, with a frequency response of 38 to 200 Hz).
I was surprised by the little invention of Toni Vargas, the distributor, who had eight RLA-3 cabinets in a 4-high configuration already mounted in a highly portable aluminum rack (there are also some interesting images on the manufacturer’s website).
For the console we used an Allen&Heath Wizard, a Sony CD player (connected balanced), Crown power amps and a BSS active crossover, set according to the manufacturer’s basic parameters. In all, three ways: one feed for the ribbon highs, another for the mids and another for the two 15" drivers acting as the subwoofer.
I must admit that the test setting is not the most suitable, but I will try to extrapolate all the results to a better configuration. Obviously, I can’t speak about the stereo image, although the perception of the highs (never biting, and quite evenly spread) earned a good mark in that respect.
Using a 6.5" driver can be a problem in reproducing the low-mid frequencies. The manufacturer specifies a slight dip just before 400 Hz, a critical frequency for certain acoustic instruments and even low female voices. But Tracy Chapman’s warm, present voice came through solid, something I certainly appreciated. It is true that you can notice a certain hollow in that area, but trying to recover it with EQ produces a noticeably unbalanced, rather nasal sound. This would perhaps be the only “con” of a cabinet that has “pros” nearly everywhere else.
The midrange frequencies are crisp and precise, as I confirmed with the album “Tiempos” by Luis Robisco (with that Spanish guitar always well present). Thanks to Crown’s fast amplification, it is easy to see (better, to hear) whether the RLA-3s are fast too. And indeed they are. They reproduce transients well, with just a tiny hint of compression, perhaps due to the cabinets not yet being broken in (so, entirely negligible). The highs, as I’ve already said, are very present without becoming biting or shrill. In fact, the whole package is very malleable, responding quickly and very effectively to slight parametric EQ adjustments made directly on the Allen&Heath console. Mix engineers will appreciate the speed and subtlety they offer.
The 110° of horizontal dispersion that the manufacturer advertises, without any measuring device in hand, may well be real (you know the differences between what is said and what is “heard”). Perhaps to the point where you won’t need to pay much attention to the cabinet’s horizontal orientation. In the vertical plane, the manufacturer supplies a very complete software program that, from basic data, reports on cabinet placement in plan view, their aiming, and so on. To make the task easier, the rigging system is numbered and well thought out, which lets almost anyone achieve the aiming proposed by the program.
As for sound pressure, the specifications state 114 dB for the highs and 118 dB for the mids (with peaks of 120 and 127 dB respectively). Enough on paper. In practice, at about 12-15 meters on the horizontal axis (we didn’t fly them in the tests), the feel is very good, with a more than adequate level and a rather low console output.
Even when turning the volume down to still lower levels (what many of us would call a “whisper”), mids and highs coexist effectively, maintaining, up to a point, that tonal linearity we rarely achieve. Surely thanks to the ribbon tweeter and the use of several (in my case, 4) small-diameter midrange drivers rated for 100 W.
Conclusions
One of the conclusions I was most interested in with this system was seeing its possibilities “on the ground.” Unfortunately, in our country many gigs allow only a few hours for setup. That leaves no time to use complex programs based on mathematical algorithms that deduce the best position of an “array” system from the space, either for lack of time or because nobody paid for that “extra.” You arrive, set up, test and go. For rental companies, having varied equipment for every situation means a far from negligible investment, in addition to the extra management and production it involves.
By testing these cabinets without flying them (and keeping in mind that they are very manageable), and above all by seeing their more than good results, it’s easy to deduce that as a “quick” solution it is also possible. We could buy about 16 of these “little boxes” and offer a top-notch service for certain situations, or split them in two and do two gigs of this kind. The RLA-3’s high efficiency (94 dB for the midrange and 101 dB for the high frequencies at 1W/1m) will let you take advantage even of the new digital power amps, which offer good current delivery at high power in compact spaces (and weights!).
They thus become a more than attractive option, combining a versatile, multipurpose and lightweight cabinet for almost any kind of application: from speech (at conventions, the client will appreciate their compact size, sick of seeing bulky black boxes all over their ballrooms), to acoustic music (I’m sure they’ll fit like a glove in jazz or similar situations), and even rock/pop (taking special care in choosing the subwoofer). Invisible sound? Well, someone will have to pay the 999 euros each unit costs.
Management software
The inclusion of dedicated software that makes it easier to place and adjust the cabinets in “array” mode is welcome, especially considering that the program is developed by and for SLS and the cabinet model reviewed.
The program is not very intuitive for a newcomer, but it does quickly resolve the doubts of the initiated.
From a few basic parameters we can adjust the “array” system to achieve the desired coverage; and once it is ready, the program indicates how to hang the “array,” what angle to set for each cabinet and the throw distances in three-dimensional space. Easy and fast.
