SLS Loudspeakers RLA/2 Line Array -

SLS Loudspeakers RLA/2 Line Array

When you mention ribbon drivers to some tour sound engineers that require massive amounts of SPL from their loud speakers they cringe. That's because they are still under the old impression that ribbon drivers can't handle outputting the same SPL as a horn-loaded line array. Well the reality is, that's not true at all and SLS RLA/2 proves just that.
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(click thumbnail)When you mention ribbon drivers to some tour sound engineers that require massive amounts of SPL from their loud speakers they cringe. That's because they are still under the old impression that ribbon drivers can't handle outputting the same SPL as a horn-loaded line array. Well the reality is, that's not true at all and SLS RLA/2 proves just that.
Fast FactsApplications: Live sound, sound reinforcement, installation

Key Features: Two-way; twin 8-inch woofers; PRD1000 ribbon tweeter; 13-ply, 3/4-inch Baltic birch cabinet

Price: $2,410 per module

Contact: SLS Loudspeakers at 417-883-4549,

The RLA/2 is a true source line array module that brings a whole new level of clarity to the line array market. The key feature of the RLA/2 is the high performance PRD1000 planar ribbon transducer that generates a silky smooth high end different from any horn loaded or dome tweeter speaker you will ever hear. The ribbon driver can also displace heat more efficiently while handling an enormous amount of power making it tour capable.

For the low frequency, the RLA/2 uses two 8-inch drivers utilizing a demodulation ring magnet system providing a third less harmonic distortion and reducing inductance modulation. The drivers feature die-cast basket with a patented Intercooler system with handling capability of 500 watts RMS.

The RLA/2 box is constructed with a 3/4-inch 13-ply Baltic birch cabinet wrapped in a rugged weather resistant latex paint. The cabinets are available in black, white or paintable natural birch. Rigging is also included on each box with splay angels from 1 degree to 10 degrees. The total box weight is 60 pounds.

The operating range for the RLA/2 is 80 Hz to 20 kHz with a sensitivity (1W/1m) for the low frequency at 98 dB and high frequency at 103 dB. The horizontal coverage of the RLA/2 is 110 degrees that make for smooth and accurate coverage over a wide listening plane. The recommended amp power for the RLA/2 cabinet is 1,000 watts low frequency and 140 watts high frequency.

In Use

As the lead audio engineer for Merestone, a national production/install company, I constantly have to work in different environments that were clearly built without any consideration for audio. So with that in mind, it can be extremely difficult to achieve the kind of clarity and coverage we have grown accustomed to. In addition, today's audiences having a much more discerning ear, so it is very important that they hear the same quality of audio in a live venue as they would from their home theater systems. This is where using the right speakers that are sonically consistent yet dependable in a vast array of rooms and acoustical environments is so important.

Since I have been working with the RLA/2 line array I have had nothing but great results and a lot of compliments. While working on the Wells Fargo Star Conference in San Diego Cal., I utilized two different RLA/2 rigs simultaneously in two completely different venues across town form one another. This had to be one of the best tests of a systems consistency from venue to venue. For the Wells Fargo main session, we flew six RLA/2 cabinets in each corner with four FF2605 front fills and eight LBS8115 subs. The room dimensions were approximately 130 feet x 230 feet which requires a lot of coverage from this mid size line array. The RLA/2 not only covered the room but the consistency from front to back was amazing.

On the second night of the main session Wells Fargo bused all the attendees to the Bob Hope Theater located on the Miramar Marine Base. This theater was obviously designed with acoustics in mind but sometimes when you introduce an amplified audio system into an acoustically tuned room the results can sometimes be disastrous. We had to ground stack four RLA/2s per side with one complementary subwoofer per side and that worked very well based on the room size and what the LASS software had determined. The end result, the sound was just as good in the Bob Hope Theater as during the general session. That just proves all the more that SLS's RLA/2 is a speaker that you can depend on. It wasn't just me who was impressed, even the audience was constantly commenting on the quality of audio. To wrap up the event, Wells Fargo Flew Jay Leno down to perform during the last nights grand finally and what a difference it makes to hear ribbon technology at its finest.

Furthermore, during the entire show I never once felt any ear fatigue and even at higher levels of SPL. With that in mind it is very easy to grow accustom to the SLS speakers.

The RLA/2 line array can easily setup and flown in a matter of minutes between two people. This is due to the splay angles being clearly marked on the rigging hardware and the ease of use. The pins that come with the hardware are okay but I would strongly recommend the upgraded heavy duty pins if this is a system that will be transported a lot. For selecting the proper splay angles SLS offers the LASS software as a free download from their website. The LASS software is a CAD-based software that allows the user to match the speaker geometry to the room instead of trying to over compensate with processing. This software is very easy to use and from my personal experience, absolutely necessary to achieve accurate coverage.


In the past six months, the SLS RLA/2s have been in more diverse situations from tents and ballrooms to live venues and really put through the paces. They are rugged and dependable speakers with a clarity that sets SLS apart from anything else I have heard in a long time. Everyone at SLS was more than accommodating and gave extra personal attention. If you are in the market for a new line array, I highly recommend checking out the SLS RLA/2 system.

Review Setup

RLA/2 LS8800, FF2605 speakers, RLA/LF LSB8115 subwoofers; Lab.gruppen FP6400 amps; XTA 428 processors.

SLS - PRD1000 Planar Ribbon Transducer

The PRD1000 planar ribbon transducer is one of the key features to the SLS RLA/1, 1.5, and RLA/2 cabinets. This high performance ribbon features a Kapton diaphragm with an etched aluminum conductive trace that is symmetrically driven by symmetrical push-pull neodymium magnets. The driving force directly acts on the diaphragm and is evenly distributed over the radiating surface providing freedom from break-up resonance, transmission delay and losses. A flat diaphragm provides the ideal shape for sound radiation that is frequency independent and the result is an even and coherent wavefront with even dispersion, no wave cancellation, no signal delays, and no horn throat related colorations.

Extremely light, the PRD1000 is over 100 times lighter than a typical four inch titanium compression driver diaphragm and over 50 times lighter than a typical Hi-Fi dome tweeter diaphragm. As the diaphragm compares by mass to associated vibrating air volume, an extremely light diaphragm creates ideal conditions for sound energy transfer, accurate signal resolution, and very high sensitivity with high frequency output extension.

Besides being light weight, the PRD1000 can also handling temperatures of up to 750 degrees Fahrenheit due to positioning an acoustically transparent metal mesh intimate to the aluminum trace. This efficient heat displacement allows the PRD1000 ribbons to handle even more power than compression drivers.

The PRD1000 driver can be used with its standard flat faceplate or with specially-designed cast aluminum 70-degree x 40-degree horn.