One of the first interesting moving LED products I had the pleasure to see was an early frying pan-shaped moving head fixture. It was easy to be impressed by any LED tech at that point. This was the mid-2000s, and to the extent that LED fixtures existed, they largely recapitulated the familiar forms of moving-head fixtures. Pixel control of moving head fixtures was almost unheard of, largely because it was totally irrelevant: nobody needed or wanted to control individual red, green, and blue dots. These were trying times.
We progressed, we built new things, and we broke out of the traditional moving-head form. Miniaturization and collimating lenses made high-powered lights with pixel-mapping a practical possibility, and eventually, a new class of light entered the scene — the moving linear batten. Today, we’re looking at one such batten, the Tetra1 from Robe.
The Fixture’s Features
Physically, the Tetra1 (and its identical-except-bigger brother, the Tetra2) resemble a standard LED batten, with the head being encased on either end by its yoke. Within the batten sit nine large pixels that travel forward and backward within the head to effect the zoom function of the light.
The sources are nine 40W RGBW LED emitters for a total output wattage of 360W. The emitters are topped with an optic to bring the native Lambertian distribution down to something more manageable and homogenize the output of the four emitters. These do an excellent job — there are no multicolored shadows anywhere within the range. The front lenses are large — about 1 7/8 inches, or about 47 mm across, and form an attractive front face with minimal spacing between adjacent cells. The 18-bit dimming is extremely smooth, with no noticeable dips or spikes in the output, even at the very lowest levels before blackout. I measured 1,730 lux at 50% zoom from five meters away, after allowing the fixture to warm up and come to thermal equilibrium, and rather surprisingly, I measured no thermal droop on this fixture. I suspected, and Robe confirmed, that the LEDs are run slightly below maximum power to keep output consistent as the fixture heats up and to increase the lifespan of the emitters. The dimming curve nearly identically followed an ideal square law curve, with a linear option available through the menu. The Tetra1’s default PWM speed is 300 Hz, which is a little slow these days, and could cause banding with CMOS sensors. There is an option to set it to 1,200 Hz, with additional adjustments up or down relative to the chosen “base” setting, for those times when you have a tricky camera sensor to contend with.
There are several large, thermostatically-controlled fans that don’t run until necessary. In my testing, the cooling system tended, somewhat distractingly, to cycle on and off every ten seconds or so, which in noise-sensitive environments might be an issue. The test unit I was provided did not have an option to throttle the light output back to keep the fans low; Robe says this option will be available soon in a software update.
Colors are as expected from an RGBW unit, with the white helping fill out the pastel parts of the range. Like nearly all of Robe’s LED range, the Tetra line includes a variable CTO channel with what Robe refers to as “Tungsten lamp emulation,” which emulates a tungsten red shift as the light is dimmed in certain color temperature ranges. Tungsten emulation is always a tricky thing with LED. Personally, I usually find the utility of these sorts of features limited, because RGBW (without other emitters) is strikingly poor at emulating low color temperatures. Your mileage may vary. The Tetra1 includes a variety of control modes for controlling and mapping the pixels. In addition to accepting Kling-Net input, the user can also control individual pixels via DMX. The fixture makes this easy, with background and foreground color controls, the ability to crossfade between the two colors, and a variety of built-in patterns that can be manipulated with crossfade, color, repeat, speed, and other parameters. The patterns feature, in particular, helps to speed up programming when you don’t have time to create complex pixel effects from scratch.
The Flower Effect
What Robe calls the “Flower Effect” is the standout feature of this light, first seen on their Spikie fixture and later on the Spiider and Tarrantula lights as well. The central pixel of the unit, unlike the other pixels, does not have its homogenizing optic permanently fixed over the LED chips. Instead, it swings out of the way on command, and the die is focused through a lens and prism to project an image of the lit LED emitters in the air or onto scenery, with the prism rotating both directions at variable speed. One consequence of focusing directly on the dies is that the colors aren’t homogenized — turn on red and white, and you don’t get pink, you get individual red and white spikes of light coming out of the fixture. The effect is similar to a star field gobo, but the individual color aspect really sets it apart. There is no separate lens group for focus, so the sharpness of the projected dies is determined by the zoom, which come into focus at around 75% of the zoom range. With the homogenizing optic out of the optical train, the center pixel can also get a tight, harder-edged beam on it than the other pixels, particularly when zoomed down to minimum. We note that the Tetra 2 model has two separate cells with flower effects, and each bank of nine cells has its own zoom control.
The Tetra1’s tilt range is 205°, and the fixture covered its tilt range in about one second — very snappy. Slow movements are possible, and I saw no jumpiness or judder in even one-minute-long tilt sweeps. The zoom function ranges from 4° to 45° degrees and covers its range in approximately one second. The narrow ranges are tight and punchy, creating a beautiful, solid curtain of light. The fixture can maintain a hard edge of light when wanted.
The fixture is moderately well-behaved in resets, blacking out before moving and resetting most of its mechanical effects (with the exception of zoom) before beginning to output again. From a cold start, it homes in just above 16 seconds, which is blazing fast for intelligent lights. Physically, the fixture stands 270mm (10.6 inches) tall, with a base 142mm (5.6 inches) deep and 508mm (20 inches) long, and weighs 11.3 kg (24.9 lbs.). The fixture accepts power in though a Neutrik PowerCON TRUE1 ins and pass-throughs, and DMX / RDM in through five-pin XLR ins and pass-throughs. Network data (Art-Net, MANet, MANet2, sACN, Kling-Net) is accepted via EtherCON ins and pass-throughs. Wireless data in can optionally be accepted via LumenRadio’s CRMX. The fixture sports the standard Robe full-color touchscreen menu system, which provides comprehensive access to all of the fixture’s features and settings, many of which are also able to be set via DMX. There is a sturdy tilt lock for transport, as well as another welcome feature — a side lock, which extends two pins out of the side of the unit for locking adjacent Tetras into a nice, unbroken line. Rigging is via two of the familiar Omega brackets fitted with the rigging hardware of your choice.
At A Glance:
A Solid-Performing LED Batten
The Tetra1 is a solid automated LED batten from Robe. I particularly love the flower effect, the high-quality of the dimming, and the large and attractive output lenses. With quality construction and high lumen output, it will be at home on a huge variety of stages as an effect and wash light.
PROS: High-quality dimming and mechanical effects; solid construction.
CONS: I wish the flower effect was on all the pixels.
FEATURES
- 4,225 Lumen Light Output
- 20,000+ Hour LED Life Expectancy
- RGBW or CMY Color Mixing Modes
- Individual Control of Each RGBW Pixel
- Variable CTO: 2,700K – 8,000
- 2,700K-4,200K Tungsten Lamp Effects
- Preprogrammed Pixel, Strobe and Pulse Effects
- Motorized Zoom
- Smooth 100-0% Dimming
SPECS
- Light Source: 9 x 40W RGBW LEDs
- Wattage: 360W
- Zoom range: 4°-45°
- Tilt Range: 205°
- Size: 20” x 10.6” x 5.6” (LxHxD)
- Weight: 24.9 lbs.
- MSRP: $6,859 (in cardboard)
Manufacturer: Robe
More Info: www.robe.cz
