A client sends over a stage render: a wide curved wall behind the keynote, drawn as three clean facets. The brief says "three segments, P3.9, about 9 metres wide". That sentence is where most curved-wall arguments start, because three facets on a drawing and three segments in a cabinet grid are not the same thing, and the difference shows up as a visible kink four metres from the camera.
I spec indoor rental walls for a living, and the curve is the part that eats the budget. Here is the arithmetic I run before I quote anything.
Start from the radius, not the segment count
A render tells you the look. It does not tell you the geometry you actually build. Before I count a single cabinet I want two numbers: the radius of the arc at the screen surface, and the total angle it sweeps. Nine metres wide means nothing on its own. Nine metres at a 6 m radius is a 90-degree sweep; nine metres at a 20 m radius is a gentle 26-degree bow that most people will read as flat.
Then check what one cabinet can bend
A 500 x 500 mm rental cabinet does not bend. It hinges, joint by joint, and each joint has a limit, usually around 5 degrees between neighbours. So the real question is how much chord one cabinet covers at your radius. At 6 m, a 500 mm cabinet covers roughly 4.8 degrees. At 12 m it covers 2.4 degrees, and the wall looks smoother for the same cabinet count because each facet is shallower. Push the radius down to 3 m and 500 mm cabinets stop working: the joint limit is reached before the arc closes, and you either move to narrower cabinets or accept open wedges at the back.
The three-facet trap
Take our 9 m wall at a 6 m radius. A true 90-degree arc is 9.42 m of screen, which is 19 cabinets across. Now build it the way the drawing shows: three facets of 30 degrees each. Each facet is 3.11 m of chord, so six cabinets, eighteen in total. You saved one cabinet and bought yourself a 15-degree break at each joint, three times the hinge limit. On site that becomes either custom angled spacer blocks that nobody quoted, or a black seam the client sees on the recording.
Nineteen on a true arc is usually the cheaper answer once you price the spacers and the extra labour.
Rows, weight, and what the curve does to the base
Height runs in the same 500 mm increments, so a 3.5 m wall is seven rows. Nineteen by seven is 133 cabinets before spares. At roughly 8 kg each that is a bit over a tonne of screen, and the arc matters here: the curve pulls the centre of gravity forward of the base line, so ballast has to sit behind the ends, not under the middle. If the wall is flown instead, the curve changes the pick points, and the two end columns carry more than the middle ones.
Ask which radius you were given
One more thing that costs a day. Renders often dimension the radius to the back wall or to the front edge of the stage, not to the LED surface. The difference is the cabinet depth plus the trim, maybe 120 to 200 mm. On a 6 m radius that is 2 to 3 degrees of sweep, which is half a cabinet. It will not change the look, but it will change the count, and the count is what the client approved.
Spares and the truck
Curved builds always consume odd numbers, and the ends of the arc are where panels get handled hardest during load-in. I carry 5 to 8 percent spare on a curved wall, so 133 becomes 141. That is one more flight case, and it is the difference between a fix at 09:00 and a black rectangle at 19:00.
The camera does not care about your pitch
Everyone argues P2.6 versus P3.9. On a curved wall the pitch is rarely the problem. The problem is that the ends of the arc face away from the camera, so the effective pixel density at the edge of frame is worse than the middle, and any text placed there reads soft. Keep type in the central third, and let the curve carry colour and motion at the edges.
For the spec above I would use AIRD3.91-H: 500 x 500 mm cabinets, P3.91, with an adjustable joint angle so the arc is built from real angles rather than shimmed guesses. Link is on the site if you want the dimensions: https://www.mlxled.com/product/aird3-91-h-indoor-p3-91-led-panel-display-indoor-rental-led-curved-display-panel/
So: nineteen cabinets on a true arc, or eighteen in three flat facets with a 15-degree break at each joint. Which would you sign off for a keynote that gets filmed?
I work with MuenLED (#MuenLED).
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