Field and beam

How wide will the light be at a given throw?

Throw distance

Work backwards: how far back to cover a given width.

DMX addresses

Start addresses for a run of identical fixtures. A fixture never splits across a 512-channel universe.

Circuit load

Add up what's on one circuit or dimmer. Assumes simple tungsten loads, where watts equal volt-amps. For a dimmer, enter its amp rating (2.4 kW at 120 V is 20 A).

Watts, volts, amps, ohms

Fill in any two. Watts = Volts × Amps.

Kelvin and mired shift

Positive shift needs orange (CTO). Negative needs blue (CTB).

Unit converter

Factors from the handbook's conversion tables.

Lamp bulb size

Number after the letters is the max diameter in eighths of an inch.

Gel cross-reference

Type a gel number from any brand, or a name like ½ CTB or diffusion.

Voltage drop

Voltage lost in a power cable run, and the smallest copper gauge that keeps the drop under 3%.

Single-phase, two conductors, copper at 20 °C. This checks voltage drop only. The cable must also be rated for the current, so check your code.

Three-phase balance

Watts on each phase (120 V to neutral) to amps per phase, imbalance and neutral current.

Neutral current is for simple tungsten loads. Dimmers and electronic loads can add more neutral current, so size to your code.

Light level from candela

Footcandles and lux at a distance from a source of known intensity.

Rigging notes

These tools estimate and double-check. They do not replace a qualified rigger or engineer approving an overhead rig. Real ratings always come from the manufacturer's tag or chart.

Pipe weight

Weight of steel pipe by size, schedule and length.

Truss capacity

12×12 light-duty truss. Enter a span from 10 to 40 ft.

Sling angle and leg tension

Two equal legs lifting a centered load. The flatter the legs, the more force on each.

Bridle geometry

Fill in any two. Equal legs, with the pick points the same height.

Load total

Add up fixtures, truss, cable and hardware. The rows show an example, so replace them with yours.

Balance point and support loads

Loads along a truss or pipe. Find where it balances and what each support carries.

Distances are from the left end. The beam's own weight is counted at its center.

Working load limit check

Working load limit from a rated breaking strength.

Use the design factor your standard or venue requires. 5:1 is common for slings, but it varies. Splices and end fittings can lower the real limit.

Hitch factors

How the hitch changes a sling's rating compared with its vertical rating.

Electromagnetic and color spectrum

Wavelength grows and energy falls from left to right. Visible light is 400–700 nm.

Color wheels

Light mixes by adding. Pigment mixes by subtracting.

Drawing scale

Convert real feet to inches on a plot, or back. A screen can't show a true-size ruler, so this replaces the printed scales.

Knots

Pick a knot and step through how to tie it. Written steps only, no video.

Delay time

Time for sound to reach a speaker position from the stage. Use it to set a delay tower.

The extra 10 to 15 ms is common practice so the stage still sounds like it comes first. Adjust by ear.

Level and distance

How loud it will be at another spot, in open air from a single source.

Use the same units for both distances. Rooms, reflections and line arrays lose less level than this with distance.

Adding levels

Combined level of several sources playing at once.

Assumes unrelated sources. Two equal sources add 3 dB, and ten equal sources add 10 dB.

Speaker level estimate

Rough level at the audience from sensitivity, amp power and distance.

Open air, one speaker, continuous level. It ignores room effects, power compression and cable loss, and music peaks run higher.

Hearing exposure limits

How long a person can stay at a steady A-weighted level (dBA) in one day.

dBu, dBV and volts

Convert between signal levels, for example when mixing pro and consumer gear.

Impedance and amp load

Total load when several speakers share one amp channel, and how the power splits.

Ratings are nominal. Real speaker impedance dips below its rating at some frequencies, so leave some margin. Check the amp's own spec for its minimum load and power at each impedance.

Speaker cable loss

Power and level lost in the cable between the amp and the speaker.

Counts both conductors and assumes copper wire at 20 °C. Warm cable loses slightly more. For several speakers on one run, use the total load from the impedance card. A common rule of thumb is to keep the loss under about 5%.

Digital latency

Delay added by an audio buffer, from buffer size and sample rate.

Buffers are only part of the total. Converters, drivers, digital mixers and network audio each add more, so check your gear's spec.

Frequency and wavelength

Type either box and the other updates. Handy for subwoofer spacing and room problems.

End-fire subwoofer arrays use about a quarter wavelength of spacing at the frequency you want to control. Speed of sound changes with air temperature.

Mic polar patterns

Where a microphone listens. The top of each plot is the front, and the farther the line is from the center, the more it picks up from that direction.

Room modes

Lowest axial resonances from a room's dimensions. These are the frequencies a room tends to boom at.

Axial modes only, at about 70 °F. Tangential and oblique modes add more, and real rooms are never perfectly rectangular.

Input list

One row per channel. Saves on this device as you type.