Bass muss FCKN

Sub arc calculator. Because low end is not a suggestion.

·  by Simon Häring

Environment

Audience area

Evaluation
FOH position

Subwoofer

Layout

Arc angle and tapering

Main and side hangs

Advanced

Standard

Current setting

Arc Advisor beta — click to show

Advice on manual settings

ARC ANGLE

Recommended angle —
TAPERING

Advice —
0°30°60°90°
clean, punch-oriented coverage-oriented summation breaks down smallest angle that reaches the design coverage target, without taper angle currently set

Plan view with level map

Sub Arc level over angle

Delay and gain per stack

Stackx (m)y (m)φ (°)Delay (ms)Gain (dB)

Free-field model with one point source per stack, without ground reflection, audience absorption or cabinet response. Cardioid is approximated as a directivity pattern and does not reproduce any manufacturer preset. Absolute levels are to be read as relative. Rating uses four frequencies across the working range. Check delays and gains against a second source before transferring them.

About this calculator

Bass muss FCKN is a planning tool for horizontal subwoofer arrays in live sound. You tell it about the audience area and the subs, and it gives you a delay and a gain for every stack, plus the arc angle and tapering that fit the room. It all runs in your browser: nothing gets uploaded, there's no account, and once the page has loaded it keeps working offline.

What an arc array does

A straight row of subwoofers acts like one wide source. It's loud on axis and much quieter to the sides, and the wider you build it, the narrower that pattern gets. Delaying the outer stacks bends the wavefront as if the row were curved, which buys you width at the cost of some summation. The arc angle is how far it's bent. Tapering turns the outer stacks down to even out the level across the area.

How to use it

Enter the width and depth of the audience area and where the mix position sits, then pick the speaker and the preset you'll load into the controller. Set the spacing or the available width, and you get a broadband level map, a polar plot and a delay-and-gain table to copy into the controller. The Arc Advisor goes further and searches spacing and angle for you, in three variants: PUNCH for the tightest setup that still covers the area, BALANCED for even levels along the audience, COVERAGE for the largest usable area.

Supported subwoofers

L-Acoustics KS28, SB28, KS21, SB18, SB15m and CS1, each with its own factory presets, frequency range and directivity. Meyer Sound 1100-LFC, 700-HP, 2100-LFC, USW-121P, 900-LFC and 750-LFC — Meyer doesn't ship factory presets for these, so you pick the crossover directly: 60, 80 or 100 Hz, each with a cardioid variant. Any cardioid preset needs at least three cabinets per stack.

Main and side hangs

Switch this on to see how the low end of your line arrays gets along with the Sub Arc below 100 Hz. Enter the hang the way it's rigged, with K2 underneath if you fly K1, and the tool builds it from that: one source per element at its real height, plus its reflection off a hard or porous floor. The Sub Arc view shows the same map as without the hangs. It assumes main and Sub Arc are time aligned at the alignment point, the way you'd line them up with a measurement mic, and equally loud there in their own passbands, like a flat system. Filters only shape the level, and each element counts as omnidirectional down there. What changes from seat to seat is geometry, and that's what the map shows. In System and Difference, broadband runs up to 100 Hz, where hangs and Sub Arc overlap. Difference tells you what the hangs add to the Sub Arc or take away from it. Each side is time aligned to its main, by default 15 m into the audience where the −6 dB edges of both overlap. The edges come from the datasheet coverage, 90° for K1 and 70° for K2, K3 and Kara II. The arrival window marks where main and Sub Arc arrive within a quarter period of each other. It is measured from the geometry alone: the centre of the hang against the first wavefront of the Sub Arc, relative to the alignment point. That is the condition for coupling, not a guarantee. Whether they really add up at a seat also depends on L against R, on the length of the hang and on the floor, and that is what Difference shows.

What it doesn't do

This is a planning aid, not a measurement. It models free field with one point source per stack and shows relative levels, so it's for comparing options, not for predicting absolute SPL. Check delays and gains on site before you trust them.