Subwoofer Array Simulator

After building the loudspeaker array simulator, I needed something similar for subwoofer arrays.

Why Sub Arrays

A single subwoofer radiates omnidirectionally at low frequencies. Point it at the audience, and as much energy goes backward toward the stage as forward. End-fire and gradient arrays use the interference between multiple subs to create directivity - more output toward the audience, less toward the stage.

The physics is simple but the results are counterintuitive. You’re deliberately creating cancellation, which feels wrong until you see it work.

What It Does

The simulator models 2 or 3 subwoofers with configurable:

• Spacing - Distance between subs (asymmetric spacing supported for 3-sub arrays)
• Delay - Per-sub delay in milliseconds (auto-calculated for preset array types)
• Gain - Individual level adjustment
• Phase - 0° or 180° polarity flip
• Allpass filters - Frequency-dependent phase shift without affecting magnitude

For each configuration, you get a frequency response plot at multiple angles (0°, 45°, 90°, 135°, 180°) and a directivity polar plot at the selected frequency.

End-Fire and Gradient Arrays

The end-fire preset arranges subs in a line with progressive delays - each sub fires in sequence from back to front. All subs share the same polarity. The delays align their output in the forward direction while creating destructive interference rearward. End-fire arrays can achieve tight patterns but require significant depth.

The gradient preset uses polarity inversion instead of pure delay stacking. The rear sub is flipped 180° and delayed so its output cancels the forward sub’s rear radiation. Spacing is typically a quarter wavelength at the target frequency. This achieves cardioid-like patterns with just two elements and less depth than end-fire, though with somewhat less pattern control.

The comb filtering you see in the frequency response at off-axis angles is the mechanism creating the directivity. Those nulls are doing the work.

Allpass Filters

Sometimes you want to adjust phase relationships without changing magnitude response. Allpass filters let you do this - they rotate phase as a function of frequency without affecting level.

Each sub can have an independent allpass filter with selectable order (1st through 4th). Higher orders give steeper phase rotation. This is useful for fine-tuning directivity at specific frequencies or matching phase response to other system components.

Limitations

This models point sources in free field. Real subs have finite size, rooms have boundaries, and ground planes change everything. Use this to build intuition about how spacing, delay, and phase interact - not as a substitute for measurement.

Try It

Subwoofer Array Simulator - runs in browser, no installation.