🔰 BEGINNER LEVEL: Why Time Alignment Matters
The Precedence Effect
Human hearing localizes sound sources primarily by detecting which ear receives a sound first (interaural time difference, or ITD). The brain uses arrival time, not loudness, as the primary cue for direction.
This is the precedence effect: if two identical sounds arrive at slightly different times, the brain attributes the source to the first arrival. The second sound is perceived as coming from the same direction as the first, as long as it arrives within about 30ms (after 30ms it becomes a separate echo).
In a car: Your left tweeter might be 24 inches from your left ear and 44 inches from your right ear. Your right tweeter might be 42 inches from your right ear and 60 inches from your left ear.
Without time alignment, the left tweeter always reaches your left ear first — everything images left. With time alignment, we delay the closer speaker so both tweeters arrive simultaneously.
Illustration note: Top-down view showing speaker-to-ear distances and delay correction concept
Measuring Distances
Measure from the dust cap of each driver to your ear position (centered in the driver's headrest):
- Use a flexible tape measure or string
- Hold one end at the driver's dust cap
- Route the tape to your ear position (approximate center of where your ear would be while seated normally)
- Record the measurement in inches
Illustration note: Distance measurement diagram for full 3-way system with delay calculation table
Reference driver: The driver with the longest distance from your ear becomes the reference — it receives 0ms delay. All closer drivers receive delays to match.
Delay_n = (D_ref − D_n) / 13,500 in/s × 1000 ms/s
Example:
| Driver | Distance (in) | Delay (ms) |
|---|---|---|
| Right tweeter | 62 in (reference) | 0.00 ms |
| Left tweeter | 24 in | (62−24)/13,500 × 1000 = 2.81 ms |
| Right midbass | 56 in | (62−56)/13,500 × 1000 = 0.44 ms |
| Left midbass | 28 in | (62−28)/13,500 × 1000 = 2.52 ms |
| Subwoofer | 58 in | (62−58)/13,500 × 1000 = 0.30 ms |
These calculated values are the starting point. Fine-tune acoustically or with measurement.