Time Alignment And Acoustic Integration

Video Companion

Basic System Tuning places channel verification, polarity, protective filters, individual measurements, level, time, acoustic crossover, EQ, spatial checks, and release in one measured order.

What You Will Be Able To Do

• Separate polarity, phase, delay, latency, impulse response, group delay, and acoustic center.
• Calculate useful starting delays from path-length differences.
• Measure relative arrivals with a repeatable timing reference.
• Align the stereo image without confusing level imbalance with timing error.
• Integrate adjacent drivers through their crossover region.
• Integrate the subwoofer through magnitude and phase rather than one impulse peak.
• Document the final result and the single-seat or multi-seat compromise.

There Are Three Different Alignment Jobs

Core Terms Before You Start

Equipment And Preparation

• DSP with independent channel delay, level, polarity, and crossover control
• calibrated measurement microphone and stable stand
• measurement software such as REW
• repeatable wired or acoustic timing-reference method
• safe sweep level and known crossover protection
• worksheet or the Time Alignment Workflow Card

1Define The Reference Position And Goal

Place the microphone where the alignment decision is supposed to work. For a driver-seat tune, use a repeatable point near the head or ear reference and document it precisely. For a multi-seat goal, define every position that will be checked.

Before measuring, write down which job you are doing:

• left-right image
• one adjacent-driver crossover
• subwoofer-to-midbass integration
• multi-seat compromise

2Build A Safe Baseline

1. Verify gain structure and establish a safe measurement level.
2. Set protective crossovers from driver capability and intended design.
3. Start with EQ neutral unless a required response-shaping filter is part of the crossover target.
4. Record all polarity states.
5. Set initial delay to zero or preserve the known baseline.
6. Save the preset before making changes.

3Calculate Starting Delays From Distance

Use consistent physical landmarks and treat the result as a first approximation:

Starting delay (ms) ≈ path difference (inches) / 13.5
Starting delay (ms) = path difference (metres) / 343 × 1000

Example: the near tweeter is 38 inches closer than the reference tweeter.

38 / 13.5 = 2.81 ms

Add approximately 2.81 ms to the earlier, closer tweeter as the starting point.

4Establish A Common Timing Reference

Relative delay and phase comparisons require a shared clock reference.

Wired loopback

A spare interface output and input create a direct timing reference. This is often the most repeatable method when the hardware and routing allow it.

Acoustic timing reference

A separate reference channel or speaker plays a timing signal before the sweep. The reference source must remain active and unchanged for every measurement being compared.

Do not compare delay or phase traces captured with unrelated timing references or arbitrary time-zero positions.

5Measure Every Driver Individually

1. Keep the microphone and timing reference fixed.
2. Mute every driver except the one being measured.
3. Measure with its intended crossover and polarity state.
4. Record the impulse, magnitude, and phase traces.
5. Name the trace with channel, driver, polarity, delay, level, and filter settings.
6. Repeat for every driver in the alignment group.

Trust phase only where the response has adequate magnitude and signal-to-noise ratio.

6Align The Stereo Image

1. Compare left and right channel level and frequency response first.
2. Apply starting delay to the earlier side.
3. Confirm that polarity and channel routing match the intended design.
4. Measure or inspect relative arrival in the image-forming band.
5. Listen to centered mono vocal, speech, or correlated noise at a safe level.
6. Adjust level and delay in small deliberate steps, recording each change.

A left-pulled image may be caused by earlier arrival, higher level, different response, reflection, or channel error. Do not assume delay is the only control.

7Align Adjacent Drivers Through The Crossover

1. Measure both individual responses from the same timing reference.
2. Confirm that their measured acoustic slopes reach the intended crossover shape.
3. Compare relative phase through the overlap region.
4. Measure the pair in the intended polarity.
5. Invert one driver and measure the reverse-polarity response.
6. Adjust delay, level, polarity, crossover, and EQ only as the measured evidence requires.
7. Repeat the normal and reversed sums.

A useful result normally shows a controlled normal sum and a repeatable reverse-polarity null near the intended crossover. Null depth and shape are diagnostic evidence, not the only design goal.

8Integrate The Subwoofer

Do not force the broad subwoofer impulse peak to match a tweeter or midbass peak.

1. Measure the subwoofer alone and the adjacent band alone using the same timing reference.
2. Confirm useful magnitude overlap and safe filters.
3. Inspect relative phase through the crossover region.
4. Sweep subwoofer delay over a reasonable range while observing the summed response.
5. Test polarity when appropriate.
6. Select a region that produces robust summation rather than one fragile single-frequency peak.
7. Repeat at nearby microphone positions.
8. Listen for localization, impact, decay, and tonal continuity.

9Check Group Delay And Decay In Context

Once magnitude and phase are stable, inspect impulse response, decay, and group delay for resonances or excess-delay behavior.

• Remove or document bulk system and propagation delay.
• Compare group-delay features with magnitude and phase.
• Use minimum and excess group delay when supported.
• Do not apply one universal millisecond audibility limit to every frequency.
• Repeat suspicious features at nearby positions before changing the system.

10Evaluate The Seating Tradeoff

A delay optimized for one ear position can worsen the opposite seat. Choose the goal honestly:

Troubleshooting Matrix

Document The Result

Record:

• vehicle, preset, date, temperature, and measurement system
• microphone position and timing-reference method
• driver, channel, polarity, crossover, level, and starting distance
• initial and final delay
• normal and reverse-polarity crossover results
• subwoofer integration range and nearby-position checks
• single-seat or multi-seat target
• final listening notes and saved measurement files

Open the printable Time Alignment Workflow Card →

Related Resources

• Delay
• Polarity
• Phase
• Impulse Response
• Acoustic Center
• Crossover Summation
• Group Delay