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One-Seat Stereo Tuning Reference
DSP Tuning Method — norcalrep.com
Dealer Tool
One-Seat Tuning Method
The Correct Order of Operations
Each step depends on the previous one being correct. Doing them out of order produces results that cannot be diagnosed or fixed by ear.
Order is not optional
Polarity before delays. Delays before crossovers. Levels before EQ. If you start with EQ you are tuning the wrong problem. Every step assumes the previous one is already correct.
Step 01 — Foundation
Confirm Electrical Polarity
Verify all speakers move in the same direction when given a positive voltage. Use a polarity checker or measurement mic with oscilloscope. Do not use your ears — listening to speaker pairs will not reliably reveal polarity errors.
✕ Never set polarity by listening to pairs of speakers
Step 02 — Timing
Measure Distances & Set Delays
Measure from each speaker grille or dust cap to the microphone tip at the listening position. The nearest speaker gets the most delay. The farthest gets zero delay. Use the Delay Calculator in Tab 02.
Formula: (max distance − each distance) ÷ 13,584 in/sec × 1000 = ms
Step 03 — Integration
Set Crossover Points & Slopes
Use 4th-order Linkwitz-Riley (LR4) at 24dB/oct. Set sub low-pass one-half octave below the midbass high-pass. Choose crossover frequencies based on speaker dispersion, not preference. See Tab 03.
Sub LP = ½ octave below midbass HP → midbass HP @ 80Hz = sub LP @ 60Hz
Step 04 — Level
Set Levels Against Target Curve
Play pink noise through the left channel only. View in RTA. Adjust amplifier input sensitivity controls to bring the overall level close to the target curve before touching any EQ settings.
RTA: 1/3 oct · FFT 16384 · 16 avg · Rectangular window · 50% overlap
Step 05 — Correction
EQ Left Channel to Target
Tune left channel to the reference target curve using parametric EQ. Q = Frequency ÷ Bandwidth (at −3dB points). Verify a peak is real before boosting — it may be phase cancellation from a delay error.
✕ Never EQ with both channels playing simultaneously
Step 06 — Match
Match Right Channel to Left
Tune the right channel to match the left channel's response, not to independently hit the target curve. This ensures equal contributions from both channels and a stable center image.
Unfixable dip on one channel → mirror that dip in the other channel
Step 07 — Verify
Play Both Channels Together
Play both channels simultaneously in mono. A dip of 9dB or more indicates a delay error or polarity problem, not fixable with EQ. A peak over 6dB should be equalized equally in both channels.
✕ Dip ≥ 9dB when summed = delay/polarity error — EQ will not fix this
Step 08 — Confirm
Confirm Image With Test Tracks
Use bandwidth-limited pink noise tracks for center placement. Use full-range tracks for image width verification. Use a noise track to check noise floor — adjust all amp sensitivity controls equally at that point.
Download a REW target curve .csv and test tracks from your DSP manufacturer's support site
What delays actually do
Delays compensate for speaker-to-listener distance differences so all signals arrive simultaneously. They do not move the soundstage, do not extend image width, and do not change stage depth. Setting delays by ear is unreliable because level and frequency response differences will fool you every time. Measure and calculate.
The target curve is not flat
The standard car audio reference target has roughly 10dB of bass boost below 60Hz, transitioning to flat midrange between 60–160Hz with a gentle HF rolloff. Import the .csv target file into REW via: File → Import Frequency Response → click No on the C-weighting dialog.
Step 02 — Timing
Delay Calculator
Measure from each speaker's grille or dust cap to the microphone tip. The farthest speaker gets zero delay. All others are delayed to match it.
How to measure
Tape measure from grille surface (or dust cap on open baffle) to mic tip at the listening position. Measure in inches or centimeters. Your DSP takes milliseconds — the calculator handles the conversion. A 6" error is tolerable within a speaker's crossover band.
Speaker Distances
Small errors are tolerable
Even a 6" measurement error doesn't matter much within a speaker's crossover band. The formula is far more reliable than ear-based alignment. Aim for within 1 inch.
Delay Settings (ms)
| Speaker | Dist | Delay |
|---|
FORMULA:
delay = (max − dist) ÷ speed × 1000
speed of sound:
13,584 in/sec
34,544 cm/sec
delay = (max − dist) ÷ speed × 1000
speed of sound:
13,584 in/sec
34,544 cm/sec
Step 03 — Integration
Crossover Selection
Crossover points should be chosen based on speaker dispersion, not preference. The table shows ideal (green) through avoid (red) zones.
Why LR4 at 24dB/oct
4th-order Linkwitz-Riley crossovers produce a flat summed response with correct polarity, and a large dip with inverted polarity — which functions as an automatic polarity check. They're also the most forgiving of small delay errors and changes in listening position.
Sub / Midbass Integration Calculator
Set your midbass high-pass frequency. The subwoofer LP is placed one-half octave lower to maintain phase alignment through the crossover region.
Hz
Calculating...
Green: Ideal (λ ≥ 4D)
Yellow: Acceptable (λ = 2D)
Orange: Marginal (λ = 1.5D)
Red: Avoid (λ = D or smaller)
| Speaker Size | Green Zone (ideal) | Yellow Zone (OK) | Orange Zone (marginal) | Red Zone (avoid) |
|---|---|---|---|---|
| 1" tweeter | ≤ 3,390 Hz | ≤ 6,780 Hz | ≤ 9,040 Hz | > 9,040 Hz |
| 2.5" midrange | ≤ 1,356 Hz | ≤ 2,712 Hz | ≤ 3,616 Hz | > 3,616 Hz |
| 3.5" midrange | ≤ 969 Hz | ≤ 1,938 Hz | ≤ 2,584 Hz | > 2,584 Hz |
| 4" midrange | ≤ 848 Hz | ≤ 1,696 Hz | ≤ 2,262 Hz | > 2,262 Hz |
| 6.5" woofer | ≤ 521 Hz | ≤ 1,042 Hz | ≤ 1,390 Hz | > 1,390 Hz |
| 8" woofer | ≤ 424 Hz | ≤ 848 Hz | ≤ 1,131 Hz | > 1,131 Hz |
The 2-way dispersion problem
Crossing a 6.5" woofer and 1" tweeter at 5kHz puts the woofer deep in the red zone. This creates a hole in reflected sound that EQ cannot fix. The solution is a 3-way system with a 2.5" or 3.5" midrange, not a different crossover point.
Crossover Slope Comparison
| Order / Slope | Polarity Correct | Polarity Flipped | Verdict |
|---|---|---|---|
| 1st order (6dB/oct) | Gradual rolloff, wide transition | Large overlap / cancellation | Avoid |
| 2nd order BW (12dB/oct) | 3dB peak at crossover | Cancellation dip | Avoid |
| 3rd order BW (18dB/oct) | Flat sum | Flat sum | Acceptable |
| 4th order LR4 (24dB/oct) | Flat sum | Large dip (polarity indicator) | Recommended |
Step 05 — Correction
31-Band Parametric EQ
31 fully independent bands. Per-band frequency (10Hz–20kHz), Q, gain (±0.1dB steps, +18 to −24dB), and filter type. Load a scenario to practice, or build your own EQ from scratch.
Frequency Response
EQ Sum
Measured
Target
← Swipe left for Q →
| # | On | Type | Frequency | Gain (dB) | Q |
|---|
Field Reference
Quick Reference Card
Everything at a glance. One-seat stereo tuning method.
Never Do This
- Set polarity by listening to speaker pairs
- Set delays by ear
- EQ with both channels playing at once
- Start with EQ before polarity, delays, and crossovers
- Use 1st or 2nd order crossovers
- Use delay to fix sub/midbass phase alignment
- Equalize a dip caused by phase cancellation
Always Do This
- Confirm polarity first with a polarity checker
- Measure speaker-to-mic distance with a tape measure
- Use 4th order LR4 at 24dB/oct
- Set sub LP one-half octave below midbass HP
- Adjust amp sensitivity levels before EQ
- Tune left channel first, then match right to left
- Check noise floor after tuning; adjust all gains equally
REW RTA Settings
- Mode: RTA 1/3 octave
- FFT Length: 16384
- Averages: 16
- Window: Rectangular
- Max Overlap: 50%
- Update Interval: 2
- Import target: File → Import Freq Response → No on C-weighting
Delay Formula
- Identify farthest speaker → assign 0ms delay
- Subtract each distance from the maximum
- Divide by 13,584 (in/sec) × 1000 = ms
- Measure grille or dust cap to mic tip
- cm: divide by 34,544 instead
- Use Tab 02 calculator to avoid manual errors
Diagnosing Both-Channel Issues
- Dip ≥ 9dB when summed → delay error or polarity flip. Re-check Steps 1 and 2.
- Peak > 6dB when summed → EQ both channels equally
- Unfixable dip one side → mirror it in the other channel
- Dip shifts with position → phase problem, not EQ
EQ Q Values
- Q = Frequency ÷ Bandwidth (at −3dB points)
- Q 8–12: narrow notch, sharp room mode
- Q 3–6: speaker resonance correction
- Q 0.7–1.5: broad shelf, overall tilt
- Sub/midbass gap: single boost ~80Hz both channels
Q Value
0.70
0.1 — Very Wide
32 — Surgical
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