🔧 INSTALLER LEVEL: EQ Workflow and Filter Strategy

The Correct EQ Approach

Always cut before boosting. Every boost increases the signal level at that frequency, risking clipping at some point in the signal chain and requiring increased gain elsewhere to compensate. Cuts don't cause these problems.

Maximum boost: 6 dB. If a frequency needs more than 6 dB of boost, there's a deeper problem — driver capability, enclosure, or crossover.

Illustration note: Before and after EQ response graphs showing measured, corrected, and target curves

Systematic workflow:

Step 1 — Measure:

In REW, measure the frequency response at the listening position. Use a calibrated microphone (UMIK-1 recommended). Average 4 positions within 12 inches of the listening position.

Step 2 — Identify problems:

Look for: - Peaks > 6 dB above target curve: identify center frequency and width - Dips > 6 dB below target: check if they're caused by phase cancellation first (EQ cannot fix phase cancellation — only phase adjustment can)

Step 3 — Apply filters:

Work from low to high frequency:

Start below 200 Hz. These are typically broad resonances (low Q ≈ 0.5–1.0). Use wide-band filters.

Proceed to 200 Hz–1 kHz. Seat and body reflection zone. Medium Q filters (1.0–2.0).

Address above 1 kHz last. Narrow resonances possible (Q 2–5) but avoid over-correcting — small positional changes affect HF significantly.

Step 4 — Re-measure, compare, iterate:

After each batch of EQ filters, re-measure. Compare to target. Do not adjust more than 4–6 filters at a time before measuring again.

Identifying and Handling Phase Cancellation

Symptom: A sharp dip that stays narrow across all microphone positions. EQ boosts at that frequency produce no audible improvement.

Test: Disconnect one channel (sub only, or one speaker). Does the dip disappear? If yes — phase cancellation between two sources.

Fix: Adjust time alignment or polarity of the canceling driver. Re-measure before continuing EQ.

EQ cannot fix phase cancellation — boosting at a cancellation null increases level from both sources, and they still cancel. Result: more distortion from both drivers working harder, same acoustic null.