EQ, High-pass Filters, Dynamics, Delay & Feedback Reduction

Est. 55 minCompetency: Apply EQ, dynamics, delay, and feedback reduction appropriately.

Learning objectives

Apply EQ and high-pass filters to improve intelligibility.
Use dynamics (compression/limiting) safely.
Apply delay for speaker alignment.
Use feedback reduction without over-processing.

Vocabulary

Equalization (EQ): Adjusting frequency balance to improve clarity.
High-pass filter (HPF): Cuts low frequencies below a point (e.g. 120 Hz) to reduce rumble.
Compressor/limiter: Reduces dynamic range; a limiter prevents peaks from clipping.
Delay: Time-aligns speakers at a distance.
Feedback reducer: Narrow notches that cut the frequency feeding back.

Lesson content

Processing should be surgical: fix the room and the mics, then stop. Over-EQ'd, over-compressed audio sounds worse than a light touch.

EQ and high-pass filters

Apply a HPF (e.g. 120 Hz) to mics to cut HVAC rumble and table thumps.
Use gentle EQ to improve intelligibility (often a small boost in the presence band).
Cut problem frequencies, do not boost broadly.

Dynamics: compression and limiting

A compressor gently reduces level variation; a limiter is a hard ceiling.
Use a limiter on the speaker output to protect against clipping and feedback spikes.
Avoid heavy compression — it pumps and fatigues listeners.

Delay for alignment

1If speakers are at different distances from listeners, delay the closer one.
2Sound travels ~1 ms per foot (~3 ms per meter); align so arrivals coincide.
3Verify by ear from a representative seat.

Feedback reduction

Feedback is a loop: mic → speaker → mic at a frequency the loop gain exceeds 1.
Fix it first with mic placement and gain; use a feedback reducer for the last stubborn notch.
Notch out the specific frequency; do not flatten the whole response.

Order of operations

Placement and gain first, then HPF, then gentle EQ, then a limiter, then feedback notches only if needed. Fix the physical problem before adding processing.

Worked example

A conference room: HPF 120 Hz on all mics; a small +2 dB presence boost; a limiter at -3 dBu on the speaker output to prevent clipping; 2 ms delay on the near ceiling speakers to align with the far ones; one narrow notch on the feedback reducer for a recurring ring.

Implementation checklist

✓HPF on mics to cut rumble.
✓Gentle EQ for intelligibility.
✓Limiter on outputs to protect against clipping.
✓Delay for speaker alignment.
✓Feedback notches only after placement/gain are right.

Downloadable study guide

study-guide.txtcopy-paste ready

01. HPF (~120 Hz) cuts rumble; gentle EQ improves intelligibility.
02. Limiter = hard ceiling; avoid heavy compression.
03. Delay aligns speakers (~1 ms/foot).
04. Fix feedback with placement/gain first; notch only the offending frequency.