Stage Plot vs Reality: Feedback at the Worst Moment
You are mixing a 4-piece indie band in a 250-capacity room with a low ceiling and a hard back wall. The stage plot puts the vocalist centre-front with a cardioid dynamic mic on a boom, two guitar amps behind her, and the drum kit upstage. During the first song, the vocal mic feeds back at around 1.2 kHz whenever the vocalist moves toward the drum riser. The mains are on stands 2 m either side of the stage, angled slightly inward. You have a 31-band graphic EQ on the mains and a monitor wedge at the vocalist's feet.
1. Identify the likely causes of the feedback and explain why it happens only when she moves toward the riser.
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Feedback occurs when gain around the loop (mic → console → amp → room → mic) reaches unity at a frequency. The 1.2 kHz ring is the frequency where the system has the most gain and the least loss.
Why only near the riser:
- Moving back puts the mic closer to the drum kit and the hard back wall, increasing reflected energy returning to the mic.
- The cardioid pattern has a rear null, but at 1.2 kHz the pattern is less perfect, and the mains angled inward may be projecting into the rear/side of the mic as she moves off-axis.
- The low ceiling and hard back wall create strong early reflections that raise the room's gain at that frequency.
So the cause is a combination of mic position relative to the mains and reflective surfaces, plus likely too much monitor or mains gain at 1.2 kHz.
2. Give your corrective actions, distinguishing what you do immediately during the song from what you change at the break.
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Immediately (during the song):
- Pull the vocal fader slightly and reduce the monitor send to the vocal wedge - the wedge is the most common feedback path.
- Cut 1.2 kHz narrowly on the graphic EQ on the mains and/or monitor, just enough to stop the ring (2–4 dB), not a wide scoop.
- If needed, move the vocalist forward off the riser with a hand signal.
At the break:
- Re-aim the mains so they do not fire into the mic's rear/side, and consider moving the stands forward.
- Reposition the vocal mic so the vocalist's working area keeps the mic in the mains' null.
- Ring out the monitors properly: raise gain until each frequency rings, cut it narrowly, repeat, then back off a few dB.
- Address the room: suggest the venue add absorption on the hard back wall, or move the drum riser.
Justification: during the song you only need to break the loop with minimal tonal damage; at the break you fix the geometry and gain structure so it does not recur.
3. The venue owner says feedback is 'just part of live music' and refuses room treatment. How do you respond and what do you document?
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I would stay professional and reframe it as a business issue, not an argument: feedback drives customers away and damages the band's show, and repeated feedback can damage the PA's HF drivers, which costs the venue money.
Practical response:
- Offer no-cost or low-cost fixes: re-aiming the mains, moving the vocal position, using the graphic EQ, and bringing two moving blankets or a portable absorber for the back wall.
- Explain that treatment is not required for a good show, but speaker placement and gain structure are, and those are within my control.
What I document:
- The feedback frequency and conditions in my show notes.
- The owner's refusal of treatment, in a dated email summarising the conversation and the mitigation steps I took.
- Any equipment risk (HF driver stress) noted to the venue.
This protects me if the venue later blames the mix, and it keeps the relationship workable.