Acoustic Guitar Live Sound: Clear, Full and Feedback-Free, by the Numbers
I'm a full-time acoustic musician — most nights it's me, a guitar plugged straight into an Allen & Heath CQ12T, and a room, with nobody out front mixing it. So I've spent years beating the three things that go wrong with an acoustic through a PA: the guitar that feeds back the moment you turn up, the thin, quacky, boxy sound a pickup makes that's nothing like the guitar in your hands, and the guitar that turns to mud when the room fills up.
This is the plain-English version of how I fix all three — the order I touch the desk and what each control is actually doing. The exact start-here numbers — gain, every EQ move, the compressor, the full feedback routine, laid out as a sheet you copy at soundcheck — are in the book at the bottom. This page gets you most of the way for free.
How to stop acoustic guitar feedback live
Feedback is the acoustic player's number-one problem, and it's worse than it is for a singer — the hollow body of the guitar is a drum tuned to one low note, and your speakers will set it ringing given half a chance. The good news: it's the most fixable thing on this list, and you fix it in layers, cheapest first.
- Put a soundhole cover in. This is the single biggest fix, and it costs a fiver. It damps the body's main resonance at the source, so the speakers have far less to grab. If you do one thing, do this.
- Notch the body resonance. An acoustic almost always howls first at one low frequency — its body resonance, usually down around 100 Hz. One narrow cut there kills most of the trouble without thinning the guitar.
- Use the desk's feedback tools properly. On the CQ12 the Feedback Assistant sits on the output, not the channel — ring the room out at soundcheck so it sets fixed notches, then arm the live filters to catch anything that creeps up mid-gig.
- High-pass the rumble. Rolling off everything below the guitar's low E clears boom and handling thud and makes the whole thing far harder to set off.
- Mind the room. Mains ahead of where you stand, sensible stage volume, and don't point a monitor straight at the soundhole.
Do those in order and a guitar that howled at half volume will sit there clean all night. My full ring-out routine and the exact notch settings are in the book.
Why your acoustic sounds thin, quacky or boxy through the PA
That brittle, nasal "plugged-in" sound — the one that's nothing like the guitar acoustically — is the pickup, not the guitar. Under-saddle pickups especially have a honky spike the PA exaggerates. Two things fix it, and neither is a magic pedal:
- Set the level with the gain, not the fader. A pickup is a quiet, fussy source; if the gain's wrong, everything downstream is fighting it and the sound goes thin and brittle. Get a strong, clean signal in at the front first — that alone fixes half of "thin and weak".
- Cut the honk. The boxy, quacky character lives in a narrow band up around 2.5 kHz. A confident cut right there is the single move that turns a piezo quack back into something that sounds like wood. Add a little body back in down low and a touch of air up top, and you've got the guitar you hear in your hands.
The principle: cut what's wrong before you boost what's missing. Most "thin" acoustics are really honky and boomy at the same time — fix those and the fullness is already there. Exact frequencies and amounts are in the book.
Do you need a DI box for an acoustic guitar?
Usually yes — and it's the difference between a sturdy sound and a weak, noisy one. A bare piezo pickup puts out a fussy, high-impedance signal that doesn't like long cable runs into a desk. A DI box fixes the handover: it gives you a strong, balanced signal down an XLR into the mixer's mic preamp, which is exactly what you want to work from.
- Active vs passive: an active DI suits a passive (battery-less) pickup best — it has the input the pickup wants. A passive DI is fine if your guitar already has an onboard preamp. Either beats plugging a jack straight into a line input.
- The exception: if your guitar has a strong onboard preamp with a line out, it can go straight into a line jack — but a DI into the mic input is still the more reliable way in for most players.
The book walks the whole signal path — pickup, DI, cables, what plugs where — once, properly, so it stops being a mystery.
How to EQ an acoustic guitar live
Same honest problem as vocals: out in the room you can't really hear what you're shaping, so you don't EQ by feel — you dial in a proven shape and trust it. The moves, in order:
- High-pass to clear the rumble and boom below the guitar.
- Cut the boom — a gentle dip in the low-mids tames the "boof" that builds up in a small room.
- Cut the honk around 2.5 kHz — the big one, above.
- Lift a little sparkle and air up top, gently, so the strings shine without getting fizzy.
Cut confidently, boost gently — every boost up top is a step closer to feedback. My exact band-by-band moves are in the book.
Compression, and the chain in order
A strummed acoustic has a big gap between a gentle fingerpicked verse and a hard-strummed chorus. A little compression — gentle, just a few dB on the loud bits — evens that out so the guitar stays present without you riding a fader. Done lightly it's invisible; pushed hard it squashes the life out of the strings. The whole chain, in order: in through the DI, set the gain, high-pass, EQ, a touch of compression, a little reverb, out. Get that order right, save it as a scene, and your sound is the one thing on stage you never worry about again.
Sounding good as a solo acoustic act (mixing yourself from the stage)
Here's what nobody tells you when you buy the mixer: at a solo gig you can't hear what the room hears — the speakers face away from you. So you stop chasing the sound by ear in the moment and instead build one known-good setup, save it, and trust it every night. Walk out front during soundcheck if you can, or drive the desk from your phone from the middle of the room. Clear beats loud — a clean, honest guitar at a sensible volume wins every pub gig over a loud, boomy one.
Balancing the guitar under your vocal
If you sing too, the guitar's job is to support the voice, not fight it — the most common solo-act mistake is a guitar so loud the words get buried. Set your vocal as the thing that cuts through, then bring the guitar up underneath it until it feels right from out front. Your voice is the other half of this — I wrote The Vocal Chain for exactly that channel; together they cover the whole solo rig.
The free version ends here
That's the 80% — the order, the principles, the fixes that matter most. What the book adds is the exact numbers: the gain targets, every EQ frequency and amount, the compressor settings, and my full feedback ring-out routine, all laid out as a sheet you copy straight onto the CQ12 at soundcheck. If you play out, it pays for itself the first night your guitar behaves.