Audiobook recording setup for ACX (UK)

ACX (the Audible/Amazon audiobook platform) has technical specifications that are stricter than most podcasting and YouTube voiceover work. UK narrators access ACX through the same global platform as US narrators — the technical requirements are identical, but the gear procurement is different (Amazon availability, slightly different brand lineups).

The headline specs:

• RMS (average loudness): between -23 dB and -18 dB
• Peak: never above -3 dB
• Noise floor: below -60 dB
• Format: 192 kbps or higher MP3, constant bitrate, 44.1 kHz, mono
• Room tone: at least 0.5 seconds of silence at the head and tail of each chapter

The two specs that trip beginners are RMS and noise floor. RMS is fixable in editing. Noise floor is what your room and equipment produce — fix it at recording time or you lose the recording.

Why noise floor matters most

The -60 dB target is strict. To put this in context, a "very quiet room" measured with a smartphone app typically reads around -40 to -50 dB. To hit -60 dB, you need to actively reduce sound — not just record in a quiet room.

The fix is layered:

1. Pick the quietest room. Usually a bedroom or closet, not the kitchen.
2. Turn off everything that hums. Heating, fridge (if accessible), computer fans, phone airplane mode.
3. Add absorption. Soft surfaces around the mic kill reflections.
4. Use a directional mic. Cardioid pattern picks up your voice in front, rejects sound from behind.

Microphone choice

For audiobooks: cardioid dynamic or condenser mic with low self-noise.

Dynamic mics (less sensitive, more forgiving):

• Shure SM7B — gold standard for podcast and audiobook narration. Requires a preamp boost (Cloudlifter or similar) because output is low.
• Shure MV7 — USB+XLR, less expensive, doesn't need the preamp boost. Often the better first-time pick.

Condenser mics (more sensitive, more demanding):

• Audio-Technica AT2020 — workhorse condenser. Wider tonal pickup, picks up more room sound.
• Rode NT1 — exceptionally low self-noise (5 dBA), one of the quietest condensers at any price.

If your space is untreated, pick a dynamic. If you've got a treated room or a closet full of clothes, a condenser will give you more detail.

Audio interface — required for XLR mics

• Focusrite Scarlett Solo or 2i2 — UK-made, the most common starter interface. Solid preamps, USB-powered, £100-180.
• PreSonus AudioBox USB 96 — budget alternative.

If you pick the SM7B you'll need a Cloudlifter or FetHead (~£100-130) to boost output before it hits the interface.

Pop filter and shock mount

ACX rejects recordings for plosives about as often as for noise floor. A pop filter costs £8 and prevents 95% of plosive issues.

A shock mount isolates the mic from desk thumps. If you record at a desk, you need one.

Headphones — closed-back only

• Sony MDR-7506 — industry standard for narration. Closed-back, accurate, comfortable over long sessions.
• Audio-Technica ATH-M40x — alternative at similar price.

Open-back headphones leak sound back into the mic. Worse for narration than £30 closed-backs.

Recording space — the closet trick

The best audiobook recording space in your house is probably a wardrobe full of clothes. Clothes absorb sound; a wardrobe has no parallel hard walls; the size keeps the proximity effect controlled.

If you don't have a wardrobe that works, the next best thing is a corner of a bedroom with a portable vocal booth or reflection filter behind your mic. These cost £80-150 and convert any room into a passable narration space.

Realistic UK kit cost

• Mic (Shure MV7 or AT2020): £180-220
• Audio interface (Scarlett Solo): £110
• Pop filter: £8
• Boom arm with shock mount: £40
• Reflection filter or wardrobe setup: £100
• Closed-back headphones (MDR-7506): £75
• Software (Audacity free, or Reaper £50)

Total: £510-600 to hit ACX spec.

You can go cheaper — a Samson Q2U USB mic plus a wardrobe plus Audacity will get you to ACX spec for under £130 — but the recording will take longer to clean up in post.

Royalty math

ACX royalties depend on exclusivity:

• Exclusive: 40% royalty
• Non-exclusive: 25% royalty (you can also distribute via Findaway Voices)

UK narrators sell into both Audible UK and the global ACX market. The royalty rates are set by ACX, not regional. Run real numbers on the ACX royalty calculator and Findaway Voices calculator to see which model pays you better.

HMRC tax note

Audiobook royalty income is self-employment income for HMRC. The gear is an allowable expense (or capital allowance, depending on price). See allowable expenses guide and side-hustle tax calculator.