How Bass Boost Works
Bass boost applies a low-shelf EQ filter centered at 100 Hz. Everything below this frequency gets amplified by your chosen amount — frequencies above remain untouched. This is the same type of filter as the “bass” knob on a stereo or car audio system.
Because boosting bass adds energy to the signal, loud passages can exceed the digital ceiling and clip. Convertio automatically applies a brick-wall limiter after the bass filter to prevent distortion while preserving dynamics.
The processing chain: your audio → bass shelf filter (100 Hz, +X dB) → limiter (ceiling at −0.5 dBFS) → WAV encoding. The uncompressed WAV output preserves the bass enhancement perfectly without any lossy compression artifacts.
Bass Boost Settings Guide
| Level | Gain | Best For |
|---|---|---|
| Off | 0 dB | Original audio, no enhancement |
| Subtle | +3 dB | Gentle warmth for headphone listening |
| Moderate | +6 dB | Good for earbuds and laptop speakers |
| Strong | +10 dB | Car audio, gym playlists, Bluetooth speakers |
| Heavy | +15 dB | Powerful bass for EDM, hip-hop, trap |
| Extreme | +20 dB | Maximum impact, meme-level bass, subwoofer testing |
M4A Bass Boost: Vocal Warmth for Voice Recordings
M4A files from iPhone Voice Memos consistently lack low-end warmth because the microphone hardware prioritizes intelligibility over fullness. The tiny MEMS microphone capsules in iPhones are physically optimized for the 1–4 kHz speech clarity range — the fundamental frequency of human voice (85–255 Hz) is partially attenuated.
For podcasters recording field interviews on iPhone, a +3 to +6 dB bass boost restores the natural chest resonance and warmth that a studio microphone would capture. Male voices benefit most from boosting around 100–150 Hz (fundamental frequency range), while female voices respond well to 150–200 Hz enhancement.
The WAV output is ready for immediate import into GarageBand, Logic Pro, Audacity, or any DAW. The bass enhancement is baked in, so no additional EQ processing is needed during editing — though you can refine further if desired.
For Voice Memos: +3 dB adds subtle warmth, +6 dB gives a noticeable “studio mic” quality. Keep boost moderate for speech — excessive bass causes muddiness in voice recordings.