// effects · tool 23
Stereo ↔ Mono
Downmix stereo to broadcast-safe mono with channel balance — or take a flat mono recording and give it stereo width with a Haas-effect widener.
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Two converters on one page
Stereo → Mono
Sums both channels into one with a proper equal-weight downmix (−6 dB per channel so the sum can't clip). The Balance knob weights the mix: centered uses both channels equally, full left or right uses just that channel — the instant fix for interview recordings where the mic only captured one side, or for podcast distribution where mono is the platform standard. Mono also halves WAV file sizes and guarantees identical playback on every speaker, PA system and phone earpiece.
Mono → Stereo widener
True stereo can't be conjured from one channel, but spaciousness can. This widener uses the Haas effect: the right channel gets a copy of the signal delayed by 5–35 ms. Below roughly 35 ms your brain fuses the two arrivals into a single, wider sound instead of hearing an echo. At 100% width the effect is dramatic on headphones; around 50–70% it just makes flat voice memos and old mono recordings breathe. One honest caveat: heavily Haas-widened audio can comb-filter if a platform later collapses it back to mono — keep width moderate for anything destined for TikTok or phone speakers.
FAQ
Why convert stereo to mono?
Identical sound from every speaker (phones, PA, voicemail, IVR), half the uncompressed file size, and a fix for one-sided recordings.
What does the balance control do?
It weights the left/right contribution to the mono mix. If one channel is noisy or empty, slide fully toward the good one.
How does the widener work?
The Haas effect: a 5–35 ms delay on one channel reads as spaciousness, not echo. Keep width moderate if the audio may be summed back to mono later.
Is my file uploaded?
No — everything runs in your browser via the Web Audio API.