Mono to Stereo Converter
Turn a mono file into stereo, downmix stereo to mono, or adjust the stereo width of a stereo file — then export a lossless WAV, all in your browser.
ℹ Converting mono to stereo just copies one signal to both channels (“dual mono”). The optional widening uses a small Haas delay to fake a sense of space — it cannot recover true stereo that was never recorded, and heavy widening can sound hollow if the file is later re-summed to mono. Output is WAV (browsers can’t write MP3/AAC). Everything runs locally — your file is never uploaded.
How It Works
Your file is decoded to raw samples in the browser. Mono → stereo copies the single channel to both left and right (dual mono); the optional width control adds a short Haas delay to one channel so it feels wider — a psychoacoustic trick, not real stereo. Stereo → mono averages the channels, (L+R)/2. Adjust width uses mid/side processing: it splits the signal into mid M=(L+R)/2 and side S=(L−R)/2, scales the side by your percentage (0% collapses to mono, 100% is unchanged, 200% is twice as wide), then rebuilds L=M+S, R=M−S. The result is exported as a lossless 16-bit WAV. Nothing is uploaded.
Real stereo carries information captured by two microphones (or panned in a mix). No tool can invent that from a mono recording — widening only simulates space. If you’ll re-sum the audio to mono later (some phones, club PAs), heavy Haas widening can partially cancel, so keep it modest. For MP3 output, re-encode the WAV in a desktop app.