Fix stereo width
Mix goes thin on a phone speaker? fix.fm measures your stereo width, spots fake stereo and narrows a mix that's too wide. Free, and nothing is uploaded.
Updated
Never uploaded. Everything runs in your browser.
In short
A mix is too wide when its sides, what differs between left and right, are as loud as its centre. Stereo wideners cause it, and phone and Bluetooth speakers, which play only the centre, lose much of the mix. fix.fm turns the sides down and leaves the centre alone. On our sample the sides went from +1 dB against the centre to -6 dB.
What's happening
Every stereo file has two parts. The centre is what left and right share, usually vocal, bass and kick. The sides are what differs: wide pads, the room, stereo effects.
Phone speakers and many Bluetooth speakers play only the centre. Stereo wideners and enhancer presets sound huge on headphones because they turn the sides up. Once the sides match the centre, much of the mix disappears on those speakers and the rest sounds thin.
fix.fm compares the sides with the centre and checks how alike left and right are. The fix turns the sides down to about 6 dB under the centre and leaves the centre untouched. Two identical sides are mono saved as stereo, so it says so and changes nothing.
Audacity has no width control. Vocal Reduction and Isolation gets close: Isolate Center on one copy, Remove Center on another, turned down. A mid/side plugin is simpler.
How far the width fix goes
Music with its sides +1 dB over the centre read moderate and after the fix fine, with the sides 6 dB under it and the mono sum unchanged. A mono reading saved as stereo was noted and left exactly as it was. Measured on with the samples described in how we test.
The width fix looks for one thing: sides as loud as the centre, with left and right that barely agree. The cases below are synthesised music, widened in software, and a clean reading saved as stereo, so we know exactly what was there before and can check what the fixer changes.
Synthesised music widened in software, then run through this page's fixer at full amount, and a clean reading saved as stereo. Every clip is matched to -23 LUFS. Use headphones: width is what differs between your ears.
Music as mixed
The reference. Bass and tune sit in the middle, the drums step left and right, and the chord pad spreads out to both sides.
Music widened too far
On headphones it sounds huge and a little vague. The pad and the drums pull out to the edges and the middle feels empty.
Widened music, after the fix
Still stereo, but the sides sit back behind the middle again, close to how it was mixed.
Widened music, as a phone plays it
Left and right added together. Much of the pad and drums cancels out. The fix leaves this exactly as it is, because it never touches the centre.
Mono in a stereo file
A reading copied to both sides. It sounds like it comes from the middle, because it does.
Mono in a stereo file, after the fix
Identical. There is no width to fix, so the fix leaves it alone.
Music synthesised by fix.fm and a public-domain LibriVox voice. The widening is done in software rather than with a real plugin, so the music as mixed really is what was there before.
| Case | Sides against centre | Correlation | Lost in mono |
|---|---|---|---|
| Music as mixed | -16 dB fine | 0.95 | -0.1 dB |
| Music widened too far | +1 dB moderate to -6 dB fine | -0.09 to 0.60 | -3.4 dB to -1 dB |
| Mono in a stereo file | under -60 dB note to under -60 dB note | 1.00 to 1.00 | 0 dB to 0 dB |
The widened music had its sides +1 dB against the centre, which the check reads as moderate. After the fix they sit 6 dB under it and it reads fine. The music as mixed sat at -16 dB, so the fix lands between the two: still stereo, no longer leaning on the sides.
The fix only turns the sides down. The centre, which is all a phone plays, comes back sample for sample, so the mono version sounds exactly as it did. What changes is the stereo version: it stops promising width that a phone listener never hears.
The reading saved as stereo has two identical sides. The check notes it as mono in a stereo file and the fix leaves every sample as it was.
What this does not prove: the widening here is a clean mid/side boost. Real wideners also use delays and phase tricks, and a part that cancels in mono is gone from the centre for good. Turning the sides down makes the stereo and mono versions agree; it can't bring back what the centre lost. How we test has the pass marks behind the check.
How it works here
- 01
Splits centre from sides
It measures what left and right share (the centre) against what differs between them (the sides), and how alike the two are, every half second.
- 02
Brings the sides in
On a mix that's too wide, it turns the sides down to about 6 dB under the centre. The centre, which is what a phone plays, isn't touched.
- 03
Stays on your computer
Your file is never uploaded. The width fix runs in this browser tab.
Questions
Why does my mix sound thin on my phone?
A phone speaker, and most Bluetooth speakers, play left and right added together. Anything that is only in the sides cancels out, so if a widener or a stereo enhancer pushed a lot of the mix into the sides, the phone loses it and what's left sounds thin.
What is mono compatibility?
How well a stereo mix holds up when left and right are added into one channel, as on a phone, a smart speaker or a mono PA. A mix with a solid centre loses a little; a mix that leans on the sides loses a lot.
Is a wide mix bad?
No. Width is part of what makes a mix feel big on headphones. It becomes a problem when the sides get as loud as the centre or louder, because then a lot of the mix depends on the listener having two speakers. fix.fm only flags it from that point.
Does this make the song mono?
No. It turns the sides down, not off, so the stereo picture stays, just narrower. The centre is left exactly as it was, so the mono version you hear on a phone doesn't change at all.
My file says mono in a stereo file. Is that a problem?
Not for speech. Many recorders, phones and call apps save one mic to both sides. It plays the same everywhere, and there is nothing to fix unless you wanted a stereo sound.
Is my audio uploaded anywhere?
No. The file is read and fixed inside this browser tab and never leaves your computer.
Understand the next step
Related fixes
Often turns up with Stereo width- FX-06One earVoice only on the left or right
- FX-05Too quietLevel to podcast volume
- FX-13DC offsetWaveform sitting off centre
Working on a song? Fix music checks it for this and every other problem a mix can have, in one pass.