Spread: free stereo widener plugin that keeps your low end mono

What a stereo widener plugin does

A stereo widener makes a sound feel wider than the speakers by increasing the difference between the left and right channels. Spread does this with mid/side processing. The mid is what both channels share, the center of the image. The side is what differs between them, the width. Width turns the side up or down against the mid: 0% is mono, 100% leaves the sound untouched, and 200% doubles the side for an extra-wide image.

Because mid/side width only rebalances what's already there, it keeps the sound mono-compatible: sum the track to mono and the side cancels, leaving the original center. That also means it can't widen a sound that has no side signal at all, like a mono vocal or a mono synth. That's what Haas is for.

Mid/side width vs Haas delay

Spread has two ways to widen, and they suit different sources.

Keep Haas below about 10 ms. Beyond that the delay starts to sound like a separate echo instead of width, and the mono-sum problems get worse.

Mono bass: keep the low end centered

Low frequencies should sit in the middle. Kick, bass and 808 carry most of a mix's energy, and when they spread across the stereo field the low end gets weaker on mono systems, unstable on headphones and harder for a mastering limiter to control. Mono Bass keeps everything below its cutoff (20 to 300 Hz) in mono, however wide you push the rest.

• 100 to 150 Hz: a safe default for most synths, keys and buses. Subtle Wide uses 150 Hz.
• 180 to 200 Hz: for very wide pads and stacked vocals, where low-mid smear builds up. Vocal Spread and Huge Chorus use these.
• Below 100 Hz: only when the source has important stereo content in the low mids that you want to keep.

Stereo widening presets and where to use them

Subtle Wide (120% Width, no Haas) is the one to reach for first: a pad or keys part opens up without drawing attention to itself. Vocal Spread adds 4 ms of Haas to 130% Width for backing vocals. Huge Chorus goes to 180% with 8 ms of Haas, for supersaw leads and pads in a drop. Mono Check sets Width to 0% so you can hear the track in mono.

On the pad demo, switch from Default to Subtle Wide and the chord moves out from between the speakers while the low end stays solid in the middle.

Then load Mono Check. If the pad gets noticeably quieter or thinner, it relies on width that won't survive phone speakers or club systems, and you should reduce Width or Haas. A wide part that still sounds good in mono is the goal.

Stereo imaging in a mix: what to widen and what to keep centered

A wide mix has contrast: a solid center and wide edges. If everything is widened, nothing sounds wide. Keep the kick, snare, bass, 808 and lead vocal in the middle. Widen pads, synth layers, backing vocals, ambient effects and reverb returns. Contrast over time works too: automate Width from about 110% in the verse to 150% in the chorus, and the chorus feels bigger without anything getting louder.

• Pads and chords from a synth such as Nova: Subtle Wide or Huge Chorus, depending on the section.
• Backing vocals and ad-libs: Vocal Spread, or pair Spread with the Double control in Velvet for a stacked sound.
• Reverb and delay returns: 120 to 140% Width spreads the space around a centered source.
• The mix bus: use small amounts only, 110% or less, and always with Mono Bass on.

Chorus is another way to add width, using pitch modulation instead of mid/side balance. For how it compares, see what a chorus effect is.

Using Spread in Ableton Live, FL Studio and Pro Tools

Spread goes on the track or bus as an insert, near the end of the chain: after EQ and compression, before reverb sends if you want the reverb to receive the widened signal.

• Ableton Live: drag Spread from the Plugins section of the browser onto the track. Live's tracks are stereo, so Haas works on mono recordings too.
• FL Studio: load Spread in an effect slot on the Mixer insert. Mixer inserts are stereo, so both Width and Haas work on any source.
• Pro Tools: insert Spread (AAX) on a stereo track or a stereo Aux Input. Mid/side width needs a stereo signal to work with.
• Logic Pro: load the AU version in an Audio FX slot on a stereo channel strip.

For a quick mono check of the whole mix, put Spread on the master with Mono Check, listen, then bypass it before you bounce.

Free stereo widener plugins: what to look for

Free wideners are easy to find; Wider from Polyverse is one well-known example. What separates a useful widener from a risky one is how it behaves when the width goes away. Check three things before you trust any widener on a mix.

• Mono compatibility: load it, then sum the track to mono. The sound should return to roughly the original, not turn thin, quiet or phasey.
• Low-end control: a way to keep bass in mono, like Spread's Mono Bass, so you can widen a full-range pad or bus without weakening the kick and bass.
• Level matching: more width often means more level, and louder always sounds better. Use Output to match the bypassed level before you decide.

Spread is free with no time limit, in VST3, AU and AAX. It pairs well with our other free plugin, Pump: widen the pads with Spread, then let Pump duck them around the kick.