Put a stereo widener across a mix, turn it up until the chorus opens, and listen to the bass. It got smaller. Not quieter on the meter, necessarily: smaller, looser, less like one instrument.
This happens for a reason that has nothing to do with the quality of the widener, and once you know the reason the fix is straightforward.
Why width costs you low end
Widening works by changing the balance between the mid and the side channels. More side content relative to mid reads as a wider image.
Bass lives in the mid. Low frequencies are usually centred, both because that’s how records are mixed and because it’s what vinyl cutting and club systems want. So when you raise the side channel to get width, you’ve raised everything except the bass, which amounts to turning the bass down relative to the rest of the mix.
There’s a second effect underneath that one. Low frequencies have long wavelengths, and when you spread them across the stereo field the two speakers stop reinforcing each other cleanly. A 60 Hz wave is about 5.7 metres long. Send slightly different versions of it to two speakers a couple of metres apart and they partially cancel: at the listening position, in the room, and completely if anyone sums to mono. The bass doesn’t just sit lower in the balance. It gets less solid.
The fix is a crossover
Split the signal by frequency and widen only the part that can take it.
Everything below the crossover point stays exactly as it arrived: centred, mono-solid, both speakers reinforcing. Everything above gets the width. The bass keeps its weight and the chorus still opens up, because the width you hear is coming from the guitars, the pads, the cymbals, and the reverb tails, none of which live at 90 Hz.
A sensible starting point is 100–150 Hz. Lower than that and you’ll still get some looseness from the bottom of the bass guitar. Much higher and you start narrowing the body of the snare and the low mids of the guitars, which makes the mix sound thin in a different way.
Set it by ear, not by number. Push the crossover up until the low end feels locked, then back it off until the mix stops sounding pinched in the low mids. The right value depends on the arrangement. A track built on a sub bass wants a different point than one built on a drum loop and a piano.
Check it in mono
This is the step people skip, and it’s the one that catches the damage.
Sum to mono. The side channel cancels, so anything you added there disappears. What you’re listening for isn’t whether the mix gets narrower; of course it does. You’re listening for whether anything changes level or changes tone.
If the chorus gets quieter in mono, you moved a part that mattered out into the sides. If a synth vanishes, it was already close to out of phase and the widening finished the job. If the whole thing sounds hollow, you’ve pushed past the point where width was free.
Some amount of mono loss is normal and fine. Every stereo record loses something in mono. The question is whether the thing you lose is decoration or the hook.
What “wider” should mean
Two ways to get a bigger-sounding chorus, and only one of them is a plugin.
The first is arrangement. Double the guitars and pan them hard. Put the pad up an octave. Leave the verse sparser so the chorus has somewhere to arrive. Width built this way is real. There’s different content in each channel, and it survives mono because the parts are still there, just narrower.
The second is processing, which redistributes what’s already on the file. That’s useful for finishing, for pushing a chorus a little further than the arrangement took it, and for fixing a mix that came in narrower than it should be. It can’t invent stereo information that was never recorded.
When a chorus won’t open up no matter how far you turn a width control, the answer is usually in the arrangement rather than the plugin. The widener is doing what it can with what’s on the file.
A working order
- Get the mix balanced in mono first, with the low end solid.
- Add width above a crossover set somewhere around 100–150 Hz.
- Push it further than sounds right, then back off. The last 20% is usually the part that breaks in mono.
- Check mono. Listen for level and tone changes, not for narrowness.
- Check on a phone speaker if you have one nearby, because that’s a mono speaker and it’s what a lot of people will hear first.