A track that sounds huge in headphones can lose half of itself on a club system, a phone speaker or a festival stack, because much of that width is two channels fighting each other. This page says what is actually happening, how to see it in the free Hardwave Analyser, and what to do about it.
What mono collapse is
Stereo width, in most plug-ins, is the difference between the left and the right channel. When a system sums those channels to one, and many do, the parts that were different cancel each other out. Whatever lived only in that difference is gone, and what is left can be thinner and quieter than the mix you approved.
That matters most at the bottom. Club and festival rigs are effectively mono below a few hundred hertz, and a kick whose low end is wide loses the very energy it was built for.
Seeing it, instead of guessing
The Hardwave Analyser is free with a Hardwave account and shows the two readings this comes down to.
Correlation. One number between -1 and +1. Near +1 means the two channels agree and the sum stays intact. Near 0 means they share little. Below 0 means they actively cancel, and that is where mono collapse comes from. On a hardstyle kick, correlation near +1 through the low end is what you want.
Per-band width. Width as a percentage, band by band, rather than one number for the whole track. This is the useful one, because a mix can be correctly wide in the highs and quietly broken in the lows, and a single number hides that.
The practical check: play the loudest part of your track, watch the low band, and see whether its width climbs while correlation falls. If it does, the low end is where your mono problem is.
Fixing the low end without losing the width you want
The rule most producers land on is simple: keep the bottom mono, widen above it.
- Keep the sub and the kick body centred. A wide sub buys you nothing on a big system and costs you level.
- Put the width where the ear hears it. Reverb tails, screeches, top-end percussion and stereo synth layers carry a sense of space without risking the low end.
- Check the result in mono, every time. Sum to mono, listen, and go back to the meters. The correlation reading tells you whether the change did what you thought.
Where WideBoi fits
Hardwave WideBoi is our stereo tool, and it is built around exactly this split. It divides the signal into three bands with a Linkwitz-Riley crossover, defaults at 200 Hz between low and mid and 3 kHz between mid and high, both movable, and gives each band its own width control. Set the low band's width to 0 per cent and everything under the crossover is mono while the mid and high bands stay as wide as you want. There is also a Mono Bass switch for the same job in one click.
WideBoi is in early access and ships with a Hardwave Pro subscription. The Analyser is free, with no time limit, and it is enough on its own to find the problem.
The short version
Width that disappears in mono was never width, it was cancellation. Watch correlation and per-band width together, keep the bottom centred, and spend the stereo where it survives the sum.