Check stereo width and mono compatibility with Utility

Use headphones or stereo speakers for the width comparison. This original synthetic source deliberately combines a shared centre signal with a different signal of opposite polarity in the left and right channels. After four seconds, the shared component becomes much quieter. Nothing is wrong with playback: that second half is a controlled example of a fragile stereo sound, not a recording of a real mix.

Three passes through the same eight seconds

1. Listen with Width at its starting 160%, Mono off and Balance centred. Follow the change halfway through. Gain is −6 dB to give the widened signal some headroom.
2. Enable Mono and replay. The channels are summed to their shared component. The deliberately opposite-polarity material cancels, making the second half much quieter. It is not completely silent because a small centre signal remains.
3. Disable Mono, reduce Width to 100%, then try 50%. Listen for less side information without the complete collapse of the mono check. Return to 160% to make the contrast clear, then settle nearer 100% before judging your own material.

Width scales the side component: the difference between left and right. At 100% that component is unchanged; at zero it is removed. Mono also removes it and overrides Width while enabled. Width does not manufacture a meaningful stereo image from two identical channels. Increasing it can raise peaks as well as apparent spread, which is why a louder result is not proof of a better stereo balance.

Narrowing is not the same as restoring a missing centre

The mono sum of this source does not acquire the cancelled notes just because you turn Width down. Narrowing reduces the difference you hear in stereo; it does not rewrite the original channel relationship. If an important musical line lives almost entirely in that difference, revisit the source or the processing that created it. Keep a stable centre version when the arrangement requires the line to survive mono.

Polarity is a diagnostic, not a width preset

Return Width to 100%. Enable Mono, then toggle Ø R. In this deliberately constructed source, inverting the right input makes the former difference information survive the sum instead of the former centre. Listen for a different set of tones rather than just more volume. Turn Ø R off and disable Mono to restore the starting channel relationship.

The Ø buttons invert polarity; they do not shift a channel in time or automatically repair phase differences at every frequency. Inverting both channels preserves their relative relationship. The input selector also matters: Left and Right copy one selected channel to both outputs, while Swap exchanges them. These modes are not alternatives to a careful mono sum when checking a complete stereo mix.

Keep low width and output level separate

Bass Mono reduces low-frequency side information below an adjustable region from 50 to 500 Hz, leaving the shared signal intact. To make its action obvious on this example, try it near 500 Hz with Mono off, then compare 120 Hz. The source’s prominent side tone sits around 330 Hz, so the higher setting affects it more. Return to 120 Hz and switch Bass Mono off afterward; 500 Hz was a demonstration, not a universal bass rule.

Gain trims the final level. Balance changes the relative output levels and should remain centred for these tests. DC is a very low-frequency cleanup filter, not a general bass-cut control; Mute silences the output. Use local audio replacement to check a real stereo part, keeping comparisons level-matched. Utility can reveal a mono-compatibility problem quickly, but it cannot infer which cancelled musical information you intended to keep.