Sound & signal
Stereo image
Stereo image is where sounds appear to sit between the left and right speakers. In club production the low end is almost always mono and the width lives in the pads, effects and top end.
In practice
Bass is mono because width cancels when a system sums. Everything you hear as wide is happening up top.
Be sceptical of width you hear only in headphones — the separation is extreme there and nothing like the floor’s experience. If you make edits, keep the low end mono below roughly 120 Hz for the same reason producers do. And treat a record that sounds spectacularly wide on cans and thin in the room as a phase problem rather than a mastering choice; the mono-sum page covers how to check it.
Mono
Where the bass sits
~120 Hz
Below which to keep it centred
Headphones
Where width misleads you
Where these come from: Standard production and system practice — conventional, not catalog figures. For what we can measure, see what happens when it sums.
Why it matters
The reason bass is mono is practical rather than aesthetic: a wide low end partially cancels when a system sums to mono, which club systems do more than people realise, and the energy simply disappears. Producers centre it so it survives the room.
For a DJ the consequence is that width is almost entirely a top-end phenomenon, so it rarely causes mixing problems — two wide records do not collide the way two bass-heavy ones do. Where it matters is in the booth, where you are standing far too close to the speakers to hear the image the floor gets.
Frequently asked
Why is bass always in mono?+
Because a wide low end partially cancels when a system sums to mono, and the energy disappears. Centring it is how producers make sure it survives a real room.
Does stereo width cause mixing problems?+
Rarely. Width lives in the top end where two records interleave easily, unlike the low end where they collide.
Why does a track sound wide in headphones and thin in the room?+
Usually a phase issue that only shows when the system sums. Headphone separation is extreme and hides it completely.
Related terms
Mono sum and phase
Summing to mono adds the left and right channels together. Anything out of phase between them cancels rather than adding, which is why a wide stereo bass can lose most of its weight on a mono system.
Sub-bass
Sub-bass is the lowest band of a record, roughly below 60 Hz — the part a club feels through the floor rather than hears. It is where most of a track’s physical impact lives.
Room modes
A room mode is a standing wave between parallel surfaces, where a frequency related to the room’s dimensions reinforces itself. It makes some bass notes boom and others vanish depending on where you stand.
Joint stereo
Joint stereo encodes what the two channels share once and only the difference separately, rather than encoding each channel in full. At normal bitrates it buys quality; at very low ones it can narrow the stereo image.
Explore: Stereo to mono · Mono sum and phase · Sub bass · All DJ terms