Sound & signal
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.
In practice
Keep the low end mono: a club rig sums the bottom in the room whether or not your mixer does it first.
The check is one button. Sum your monitoring to mono and listen to whether the bass survives — if it thins out or the level drops, something down there is fighting itself. In a booth the practical version is to be careful with wide stereo effects on bass-carrying records and to trust a big system to reveal a problem headphones hide. Above roughly the low mids, stereo width costs nothing and does what you want.
Below ~120 Hz
Where mono matters
180°
The angle that cancels
One button
The mono check
Where these come from: Production and system-tuning conventions, not catalog figures — our analysis runs on a summed signal, so nothing we store describes a track’s stereo image. We analyse a mono sum, so we can measure how much low-frequency weight a track carries but not whether that weight survives being summed. Nothing on this site describes a record’s phase behaviour. For what we can measure, see the frequencies this affects.
Why it matters
Most club low end is effectively mono whether or not the mixer says so. Subs are usually fed a summed signal, and a room adds its own arrivals on top, so a bassline that only exists as a stereo difference is a bassline that may not reach the floor.
It also explains an effect that seems to cost nothing. A wide stereo effect on a bass-heavy record sounds enormous on headphones and can subtract from the very frequencies the mix was built on once the system sums it.
Frequently asked
Why should bass be in mono?+
Because it is the range most vulnerable to cancellation and the range with the least stereo information worth keeping. Centring it means the whole system reproduces it rather than only part of it.
How do you check mono compatibility?+
Sum your monitoring to mono and listen for anything that thins, drops in level or disappears. A record that loses its bass on that switch has stereo content down there that a summed system will remove.
Does a DJ mixer sum to mono?+
Many have a mono switch and most booths feed subs a summed signal regardless. Assume the low end will be summed somewhere between your mixer and the floor.
Related terms
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.
Bassline
The bassline is the low melodic part that moves underneath the drums. It carries the track’s harmony as much as its weight, which is why two of them at once clash in a way two melodies do not.
Kick
The kick is the low drum that states the beat — in most dance music, on every one of the four beats in a bar. It carries the pulse and most of the energy a floor actually feels.
Three-band EQ
A three-band EQ splits each channel into low, mid and high and gives you a knob for each. It is the primary tool for deciding which parts of two records are audible at any moment.
Explore: Sub-bass · Mixing guides · Bassline · All DJ terms