A phone guest hearing themselves half a second late, a loop that climbs into a whistle, a voice doubling back on air: nine times out of ten the culprit is not the gear but a badly planned feed. The fix has a name every radio, TV and podcast studio eventually learns by heart: mix-minus, also called N-1. The idea is as simple as it is often neglected — you send each remote participant the entire mix, minus their own voice.
The problem: why you can’t send back the full mix
Picture a show with a host in the studio and a guest on the phone. If you send the guest the main mix — the one that also contains their own voice — here is what happens: their voice goes down the line, makes the round trip through the network (which always adds latency), then comes back into their ear delayed in time. The result is that they hear themselves in echo, which makes conversation almost impossible. Worse: depending on the line, that re-injected voice can loop back and build into feedback. Mix-minus removes the cause at the root: since the guest does not need to hear themselves (their own voice is already in their head), you take it out of their feed.
What each participant actually receives
A mix-minus is therefore a bespoke blend: the whole programme, minus one voice. The phone guest hears the host, the other contributors, the jingles, the music beds — everything except themselves. Hence the other name, N-1: out of N sources, the feed contains N minus one. And that is where the real catch lies: if there are two remote participants, you need two separate mix-minus feeds. Each must receive the programme stripped of their own voice alone, otherwise you recreate the echo for the other. Three guests, three mix-minus feeds. This is why broadcast consoles and serious codecs offer so many auxiliary buses.
How you build one, in practice
The classic method on a console relies on an auxiliary bus (or a dedicated mix bus). You send every source except the relevant guest’s channel to that aux, and it is that aux that feeds their return line. On a desk short of auxiliaries, you sometimes use the built-in mix-minus output on the phone channels, or a carefully set pre-fader send. The points to lock down are always the same:
- absolutely exclude the participant’s voice from their feed — that is the whole point;
- include everything else: host, other guests, sound cues, beds where relevant;
- one mix-minus per remote participant, never a shared feed;
- check the send level so the guest hears comfortably without overloading the line.
All-in-one podcast consoles made this setting mainstream: on the RØDECaster Pro II and the Tascam Mixcast 4 alike, mix-minus for the Bluetooth, USB or phone channels is handled automatically behind the scenes, precisely because it is the step everyone used to forget.
Phone, video, codecs: the same principle everywhere
Mix-minus is not just for the phone desk. The moment a round-trip link with latency is involved, it becomes essential. A telephone hybrid expects a mix-minus reference signal to cancel line echo properly. A guest on video (Zoom, Teams, VoIP) has exactly the same need: send them the blend without their own audio image. And on a contribution codec link between two studios, the feed you send the remote site is, again, a mix-minus. People sometimes confuse it with IFB (a presenter’s interruptible programme feed) or with production intercom, but the underlying logic is identical: give each person what they need to hear, without feeding them back to themselves.
The mistakes that keep coming back
The most common: a single mix-minus shared between two remote guests — one hears the other, but also themselves, and the echo returns through the back door. Next, forgetting to include a source in the feed: the guest doesn’t hear the cues and talks over them. Finally, confusing “muting the voice in the feed” with “muting the voice on air”: the participant must of course be present in the broadcast programme, they simply must not come back in their own headphones. A quick check in rehearsal, headphones on in the guest’s place, is enough to settle any doubt before you go live.
My take
Mix-minus is one of those invisible settings that separate a clean live show from one that stumbles. You never notice it when it is done right; you hear nothing but it when it is missing. The good news is that it needs no exotic hardware: a well-planned auxiliary bus and a little discipline about “who hears what” is all it takes. The habit to keep: as many remote guests, as many bespoke feeds. Set that principle once and for all, and live calls stop being a source of dread.
