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How Dirac Live Works

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The short version

Beginner

Dirac Live measures how each of your speakers actually sounds in your room, at several seats, then builds a correction filter for each speaker so the sound at those seats gets closer to a chosen target. The filters run inside your AV receiver, processor or amplifier every time you play something.

Why your room changes the sound

Your speakers do not play into open air. Sound bounces off the walls, floor and ceiling and reaches your ears a fraction of a second after the direct sound. In the bass, the room’s dimensions create peaks where notes boom and dips where they disappear. The result is that two identical speakers can sound quite different depending on where they sit and where you sit.

What Dirac Live corrects

  • Frequency balance: bass that booms on some notes and vanishes on others, a speaker that sounds brighter or duller than its partner.
  • Timing: Dirac measures the full impulse response, so it can correct when sound arrives, not just how loud each frequency is. Dirac’s own description is that it “corrects both magnitude and timing problems using mixed-phase filters”.
  • Level and distance: each speaker’s volume and delay are set so they all arrive at the listening position together and at the same loudness.

What it cannot fix

  • A deep dip caused by sound cancelling itself at your seat. Boosting it makes the speaker work harder without filling the hole. Moving the speaker, the seat or adding a second subwoofer is the fix.
  • Reflections at every seat. Correction is a best fit across the positions you measure, not a perfect result everywhere in the room.
  • A room that rings for a long time. Dirac Live Active Room Treatment (ART) goes further in the bass, but physical treatment still matters. See Room Treatment.

The four steps

  1. Measure: place the microphone at each seat position the app asks for and let it play test sweeps through every speaker.
  2. Design filters: pick a target curve, which is the tonal balance you want the room to end up with. The app then calculates the filters.
  3. Export: send the filters to your device and save them to a preset slot.
  4. Listen and check: compare with the correction on and off. If you have a measurement mic and REW, measure the result too.

What you need

  • A device with Dirac Live built in, or Dirac Live Processor on a computer. See Compatible Hardware.
  • The Dirac Live app on a Windows or Mac computer, or the phone app where your device supports it.
  • An omnidirectional measurement microphone. Dirac’s help centre explains why cardioid and bi-directional microphones cannot be used.
  • A quiet room. Switch off fans, air conditioning and anything else that hums.

Ready for more? The Advanced section below explains mixed-phase correction, measurement positions and correction limits.

How it works in detail

Advanced

Impulse response, not just frequency response

Most room EQ systems reshape the frequency response only. Dirac Live works from the measured impulse response of each speaker in the room and designs mixed-phase filters, so it can adjust phase and timing as well as magnitude. Dirac’s position is that timing errors from the room “smear transients, blur imaging and turn clean bass into resonance”, and that correcting the impulse response is what addresses them.

A listening area, not a single point

A filter that perfectly corrects one point in space makes things worse a short distance away. Dirac models the sound across the measured listening area and designs a correction that works across those positions, which is why the number and spread of measurements matters.

Measurement positions

  • Dirac co-founder Mathias Johansson has said nine positions is a good rule of thumb, with more or fewer still able to give good results. He suggested three measurements at the main listening position and two at other seats, covering the area where people will actually sit.
  • StormAudio’s Dirac Live basic calibration guidance adds: do not measure outside the listening area, keep positions at least 20 to 25 cm apart and away from armrests and headrests, and avoid putting positions on the same horizontal, depth or height line.
  • Keep the room quiet and still during sweeps. Imprecise-measurement warnings usually mean the app could not get clean timing or phase data from that position, and repeating the sweep or moving the microphone slightly often clears it.

Correction limits

Dirac lets you set the frequency range each speaker is corrected over. Every Dirac target curve file carries a low and a high limit, and Dirac sells Room Correction in two licences: Full Bandwidth, which corrects from 20 Hz to 20 kHz, and Limited Bandwidth, which corrects up to 500 Hz. Many experienced users choose to stop correction well below 20 kHz, because above a few hundred hertz a single in-room measurement is dominated by reflections and position, and the speaker’s own design usually does a better job. See Full vs Limited Bandwidth.

Filter resolution

Dirac Live combines FIR and IIR filtering. How finely it can correct in the deep bass depends on how much filter length (taps) the manufacturer’s hardware provides at its processing sample rate, which is one reason the same Dirac version can perform differently on different devices. Treat published tap counts as manufacturer claims unless they come from the manufacturer’s own documentation.

Where the tiers fit

  • Room Correction: per-speaker mixed-phase correction, as described above.
  • Bass Control: takes over bass management and optimises how the subwoofers and main speakers blend through the crossover, and between multiple subwoofers. See Bass Control.
  • Active Room Treatment (ART): below 150 Hz, lets bass-capable speakers support each other through a multiple-input, multiple-output (MIMO) filter matrix to reduce decay and even out the bass across seats. Above 150 Hz it reverts to per-speaker correction. See Active Room Treatment.

Sources

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