Processing mode

Use the Processing Mode button in the bottom bar to choose how EQ processing is carried out. For the vast majority of sessions, either Zero Latency or Natural Phase modes give flawless results, and whenever linear-phase processing is required, Linear Phase mode is ready with a resolution you can adjust.

Zero Latency

With Zero Latency mode active, Contour reproduces the magnitude response of analog EQing as faithfully as it possibly can, and naturally does so with no added latency at all. This is the leanest of Contour's processing modes, and more than enough for the great majority

Natural Phase

The Natural Phase mode that sets Contour apart goes a step further still. Beyond faithfully reproducing the magnitude response of analog EQing, it also tracks the analog phase response very closely. The result is the truest frequency response and the finest sound quality, right down to the lowest frequencies and up to the highest Q settings, all without audible pre-ring or lengthy latency.

To make the contrast between the two modes clear, we've graphed both the magnitude and phase response of a Bell filter at 15 kHz, and we've set that alongside conventional digital EQing of the kind most DAWs build into their stock EQ plug-ins.

The red curve traces the magnitude response of conventional digital EQing, which is genuinely a long way from ideal. The blue curve represents Contour's Zero Latency mode, which comes remarkably close, aside from a slight drop above 18 kHz. The green line marks Contour's Natural Phase mode: it lands exactly on the theoretical analog magnitude response!

Now consider the phase response. Once more, the red curve stands for conventional digital EQing, and the blue curve for Contour's Zero Latency mode: neither has an ideal phase response. The green line shows the response of Contour's Natural Phase mode. Setting aside a tiny, inaudible drift above 20 kHz, it lines up perfectly with the theoretical analog phase response.

Linear Phase

As they shape audio, conventional analog and digital filters alter not just the magnitude but the phase along with it. In practice, the phase of the various frequencies within a signal ends up shifted by differing amounts. That can be audible in the result, though not always for the worse. In many situations, such as a straightforward bell or shelving filter, these phase shifts stay so subtle that they are barely perceptible. For steeper, higher-order filters such as aggressive low cut or high cut filters, however, the consequences grow far more obvious, since the phase distortion begins to smear transients and can rob the sound of its clarity.

Trouble also appears once you blend a filtered, phase-shifted signal with another comparable signal that was left untouched, or that was filtered in some other manner. Under these conditions the differing phase components of the two signals are unlikely to align, and they will partly cancel one another out. A scenario like this often turns up while mastering. A frequent practice is to equalize just one section of a track, fading in and out at the boundaries of the treated region. Since the phase content of the original and processed sections differs, those fades fail to behave the way you expect.

Linear-phase processing offers a way around these difficulties. A linear-phase filter alters only the magnitude of the audio and leaves the phase completely intact. That said, linear-phase filters carry drawbacks of their own. To begin with, they add latency: the whole signal is delayed as it travels through the plug-in. A higher processing resolution (which improves the response in the low frequencies) means longer latency, yet it can regrettably bring 'pre-ring' that saps the punch from transients such as a kick drum.

Selecting Linear Phase processing reveals a Processing Resolution button. Settling on the right resolution is a trade-off that hinges on the material you're working with and on your own taste. These are the resolutions on offer:

• Low delivers linear-phase processing at the smallest possible latency. Reach for it only with modest Q settings, or when you're adjusting just the mid-to-high region of the spectrum. At a sample rate of 44.1 kHz, this yields a total latency of 3072 samples (about 70 ms).
• Medium strikes a sensible balance between low-frequency detail and added latency, and it is the setting we suggest for everyday linear-phase work. The total latency is 5120 samples at a sample rate of 44.1 kHz (about 116 ms).
• High delivers excellent low-frequency resolution. Reach for this mode whenever you apply steep Q values while reshaping the bottom end of the spectrum. The total latency is 9216 samples at a sample rate of 44.1 kHz (about 209 ms).
• Very High pushes low-frequency resolution even further. The total latency is 17408 samples at a sample rate of 44.1 kHz (about 395 ms).
• Maximum yields extremely fine low-frequency resolution, but at the cost of a very long latency and a risk of audible pre-echo. The total latency here is 66560 samples at a sample rate of 44.1 kHz (about 1509 ms).

Note: if you enable both L/R-specific bands and M/S-specific bands together, the linear phase processing runs in two distinct passes: the L/R stage first, then the M/S stage. Keep in mind that this effectively doubles the latency.

Sweeping EQ band frequencies while in Linear Phase mode stays every bit as smooth as in the other modes, with no zipper effects at all. That may seem minor, but it is genuinely rare in linear-phase processing!

Deciding on the right processing mode

As noted above, for nearly every ordinary mixing and mastering scenario, Zero Latency mode or Natural Phase mode (with its even greater accuracy and phase response) will serve you best. It is worth remembering that linear-phase processing is not inherently better or more transparent than normal processing, it is simply different! Linear-phase EQing is a corrective tool, generally reserved for avoiding phase cancellation problems. To dig deeper into linear-phase vs. normal EQing, watch our detailed video tutorial on the topic: EQ: Linear Phase versus Minimum Phase .

Notes

• Dynamic and Spectral EQing function in Linear Phase mode as well, though only with Processing Resolution settings up to 'High'. See Dynamic EQ.
• Spectral bands always switch to linear phase processing on their own. See Spectral dynamics.
• At other sample rates, the latency in samples of each linear-phase mode may shift so that you still obtain roughly the same low-frequency resolution (and the same latency in ms).
• Thanks to Contour's refined architecture, CPU usage stays very low, even with up to 24 EQ bands active, and it barely varies across the different linear-phase processing modes.

Next: Character mode

See Also
Overview
Display and workflow