After we unveiled our modern take on linear phase equalizers, the best mastering engineers heralded their unparalleled clarity and transparency. To develop a classic PEQ for recording and mixing, we knew that no single style could satisfy all the different flavors and genres passing through your desk. Intensive R&D followed by careful attention to UX, the user experience, resulted in thEQblue, a parametric equalizer with twelve different aspects. It contains the most complete collection of classic, vintage, modern and experimental equalizers ever in one plug–in. We know you’ll find your favorite flavors for each application and obstacle. To avoid any hassle with trademark, we haven’t assigned any brand names to each type. Being the geeks that we are, we instead gave each of them nondescript names related to their technical classification. You are invited to discover the sonic nuances of each one, and assign your own corresponding brands and/or products.
The Most Comprehensive…Ever
With thEQblue, you can call up twelve Sections, each one from the twelve flavors available. For each Section, choose five freely assignable parametric filter types, including bell, low or high shelf, and low or high cut. The most significant filters determining the equalizer name are bells. Set to a certain Q, different bell filters change their bandwidth in a specific way depending on the amount of boost or cut. To allow practical comparison between different equalizer types in the Classic PEQ Blue, the bells in all PEQs have been normalized to 6 dB of boost, i.e., a separate bell looks identical for 6 dB boost and the same Q, independent of chosen PEQ type.
The Classic Symmetrical is the most popular bell shape used in many mixers and outboard equalizers. It is almost “constant Q.” That is, as resonant frequency changes, the Q or Quality Factor changes, widening as the frequency goes from low to high to maintain a constant ratio of center frequency divided by bandwidth. Constant Q is roughly the way our hearing perceives an EQ’s effect.
The three Proportional PEQs emulate bell characteristics which change their bandwidth proportional to their boost or cut. Many think they behave more musically as you don’t have to correct the Q after every amplitude change. There are also three other constant–Q equalizers available, with characteristics similar to some classic American brands.
thEQblue also offers two proprietary constant–Q varieties. The first, Constant-Q Ideal, is a perfect version of the Classic Symmetrical equalizer, having exactly the same bandwidth at any amplitude within its range of Q. This is measured 3 dB below maximum amplitude at and above +6 dB of boost. Such PEQs are impossible to implement in the analog domain, hence the “ideal” name. Another specialty variety is the Constant-Q New, which follows a new Q definition. It preserves exactly the same bandwidth at the half of the maximum amplitude for all amplitude values. Unlike the classic Q definition, this includes the range below 6 dB of boost. Due to its amplitude/bandwidth dependency in terms of a classic Q definition, this new kind of constant-Q PEQ could also be thought of as a member of the proportional group.
Finally we emulated two vintage parallel equalizers. With parallel construction, the main input feeds every filter in parallel, with each filter’s output being summed together for the final composite output. With a serial implementation, filters are cascaded; each fed from the output of the previous filter. Unlike a serial parametric equalizer (almost all paramets are serial), parallel–connected filters combine or cascade differently. They also behave differently in terms of phase. Their special interactive behavior between bands is offset by a pleasing sonic character. Our Parallel LC emulates old skool parallel passive PEQ circuitry built with inductors and capacitors. The Parallel Feed–Forward/Feedback topology emulates the feed–forward/feed–back designs still popular in low noise analog graphic EQs. While the feed–forward path is trivial to implement, the feedback path is impossible to implement in traditional digital signal processing, because of the need for so called “delay–free” feedback loops. In thEQblue, we apply a unique and very elaborate technique for true emulation of delay-free feedback. The result is a characteristic sound and perfectly complementary filters for boost and cut.
The Filter Library
In thEQblue, not only are various bell–shaped filters available but also different kinds of shelving filters. Nine of the serial equalizers use a special shelving design characterized by a cut–off frequency defined in the middle of the transition region. We found these filter definitions more intuitive than the classical “–3 dB below maximum.” The old skool definition is only used in the Classic Asymmetrical flavor in order to conform to its analog antecedent. All 2nd order shelving filters have a Q adjustment to emulate vintage characteristics, with their inherent and specific bumps at higher slopes. Also, the parallel equalizers are equipped with respective shelving filters shapes that are typical of old parallel PEQs. They also have interacting bands as did their analog predecessors.
Every complex PEQ is equipped with cut filters. With thEQblue, each of the twelve equalizer flavors can provide 1st and 2nd order cut filters. The 2nd order filters have a Q adjustment to create resonant filter response, and can be combined to provide very steep “brickwall” filters by cascading several Sections.
Best of Both Worlds
thEQblue is a creative equalizer tool combining the best of both the analog and digital domains. To avoid bell filter asymmetry at high frequencies for baseband sample rates, typical of many digital equalizers, we have applied reference–quality upsampling, which automatically kicks in for 44.1 or 48 kHz. By using proprietary filter algorithms, we have achieved a huge dynamic range, as well as extremely low noise and distortion. This yields unparalleled sonic purity, impossible for any analog circuitry.