The Massive Passive from Manley Labs offers two channels of 4-band parametric equalization with additional 5-band high pass and low pass filters. Its design draws from vintage EQs using passive, parallel topology to create a natural and organic tone. Simple circuits with premium-quality components, like metal film resistors, film capacitors, and hand-wound inductors are used for sculpting the sound.
Each of the 4 bands offer Pultec-style controls, each with fixed frequency selections, variable bandwidth, and either 20 dB of boost or cut. This design allows for twice the control resolution over conventional EQs and eliminates the problem of a center detent not guaranteeing a flat response. The parallel topology allows for massive tone shaping without over driving the outputs. For instance, if you were to boost 4 bands at 1 kHz by 20 dB, the output would still only be +20 dB, whereas a conventional "series" EQ would output upwards of +80 dB.
Additional features include individual band bypass and the ability to switch each band from bell curve to shelf. The two left-most bands offer low shelf capabilities, while the right two offer high shelf. The bandwidth knob changes the properties for each of the shelves as well. The unusual "Constant Bandwidth" controls offer unique tone shaping capabilities. In bell mode, they behave like most "Q" controls of a parametric EQ with a wider shape when set fully counterclockwise, and narrower when set fully clockwise.
The shelf modes offer a special function. When the knob is set fully counterclockwise, the curves are similar to most shelf EQs. As you increase the bandwidth clockwise, a gradual bell-shaped dip is introduced as the slope increases, which modifies the overall shelf shape. It's rare to find an analog EQ with adjustable high shelf curves.
The high and low pass filters are individual circuits selected by switch settings, and each has specific slopes catering to their respective frequency range. All the filters are entirely passive and "inserted" between the boost and cut sections. The two "EQ In" push buttons engage the EQ on their respective channels. When bypassed, the EQ section and tubes are bypassed, but audio signals are still passed through the line amplifier and balanced output transformer. The -6 to +4 dB gain trims are intended to help level match between the "Bypass" and "EQ In."
There are no dedicated meters on the Massive Passive, instead bright blue LEDs indicate "EQ In," while red and green LEDs indicate cut and boost engagement respectively. Hand-made in the USA, the unit is housed in a 3U steel chassis with a CNC-machined 1/4" faceplate that is also inlaid with laser-engraved inserts. The Massive Passive ships with an IEC power cable.