New SPL PASSEQ Passive Mastering Equalizer for Pro Audio Applications (Red)

Designed for mastering engineers—and boasting a few advantages over the original unit—the SPL PASSEQ is a six-band, passive equalizer presented here in a stylish red finish. Its passive circuitry allows for smooth, musical implementation, allowing you to cut or boost frequencies at values that might be harsh on active EQs.

As with the original unit, this equalizer sports passive coil filters for an authentic inductive-EQ sound, as well as a total of 144 filters, stereo XLR I/O with relay-hard bypass, and 120 VDC Audio Rail technology. SPL employs this technology to ensure low noise, increased headroom, and minimal distortion—even when driving the unit for tonal effect.

This updated PASSEQ provides several improvements over the original, including an extended high-frequency range, now going all the way up to 35 kHz for true air-band processing. You’ll also notice that the Mid-Frequency Cut Switch now reaches down to 200 Hz, rather than 1 kHz, so you can really dig out tubbiness, woofiness, and other euphemisms for low-mid nastiness.

This unit takes up four RU of rack space. For a walkthrough of the PASSEQ’s operation, please peruse the feature section.

The PASSEQ Explained This EQ may seem intimidating at first glance, but upon closer inspection, the unit’s controls are intuitive and extensive.

Take a look at the left channel: the most prominent feature is a large knob that controls the overall output level of the left side. Below this knob, at the bottom of the device, you’ll note four dials that are your low end. Immediately above these dials are four controls for midrange, and above that center row, you’ll see five knobs for your top end. All controls are duplicated on the right side of the unit; in that case, these knobs control the right channel.

Again, orient yourself around the prominent output-level knob: all of your boosting controls are on the right side of this knob, while all of your attenuation controls are on the left. This is true for both channels.

For each channel, you’re provided with two band controls: one for boosting and the other for cutting. For readability, they are labeled with plus and minus signs, so LF- is for cuts on the low frequencies, while LF is for boosts on the low frequencies. Each band control is segmented into 12 different frequency centers, and each band control has its own level potentiometer, adjusting the amount of boosting or attenuation in 41 precise steps.

You’ll note the high section sports one more control than the rest—a bandwidth knob to control how narrow or wide the Q of your high-range boost is. If you’re familiar with the original PASSEQ, you’ll also notice an extended high-frequency range on this model, all the way up to 35 kHz for the air band, giving you the ability to add sparkly highs. Also expanding its usability, the Mid-Frequency Cut Switch now extends down to 200 Hz, rather than 1 kHz, so you can really dig out tubbiness, woofiness, and other euphemisms for low-mid nastiness.  

Also useful is the Automatic Bypass switch with an Interval control; this forces the EQ to automatically go in and out of engaged states at automated intervals, so you can focus on the sonic differences and not be fooled by the “eureka!” feeling of clicking the processor on.