The naming of Manley Labs Massive Passive stereo equalizers is a textbook case of truth in advertising: at three rack slots tall, they're certainly massive. And with their unique circuit design exploiting the natural qualities of simple passive components, the rhyme pretty much writes itself. These aren't graphic EQs and they're not the most compliant hardware you'll find but what they give you in return for their personality is something far better. In short, they're art for art, taking technology to an art form to help musicians realize their own visions. A Massive Passive EQ blends the best traits of Pultecs, consoles, parametrics and graphics to give you tons of EQ muscle while going easy on coloration.
So which model is the right choice for your setup? That depends mostly on how important repeatability is for you. If you want to be able to dial in identical settings with precision again and again, your best bet is probably the Manley Massive Passive Stereo EQ Mastering Version. It uses mechanically detented knobs for gain and bandwidth control, which makes it possible to recover your past settings without the need for Grayhill switches across the board. If you'd prefer a more conventional set of pots, you'll be all set with the standard edition Manley Massive Passive Stereo EQ. The controls are the biggest difference between it and the Mastering Version, with both models based on the same passive, all tube, make up gain design that gives them their legendary headroom and performance.
Looking closer at the extra steep filters, the "parallel" circuit layout, and the way gain and bandwidth controls interact, it's pretty clear to see that the Manley Labs Massive Passive stereo equalizers have their own way of doing things. And that's the real beauty of them these EQs aren't designed to produce technically perfect sound as if they were in some kind of laboratory. Instead, they're built to deliver natural, organic tone even at high levels of EQ, so you can pull off huge boosts without sibilance and fatten up your sound without making it muddy. When you consider the pros and cons, those priorities are definitely in the right places.