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KIH #72 – Why keep a dog and woof yourself?

  • Separate. Activate. Stuff it. What’s that? A call to civil disobedience? A secret invite to pig out at an endless buffet? Neither. Today is about active sealed woofing.

    Inspiration came from two recent back-to-back reviews for my 6moons site. First to arrive were the Polish Cube Audio Nenuphar Mini BASiS. That mouthful stands for 8” Neodymium-powered ported widebander monitors. Those sat atop 10” sealed sidefiring active woofer cabs.

    From Lithuania the next day came 8mm audiolab’s new Linga. That was a conventionally passive 5-driver 3-way with dual sidefiring 12” woofers each ported out the back.

    Both were priced above €20K/pr and within €2’000 of each other. That meant direct competition even if at twice the height for twice the cubic volume, Linga’s visual impact played it far louder. But bigger is better. We all know that.

    Powered by 200-watt class A/B amps, the Polish subs had sufficient headroom to dial in up to 6dB of EQ boost between 30 and 50Hz. That compensates for infrasonic room loss. They had an adjustable low-pass from 50-150Hz. They had flexible gain and phase. In the same room and position, the Polish stacks utterly crushed the Lithuanians on bass reach, LF control, full-bandwidth speed, linearity, resolution and dynamic contrast.

    There were a few reasons why. Above 100Hz, Nenuphar operated as a true not approximate point source. Unlike Linga, its 7+ octaves here saw no high- or low-pass filters. They ran amplifier direct to be an easy load for a small 20-watt main amp like our Bakoon AMP-13R mini or FirstWatt SIT-3. Below 200Hz, woofers close to the floor occupied separate enclosures and could adapt their output to the room with the turn of a dial. What’s more, the widebanders had been re-tuned from versions without bass assist to ideally match this semi-activated augmentation mode.

    Comprehensive bass adjustments

    Linga’s two woofers hovered high above the ground to create time-delayed floor bounce. Then they ported at the front wall to load up the room’s front corners. This caused very noticeable ringing and massive boom. That couldn’t help but bleed into and muddy up the midband. With no means to turn down their bass shy of applying heavy EQ in a computer plug-in, the designer suggested that I disconnect his upper woofers by removing one jumper per channel. This indeed solved the overbearing bass heaviness. After compensatory twirls on his tweeter rheostats, it re-centered tonal balance even if it didn’t address remaining ported bass textures. I simply had bypassed half the cabinets’ cubic volume and ditched two expensive woofers. This left zero justification for looking at and paying for 2-meter tall giants when half the height and woofage not only sufficed but sounded better.

    Spaced mids around a horn-loaded compression tweeter; dual sidefiring 12” woofers high off the floor ported out the back.

    The half-sized Cube Audio stack had proven beyond a doubt just how well this room supports linear superbly damped quick bass down to the very limits of audibility. The culprits of the Lithuanian bass boom and mud weren’t the space or any unchecked infrasonic lust on my part. The main culprits were lack of flexible bass gain, passive drive and dual port loading. But there was more. This speaker was also summarily edged out across the vocal range by suffering both high-pass and low-pass filters on those drivers; and by clustering a mid/tweeter/mid array that wanted a larger listening distance to fully cohere. Too much speaker for the room would have been the correct generalized assessment.

    But look closer and a more specific assessment would add that sealed bass simply trumps ported bass on timing, damping, articulation and enunciation; that for equivalent reach, active bass needs far smaller enclosures than passive bass does; and that active bass adapts to our room whilst passive bass either beds in or not. If not, we’re stuffed. The upshot? Sealed active bass is a far more intelligent solution because it’s far more effective and can guarantee repeatable performance by being adaptive.

    Upstairs with 18wpc FirstWatt SIT-3

    In this case, Nenuphar easily moved upstairs into a smaller room where it performed exactly the same as it had in the 5m x 10m room with big adjoining open space. Even had I been able to carry Linga up the stairs, the sound there would have been even worse than on the ground floor.

    The moral of the story is that loud clean bass always is the costliest most size-intense aspect of passive loudspeakers. Go ahead. Compare floorstanding models in any given catalogue. Beyond a certain model, the only real differences are size and weight. Those buy a few cycles of extra bass reach and a few extra dB of loudness. Yet cost scales up entirely disproportionate to those small gains. So do size and weight. Isolating big long-throw woofers from mids and tweeters in the same cabinet does require serious cabinet builds.

    Now compare that legacy approach to a modern compact monitor like Cube’s one-way or a traditional two-way. Augment it with sealed active bass. Without LF duties, the monitor can be a lot smaller to exhibit far lower box resonance. For that it’ll also need less heroic (more affordable) builds to suppress resonances than a floorstander with big woofers. It’ll have a more benign visual footprint. It won’t have that always sonically unhappy high-pass filter on its midrange. Backed by sufficient power to run internal EQ against smaller cubic volume, our active subs don’t need ringy port gain. They can be sealed boxes for far reduced group delay. And because they’re active, they will include comprehensive adjustments to ensure that in our room, with our placement, our music and to our ears, the relative bass balance will always be perfect.

    At the end of the day, this means better performance, more intelligent performance and a visually more compact hence more attractive system.

    But never mind. We all know that subwoofers are approved and fit only for home theatre and MidFi. Real audiophiles listen to big expensive passive speakers even if they’re ugly. To opt-out, you’d have to slightly tweak our opening command:

    Become active. Separate out from the pack. If they protest, tell ‘em to stuff it.

    And just who would ever do that?

    Srajan Ebaen

    Written by Srajan Ebaen

    Srajan is the owner and publisher of 6moons. He used to play clarinet at the conservatory. Later he worked in audio retail, then marketing for three different hifi manufacturers. Writing about hifi and music came next, then launching his own mag. Today he lives with his wife Ivette and Nori and Chai the Bengal cats in a very small village on Ireland’s west coast, between the holy mountain Croagh Patrick and the Atlantic ocean of Clew Bay in County Mayo’s Westport area. Srajan derives his income from the ad revenues of 6moons but contributes to Darko.Audio pro bono.

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