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  • Green Meanie: The 12″/500W Sealed Box

    2013 - 05.31

    So previously I chronicled the construction of a set of hefty bookshelf speakers I built for my brother. They’ve got a new buddy: a 12″, 500 watt subwoofer, in matching green paint! I haven’t written about the process of building this guy near as much because the cabinetry was essentially the same process: cut up MDF, router in the driver openings, glue’n’screw together, router off hard edges, silicone seal all joining surfaces on the inside, primer paint the outside, 4 coats of green paint, and then coat the whole shebang in Enviro Tex for a piano finish.

    This time around I used a thicker, globbier primer called “gripper” in the hopes that it would more aggressively adhere to the MDF. When I put it on, it seemed like oh yeah, this stuff is gonna bond. But sure enough: I set the wet surface down on a few triangular wood blocks to dry, then each of them lifted off a small bit of the paint when dried. Seems like nothing can actually adhere itself to MDF, it just covers it. That’s going to be okay though, since the Enviro Tex finish is very thick and will seal any loose imperfections underneath.

    This is only my second attempt at building a sub. The first one I built for a roommate in college. It used two Peerless XLS extra long excursion drivers, one active and one passive. Using a passive radiator extends the frequency response and lets you get some serious low frequency. The downside is that since the passive driver is, by definition, uncontrolled by a magnet, it’s free to vibrate however it wants. That will muddy up the sound. That sub was definitely LOUD as hell, and low too. We would bump that thing in the dorms and I’ll be damned if you couldn’t hear it on the other side of the building, 3 floors away. And we’re talking about a cinder-block building too!! So that thing was an outrageous amount of firepower for it’s size, which I would credit to the low frequency extension of the passive radiator. But it could never be described as tight, quick, responsive, or accurate.

    As my second attempt, I picked out a driver that could be used in a sealed box, to go for power and accuracy in the audible range. The lowest of the lows are really cool, for sure, but subs with very low frequency output are almost impractical in a sense: that low, low range is going to penetrate ANYTHING, as the cinder block dorm proved in college. You’re going to be irritating anyone within a thousand foot radius when you rock out, no if’s about it. This time around I wanted power in the range of human hearing. Yeah, that’s still going to punch through plenty of walls, but not on the level that <30Hz will.

    I went for a 12″ as a compromise between tightness/control and low frequency extension in a sealed box. The lowest audible frequency, referred to as “f3″, should be somewhere in the high 30s. The driver is a Dayton Reference Series 12” model “RSS315HO-44″ with 4ohm impedance. It’s a dual voice coil driver, although I’ll only be powering one. The T/S parameters of this thing call for a one cubic foot sealed box for its optimum response, which is fairly small for a sub. This would be a superb driver for a car sub, where more amps would be geared toward handling that brutal 2ohm impedance you’d get by wiring the dual voice coils in parallel.

    Supplying the power, we’ve got a 500 watt amp made by Yung International, with a +6dB boost at 25Hz. I went for the 6dB boosted model as opposed to the normal model, with aim of pushing the f3 out a little lower than the driver would normally achieve. Why not use that EQ to my advantage!

    First impressions?  Punchy-est 12” in recent memory!  It’s bass drum hits are concise.  Basslines are even, with no ‘bloated’ notes that pop out louder than the rest.  And the lowest audible pitch notes are there.  The tune “To Feel Good” in the music section is a great test of super low bass, since we used a sine wave bassline at -1 octave to the main bassline synth you hear.  That makes for some low, deep notes!

    Really digging this puppy so far.  Gonna be a hell of a sound system for this fall….

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