Primacoustic Cumulus Tri-Corner Bass Traps

Harmony Central, Phil O’Keefe  March 20, 2014
Unobtrusive and easy to install, these broadband traps make a welcome addition to practically any room.

Walls and ceilings in a room tend to function as waveguides, and bass tends to build up in areas where walls join. Because of the way sound propagates within a room, corners are an excellent place to position bass traps and broadband acoustic absorption panels. The tri-corners where the walls and ceiling meet are especially important to treat if possible, but the geometry doesn’t always make it easy to mount a acoustic panel in this location. Primacoustic, a division of Radial Engineering, has a clever and effective solution called the Cumulus Tri-Corner Bass Trap that’s designed specifically for corner mounting. Let’s take a look at the specifics.

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What You Need To Know

•Each Cumulus panel is made from a piece of compressed fiberglass (six pounds per cubic foot density) 2″ thick. The panel’s shape is an equilateral triangle measuring 24″ on each side. This results in the panel extending outward in all three directions (from the center of the corner) a distance of about 17″ when it’s mounted into a corner.
•The fiberglass is encapsulated in a micro mesh to prevent fibers from escaping. The side edges are hardened with resin for strength. The fabric covering is acoustically transparent.
•Cumulus traps are sold in pairs.
•You have three choices in terms of the color of the panel’s covering fabric – black, grey, or cream.
•All mounting hardware is included. You’ll need a drill a small pilot hole (1/8″ or 5/16″) for one eye screw per corner trap. The only other tool you might need is a small hammer or mallet, and only if you need to use the included butterfly anchors for the eye screws, which is the case when inserting them into drywall as opposed to a location that’s backed with a wood stud.
•The panels mount to the corner with a clever system of cleats and springs attached to a center ring, along with a large, heavy-duty cable tie that attaches the ring to the corner / ceiling-mounted eye screw. The springs provide gentle tension that pulls the panel up and snugly into the corner.
•Mounting the Cumulus panels is quite easy, and can be done quickly, and by a single person with no assistance.
•The backside edges of the panel are beveled to match the angles of the tri-corner wall / ceiling surface that it’s intended to mount to, so that the panel essentially sits flush into the corner.
•Absorption of the panel is broadband, and extends well into the bass region of the audible frequency spectrum. Primacoustic rates them as being effective down to 100Hz. According to the test data from Riverbank Acoustical Laboratory, they have an absorption coefficient of 0.45 @ 125 Hz, which is very good for a 2″ thick panel.
•Fire safety is important, and the Cumulus panels meet the USA and Canadian ASTM and CSA testing requirements for flame spread and smoke density, and have a Class-A fire rating.

Limitations

•The clips or “cleats” that hold the  panel in place are covered with rubberized end caps that help prevent the ends from damaging the trap’s fabric covering. Unfortunately, they’re a cream color, which makes them somewhat visible against the black fabric of the review panels despite the relatively small size of the cleats. If this bothers you, they can be touched up with a black Sharpie permanent marker to make them less visible. This is obviously not much of a concern if you opt for the cream-colored fabric, although it’s probably still a bit noticeable against the grey fabric covered versions of the Cumulus traps.
•The Primacoustic Cumulus adds welcome broadband absorption to any room, but it’s not a singular cure-all, and should be considered as part of a larger acoustical treatment plan. Don’t expect to install just a pair of these traps and to have all of your acoustical issues magically disappear.

Conclusions

Vocal booths, practice rooms, home studios, control rooms, home theater and A/V rooms… any place where you can use extra broadband absorption is a good place to use Primacoustic Cumulus Tri-Corner Bass traps. I like that the installation is so easy, and leaves minimal damage to the existing walls – just one small screw hole per trap is all it takes, and you can install them quickly, without needing a helper.
The corner mounting system is clever, easy to install, and does a good job at keeping the traps in place, and the material used and the corner mounting placement is effective from an acoustical standpoint. Another benefit of the corner mounting is that it is up high and out of the way, and doesn’t infringe on the room space in any significant way, making Cumulus traps an excellent choice for use in tight quarters and small spaces like vocal and iso booths (where additional low-mid and low frequency bass trapping is usually badly needed), but that suffer from space limitations. The fabric color choices are somewhat limited, but the black fits in well with my other acoustic treatments and doesn’t look at all out of place. In fact, the overall look of the product when installed is rather classy. More importantly, they perform as advertised from an acoustical standpoint, and the price is quite reasonable too. They’re a solid product that will be a great addition to just about any room, and I’m sure I’ll be buying more of them in the future.