Acoustic Geometry Curve System room treatments

For a few weeks each year in the high summer of Minnesota, the corn sold from rickety roadside stands is so sweet and tender it is best eaten unadorned. For the wise and lucky nibbler willing to forgo condiments, the rewards of eating these naked kernels are the pure taste of Midwestern soil and sun transformed into a juicy, golden confection. I've begun to wonder if the yearly encounter with this magnificent and ephemeral sweet corn reminds Midwesterners of the joys of simplicity and plainness. Though my hypothesis is a stretch, it sure would explain a great deal about the Midwestern mentality. Perhaps Midwesterners subtly learn from this corn that if we get too fancy or try too hard, we can often screw up what nature has already made perfect. Conversely, we learn that no amount of fancy accoutrements will make a bad ear of bland, mealy corn come alive in the mouth.

What I've learned from room acoustics, room treatments, and room corrections are very like the lessons I've learned from eating the sweet corn of summer. Like drenching in butter a starchy ear of corn, there's just no way you can make a bad room sound great. If your listening room's floor vibrates like a kettle drum, your walls are glass, and your ceiling only 6' high, all I can say is: Good luck. Every attempt I've heard to treat a fundamentally bad-sounding room with panels and equalization at best trades off one sonic problem for another. On the other hand, when a decent-sounding room is turned over to a company selling panels or corrective components, often the natural goodness of the room's sound is destroyed in a quixotic quest to even out the bass response or null every standing wave. Though such rooms might end up measuring better, they don't always sound better. Adding too many acoustic panels to an okay-sounding room is akin to ruining the perfect ear of corn with too much salt.

So it was with a sense of hope that I encountered Acoustic Geometry's new Curve System of room treatments. Unlike most products designed to treat rooms by absorbing sounds, the Curve System treats room acoustics predominantly through diffusion. I was intrigued by the approach, and as Acoustic Geometry products are made close to where I live, in Chaska, Minnesota, I thought it might be convenient and fun to see if I could get my room to sound a little better. I called John Calder of Acoustic Geometry, told him about my room's size and materials and what it's made of, and he sent a pallet of products to my door.

John Calder came to designing room-treatment products by way of the recording studio. "I started recording in the 'deaden-everything-with-fiberglass' acoustics of the '70s, which was a sonic nightmare," he says. "In the late '70s, I was a recording engineer [Neil Diamond, Joe Cocker, The Band] at Kendun Recorders, a legendary studio in Burbank, where Tom Hidley had built one of his signature octagonally symmetrical, lava-rock–diffusion control rooms. I learned through long experience that properly diffuse rooms sound far more natural than nondiffuse rooms. This exposure to leading-edge acoustics gave me a real underpinning of acoustical experience. I later used that experience to design and build control-room and studio treatments for myself and others. That's what led me to start Acoustic Geometry in 2010."

While diffusion is rarely used in the smaller space of a listening room—I know a number of manufacturers and audiophiles who believe diffusion can have no meaningful effect in a listening room of average size—Calder hears it differently. To that end he has designed the Curve System to primarily diffuse sound in a phase-coherent way: "Listening in flat-wall, overly dead rooms is unfun. We don't live in anechoic chambers! For millennia, we've existed in naturally diffuse spaces, from forests to caves to baroque churches. As a species, we're extraordinarily sensitive to phase-based directional cues—if you couldn't accurately locate a twig snap, you were a saber-toothed tiger's lunch. The importance of acoustic phase, along with a lot of experimentation, brought me to cylindrical Diffusors, which are a tried-and-true design from the '30s. They're beautifully phase-coherent (unlike quadratic-residue diffusion), relatively affordable, and can be implemented with predictable results."

Behind the Curve
The Curve System comprises a number of models, each 42" tall, and samples of all of which I had on hand for review. There are three sizes of Diffusor—Small (14" wide), Medium (21" wide), and Large (31" wide)—and three sizes of Absorber (each the same width as the corresponding Diffusor). There's also a 21"-wide Corner Trap whose front face is a Medium Diffusor. The front baffle of each Curve model is, well, curved, the arc of each model size based on a radius of different length. According to Calder, having Diffusors of different sizes in your room is very important, as repeating the same size of arc over and over along the same wall would result in audible comb filtering. Many fabric choices are available for the front panels, and custom fabric covers can be ordered.

Each Curve System model is built on a wooden frame with, on the back, a wedge-shaped cleat for hanging the product from a matching piece attached to the wall. I liked this method of installation: The user can run a horizontal piece of wood along the length of a wall, then adjust each Curve unit's placement with great ease and flexibility. As I'll show later, dialing these babies in will amply reward the listener.

Panels can be mounted vertically or horizontally. The front curved surfaces of the Diffusors are made of a "bio-degradable material that will keep its shape and diffusive properties for a very long time," says Acoustic Geometry. When I pressed for more information, Calder wouldn't say what the material actually is. It looked to me like a cross between body armor and egg cartons. Heck if I know what it is. Behind it is a thick sheet of recycled cotton (denim, from the looks of it), with metal screens on the units' ends covering the holes to the space behind each arc. Each unit's rear panel is covered with a sheet of thick vinyl, which Calder calls his Mass-Loaded-Vinyl (MLV) membrane. According to him, "MLV is highly efficient compared to fiberglass for absorbing bass; combined with their diaphragmatic absorption, Curve Diffusors help control low- and midbass frequencies and diffuse everything else. In fact, that's my basic acoustic philosophy—control the bass and diffuse the rest, with the right balance of absorption."

The Absorbers are essentially the same design as the Diffusors, but have an acoustically transparent rather than a solid diffusing front and don't include the MLV membrane; instead, they give the cotton open access to the room. The Corner Trap is a triangular wooden frame filled with recycled cotton; a Medium Diffusor serves as the faceplate. It's among the lightest corner traps I have encountered.

In Treatment
My listening room is 11' 8" wide by 18' long, with 8' ceilings at the front and 7' ceilings behind the listening position. The floor is concrete, with a very thick pad and shag—I mean frieze—carpeting. When I remodeled and renovated the room a little over a year ago, I even had the studs shimmed out to make the double-hung drywall on the sidewalls nonparallel. Even naked, it's a good-sounding room—all my audio buddies agree that I'm lucky to have this space. Normally, the room is nominally treated with four Echo Busters panels along the sidewalls, placed at the points of the first and second reflections. Until the Curve System, I hadn't tried—or even felt the need—to mess with the sound much more.

Acoustical Surfaces, Inc.
123 Columbia Court N.
Chaska, MN 55318
(888) 227-6645

deckeda's picture

I've come to the conclusion that listening rooms sound only as good as the memories created in them.

For those of us that have yet to include room treatments, either commercial or hand-made, your review shows how it can be done in a controlled, sane manner.

But I wonder about those two IKEA floor lights. You're not concerned about those loose panels flapping around from low frequencies?

Erick Lichte's picture


No, I have never had a problem from the Ikea lights making noise from the bass in my room.  I've had problems with my front door rattling, the mirror in my bathroom buzzing and my teeth shaking, but not my Ikea lamps.

I haven't written much about my butcher block audio rack seen in the photos in this review.  About a year and a half ago I refinished a 100 year old butcher block, made of solid dovetailed maple.  It weighs about 250lbs and has had a profound effect on the sound of my system, adding a stillness and resolution that was very noticable.

Doctor Fine's picture

You might raise the whole process to a higher level if you would just move all that HiFi junk, the table,  the Rogue Amps , all that clutter---to the side or back of the room.  It is ruining any chance of correct room lock and directional cues and phase alignment.

Ask yourself if you would whip out a pair of headphones and instead of putting them over your ears, first stuff some ju-ju-bee candy into your ear passage and then fuss a lot with the ear pieces trying to get best sound.  It follows that some very sketchy sound would pass by all that junk and you certainly would not hear the drivers to best effect.

I don't want to hear excuses about hydra sized cables and short runs are best.  Everybody all ways has reasons to jam their precious junk right in the middle of the whole set up.  Most of the time I suspect so we can all Ooo and Awww over the junk. 

Just try running balanced like in a studio.  Or get some transformers and balance your single ended RCAs if you have to.  Or get rid of everything else and just leave the amps behind the speaks where they are at least out of the middle, the most  critical area.

Just saying.  Pretty hopeless reviewing stuff with ju-ju-bes in your ears old pal.  Until I took my own advice believe me I wandered in the wilderness myself.

If that were MY room,  I would use the Sumiko method to assure the speakers were correctly locked into the room, acoustically.  I would take lots of time using the Sumiko method to fine tune the image dimensions and sense of "life" also.

After I then had an inkling of final placement I would start experimenting with just the highly reflective window "as is."  Perhaps it would help the soundstage.  I would check that by then completely killing the front window with a big Sonex wall sized insert to see if your setup liked THAT.  If it did then you might consider some drapes so you can either look at the view or monitor with drapes closed.

But in every case I would not even bother with the room if the ju-ju-bees, I mean HiFi junk, was still right smack in the middle of MY front stage.

My personal experience is that room treatments are usually necessary primarily on the sides and behind your head.  These are areas that the stereo or mono recording really didn't encompass with information when captured.  Thus they should be set up to not have any racket going on which detracts from the recorded signal.

Anyway, have fun.  It is all a learning process and no one (especially ME) knows it all.