XIX Acoustics: Acoustic Ramp diffuser

The modestly-sized control room of my personal studio is acoustically treated with a Primacoustic Primakit [Tape Op #36], twelve wood-panel RealTraps [#36], nine broadband RealTraps Mini/MondoTraps [#38, #48, #85], four large clouds from Acoustical Solutions [#37], and an array of Auralex SpaceCouplers [#58]. The treatment was installed over time, and at some point, I hit a point of diminishing returns; although not quite perfect, I was still very pleased with the sound of my room. Only two walls of my control room are parallel (both are well treated), and the wood-panel traps are placed on the side walls to maximize diffusion without making the space sound too dead. High-resolution frequency-response and RT60 measurements confirm that the room is quite neutral - despite its restricted dimensions (18 ft x 13 ft with a ceiling that peaks at 14 ft). When Hendrik Gideonse, a friend and former work colleague, offered to bring over a couple of his Acoustic Ramp diffusers to test in my studio, I took him up on his offer, and I looked forward to sitting down with him to discuss how his patented design performs better than other diffusers. But with all honesty, I assumed that the addition of two of his diffusers to my control room's comprehensive treatment package would lead to limited gains at best. In that regard, I was wrong. To put it succinctly, I was blown away by how much improvement I heard.

Dimensionally, the Acoustic Ramp diffuser is shaped like... well... a ramp. From the side, its cross-section is a triangle. Mounted on a wall, it takes up about 8 sq ft (45'' x 24''), with a maximum depth of just over 12'' - not very big. How can two of them - with total coverage less than 16 sq ft - markedly improve the acoustics of a room that's already well- treated? If you go to the XIX Acoustics website, you can read about the Acoustic Ramp's unique geometry reflecting and scattering energy in multiple directions, and why the variable- depth channels increase functional bandwidth. Furthermore, if you're really curious about all the science behind the design, you can download the thesis that earned Hendrik a master's degree in 2012. In the meantime, let me tell you about my experience with the diffusers.

First of all, the Acoustic Ramp has an ingenious mounting system that allows for "permanent" installation on a wall using a J-hook, or portable placement on a standard PA- speaker tripod. I use permanent in quotes because the Acoustic Ramp can still be lifted off the J-hook by one person. Therefore, you could screw J-hooks in various locations around your room and move your diffusers as needed to vary the acoustics of the room. For my afternoon of testing with Hendrik, we mounted the two Acoustic Ramps on tripods.

We began with one each positioned to the left and right of mix position, I heard immediate improvement in stereo imaging from my ADAM S3-A monitors [Tape Op #33], and the sweet spot widened significantly, allowing me to lean over farther to reach for various processors without the soundstage collapsing. After moving both diffusers to the back wall (where I have two RealTraps MiniTraps behind the ears of anyone sitting on the couch), the room "opened up" a bit, sounding less dimensionally constrained while listening from mix position.

The biggest (and most surprising) improvement was heard when the Acoustic Ramps were taken off the tripods and placed together sideways (like an unfolded book stood up) on top of the producer's desk between mix position and the rear couch. In this configuration, the room opened up dramatically, and I suddenly felt like the accuracy of my room and monitoring system went up several notches. I was quite surprised at the amount of "mud" that had been clouding what I was hearing from the speakers, despite my earlier confidence that there was little more I could do to improve the acoustics of my room without going overboard on absorption. I was also impressed - and puzzled - by the beneficial effects on the low end. In theory, a small, rigid diffuser should have little to no consequence on bass frequencies, but I could hear the lows more clearly, with lesser deviations in response as I moved my head around, searching for the nodal cancellations that exist in greater degree without the Acoustic Ramps. Hendrik confirmed that his diffusers do indeed influence low-end response below the range of standard diffusers, but he himself is not quite sure why they can reach even further down than measured. Perhaps they aren't as rigid as they seem, and they're acting as membrane absorbers? In any case, that's fodder for what could be a spirited exchange between acousticians, so I'll just let it be for now. Regardless, it's clear that the Acoustic Ramp is especially ideal for small rooms, where constricting dimensions and parallel walls lead to destructive resonances all across the spectrum. Combined with strategically-placed absorption, a set of Acoustic Ramps would certainly help to break up those resonances to make the room sound bigger - and not deader. Note that any diffuser will lose its effectiveness at close proximities. In my listening tests, I could hear the room "collapse" as I moved my ears to within a foot of the Acoustic Ramp - similar to moving your ears right up to an untreated corner.

The Acoustic Ramp is sold by Redco Audio [Tape Op #21, #49, #76], and it arrives flat-packed, so assembly is required - but do not fear, as it's not at all IKEA-like in quality. Beautifully- finished, furniture-grade maple and powder-coated aluminum give it a modern, Design Within Reach feel (or as I like to call the upscale furniture store, "Design Within Reach to Rich People"). Carefully following the assembly manual while Hendrik looked over my shoulder (so he could understand where he might make improvements in the instructions), I had one built up in 45 minutes, with Hendrik offering a second pair of hands when needed; but I'd bet that it would take me half that time to assemble another unit. Well, I'll be able to test that assertion very soon, because I ordered four Acoustic Ramps for my studio, including two custom ones in clear acrylic! ($595 introductory price, discounts for 4 or more; www.xix-acoustics.com; www.redco.com) -AH