Music in the Round #19 Page 2

These results were enlightening but curious. MRC indicates the current and target RT60s but not the degree of change. I couldn't help noticing that, of the 60 DSP filters available for the three modes, the system only used 10 (Music), 9 (2-Channel Movie), and 4 (Multichannel Movie). Most of the filters were in the 80–200Hz range, with the sub/LFE getting filters at 36Hz, 72Hz for music, and 69Hz for movies. The left front speaker was filtered at 87Hz and 109Hz, and the right front speaker, which is next to an open doorway, was filtered at 44, 79, and 90Hz in music and stereo modes. The rear speakers got minimal filters above 150Hz in all modes. The most interesting outcomes were that the center-channel speaker got no correction at all in any of the modes, and that none of the front speakers were corrected in Multichannel Movie mode (footnote 2). The filters changed the frequency responses only very subtly, whether measured by MRC, TEF analysis, or Room EQ Wizard. I could show you the waterfall graphs that indicate the consistently reduced decay times at the filtered frequencies or the improved impulse responses, but we'd have to print them each as a full page for you to see the subtle differences!

But the devil is in those details. Unlike with the apparently more invasive EQ of the Denon-Audyssey system, I don't dither in my preference for the improvements wrought by Meridian's MRC. The imaging was stable and continuous across the front, and wrapped almost seamlessly around to the rear. The bass was not greatly changed, but when I repeated the setup with the Velodyne SMS-1 subwoofer EQ system also engaged, the bass from the sub was significantly tighter and surprisingly powerful. I say surprising because it was hard to tell that the sub was doing anything at all until something really monstrous came along—such as the bass drum and cannons in Telarc's famous recording of Tchaikovsky's 1812 Overture, or the organ of St. Sulpice in Widor's Mass, Op.36. And my system was as transparent and balanced as ever. In short, there was no downside, only an upside.

Bottom line
While it may seem that my results with the Meridian and Audyssey EQ systems don't justify great enthusiasm, consider the context. Audyssey's demos with Denon and Phase Technology and at CES have been much more impressive than the Audyssey's performance in my own room. The reason is clear. Those demos showed how a basically mediocre hotel-room audio setup could be bettered, and the improvement was easily apparent. My own system simply ain't that bad. First, my listening room is reasonably furnished with carpet, soft furniture, and drapes; very little of the flat, hard wall surfaces remain unadorned. Second, the speakers are placed and angled to optimize their balance at the listening spot. And third, a number of specifically acoustic treatments improve the clarity and audibility of all sounds in the room. I just have to listen to the sound of my own voice as I enter and the effectiveness is apparent.

I got the room-treatment bug when I had on loan Ethan Winer's MiniTraps, whose acoustic effect on the room was profound. They taught me that, even though these particular traps were incompatible with our décor, the room needed some sort of treatment. Every room has its constraints, but in this one, no corner is available for bass traps. My wife nixed putting soffit-like traps along the wall/ceiling joins, and I didn't like the idea of further lowering a ceiling that was only 8' high to begin with. That left the front wall (behind the speakers) and the middle portion of the rear wall (behind the couch).

In hopes of trapping as much wideband bass as possible, I built two rectangular-section blocks for the floor/wall angle behind the front speakers. Each consists of a vertical 2' by 4' slab of 2"-thick Owens-Corning 703 rigid compressed fiberglass, atop which rests a similar 1' by 4' slab. These, purchased from Sensible Sound Solutions, are covered in a nice Guilford of Maine acoustic cloth of my wife's choosing. Inside each enclosed space I loaded three 3"-thick slabs of Owens-Corning 705, purchased from RealTraps. The result is a fairly large but unobtrusive mass of acoustically absorbent materials that also serves as a conduit to hide and guide the speaker cables.

Above this, I mounted on the front wall two 18" by 48" Echo Buster Double Busters, flanking the plasma display and between the speakers to minimize reflections and eliminate most of the remaining unoccupied space on that wall. Finally, I mounted another pair of Sensible Sound Solutions' fabric-covered, 2' by 4', 2"-thick panels on the rear wall just behind the listening position. I put off this task for months until I discovered Rotofast Panel Anchors. OC703 compressed fiberglass is fairly rigid and dense but is still quite friable, and the common mounting options, such as Z-clips or impaling clips, didn't appeal to me. Rotofast anchors are 2"-diameter, 1"-long plastic screws that self-thread right into the OC703 panel and can be attached to other surfaces in a number of ways. I used their new Snap-On model.

Installation involved: 1) screwing four anchors into each panel, 2) inserting marking plugs into the Snap-Ons, 3) holding the panel firmly in place to mark the anchor locations, 4) screwing the snap-in ratchets at the locations, and 5) completing the installation by pushing the panel onto the ratchets. A piece of cake! I modified the standard setup by mounting the ratchets on plastic standoffs my wife found at Home Depot so that the panel's absorption is extended to lower frequencies by the cavity created. Still, they went up in minutes and are perfectly level.

Measurements taken with TEF and Room EQ Wizard showed that the LF boost near the rear wall was greatly mitigated by the installation of these panels. I confirmed that by listening while reclining on the couch. In addition, slap echo was completely eliminated, at least to my ears.

First-reflection points? The floor is carpeted and cushioned, and at the side reflection points are pieces of furniture with large, oblique surfaces that effectively deflect any direct reflections away from the listener. The ceiling? Well, I'm working on that.

Net, net, as they say in some businesses. The smoothness and the decay of frequencies below 200Hz were apparent with TEF and Room EQ Wizard. As for higher frequencies, the room doesn't ring when I clap my hands, but I can hear the crispness when I snap my fingers. Voices, live or reproduced, have a natural clarity and are easily localizable. Ambient noise levels are low enough for the resolution of extremely fine detail and a wide dynamic range. TEF says that a noise criterion (NC) below 35dB is required for good home-theater performance, and that 30dB is preferable. As long as the furnace isn't blowing hot air and no cars are passing on the street, TEF gives me readings of under 25dB, which is its lowest calibrated level.

Despite all this, and a little touchup from the Velodyne SMS-1's EQ system, I can still hear the additional improvements made by MRC and Audyssey—but there isn't a lot of room left for improvement. It's hard to complain.

Next time in the Round
Waiting to be unpacked are Bryston's new SP2 A/V processor and a new home subwoofer from JL Audio, maker of monster car subs.

Footnote 2: These results were obtained during the process of adding the room treatments detailed below. When all of those were in place, MRC inserted even fewer filters (9, 5, and 5, respectively), and their amplitudes were smaller in all but one case. In addition, filters between 90 and 150Hz were no longer needed. For physical reasons, I could not A/B this change!
Article Contents
Share | |
Site Map / Direct Links