(Reprinted from the Winter 1997 Audio Ideas Guide)

     I first discovered these acoustic absorbers at the Montreal Festival du Son more than a year ago, as demonstrated by genial Yves Boudreau, about whom I have a brief anecdote: at this year’s show I ran into Yves for the third show in a row, his display in the main ballroom just over the way from ours for AIG Imagers, recordings, etc. He greeted me warmly, saying, “Ah, Mr. Marshall, how are you?” My reply was, “Fine, but please call me Andrew…” The next morning he appeared again at 9:45 just before the show opened, this time hailing me with, “Ah, Mr. Andrew, how are you?” Great guy, Yves.

     His Acco panels are made of wood-framed fibreglass covered with cloth in a variety of colours, and evenly absorb energy across the frequency range from 150 Hz up to 4000 Hz, though some absorption remains up to beyond audibility. They’re designed to control first reflections and echoes out of corners and off boundaries. After the Festival in mid March, Yves sent me home with a set of 4 display samples to try out, carefully noting the spots on the rear on the frame (which is covered in a kind of tinfoil) where holes can be made to suspend them on walls with nails or screws.

     When I got home and started to consider where to try them out, the answer was obvious when I put on a record for the first time in several days. I think it was that echo welling up from the rear of my 32-foot, tile-floored listening room that clued me in. I’d known it was there, but since I sit well forward to listen, I hadn’t felt its presence quite so strongly as I did when sitting at the computer closer to the rear wall. Moments later the panels were standing on their ends in the rear corners like wainscotting (see photo), and the echo was a distant memory rather than a close reverberation.

     The application that will appeal to many users, however, is for use in controlling first reflections off side walls, something I had already done in my room with wool wallhangings. Like baffle diffraction effects, these reflections can tend to muddy the imaging of speakers. Those after a certain timespan of milliseconds (which varies with distance and time between direct radiation and first reflection) will be ignored by the ear, this called the Haas effect. But the earlier reflections blend with the speaker’s direct sound, confusing spatial perception, and therefore should be absorbed. The Acco panels are a very good and attractive way of doing this. In fact, when I was a young audiophile in my twenties, we used to make our own panels by covering sheets of styrofoam with burlap to control the considerable echoes of the dry-walled apartments we lived in then. These panels are more effective, with more uniform absorption with frequency.

     Tube Traps they aren’t, but the Acco panels start where these marvellous standing wave control devices stop, the former operating below 150 Hz for the most part. Thus in my room there are Tube Traps at one end behind the speakers, and Acco panels at the other behind the listeners. This is not quite a live-end/dead-end room, but definitely one that is controlled but not over-damped. I recommend the Acco panels highly, and plan to get some 4 x 4′ ones for our home theatre room to make the AC-3 sound even more discrete. You should, too.

Andrew Marshall