Sonido surround conference

ASC’s 5.1 Surround ATTACK Wall
Transcript of a seminar presented by Arthur Noxon P.E., President of Acoustic Sciences Corporation, at the Surround 2001 International Conference and Technology Showcase, December 7-8, 2001, Beverly Hills, CA.
walls and corners. It’s name, “ATTACK” is an acronym that actually comes from the concept of an All TubeTrap Acoustic Control Kit, although the moreaggressive connotation is not completely by accident.

The traditional recording studio has its acoustic package either built into or mounted directly on the surfaces of the room, the walls, ceiling, floor and corners. Acoustic Sciences is fairly well known for the TubeTrap, those cylindrical bass traps that are found standing is the corners of the room and other half and quarter round traps that aremounted onto the surfaces of the room. In 1986 ASC began experimenting with something entirely different. The results were positive and engaging. The system evolved through the help and interest of many people and it is found alive and well in many recording studios today.

All studio design follows certain basic acoustic principles and so does the ATTACK Wall. We will look into how it satisfiesthe requirement for promoting a strong and clean direct signal, how it provides a reflection free zone and how it generates a time delayed diffusive backfill. The ATTACK Wall satisfies the LEDE principle in studio acoustic design for both stereo and surround mixing environments. Recording studios design is based on the well known “LEDE” type principle. Here we see a sound level in dB vs time inmilliseconds sketch of the ETC or Energy Time Curve that defines the LEDE type acoustic signature. It begins with the

The ATTACK Wall is the opposite of traditional room acoustics. It creates an acoustic space that exists well within the room, away from the surfaces. Instead of built in or surface mounted acoustics, the ATTACK Wall is a free-standing acoustic package that is set up well inside theroom, away from the

engineer receiving a strong and clear direct signal. Next is the Reflection Free Period that lasts about 25 milliseconds, during which the engineer should not receive any reflected version of the direct signal. Following this, there is to be a time delayed diffusive backfill flushing back into the engineering position.

This back fill keeps the recording space alive andcomfortable to work in. Without it, one would be working in an anechoic space and that is very exhausting, especially in those late night hours. All recording studio acoustic packages should meet the LEDE type criteria, whether the acoustics are built into the walls, mounted on the walls or set out well into the room, whether the control room is used for stereo or surround mixing.

power in alldirections. The treble range directivity has a cardioid pattern while the bass range pattern is omni. The ears of the mixing engineer are about 4 feet off the floor and so are the monitors. Unfortunately, most monitoring rooms have an 8 foot high ceiling. The direct wave from the woofer of the monitor is strongly affected by the reflections from both the ceiling and the floor. These two reflections travel 8foot round trip paths and meet together right in front of the speaker driver. This causes the air in front of the driver to have a density that is not normal, but that has been preconditioned with an 8 foot or 7 millisecond delayed version of the original signal. A downtown designer studio will have the mains mounted in the wall, typically “soffit loaded”. A monitor stand can be modified to play betterby adding a baffle. This supports the expanding bass wave, directing more of it towards the engineer and allowing less to expand in the wrong direction, away from the speaker and into the room. Baffles have to be carefully built so they do not color the speaker they are trying to help by reinforcing the wrong frequency range. A good baffle design should support the bass and absorb the midrange....