Divided We Stand

May 1, 2001 12:00 PM, Mike Safer

Divided We Stand

Versatile Audio Controller Cuts Cost of Teleconferencing/Presentation System for Divisible Room

By Mike Safer

Coast Business Communications Inc. reduced the cost and operational complexity of a sound system for a divisible teleconference/presentation room. CBC designed the system around an engineered audio controller that manages all of a room’s sound sources. Generally, systems have separate controllers for teleconferencing and presentation equipment, increasing hardware costs. CBC was able to cut costs by finding a single audio controller, the ECB 6 master controller from Rane Corporation, to route both telephone and program audio. This sound system includes two ECB 6 units to permit two simultaneous telephone conversations when the room is divided. An infrared sensor alerts the control system to the position of the movable wall in the space, assessing whether there are two rooms or one, and it then manages audio inputs and outputs accordingly.

CBC was formed in 1987 to serve the audio-visual, video, and engineered sound markets. The founders, Randy Pleasance, president, and Scott Kirchoff, vice president of operations, had worked together at another contractor for 10 years. From the beginning, they based the company on the premise that technically superior systems are conceived only by technically superior engineering talent. Over the years, CBC has focused on designing and installing audio and video systems for boardrooms, training rooms, conference rooms, and for sound masking and reinforcement. Dedicated to being the technological leader, CBC employs four engineers who specialize in audio and video system design and control system software. Their services include analysis of needs, pre-construction planning, system construction and installation, training, and extended system maintenance. CBC designs and installs audio and video systems in executive briefing centers, emergency response centers, boardrooms, auditoriums, fitness centers, classrooms and customer visit centers.

Multipurpose Area

One of CBC's clients was a major semiconductor manufacturer. The client wanted a state-of-the-art sound system for a multipurpose room, which was used for both teleconferencing and presentations. Undivided, the room holds approximately 65 people. A movable wall helps create two rooms in the multipurpose area, one with a 40-person capacity and another that holds 25 people. The client wanted both sides to be able to function independently and simultaneously, and also as one big room.

Because one of the functions of the room was teleconferencing, it was necessary to equip the room with microphones as well as speakers. The client wanted the equipment built into the ceiling because the room had no permanently installed tables or chairs, and they did not want to run wires every time the room configuration changed. The client also specified that the teleconferencing system use full duplex technology, where both parties can speak at once just like using a normal telephone. Although this is the more natural way of conducting a conversation, full duplexing can be a problem in teleconference situations, especially with microphones suspended from the ceiling. Delays occur because a user's voice comes out of a ceiling speaker and the sound from the speaker is picked up by a microphone, which sends it back to the user again. This causes the person at the far end to hear his/her own voice in their earphone a split second after speaking. This is very startling and annoying, causing most people to temporarily stop talking. Speakerphones use half-duplex technology to prevent this problem, but this is also unnatural because only one side of the conversation can speak at a time. The client wanted a state-of-the-art full duplex system that would allow both parties to talk simultaneously and without annoying delays and feedback.

The room already had a sound system in place when CBC was hired, but no teleconference system. CBC was able to use some of the existing equipment. For example, an Axcent2 control system from AMX Corporation, Dallas, Texas, with a touch panel in each room provided a unified interface making it possible to control each piece of equipment from a common user interface. Speakers in the ceiling provided the non-direction sound characteristic of telephone conversation and speakers mounted at the front of each room generated directional stereo sound for audio presentations from a VCR and computer. CBC also incorporated an existing 728PW equalizer and 884PW room combining mixer from Ivie Technologies, Orem, Utah, and three amplifiers from Crest Audio of Paramus, New Jersey.

Cost-Effective Base

With the goal of giving the client an advanced sound system at the best price, CBC chose the Rane Engineered Conference System as the audio base for the room. This system is comprised of two rack-mounted units, the ECB 6 master controller and an ECM 8 automatic microphone mixer. It also includes RaneWare software, a Microsoft-Windows-compatible program that provides a graphical interface for controlling the system and extensive on-line help. Two Telos 1 Digital Hybrids from Telos Systems of Cleveland, Ohio, were used to interface with the two analog telephone lines, one for each room.

RANE ECB 6 Base

CBC chose the Rane system for several reasons. It provided the full duplex teleconferencing functionality the client wanted, yet was also capable of managing audio from other sources such as a computer or VCR. This was the only teleconferencing system they were aware of that could also handle other audio sources, and also had the wide frequency response and low signal-to-noise ratio necessary to give the system the required performance.

The sound system was built around two ECB 6 controllers, one for each room. The ECB 6 units have six ports on the internal audio bridge with each port consisting of a digitally selected 5-input audio mixer. This configuration disallows the connection of an input to its output, avoiding possible feedback. Each port input also provides for a selective automatic level control. The ECB 6 can accommodate one to six ECM 8 microphone mixers on port 1. For this divisible room configuration, each ECB 6 controller is connected to its own ECM 8 mic mixer. Up to eight microphones can be connected to an ECM 8 mixer. The larger of the two rooms contains eight microphones in the ceiling; the smaller one has four. (The microphones were manufactured by Astatic.) The five other port inputs in the ECB 6 allow other line-level audio signals. In these rooms, input from a computer and VCR is routed into the ECB 6 units at ports 2 and 3. An optional plug-in card allows the ECB 6 controllers to accommodate stereo inputs from these sources.

Automatic Echo Canceling

The two ECM 8 mic mixers provide digitally controlled, analog, 8-channel automatic mixing. Unlike other automatic mic mixers, each channel is programmed as either last-on or gated output. Only channels placed in the last-on condition may become the master channel. In this setting, they are also equipped with the optional Rane ECA 1 acoustic echo canceller. Installation of this optional feature is a simple matter of removing the top cover of the ECM 8 and plugging the card into the mixer motherboard. If a model ECM 8A is ordered, the ECA 1 echo canceller comes pre-installed by the factory.

RANE ECM 8 Mixer

Since the echo canceller automatically adapts, there is no need for training as there is with other echo canceling systems. Training typically consists of broadcasting a hiss over the speakers for 15 to 20 seconds. During that time, the system calibrates itself and eliminates the echo. Rane's product continuously compensates for echo and doesn't have to be trained. In CBC's opinion, this is a major advantage since it works automatically without user intervention.

One feature the customer wanted to retain was the use of wireless handheld microphones during a teleconference. The audio reinforcement from these microphones comes out the ceiling speakers along with the voice of the person on the other end of the telephone. The use of a system that automatically adapts to changes in room acoustics is a major advantage when using a wireless microphone during a teleconference.

How It Works

With the system CBC designed, the divisible conference room is capable of functioning as one large single room or two separate rooms. Presentations and teleconferences may be held in both rooms simultaneously since each has its own audio controller, telephone hybrid and telephone line. The audio controller determines the source of the audio input (telephone, computer, VCR) and its volume. And it provides output to either the ceiling speakers or the front-mounted speakers, depending on the audio source. An infrared sensor determines the position of the movable wall. When the wall is open between the rooms, the ECB 6 unit that normally controls the large room serves as the master for both rooms, and calls must be initiated from the large room. In this configuration, the audio picked up by the small room's microphones is fed into the large room's ECB 6. Conversely, audio fed to the large room's speakers is also fed to the small room's speakers. When the wall is closed to create two separate rooms, each room operates autonomously.

Design Support

In the design of this audio system, CBC received technical support from Rane Corp. The AMX control system code needed to account for the moveable wall and the different room configurations was written by a Rane engineer. This engineer, Mike Slattery, even traveled to the site to get a better idea of its unique requirements.

The client also asked CBC to set up sound systems in other buildings as well. Although none of the other facilities had a divisible room, CBC had to deal with other unusual situations, such as working in a room with ceiling mics and very reflective surfaces on three walls.

For more information contact Rane Corporation, 10802 47th Ave West, Mukilteo, WA 98275. Phone: 425-355-6000; Fax: 425-347-7757; Web site: www.rane.com.

Mike Safer is applications engineer at Coast Business Communications Inc. in Hayward, California.