Sabine Welder SDA-102 사용자 설명서

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Special thanks to

Hans Drobilitsch of

Hans Drobilitsch

Audio GmbH.

(Wollersdorf,

Austria) for his

invaluable technical

advice.

Why Digital Delays?

The most intelligible sound occurs when two people speak face to face. The sound is loud

and dry and the direction of the sound aligns with the speaker. It stands to reason that the

most intelligible sound systems are the ones that come closest to emulating face to face

communication. If this is your goal, a digital delay is essential to your sound system.

Until recently, a digital delay’s cost was prohibitive for the average user. Only high-end

applications could justify the cost. But recent drops in component prices now put the benefits

of digital delays within affordable reach of every user.

There are three distinct applications for digital delays. The first and most important is

synchronization of the loudspeakers to control excess reverberation and echo. Secondly,

digital delays help control comb filter distortion, and finally, digital delays are useful for

aligning the acoustic image so the direction of the sound seems to be coming from the

performer rather than the loudspeaker.

This manual goes beyond the typical operating guide that only explains the front and back

panel adjustments. Instead, we discuss the basic acoustical concepts needed to get the

most out of your SDA-102 and present examples of several practical applications.

Loudspeaker Synchronization

Sound travels at about 1,130 feet per second in air, or about 1 millisecond per foot. On the

other hand, electronic signals travel almost one million times faster through your sound

system to the loudspeakers. The main task of digital delays is to synchronize multiple

loudspeakers so the sound traveling different distances arrives at the listener’s ears at about

the same time. Synchronizing the loudspeakers reduces reverberation and echoes for

improved intelligibility.

How to Synchronize Your Signals

There are several powerful tools available for precisely measuring the time a loudspeaker

signal takes to arrive at a certain point in the audience. Most of these tools are very sophisti-

cated and tend to be quite expensive. Fortunately, simpler tools are sufficient for most

applications.

In the 1930’s, engineers synchronized the low and high frequency speakers in movie theaters

by feeding a sharp click through the system. They moved the speakers until they could only

hear a single sharp click coming from both speakers. You can use this same method with a

common child’s toy called a clicker. Pressing the thin metal strip makes a loud sharp click.

A clicker is especially useful when synchronizing the direct sound from the performer with the

sound from the loudspeakers.

Alternatively, you can use a phase checker especially for synchronizing the signals of two

loudspeakers (either LF and HF or two full range systems) since most of the phase checkers

include a click generator and receiver. Phase checkers are quite affordable and have other

uses besides synchronizing.

Processing (or Group) Delays

Converting signals back and forth from the analog to digital domain always delays the signal

a little. These conversion delays are often called processing (or group) delays, and usually

range between 0.9 to 5 milliseconds. You will notice that Sabine delays always display the

processing delay as the smallest possible delay value. For the SDA-102, the processing

delay is 0.9 milliseconds. You can simply bypass the unit for 0 seconds delay.

THE DIGITAL DELAY ADVANTAGE:

Synchronize loudspeakers,

eliminate comb filter distortion, align the acoustic image