Operating Manual
7.3g Delay
In large installations or outdoor venues there are often many speakers in vari- ous locations to get the best coverage possible. Since sound travels relatively slow through air (1130 ft/s at 20ºC), multiple loudspeaker locations can create a situation where the original audio signal, simultaneously leaving all loudspeakers, arrives at a single point in the venue at several different times. Needless to say this causes prob- lems, and what may be crystal clear sound directly in front of any one loudspeaker can be unintelligible at the farther reaches of the venue with direct
The solution is to delay the audio signal to the loudspeakers located further away from the primary source, so that sound comes out of the distant loudspeakers at the exact time that sound from the main loudspeakers arrives. Within the 4048A, up to 682 milliseconds of time delay are available on each output channel, allowing secondary loudspeakers to be time aligned with the primary speakers up to 771 feet (235m) away.
Long Time Delay
For Remote Speakers
Speaker on
Main Stage
Secondary Speaker
200 ft from Main Stage
Short Time Delay For Driver Alignment
Example: 12 Inches
High - No Delay
Midrange Delay 12 Inches = 0.9mS
Low Delay
8 Inches = 0.6mS
Example: 8 Inches
A second application for delay is to time align discrete drivers within a cabinet or cluster. For example, a typical three way speaker cluster would have low end, midrange, and high frequency drivers all located near one another. The different drivers
for each frequency band are not necessarily the same physical depth with respect to the front of the loudspeaker cluster, so there exists the problem of the same signals (at the crossover points) arriving at the cluster "wavefront" at different times, creating undesirable wave interaction such as frequency peaks or cancellation. The solution in this case, rather than fixing the frequency anomalies with EQ, is to slightly delay the signal to the drivers closest to the cluster front.
Using the location of the driver diaphragm farthest back as a reference point, measure the distance to other drivers in the cluster, and set the output delay for each accordingly, with the driver diaphragm closest to the front getting the longest delay and the driver at the very back getting no delay at all. The minimum adjustment is
0.02milliseconds, or about ¼ inch.. When appropriate, always time align the loud- speakers before applying EQ to the outputs of the 4048A.
7.3h Limiter
A full function compressor/limiter is included on each output channel. A limiter is commonly used to prevent transient audio signal spikes from damaging loudspeakers, manage analog and digital recording levels, optimize broadcast levels, or "thicken" the sound of an audio source (compression). The adjustable parameters include Limiter In/Out, Threshold, Ratio, Attack Time, Release Time, and Limiter Link.
The limiter threshold range is from
The ratio control determines the amount of gain reduction above limiter threshold. Ratio ranges from a gentle 1.2:1 to a
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