dbx DriveRack VENU 360 Owner's Manual

dbx DriveRack VENU 360 Owner's Manual Manual pdf 49 page image

47If the crossover is configured with bands using only a high-pass or low-pass filter (such as in the 2-way example shown below)you shouldn’t have to worry about adjusting the PHASE parameter. However, if band-pass filters are used (such as in the3-way example shown below) then phase adjustments will likely be necessary.No Phase AdjustmentNecessaryHigh-PassFilter Low-PassFilterBand 1(Highs)Band 2(Lows)Adjust PhaseFor Band 2 FirstAdjust PhaseFor Band 3 SecondHigh-PassFilter High-PassFilter Low-PassFilter High-PassFilter Low-PassFilterBand 1(Highs)Band 2(Mids)Band 3(Lows)2-Way Phase Adjustment Example 3-Way Phase Adjustment ExampleTo tune the PHASE parameter, use the same “polarity” test previously mentioned and start with the highest crossoverfrequency (the crossover frequency between bands 1 and 2 in the above 3-way example). Using this example, the sine tonewould be set at 2.5 kHz, the polarity would be inverted on the mid band, then the PHASE parameter would be adjusted on themid band for the most cancellation. When done, polarity would be set back to the correct setting. This same test would then beperformed between the low and mid band by setting the sine tone to the low-to-mid crossover frequency, inverting the polarityon the low band, then adjusting the low band phase for the most cancellation. When done, polarity would be set back to thecorrect setting.The crossover should now be optimized for use with the loudspeaker system. Listen to some reference music through thesystem to see how it’s sounding. Changes to all these settings can be difficult to judge when heard in the context of thewhole system, but by zeroing in on the specific crossover frequency regions, matching levels, and inverting polarity on oneof the drivers, you are free to experiment with different settings to determine the best settings for your loudspeaker system.Adjust each of these parameters until the most signal cancellation is achieved then switch the polarity back so the drivers areonce again in phase. Optimizing these parameters using this test will allow your system to work in harmony and improve itsmagnitude, phase, and polar response.3. Setting Gain Structure & LimitersNow that the crossover settings are optimized and the loudspeaker drivers are in phase, it’s time to calibrate the gain structureof the system. This will provide ample headroom for all system components in the signal chain and optimize the system’ssignal-to-noise performance.Your amplifiers play a vital role in system setup because they are the last devices in the signal chain before your loudspeakersand offer the greatest amount of gain (that is their job after all). If your amplifiers are setup incorrectly you will not be usingyour system to its fullest potential and could potentially cause damage to your loudspeakers. When you select your amplifiermodels in the Setup Wizard, the VENU360 will automatically set the limiters and gain structure between the VENU360 andamplifiers. If your amplifiers are not available in the Setup Wizard, you should choose the “Not Listed??” option, meaning limitersettings will not be automatically set. The following section explains how you would go about manually optimizing the system’sgain structure and set the limiters to protect your amplifiers from clipping.Gain structure refers to aligning the gain of each device so that the input circuits of all devices clip at the same time – thisoptimizes the noise floor of the sound system and allows you to know exactly how much headroom you have in the entiresystem by simply looking at the mixer’s main output meter. Oftentimes, PA systems are setup with the amplifier input attenuatorcontrols turned all the way up, in the incorrect assumption that this is the only way to get the maximum level out of thesound system. Setting up your amplifiers in such a manner can help prevent someone from raising your amp attenuators anddamaging the system (this is sometimes required for permanent install applications and requires the output gain be reduced inthe device feeding the amplifier), however, system noise may be increased by doing so.