Application example – QSC Audio DSP-30 User Manual

Page 20

TRI-AMPED PA CABINETS WITH SUBWOOFER (refer to illustration at right)

Use:

Application Example

This is highly generalized, but shows the main idea in cre-

ating larger systems. In this example, the audio source

material is connected to the inputs of all four DSP’s. Take

care to keep right and left channel signals connected to the

correct channels of downstream equipment. For example,

keep all left channel signals routed through the channel 1

sections of downstream gear and all right channel signals

routed through channel 2 sections of downstream gear. This

preserves stereo imaging.

Each DSP would be setup independently with the appropri-

ate crossover response and equalization for the specific

driver being used. Refer to the speaker’s (or driver’s) docu-

mentation for recommended frequency range, drive level,

and any other applicable information. In the example at right,

DSP #1 (assigned to high frequency drivers) might be set up

for a high pass filter with a -3dB point of 6 kHz and high-

speed limiters to protect them from transients. DSP #2 (as-

signed to midrange drivers) might be set for a band pass

filter, with -3 dB points at 1 kHz and 7 kHz using mild signal

limiting. DSP #3 (assigned to low frequency drivers) might

provide a 45 Hz to 1100 Hz bandpass with EQ to remove

modal resonances of the listening environment. DSP #4

(subwoofer drive) could be assigned a low pass filter with a

-3dB point of 50 Hz and equalization as required. All the

filters mentioned above would have assignable response

type (where applicable) and assignable slope characteris-

tics enabling precise tuning of the system.

Power requirements for high frequency drivers are gener-

ally much lower than for low frequency drivers; this requires

either reduced gain in the signal processing stage or the

lower power amplifier for the high frequency drivers. The

opposite is true for the subwoofers; they generally require

the highest power to drive them, so assign your most pow-

erful amplifiers to the lowest frequency drivers. Assign your

amplifiers to the drivers according to the required power

levels .