Modern systems often use bass reflex cabinets for their woofer or
First, measure the horn length. In the case of folded woofer horns this is anything but easy. Use a design drawing or open the cabinet (usually, a flap or cabinet side wall can be opened easily, for instance, to replace a defective speaker).
We use a horn length of 1 m as an example. It will make no sense to delay the signal, because the woofer signal arrives with a
Calculate the frequency whose wavelength corresponds to twice the horn length. At this frequency the output signal will be reversed by 180° in phase when it comes out from the horn.
The frequency can be calculated as follows:
c
l = f
(see chapter 3.5.2)
Use the known values (speed of sound in m/s; horn length in m) to calculate the frequency:
343 m/s
2 x 1m
= 171,5 1/s = 171,5 Hz
Now, using a crossover frequency of 171.5 Hz and reversing the polarity of the woofer output will result in an approximate phase correction, which can be
General remarks on runtime correction
Only one speaker stack each should be measured and corrected. Begin with the highest crossover frequency and work your way downward.
+Once you have completed the runtime correction procedure, please make a note of the relative positions of the speaker, the adjusted crossover frequencies, delay times, etc. as well as of all level settings (limiters included). The next time you set up your system, you can start from these settings and with a bit of luck you will need to make just a few fine adjustments, before you can turn to the EQs.
+Never drive different speakers from the same output! The distances which the sound waves travel before they reach the listener will very likely be different and unavoidably lead to phase shifts. Additionally, the
When the speaker offset is greater than 68.6 cm you can only move the speaker cabinets. Runtime correction is not the same as the signal delay applied to offset groups of speakers. Here, the entire signal must be delayed by a much greater amount (a suitable delay circuit is included, for example, in the BEHRINGER
3.6 The limiters of the SUPER-X PRO
Limiting the signal in the crossover network is the last resort to protect the system against overloading. Otherwise, improper handling by the user could lead to serious damage in several drivers.
Each frequency requires its own limiter/compressor control times. The higher the frequency, the shorter the control times. In the
3. APPLICATION | 17 |