User manual SABINE ST-1000

[. . . ] The sound reverberates back and forth between the tile walls and floor. Just a touch of the volume fader fills the room with screeching feedback. The speakers are well away from the microphone and there are no reflections, so now we can really crank up the system without a bit of feedback. Most sound systems have characteristics that fall between these two examples, but examining the extreme cases makes it easier to understand the more common in-between situations. 1 What is acoustic feedback? [. . . ] Many industry veterans incorrectly presume that 1/3-octave EQs use 1/3-octave wide filters. If this were the case, the EQ filters would not be wide enough to create smooth curves. Instead, they would produce a notched frequency response that would make the EQ useless for shaping the sound and useless for controlling feedback frequencies between the sliders. Actually, most manufacturers use 3/4 to 1-octave wide overlapping filters placed on 1/3-octave center points. 2. ) It's important to understand that the term "1/3-octave" refers to the spacing of the sliders, not the filter width. Graphic EQs are excellent for shaping the sound, and they 2 THE FBX SOLUTION are fairly simple to use. However, using one-octave wide EQ filters to control feedback invariably causes an unnecessary decrease in the gain and fidelity of the program. It's easy to see that if feedback occurs somewhere between the sliders, you will have to pull one of those EQ sliders down pretty far to eliminate feedback. On the other hand, you'll get considerably more net gain and much better sound quality if you use wide graphic EQ filters for tone control and insist on narrow filters for feedback control. Parametric EQ In the quest for perfect sound, engineers developed very narrow tuned filters for controlling feedback points in auditoriums. In the early days of sound reinforcement, these filters were custom made to a specific frequency and width for a specific application. If you insert too many filters in the system, you ference comes after the filter is placed. Fixed filters remain on the initially detected feedback tone - they do not move. These filters provide the initial maximum gain before feedback and are set automatically during setup. Dynamic filters can release and move to new feedback frequencies and are for A PA System was set up using a microphone, mixer, FBX, power amp and two speakers. The system's gain was raised until the FBX removed nine feedback points. The EQ was adjusted while the system gain was raised to the same level achieved with the FBX. The frequency response curves of each device were then plotted. Fig. 1/3-Octave Graphic EQ will hear a degradation of the sound quality. If you set too few filters, you will not have enough mobility or gain. In this case, it is usually best to walk around the stage area until you find an area where feedback is a particular problem. Then place one or two feedback control filters to take care of that location and repeat the process in the next few areas. [. . . ] Does doubling the power from 400 Watts to 800 Watts make it sound twice as loud?In general, you have to increase the power about 10 times (or 10dB) to make the sound seem twice as loud. When engineers describe the loudness of a sound in terms of decibels, they are comparing the sound pressure level of a particular sound compared to an international standard. 4 gives several common reference points. equalizer with the 1, 000 Hz slider pulled down 12 dB. [. . . ]