A question from a Audio Masterclass visitor...
Hi I'm Griffith, I'm a sound technician at our church.
We are using 4 x 350 watts Beta 3 powered speakers, 2 x 1000 watts bass speakers (quite big, it's also used for events outside) and a Mackie VLZ pro mixer. Our church can house at around 400-450 persons.
The first row of seats is too close to the stage, that we have to put our speakers at the back portion of the stage. Thus, band and singers are in front of the speakers.
How can I achieve a good sound without feedback, and is it possible to move the speakers forward and not making the audience deaf?
According to my recollection, it actually does say in the good book that two wrongs don't make a right, although possibly not quite in those words.
And indeed the 'wrong' of the front rows of the audience being too close to the speakers cannot properly be corrected by placing the speakers behind the band.
Firstly, what is the problem with having the speakers too close to the front rows of the audience?
This is quite simple. If the level is turned up loud enough for those in the back rows, then it will be uncomfortably loud for those at the front.
And what is the problem with placing the speakers behind the band?
Also simple... the vocal microphones will pick up the sound from the speakers directly and the chances of feedback are high.
The solution is all in the siting of the loudspeakers.
If the speakers are too close to some audience members and too far from others, then the solution is to make the distances as close to being the same as possible.
And the way to do this is raise up the speakers. All the way to the ceiling won't be too far (unless your ceiling is extraordinarily high).
By doing this, the difference in distance from the speakers to the front rows, and from the speakers to the back rows will be more nearly the same. Therefore you can get much closer to a 'one level suits all' situation.
Don't forget to position the speakers in front of the band.
There are two problems however...
One is that you have now increased the distance from the speakers to all of the audience, hence it is likely that the sound is more reverberant.
The solution to excessive reverberation in live sound is to apply acoustic treatment to the auditorium, but this will be expensive so we'll try another solution.
The best you can hope for regarding excessive reverberation is to minimize the problem. And the way to do this is to consider the angle of distribution of the speakers - you'll find it in the spec sheet.
Then, angle the speakers so that they are throwing sound at the audience, not at the walls and ceiling.
Walls and ceilings reflect sound very well, causing reverberation that is often excessive in places of worship. People however absorb sound quite well.
The other problem is that for the front rows of the audience, the sound is coming from above their heads.
The standard solution is to use additional small speakers low down, at a low level, just to cover the front rows. This solution works quite well.
Raising the speakers all the way to ceiling level will take quite a lot of installation effort and therefore cost money. A 'halfway house' situation is simply to raise them as far as you can, paying due regard to safety of course.
If you do this, you will achieve benefits even without additional small speakers. The front rows will receive 'off-axis' sound from the speakers, which will not be of the best quality. However the overall compromise should be acceptable and much better than the problems you are having now.
Image credit: kristarella
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