Concert Spaces and Live Sound Production
One of the biggest hindrances to getting a good sound is the room in which the performance is staged. A bad room can make even the best PA system difficult to use. Generally, a Reverb Decay Time (-60dB) of longer than about 1.5 seconds makes it very difficult to maintain vocal intelligibility and instrumental coherence, but there are many venues - or buildings with other primary purposes used as venues - with longer decay times. We have worked in churches and cathedrals with decay times of longer than 5 seconds.
Often nothing much can be done about the room itself, or the stage or the performance space. However, the following points can sometimes help minimise the adverse effect of room acoustics:
- Choose Loudspeaker Position carefully. There are two principal aims:
- Excite the room as little as possible. This means keeping overall levels at the lowest acceptable level (the louder it gets, the more the room takes over, until all you have is a chaotic noise). With a drum kit - which doesn't have a volume control - this may present something of a challenge.
You may also be able to reduce excitation using a distributed speaker system (using delayed cabinets part of the way down the room), so that the main speakers do not need to be so loud.
- Minimise reflection from walls or other structures. As well as angling the main (and, if there are any, delayed) speakers away from the side walls, you may need to look at the placement of backline cabinets and monitors.
- Cover acoustically reflective surfaces. Highly reflective surfaces - stone or smooth plaster walls - can wreak havoc with the sound, increasing the risk of feedback and reducing intelligibility. Around the stage or performance area the reflected sound also adds to spill (the sound of one instrument being picked up by the microphone of another). Curtains - the heavier the better - or other absorbent material can make a noticeable difference. A relatively cheap option is to hang a curtain or blanket across the back wall (lighting or speaker stands can be used for this, if there isn't a handy picture rail), and if you get the band's name and logo stitched or printed onto it this can double as a banner. It may not be much, but every little helps*.
- Put a piece of carpet under the drums. This helps to reduce reflection and spill (see above), and also helps to stop the drums - particularly the kick drum and hi-hat - from slipping. Off-cuts large enough for this cost next to nothing. Get one, and make sure it travels with the drums.
- Keep loud instruments as far as possible from quiet ones. Although most microphones used in live performance are ‘directional’, what this actually means is that they are more sensitive to sound arriving from in front of them than they are to sound arriving from the back and sides. However, if the sound coming from the sides (e.g. a 100w guitar amplifier at full volume) is very much louder than the sound coming from in front (e.g. a singer with a quiet voice), the microphone will pick up both. Don't point guitar amps at the vocal mics. If the drums can be placed away from vocal microphones, there will be less spill, and the vocals will sound better.
- Market the event effectively. People soak up room reflections, and a full venue will always sound better than an empty one.
*Here, we have used ‘every little helps’ in its original sense, meaning that even small adjustments can have a beneficial effect. We do not mean ‘every little helps a ruthless profiteer to take more of your money and close more of your Post Offices’, or ‘every little helps a marketing campaign to hijack your language’.
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