Think back to the first concert you attended—the energy present in the room was undeniable. The connection you felt with the artist(s) felt uniquely yours and a fully fleshed out version of what you heard on the album. Whether it is the pounding bass and rhythms of an EDM show, or the exquisite harmonies one can find at a local symphony, how can we ensure the best possible sound quality to achieve the highest fidelity experience for both the performers and audiences? What kind of speakers would best fit the venue? Is a full PA system necessary for a small cafe?
The first point of consideration is the space itself. Are there any dead spots? Is there any sound leakage outside of the venue? Is it a large, wooden space with heavy reverberation or a carpeted basement? All of these will affect how and where you place the speakers. Consider contacting a sound engineer to test the space with a sound kit, or using a digital decibel reader to find areas of concern. If there are any obstructions, such as pillars or walls between the stage and intended listening audience, setting up smaller satellite speakers will be much easier than trying to redesign the whole night club. With these considerations in mind, let’s move on to actual speaker placement.
The size of the space will ultimately determine how many speakers and what kind of sound reinforcement will be required for the venue, however there are a few necessary mainstays to begin with. If the venue is a small cafe intended for open mics or poetry readings, only a few speakers may be necessary. Consider using a portable PA system with one or two speakers with at least a 6” woofer and 2-3 3” HF drivers at 150W. Most open mics and acoustic acts won’t need a heavy low end, so look for something with a frequency response between 70Hz-16kHz. Unless there is a dedicated audio engineer, it’s almost always best to use mono as opposed to stereo to avoid problems like phase cancellation and unwanted comb filtering. Elevated speakers, such as on a stand or a small stage above the audience will help with dispersion of sound and give the audience the best listening experience. In smaller venues like a cafe, position the speakers so that the distance between each speaker and the middle of the audience, called the “sweet spot,” forms an equilateral triangle. However, keep in mind to place the microphone behind speakers to avoid feedback. The best way to check the sound is simply listen, listen, and listen. Our ears are the best tool when it comes to listening.
For larger venues, there are a few more things to consider and the problems can increase exponentially if careful consideration is not made in the setup of the sound system. Keeping in mind all the variables of natural room reverberation, physical obstructions, size of the venue, and where the intended audience will be located, consistent sound coverage will likely be the biggest issue. For a venue with an intended audience size of 300-500, consider using four bass cabinets at a peak of 2000w and 18” driver, with a frequency response 35Hz-160Hz. This will cover the low end necessary for night clubs and EDM artists, but keep in mind that bass cabinets placed closer to corners or walls will give a stronger response than those placed towards the center of the room. For the mid-high ranges, consider four more dedicated speakers with a 1650w peak, 2 x 12” mid-high drivers and a 1 x 2” exit compression driver, with frequency responses between 80Hz-18KHz. With this set up, the space should have more than adequate sound reinforcement and response for the artists and audiences alike, and should allow for outdoor events as well if needed. The last set of equipment to consider are things like wall mounted satellite speakers to get around physical impedances like columns, staircases, or walls. This may not be necessary in every venue but it is worth considering if there are multiple rooms in the space. Consider using four more, smaller speakers with a 480w peak, 1 x 8” bass-mid driver and 1 x 1” exit compression driver with a frequency response of 70Hz to 18KHz. These will be mounted where necessary, depending on the venue, to increase sound coverage around physical obstructions. The overarching theme here is to reduce the variance in sound pressure level, or SPL, within 6dB.
When placing speakers in larger venues, inconsistencies with sound quality only increase. The first thing to consider is horizontal placement.
Ensuring total coverage for the audience is crucial for their listening experience, and this can easily be achieved with just two on either side of the stage or an added one in the middle. Be careful of hotspots in the audience where the sound can be louder in certain areas, however it shouldn’t be more than a few decibels in variance.
Next to consider is vertical placement. This can be a little more tricky and involves some planning using the inverse square law. The inverse square law basically states that the sound amplification will decrease by half every time it doubles the distance travelled. For example, you may have 12 dB at 10 feet, but at 20 feet you will only get a 6dB response. An easy way to work around this is to angle the vertical placement of the speakers so that the closest coverage of one speaker is less than half of the furthest coverage of the next speaker. Another option is a second speaker called a down-fill speaker that is angled so that it provides a deeper coverage for the audience. There are also speaker placement calculators that can help make this process easier.
The final important aspect to consider is speaker delay, particularly for fill-in speakers, to avoid different arrival times of sound for listeners at different areas of the venue. Without going too much into the specifics, the basic formula to achieve uniform sound with speakers placed at different intervals from the audience is Ds=X/C(1000), where Ds is the delay in milliseconds, X is the distance from the main speakers in feet, and C is the speed of sound in feet per second, which is dependent upon atmospheric qualities like humidity and altitude. The speed of sound at sea level, 68F, in dry conditions is 1126 feet/second, but conditions are rarely perfect and it is not always practical to measure parameters at every venue. With that being said, many audio engineers will round up to 1200 feet/second as a starting point and use their ears to determine the best audio. For example, if we have a speaker at 150 feet (X) from the main stage, we can divide that by our rounded speed of sound 1200 (C) to give us a value of 0.125, which we then multiply by 1000 to give us 125 ms for our delay (Ds). Again, this is just a starting point. Our ears will be the final determination of what sounds good at each venue.
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Sweetwater. (2017, April 17). A dummy’s guide to speaker coverage. inSync. https://www.sweetwater.com/insync/pa-speaker-coverage/
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