Each speaker in a system should have consistent phase response, and be driven with a phase correct signal. Otherwise, cancellation will occur, as one driver may be pushing air while another is pulling. This can have very noticeable impacts on the system frequency response, bass SPL, stereo imaging, and overall sound quality.
Systems that have multiple models of amplifiers, speakers, cables, etc., can easily have phase errors among different system components. This is mainly due to speakers, amplifiers, or processing components having differing polarity conventions due to design differences or wiring errors, or can be due to connection errors among system components.
To avoid these issues, it is necessary to fully characterize the input-output phase relationship of each component in the system, all the way down to the cartridges on the turntables (which could have the cartridge lead wires reversed on one channel, but correct on the other, causing Left and Right channels to be 180° out of phase), up to the individual drivers in the speakers (which may have had a driver unit replaced at some point and the lead wires connected incorrectly, or a crossover replaced with a different design). It is suggested to enlist the help of an electrical engineer for this task, as this process can become complex.
Ideally, the entire system will consist of entirely top-grade, perfectly maintained equipment and cabling, for which the phase specifications are very clear. This is often not feasible however, due to the limited budgets that many sound providers are constrained by.
A simple method for checking whether a component is phase inverting or not is to connect a Signal Generator to the input, and observe input and output (simultaneously) on an Oscilloscope at various frequencies such as 20Hz, 600Hz, and 20KHz. If a Signal Generator is not available, use a Synthesizer or a test tone record. If an Oscilloscope is not available, use a Multimeter to read the AC Voltage on the input first (let’s call this Vin), and then on the output. Then adjust the output gain until the output Voltage is the same as the input Voltage. Then measure the AC Voltage between the input and output (let’s call this Vdiff). The magnitude of the phase difference is then approximately 180° times half of the ratio of Vdiff to Vin. In the case of measuring output from a speaker, use a microphone and microphone pre-amp as the input to the Oscilloscope or Multimeter.
The layout and design of a sound system, and the positioning of speakers, lighting, dance floor areas, the dj, etc. should be designed with higher concerns in mind, such as the comfort of attendees, the design themes of the event or club, and particularly any spiritual or religious themes associated with the event, music, or attendees. As far as the underground dance community is concerned, this means the sound and lights must not be overbearing or intrusive, or otherwise obstructive to a positive, open environment.
Copied below is an example of this relating to Feng Shui, from a promotional magazine published by New York’s Club Twilo:
“FENG SHUI – FOR THE NIGHTCLUBBER:
Hang your mirror ball at least 12 feet from the dance floor. This will ensure that all the positive energy released through your scalp will have space to dissipate. Too many positive waves crushed into a small amount of air have the ability to generate a friction that may lead to sudden mood swings.
Speaker stacks, as a rule, should only ever be placed on the dancefloor itself. Never hang from the ceiling or attach to a wall. Sound frequencies must be allowed to enter through your toes first, never through your ears. This will boost your chakra from below and elevate you mentally.
Neon lights, strobes, and rotating pin spots should work on a cycle, and be evenly spaced. Lights that are placed too tightly together counteract with your aura and this leads to a negative feeling. Avoid this by measuring carefully. Remember to only mix pastels with pastels and primaries with primaries.”
These points make intuitive sense if you think of different clubs you have been to which were or were not designed along these lines. Perhaps the greatest design weakness of many club sound systems is the concept of hanging speakers at heights of 10 feet or more. These speakers cover the audience with more than enough mids and highs, while providing a disproportionately lower level of bass and subbass. By placing all speakers on the dance floor only, with a number of good bass-bins standing directly on the floor, and the full-range/mid-hi cabinets directly on top of the bins, the sound is then felt as much as heard, and the mids and highs are not so loud relative to the bass and subbass. For example, if you were to stand 20 feet from a stack of speakers, you would have basically the same view of the mid-hi/full-range cabinets as the bass-bins, and as such, the bass would remain proportionate in volume to the mids and highs. If however, the mids and highs are being radiated from above the audience in a direct path to your ears, several things occur: First, since bass bins are placed on the floor in almost all clubs, the bass is then partially blocked and absorbed by the audience, but the mids and highs are not. Second, the high frequency drivers used in most club systems are highly directional, whereas bass and subbass frequencies are omnidirectional by nature. As a result of these factors the bass and mids/highs become inconsistently matched in terms of volume, and at same time have less coherence and clarity. If you think back to times you’ve been really amazed by a sound system, more often that not it’s because you heard it on a system providing a solid level of bass and subbass, that allowed you to really feel the music.
As underground venues become more restricted by the political powers that be in many cities, clubs are increasingly where events/parties are held. Because club sound systems are typically permanent installs, they are more likely to employ overly complex and overbearing speaker placement strategies. (It may be a surprise to many, but there are people out there who don’t go out to clubs much anymore because they are tired of sound systems that are too loud (mids/highs cranked up too high) and/or don’t sound good.) Second, if it is a permanent install, the effects of such designs are long term as well. For those who work for or attend clubs where you have not had the opportunity to personally design the sound system, note that we do strongly suggest voicing your thoughts to the club management, owners, and promoters if they have one of these rock-concert style sound installations.
Another advantage of placing speaker stacks on the dance floor, rather than in numerous elevated locations throughout a venue, is that the sound is then radiated from a smaller, closer array of locations. This insures that the timing between the sound sources is better aligned, and as a result, that the clarity of the system is maximized. Because sound travels at only about 1 foot per milliSecond in air, a difference of 50 feet for example between two speakers will cause a delay of up to 50 milliseconds between when a listener hears the signals from each. Combining multiple signals together with delays of that order is destructive to the transient response (a.k.a. “impact”), frequency response, and clarity of a sound system. In some large venues these timing differences can be so large that in some areas the sound from different speaker stacks (and/or wall reflections) combines such that it sounds like a constant trainwreck. The cure for this type of sound system is combining all the speakers into no more than 2 stacks, which are spaced no more than 30 feet apart.