Acoustic Expertise: Club Sound
Jul 27, 2011 12:25 PM, By Bob McCarthy
Audio principles for nightclubs and bars.
The sound system needs for nightclubs and bars breaks down into two principal categories: performance audio and background music. We will take a look at both of these categories and consider some of their unique sound design challenges.
These types of venues are like miniature-scale concert halls with a host of giant-sized challenges. Large concert tours will bring their own rental systems rather than the house PA at the local arena. Nightly adjustments must be made for the unique venue shape and acoustic properties, yet the overall sound system experience is one of continuity. As venue size declines, so does the probability of mixing on the same system every night. The level of nightly continuity shrinks to almost nothing. Successful engineers learn to adapt instantaneously to their nightly situation. Small clubs will usually have a house PA with which the mix engineer will have to become quickly familiar and comfortable. When faced with designing a house system we need a frank assessment of the key characteristics. First, the system must be totally indestructible. The owner cares about the system surviving until tomorrow, but the visiting band does not. This presents a very real circular argument. The system must have enough power to satisfy the visiting mixers, but not so much power that it drives the audience out. But as the old saying goes, give them a dB and they will take 10, so we have to assume that the system will be operated at the highest possible level. Therefore, great care must be taken to provide limiting protection that allows the maximum long-term sustainable level as well as the highest survivable short-term peaks. It may sound awful to say this, but we must design the system as if the engineers were trying to destroy it. As my long-term mentor John Meyer told me 25 years ago, “It does not matter how great the PA sounded if it didn’t make it to the end of the show.”
The mechanical and thermal limits of speaker components must therefore be respected in the selection of amplifiers, crossover points, limiters, and more. This makes a very good case for the modern self-powered speaker systems, which have a closed circuit design topology with amplifiers and limiting structures that are pre-optimized for the particular speaker enclosure.
This point dovetails nicely to the second design principal: standardize. A nightclub is not the place to try out the new cutting-edge philandromorphic waveguide with servo-dilithium crystal amplification. Give the visiting engineers tools they can recognize. Standard tools, even if they are not their particular favorite, move the visitors toward their comfort zone, whereas your really awesome, never-heard-before system (even if it sounds fantastic with a CD) leaves them nervous. In olden times, a visiting engineer welcomed a custom system from a hippie’s garage because the mainstream manufacturers had no idea what we needed in the world of rock-and-roll PA. The best the of old garage operations are now well-established mainstream players, and they have the R&D and manufacturing capability to handle this mature market.
The next principal is K.I.S.S. (Keep it simple stupid!) We have to assume that the installation will have a revolving door of personnel: nightly changes in visiting engineers and high turnover rates in the house engineer. We also must target the operability and maintainability to a very low level. The visiting engineer has to get to know the system in seconds. The house folks need to keep it working. Therefore, keep the signal flow as simple and straightforward as possible. Fortunately, this has become easier in the digital age. Wherever possible, minimize the number of makes and models in the system. Don’t use six different amplifiers where you can get it done with two. If you think you need 80-degree speakers here and 70-degree speakers there, pick one and minimize the learning curve, the spare parts pile, and the know-how required to keep the system alive night after night.
Another application for the keep-it-simple and keep-it-standard principals is the main speaker configuration. There are two choices: Make it L/R stereo or spend every night defending and explaining your non-stereo system. The fact that a mono center cluster would have far higher intelligibility and uniformity than left/right stacks is not sufficient reason to use it here. You will end up renting gear every night. How about an advanced system such as an L/C/R configuration? In a club? Absolutely not. For an L/C/R system to work well it must have an expertly divided stream of inputs into the three channels. This can succeed in the controlled environment of Broadway or a house of worship. To create a multichannel mix requires a great deal of time walking the room to map out how each channel covers the room. In the combat zone of a club, the mixer does not have this luxury. The addition of the center channel requires a matrix approach instead of the standard L/R panning, which can lead to unexpected results. Chances are we will end up with almost the same feed to all systems: left (90 percent mono), center (100 percent mono), and right (90 percent mono). We get to hear the show three times. No thanks, thanks, thanks.
There is a balancing act between ready flexibility and reliability. Many touring bands will travel with a front-of-house effects rack so that critical sound effects and cues can be reliably performed in each new venue. The easiest way to interface such gear would be via a traditional phone-jack patch bay. The ease of reconfiguration, however, must be measured against the hazards of exposed contacts in the harsh environment of a club atmosphere. Between smoky air, the high humidity of sweaty bodies, and the physical vibration from the subwoofers, the friction contact closure of a patch bay can prove to be nail-biting suspense story. While it will certainly take more time to patch, an XLR connection is worth its weight in stress reduction.
A key question in day-to-day operations is where to draw the custody line between the visiting engineer and the house. The visiting engineers want unbridled artistic control because their job depends on pleasing Attila the Manager. We sympathize. On the other side, we have the club owners, who were shocked they had to spend more than $200 on the whole PA and they want to save money for the new video screen. The easiest place to make peace is to make the handoff at the house EQ. This is a parametric or graphic EQ patched between the main console outputs and the sound system inputs. This EQ is not part of the installed system’s tuning but rather a choose-your-favorite-color option for the visiting engineer. If the system is in good working order and provides enough level at the mix area (bonus points if it does so in other locations), this will usually provide sufficient flexibility for the mixer to meet their needs. Even if your sound system was designed and tuned with the most rigorous scientific methods available (and even if it cost a lot of money), the mix engineer should always have the flexibility to create their house EQ. This will not detune the system or endanger it and it can be reset back to neutral as soon as they leave the building. If you don’t give the mixer a house EQ, you will find it much harder to keep them out of your racks.
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