April 2018 Newsletter

April 2018 Newsletter

Audio Training - Digital Consoles

Saturday, May 5th at Evangel in Bismarck, ND

We are just about 2 weeks away from the training on Getting the Most out of your Digital Audio Console. We have several people coming in from out of town already, and we are looking forward to providing the most comprehensive training in the area. More information is available at https://www.precisionav.biz/training-slides where you can view the slides to see what is covered, and find information on how to attend. We do need an RSVP for an accurate headcount before the event starts as a meal will be provided.

Audio noise introduced by computers

A question we often come across is about problems with interfacing computers, especially laptops, with audio systems. Laptops, as well as some desktops, use cheaper power supplies and audio circuitry that not only decreases the quality of the audio provided, but can introduce a buzz on the speaker or line output. This also happens when using the microphone ⅛” input jack to record from an audio console. A simple, effective, and cheap fix is to use a USB external audio interface designed for commercial audio equipment. Many are available, but our recommendation is the Presonus Audiobox USB 2x2. We sell the item or you can find it at many online retailers for $99.99, and it will often fix the buzz issues as well as provide an audible quality difference for both inputs and outputs.

Production services by Precision AV

Precision AV offers many services for doing live events both in your existing facility or for special events at an alternate location. We have a premier audio system capable of covering speech for up to 1000 people and top quality music for as many as 800. Our system is the only digitally steerable speakers available for events in the state and can provide unparalleled even coverage and pattern control in a mobile system for reverberant spaces.

Advances in Speaker Technology - Part 2

In our March newsletter which can be found at https://www.precisionav.biz/blog we covered conventional point source speaker technology in part 1 of our Advances in Speaker Technology series. This month we are looking at line arrays and how they address the issues presented by conventional point source speakers, as well as introduce design challenges of their own.

Line arrays became widespread starting in the 1990s and are still used for most mobile production systems today as well as many permanent installs. A line array consists of several smaller speakers stacked vertically; each of these speakers tend to have a very wide throw, between 90 and 150 degrees horizontally, and control the higher frequencies vertically in small fixed increments, usually in 10-15 degree segments. The number of speakers making up the array is determined by how many speakers are needed to achieve the vertical coverage required, often between 45 and 60 degrees requires 4 to 6 speakers, and maximum throw distance that may require 1-3 extra speakers hitting the furthest point. The basic principle of a line array is based on audio decay, with a perfect line array decaying at half the rate of a standard point source speaker, and compensating for the furthest point in the room by either adding speakers hitting that section or reducing the volume of the speakers hitting closer.

The line array solves several problems we discussed in Part 1 exhibited by point source speakers. The first issue we covered on point source speakers is that the loudest part of their throw is the center of the speaker. By making the near speakers quieter, or adding more speakers hitting the furthest point in the room, a line array can have its loudest point be the furthest point in the room. So unlike conventional point source speakers where to have even coverage the center of the speaker has to be aimed at the back of the room, line arrays get even coverage without the extra reverberation. Second, line array’s horizontal coverage is extremely even from side to side without exhibiting the usual hotspot in the middle due to the waveguide design compared to the conventional cone. These methods are even across all frequencies in the horizontal throw, but as we will cover later not in the vertical throw.

There still are several issues with designing a sound system with a conventional line array. First as was briefly stated in the previous paragraph, the vertical coverage is not even across all frequencies. This is caused by the very decay characteristics that make line arrays so attractive by decreasing the decay rate from 6dB every time distance doubles to 3db every time distance doubles. If you had a perfect line array, which would be an infinitely long speaker array, you would accomplish this 3db decay rate across all frequencies, but as this is an impossible task the decay is instead dependent on wavelength. As you get into lower frequencies your wavelength increases, and in order to maintain closer to the 3db decay rate at that frequency, your array must increase in size vertically. This starts as short as 12” at 2000 hz, which is the size of a single speaker in the array. At 800 hz your array has to be 4 ft long requiring 3-4 speakers. At 250 hz the length must increase to 10 feet requiring 8-10 speakers. By the time you get to the bottom of what these arrays cover at 100 hz you are getting to arrays that have to be greater than 30 feet long requiring 25+ speakers to maintain perfect consistency. If the array lengths are shorter, it causes the lower frequencies to decay at a rate closer to the 6db of point source speakers compared to the 3db that the high frequencies of the Line Array are decaying at, causing the sound at the back of the room to sound thinner and lack lows and low-mids even with the largest of arrays.

The second issue with the conventional line array is their horizontal throw. While even across all frequencies to maintain consistent tone it is thrown at a fixed 90 to 150 degrees horizontally. This throw is wider than is needed for many rooms which causes extra reverberation off of the side walls, especially in the back corners of the room.

The third and final issue we will cover is in regards to the timing of individual speakers. Since these arrays are hung from the ceiling, where they work best, your listening distance from the top speaker to the bottom speaker is different, yet especially in the low mids you are hearing every speaker from the array. This is especially evident as you move closer to the array. It causes sound to be more muddled than a point source speaker, especially for impulse hits like drum toms.

One of the speaker manufacturers that we use, called Danley Sound Labs, has an excellent article that they wrote if you want more details about the limitations of line arrays. The article can be found at http://www.danleysoundlabs.com/danley/wp-content/uploads/2012/01/line-array-paper.pdf. While all of the limitations that they state are correct in regards to line arrays note that no speaker, including theirs, are perfect.

In the next newsletter Part 3 of our series on speaker technology will cover the new adaptations of the Line Array including the Renkus-Heinz VariaI series line array exhibiting horizontal control in addition to the vertical control, and digitally steerable arrays.

Thanks for reading! We are going to be including answers to questions or interesting developments in our local community in future newsletters. Contact us at Sales@PrecisionAV.biz with any questions, comments, or suggestions about what you’d like to see in future newsletters, or to sign up to receive them via email.