SynAudCon Library

What are the Differences Between Analog and Digital Interfaces?

by Pat Brown

Pat Brown will help you understand the pro and cons of analog vs. digital interfaces.

Are you new to digital audio? Are you confused by the landscape of formats that have emerged in the marketplace? Following is a short expose that may shine some light on this potentially confusing topic.

Inputs and Outputs

It’s all about inputs and outputs (I/O). How do I get an audio signal from one to the other? The ongoing evolution of professional audio has produced a number of viable digital interfaces to complement legacy analog I/O practices. The choices may seem confusing at first, but when you break them down the strengths and weakness of each become apparent.

In this overview, I will start with analog since it is familiar to most readers and serves as a reference for the discussion of digital formats. I will focus on professional interfaces only. While similar in many ways to consumer I/O, professional are more robust against electromagnetic interference (EMI) and allow much longer cables – both requisites for large sound systems. (more…)


Do I Need “Digital” Audio Cable for a Digital Audio Interface?

by Pat Brown

What is a Digital Audio Cable?

The audio interface provides the means of getting the signal from one component to the next. It includes the source (output) circuit, the cable, and the load (input) circuit. There are consumer (2-wire, unbalanced) and professional (3-wire, balanced) versions, the major difference being robustness against electromagnetic interference in its various forms (Fig. 1). Does a digital audio interface require a digital audio cable?

Bal-Unbal-Interface and digital audio cable

Figure 1 – Unbalanced and balanced audio interfaces.

Since increasing the cable length can have a detrimental affect on both analog and digital audio signals, the use of balanced interfaces is mandated for large room systems. A cable contains multiple wires, or conductors. A cable designed for an unbalanced interface has a two conductors, one of which is a shield. A cable designed for a balanced interface has three conductors consisting of a twisted-pair and shield (STP). For this reason, the cable itself may be referred to as unbalanced or balanced. I’ll limit this article to a discussion of balanced interfaces and cables.

Do balanced analog and digital interfaces require different cables? I will first lay some groundwork. (more…)


Directivity Reference for System Design

by Pat Brown

The key to working in the field of audio and acoustics is to understand the need to establish a reference condition. This allows changes to be assessed objectively. You need a “known” in order to determine unknowns.

An effective site survey is driven by getting the most information in the least amount of time and with the least amount of gear. If one is clever, they can acquire a meaningful set of room data, with very little site time. That’s important, because there’s never enough time. (more…)


So…Wiki is not Lucy’s husband???

By Jim Sorensen
This use of unsupported sources happens all the time, particularly in the media itself.  How often have you heard someone on TV say that the bloggers are reporting such and so?  Bloggers?  What the heck is a blogger and why does a bloggers opinion count more than mine? (more…)

War Tuba

A brief explanation of a War Tuba.

First impression this photo of a War Tuba looks like a loudspeaker. It is actually a mic.

Acoustic location devices were used by military services from mid-World War I to the early years of World War II for the passive detection of approaching enemy aircraft by listening for the noise of their engines. These typically consisted of large acoustic horns attached to stethoscope-type earphones worn by monitors. This technology was rendered obsolete before and during World War II by the introduction of radar, which was far more effective.

Photo of a War Tuba




Analog or Digital?

by Tim Hamilton

Through most of audio history, it has been an analog world. Recently, it has changed to digital. Does that mean analog is dead?

I love new gadgets and toys.  Whether it’s an audio gadget, computer toy, phone accessory, or some new electrical product, I will likely think it’s fun and exciting to play with.  As a frequent early tech adopter, it’s not uncommon for my wife to roll her eyes and graciously smile while I tear open the box of some new, recently arrived electronic gadget and then disappear to go try it out.  Admit it – most of us in the audio industry can identify with looking for the next great widget.  Of course, the world of audio has quite a few new “toys” that get released every quarter and digital mixing consoles in particular offer a plethora of new things to play with.

For much of the short history of the audio industry it has been an analog world.  But now the industry has shifted into a digital world, which means that we now have all sorts of “digital” devices we can use in audio systems (i.e., processors, mixers, microphones, etc.). But, just because we have new digital toys to play with, does this mean that analog is dead? (more…)


Take a Step Back in time to the Brussels World’s Fair 1958

Don and Carolyn Davis exhibit their HiFi system at Brussels World’s Fair in 1958

Take a step back in time to 1958.  Don & Carolyn Davis (SynAudCon founders), William H. Bell and George Petry were selected to exhibit their HiFi system at Brussels World’s Fair.   For 10 days, they staged demonstrations every 30 minutes drawing crowds which probably totaled 50,000.

What a neat article.

Newspaper article of Brussels World's Fair in 1958Brussels-News 6



Prepping for Fall Seminar: Making Wireless Work

Making Wireless Work: 2015

Making Wireless Work: 2015

Things are buzzing at SynAudCon this week, and it’s not a ground loop. Preparations are under way for two upcoming specialty seminars – SynAudCon Digital and Making Wireless Work.

SynAudCon Digital – Better Than Ever

Steve Macatee and Brad Benn flew in on Monday for a couple of days of prep.

We devoted the first day to manual revisions. Topics were added. Topics were removed. We re-balance the content of this seminar each time we have it, as dictated by new developments in the marketplace and feedback from the previous event. New demos were added for dither and noise-shaping. We capped the day with some Thai food in a local country town, talking digital the whole time.

On day two, we went through the hands-on workstations, with about half the day spent on firmware updates. The workstations include our new Cisco managed switches for computer exercises. Since last time we’ve added some fiber links using mini-GBICs on the switches. The Audio-over-Ethernet exercises include Dante-enabled products from eight different manufacturers. They’re apples, oranges, and pears, and attendees will get a good exposure to a variety of interfaces as they cycle through the workstations. We’re going to make it work, break it, and then make it work again, merging the eight workstations into a single system as the final exercise of the seminar. (more…)


How to Choose Pre/Post Service Music

By Curt Taipale

Curt Taipale addresses the question, “What music do you play before and after the worship service?”

I hear this question asked often. “What music do you play before and after the worship service?”

Curt Taipale

Curt Taipale

I might as well make you feel bad right from the start. The best choice of music to play is NOT your favorite Christian CD, not that new cool song that you want everyone to hear, not what is the most requested artist on the local Christian radio station, or anything of the sort.

Nope. You actually have to think this through. Why do we want music playing in the background as people are assembling before the service? And why do we want music playing in the background after the service as people start to leave? And how long should the music play anyway?

It may be that the best music to play before and after the service is no music at all. Why? Watch the crowd. What are they doing? Longtime members of your church are most likely engaged in visiting with their friends and people sitting nearby. They long for that ever so brief moment to interact and catch up on the past week’s events. After the service they may be praying for one another, or inviting them to lunch that afternoon, or setting a time to meet later in the week, and so on. (more…)


Ground Loop Fix: GenFen TV Wireless RF

Simple HDMI Ground Loop Fix

Ground Loop Fix: GenFen TV Wireless RF

We recently held SynAudCon seminars in Singapore, Bangkok, and Shenzhen (China). I brought along my usual case of audio gear, and each venue provided a house AV system. The evolution of the PC – in my case, a MacBook running Win7 under Boot Camp – has pushed me into using HDMI for my video output. The up side is the small connector and cabling size, which is nice for travel, along with being able to carry my own ultra portable HDMI switcher. The down side is that mixing consumer and pro interfaces can result in grounding issues.

My usual process is to setup my tabletop of gear, and then make the final connections to the house AV system. In all three venues, these final connections produced a significant hum and buzz through the house PA. In each case, disconnecting the HDMI video feed killed the hum. We went through the usual litany of “remedies” to get through the events, changing some things that shouldn’t matter in a fully pro audio system until it worked. Remember, HDMI is a consumer format and sticking into a sound system can produce grounding issues. This was a self-inflicted wound, and the price paid for the benefits of HDMI.

The ultimate fix? Another upside of HDMI is the availability of small, low-cost, RF links. The wireless HDMI link that I use in my domestic system would have solved the problem in each venue. It will now live in my travel case as a must-have for presentations on-the-road. pb

Simple HDMI Ground Loop Fix

DIY Microphone Shield / Gobo

Acoustics First shows a clever way to make a DIY Microphone Shield / Gobo.

Acoustics First understands that the Do-it-Yourself spirit in the audio world is alive and well. Here is another one of our contributions to that community  – DIY Microphone Shield / Gobo .

Photos showing the supplies needed to make a GoboThe personal mic shield… all you need is…

  • Foam safe Glue
  • a One inch thick, three ring binder
  • two 1 foot x 1 foot pieces of foam
  • 2 Minutes

Got everything together?
Do you have 2 minutes?
Let’s do this! (more…)


Sound Masking

Here are ten useful articles on Sound Masking.

Learn about how Sound Masking can help improve productivity and protect speech privacy in the workplace.

Learn about how Sound Masking can help healthcare facilities improve patient satisfaction and HCAHPS scores.

Learn about how Sound Masking can help reduce distractions while improving acoustics in call center environments.

Learn how Sound Masking can reduce financial firms’ risk of negligent disclosure of client information.

Sound masking is the addition of a familiar sounding, air conditioning-like background sound to an environment.

Eight simple recommendations for good acoustical etiquette in an open office plan.

Acoustical comfort is an important goal of modern office design. But what factors actually contribute to the perception of acoustical comfort?

Optimum masking sound: white or pink?

One of the most common concerns with demising wall constructions involve the resulting acoustical privacy between the two spaces. Fortunately, a metric known as the Speech Privacy Potential (SPP) has been developed to answer this question quickly and easily.

Unique performance advantages of a Qt® Quiet Technology™ sound masking system.


Tall Microphone Stands for System Tuning

by Pat Brown

Pat Brown show how he uses tall microphone stands for system tuning.

One of the most valuable tools for sound system tuning is a tall microphone stand. This allows you to get the measurement microphone away from the seating plane. Why?

The Floor-Bounce Effect – FBE

The first reflection to show up on the measured impulse response of a loudspeaker is usually the reflection from the floor. This produces comb filtering in the measured response that is position-dependent over the listening plane (Fig. 1). See my article from 2011 for some measurements.


Figure 1 – The Floor-Bounce Effect (more…)


OptEQ – Optimized System Tuning

by Kent Margraves

OptEQ – System tuning and equalization in a logical, accurate and repeatable process…

OptEQ Class Photo

Attendees of the OptEQ workshop at the American Airlines Center in Dallas, with instructors (left to right) Pat Brown, John Murray and Deward Timothy up front.

AS THE NAME IMPLIES, “OptEQ”is an optimized sound system tuning process developed by SynAudCon (Synergetic Audio Concepts), and it was presented to an audience of more than 100 consultants, contractors and end users over the course of two days in early January at the American Airlines Training Center in Ft. Worth. I was fortunate to be one of those attendees.

As usual, the workshop was brilliantly prepared, hosted, and presented. Pat and Brenda Brown of SynAudCon are simply the best in the pro audio business at delivering exceptional education and training in both audio theory and practical application. The course manual, loaded with relevant information,analogies, and useful graphics, is worth the cost of the workshop alone. (more…)


How To Model Audience Absorption

by Richard Honeycutt

This article shed some insights on a method for modeling audience absorption.

Many contractors, and not a few consultants, may not have given much thought to the best method of modeling audience absorption. Back in the early days of manual Sabine calculations, audience seating was characterized in terms of sabins per person. However, it was discovered that more accurate calculations resulted if the size of the seating area was used, its surface area being multiplied by a laboratory-measured absorption coefficient for the type and occupancy level of the seating. Such coefficients are available both for solid seating areas and for those including aisles, with wooden seats, lightly or medium upholstered seats, pews, etc. There are even some values in the literature that distinguish between the effects of summer and winter clothing. The superiority of this method of accounting for audience absorption can be attributed to the wave nature of sound, which makes a large block behave differently than a group of small objects.

With the advent of computerized acoustical modeling in the last decades of the 20th century, new variables entered the mix. (more…)


Rabbits Explaining Acoustics

A great illustration showing rabbits explaining acoustics. It’s quite humorous and fun too.

A member sent this to me.  We unfortunately do not know who the author is to give him/ her the credit.

The author was quite clever with good a sense of humor.  Enjoy!!

Brenda Brown

An great illustration of rabbits explaining acoustics.

Julian Treasure – City of Lancaster

In the 6-minute video by Julian Treasure, he explains the benefits of the music played from the outdoor sound system and it’s effect on the people.

Enjoy this video interview with Julian Treasure and Major of Lancaster.


Making Hospital Quiet – Acoustics in Healthcare Facilities

In this podcast. Dr. Gary Madaras discusses sound issues faced by hospitals and what is being done to address them.

One of the top complaints of patients in a hospital setting is noise. What can we as audio professionals do about this?

Dr. Gary Madaras discusses sound issues faced by hospitals and what is being done to address them. I found this podcast to be informative.


Loudspeaker Impedance Variance

by Pat Brown

A recent project required the measurement of the electrical impedance of a family of loudspeakers – nine units total. These are all “16 ohm” rated devices (Figure 1).

It serves as a reminder as to why we drive loudspeakers from “nearly zero” output impedance amplifiers. This buffers the amplifier and loudspeaker response from variances in the impedance curve.

A modern amplifier would have the same frequency response into any of these loads.

All of these devices have a relatively flat axial frequency response magnitude.

The curves were measured by the constant voltage method using Monkey Forest.  pb


Figure 1 – Nine overlaid loudspeaker impedance curves.


The Loudspeaker Toaster Test Revisited

by Pat Brown

It’s been nearly a decade since I cooked up the Loudspeaker Toaster test for finding the maximum input voltage (MIV) to a loudspeaker (a shout out to Charlie Hughes for coining the term “MIV”). If you are already familiar with the procedure, read on. If not, here are a couple of links to get you up-to-date.

Loudspeaker Toaster – An Abbreviated Power Test You Can Do At Home  by Pat Brown

Loudspeaker Maximum Input Voltage Test Results  by Charlie Hughes

The Toaster Test is a non-destructive (usually) method for quickly and accurately determining the MIV of a loudspeaker based on its thermal limits. The test itself is relatively unchanged since its inception. One of its strengths is that many choices exist regarding the instrumentation used to conduct it. If you have been involved in audio for awhile at the technical level, chances are you already have everything you need. I have refined my own process a bit from the method described in the original article.

The Gear

The original Toaster Test used an old version of SmaartLiveTM to monitor the transfer function of the device-under-test (DUT). Subsequent versions of SmaartLive do not support the needed “Subtract from Reference” feature, so I migrated to ARTATM. See Figure 1. Any dual-channel FFT analyzer with a “Show Difference from Overlay” feature should work.


Figure 1 – ARTA is used to monitor the response of the DUT.

I now use an NTI MR-Pro as the program source. It displays the drive level to the amplifier in dBV (or dBu), and allows precision incrementing of the drive level with its rotary encoder. The balanced XLM output is also nice. Pink noise is on board, but you can add a preferred noise type by importing a WAV file. I typically use IEC noise, but there are many choices. (more…)


Improve Your Critical Listening Skills

Improve Your Critical Listening Skills by downloading this free, beta version of their “How to Listen” software – produced by Harman.



Harman International, parent company of JBL,Lexicon, Digitech, AKG, Soundcraft, Crown, BSS Audio, and more fine brands, is offering a great,  free opportunity for you to improve your critical listening skills. A free, beta version of their “How to Listen” software is available for download.

The software supports stereo and multi-channel audio playback of WAV files and provides a variety of training exercises where different kinds of timbral, spatial, and dynamic distortions are added to music — simulating situations often encountered in recording and audio playback chains. As you work your way through the exercises, the software automatically adjusts the difficulty of successive exercises based on your performance.

Both Mac and Windows platforms are supported.


Videos – Understanding the Ear by Leslie Samuel

Here are 5 great videos to help you understand the ear.

As an AV professional, I think most everyone has a natural curiosity to understand the ear and the hearing process. Here’s 5 short training videos that will help you understand this.

The videos are produced by Leslie Samuels. He has a passion to teach biology in a fun and interactive way.

I found the videos to be extremely fascinating and interesting. I would urge you to watch the videos in order. I think you will enjoy them and find yourself sharing them with others. Brenda Brown

An Overview of the Mechanism of Hearing

In this 8-minute, Leslie Samual talks about how we hear sounds. From the external ear to the eardrum, down to the 3 bony ossicles, then to the cochlea to be sent as signals towards the brain, it is all explained in this video. (more…)


FIR-ward Thinking – Part 2

by Pat Brown

In this Part 2 of a series on FIR filters, Pat Brown will show you how to create a FIRs Filter.

In Part 1 I laid out a few guiding principles regarding FIRs. Here’s a quick review.

1. With FIR filters I can have VERY steep LP and HP filters, such as might be used in a crossover network, that have linear group delay (same delay for all frequencies).
2. The magnitude and phase response of a FIR filter can be adjusted independently. In an IIR filter they are interdependent – you can’t change one without changing the other.
3. WAV impulse responses by definition are FIR filters, since they are fixed in length and cannot (theoretically) decay for infinity. Any IR you measured can potentially be used as a filter.

So, let’s create some FIRs. (more…)


FIR-ward Thinking – Part 1

by Pat Brown

This is Part 1 of a series that will examine the use of FIR filters in sound reinforcement systems.


Finite Impulse Response (FIR) filters (pronounced either “F-I-R” or alternately, like the tree) are the rage these days. Like many things in audio, they have been around a very long time, but technology has now evolved to allow their practical implemenation. Is this the panacea that we have been waiting for, the “filter messiah” that will finally allow perfect sound reproduction? Of course not, but they are pretty cool none-the-less and they can be a game changer for some applications.

This is Part 1 of a series that will examine the use of FIR filters in sound reinforcement systems. There are plenty of textbooks and resources on the Internet that delve into the mathematics and the deep theory. That’s a bottomless well that can never be exhausted. In this series I’ll use a broad brush stroke to give some “take-aways” on FIR filter theory along with practical implementations and examples. These will hopefully prove beneficial for understanding FIRs and integrating FIR filter technology into your projects. I will assume an understanding on the part of the reader of basic signal theory, including the time and frequency domains of signal analysis as implemented by modern audio and acoustic analyzers. (more…)


Installing Hearing Loop Systems and Costing

This document will address various factors contributing to the total installed cost of various examples of Hearing Loop system and the importance of the information a properly completed Clarification Form provides in creating an effective design.

AFILS (Audio Frequency Induction Loop Systems) aka Hearing Loops, can present challenges to a contractor/integrator in establishing a ballpark price upon which a client is able to make a decision. Critical installation factors can change the installed cost of a system by a factor of 2 –to- 5 times.



Assistive Listening and ADA Compliance

by Cory Schaeffer

This articles presents the new rules that the US Department of Justice released in 2010 in regards to ADA compliance and assistive listening.

Assistive Listening and ADA Compliance

As the name applies, an Assistive Listening System provides an enhanced personal audio experience for those who might need extra assistance in hearing.  This can be due to a hearing loss or the ambient acoustic environment.  We’ve all experienced venues where, due to reverberation, poor acoustics, inadequate sound systems and/or poor microphone technique, it’s been a challenge to “hear”.  We all experience some degree of hearing loss.

What audio sources should you put into an assistive listening system?  Some AV integrators will send all audio through the ALS system, which causes intelligibility issues.  There is no need to send sources other than voice through an ALS system.  The best solution would be to use a separate output from the mixer. Allow for a separate mix to the assistive listening transmitter so that you can leave out things that are unimportant to these listeners.  For example, the priority should be the channels which have an emphasis on speech.  Many of the other channels can be greatly reduced or even completely omitted from the ALS mix. (more…)


Dispelling the Myth of Induction Loop Technology

by Cory Schaeffer

In this article, Cory Schaeffer explains the benefits of Induction Loop Technology.

Induction loop technology wirelessly broadcasts the audio system directly to hearing aids that have a t-coil. It’s widely used outside of North America for assistive listening. With the recent 2012 changes in the America’s with Disabilities Act (ADA), this technology has had a surge of interest from the hearing impaired community. I remember over ten years ago when I first “heard” a loop receiver and what my impression was. In brief, I was less than impressed and I wondered why anyone would use a loop system.

The past two years have been very educational for me and what I’ve learned is that induction loop is a technology. Like any technology it has its pros and cons. It’s not fair to jump to a conclusion and blame the technology based one poor experience as there are many factors at play. As Pat Brown always says when we ask him a question about technology, “It depends…” (more…)


Assistive Listening ADA Compliance Update

In this article Cory Schaeffer recaps the 2010 ADA changes as it relates to the requirements around assistive listening in projects.

Photo of people wearing assistive listening receiversBy Cory Schaeffer

Navigating through the Americans with Disabilities Act’s (ADA) most recent changes to the assistive listening section can prove to be a challenge. To be clear, these changes affect every project being done today and beyond if the AV System is being upgraded or added into projects. Let’s recap the changes as it relates to the requirements around assistive listening in projects.

The ADA Act was last updated on September 2010 with changes that affect assistive listening in AV projects. It’s important that our industry stay current on this change as there are a growing number of advocates raising awareness on these new changes. The ADA did allow for phased compliance with the various changes to the requirements from September 2010 to March of 2012. However, as of March 15, 2012, the ADA standard for assistive listening must all meet the recent revised standard. (more…)


Vibration Isolation Demonstration

by Acoustics First

Teaching Video showing how acoustical materials can prevent spread of mechanical noise and vibration.

Vibration Isolation: This simple vibration demonstration to provide a basic understanding of how acoustical materials may be used to prevent the spread of mechanical noise and vibration through existing structures like walls, floors and ceilings. (1-minute video)


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