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Listen, Measure, Predict

The major attributes of sound system performance can be calculated with very good accuracy and should be predicted, even when you don't think you need to.

IF YOU'RE serious about working in the audio field, there are three paths you need to follow. They run parallel, so what you learn on one will help you on the others. The road signs on these paths read “Listen,” “Measure,” and “Predict.” These are somewhat self-explanatory, but I'll elaborate a bit on all three.

First, the one we all do naturally is listen. But there's a difference between listening and motivated listening. Everyone listens to a sound system, but audio people must listen critically.

You have to pick apart what you hear. I got a lot of practice at this in my high school years by picking the guitar parts out of popular songs in order to learn them. Humans, unlike analyzers, have the ability to dissect what we hear and focus our concentration on some specific detail, such as the timbre of a saxophone or the high frequency response of a loudspeaker.

I visited some of the demo rooms at the recent NSCA show in Las Vegas. In these rooms, manufacturers play back their loudspeaker products for people to hear. One could instantly spot the motivated listeners. They were walking the coverage patterns and bobbing their heads listening for crossover artifacts. Some wandered over to the signal processing to see what equalization curve was being used. One guy even walked up with his own CD and asked “Can you play this?” That's motivated listening, and I'll bet these individuals design some pretty nice sound systems.

As important as the listening process is, you can't be an audio professional armed only with your ears. Some people think they can, but they're easily deceived. The human auditory system isn't calibrated, and it isn't consistent. It can easily detect tonal shifts and other artifacts, but it can't identify the cause without further investigation.

An important supplement to the listening process is the use of high-resolution time and frequency domain measurements. My first analyzer that could do this was the TEF 12 (circa mid 1980s). This amazing machine allowed both the time and frequency responses of loudspeakers to be measured in great detail. I knew at that time that this was the future of audio. I laid out the $12,000 for the TEF and accessories (and those were 1980s dollars!), and my career was launched.

I can honestly say that the acquisition of this piece of gear was one of the biggest steps of my audio career. It opened doors and provided insight into sound and audio that I would have otherwise missed. The key to understanding is often simply having the right picture, and high-resolution analyzers provide it.

But owning a TEF was only a small part of the equation. It took a very long time to become proficient at using it. The learning curve was steep, and I was seeing characteristics of loudspeakers and rooms that I had never seen before. Listening was never this difficult. The measurement process was foreign to me and seemed out of context.

Contrary to my expectations, the TEF didn't make money for me. In fact, it reduced the bottom line on virtually every project I did. Why? Because it takes extra time to measure and learn, and this extra time isn't billable to the customer. The extra days on job sites paid off big time in the long run, but in the short run it was a disaster. You'll experience the same thing on any measurement platform, so don't promise the boss that the new instrument will pay for itself unless he or she is willing to look at the bigger picture.

Today's audio practitioners can pick from a number of very capable measurement platforms. These include TEF, EASERA, SmaartLive, and others. All of them allow both time and frequency domain measurements, and have the same steep learning curve that my old TEF had. It's not that they aren't well written, and there's nothing wrong with the user interfaces. Rather, the effective use of any of these tools requires a great deal of understanding on the part of the user. The 20-plus years of audio evolution since the early TEF days hasn't reduced the time required to learn about measurement — not by a millisecond.

The other absolute essential for today's audio practitioner is proficiency at the art and science of prediction. It's unconscionable with today's tools to specify a sound system without doing some performance predictions in advance.

The major attributes of sound system performance can be calculated with very good accuracy. These include sound pressure level and coverage. There's simply no reason to guess on these — they should be predicted, even when you don't think you need to.

The performance of any sound system is significantly affected by the room's acoustics. The same programs that predict the coverage and SPL can simulate the room's acoustics. Acoustical predictions provide a “virtual” measurement environment that will allow you to spot problems before they occur. Acoustical modeling is perhaps the toughest part because the study of acoustics is a field all by itself.

It's common to hear the complaint “bad user interface!” with regard to room modeling programs. The user interfaces aren't bad; there are just a lot of aspects to running these programs.

We live in an age when people have become accustomed to getting up and running on a new software application in a few mouse clicks and maybe a short tutorial. That's just not going to happen with a room modeling application, unless you're already intimately familiar with the operation of one and are migrating to another.

The modeling process can be broken down into three major sections: room geometry, direct field prediction, and acoustical prediction. One could make a life's study of any of these, but you have to learn all three in order to to use these programs effectively.

The two programs I spend the most time in are EASE and CATT-Acoustic. Neither program is easy to use, and both required many months of self-study and even some seminars to gain enough proficiency to use them to do something useful. I find that the major limiting factor of both programs is the same — me. The more I learn about loudspeakers and acoustics, the more I understand how to use room modeling in a meaningful way.

If you want to ensure your long-term viability in the audio industry, invest your time and money in achieving proficiency at listening, measuring, and predicting. All audio companies need people with these capabilities, and they'll never go out of style. The possession of the tools is a small first step. They must be mastered before they're useful, and this mastery comes at a price.

I wonder how many people acquire one of these tools and then let it lie dormant because of the learning curve. I know I did.

But when the wakeup call comes that says “Get into this thing, and learn how to use it!” the door will open to a fulfilling, life-long study of audio.

And perhaps the best part is that you don't have to worry about running out of things to learn.

FOR MORE INFORMATION

Today's audio practitioners can choose from a number of very capable measurement platforms that allow both time and frequency domain measurements.

CATT-Acoustic +46-31-145154, www.catt.se

EASE/EASERA 949-588-9997, www.renkus-heinz.com

SmaartLive 877-SMAART3, www.siasoft.com

TEF 203-938-2588, www.gold-line.com

Pat Brown is president of Synergetic Audio Concepts (Syn-Aud-Con) Inc. and Electro-Acoustic Testing Company (ETC) Inc. Syn-Aud-Con conducts training seminars in audio and acoustics worldwide for those who operate, install, and design sound reinforcement systems. ETC Inc. performs precision loudspeaker testing for the audio industry. He can be reached at pbrown@synaudcon.com.



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