How To: DIY Audio Measurement

What are we measuring, anyway?
The fundamental goal of a high-quality audio system is to replicate the audio signal that comes into it. To do this, the system must have a flat frequency response — in other words, it must respond to all frequencies of sound equally instead of boosting certain frequencies at the expense of others. Using measurement gear, we can find out quickly and precisely if the sound that arrives at your ears is reasonably similar to the original signal.

For the purposes of this article, we’re going to focus on measuring bass response. The acoustics of most rooms will mangle the output of a subwoofer or a full-range speaker, turning a theoretically smooth frequency response into a graph that looks like the Grand Tetons. By measuring, we can find out which frequencies your room is treating unfairly. You can then move your subwoofer or speakers, adjust your subwoofer crossover, add more subwoofers, or add an equalizer, then run the measurement again to see if you fixed the problem.

Measurements are less valuable at frequencies above 200 Hz or so, because the response of an audio system in a room tends to be much smoother at these frequencies. However, you will be able to see if your system is severely boosting or cutting midrange and treble (reason, perhaps, to upgrade your speakers), and you’ll also be able to confirm that all your speaker drivers are operating properly.