This is why everyone
should must calibrate their multi-channel audio system — no matter what or where it is. Speakers aren’t designed for rooms, they’re designed to be set up in rooms. Without calibration, the audio won’t be optimal, and, as Adam Pelz, senior design engineer at REAL Audio Video, noted, “the difference between what the speaker is playing and what you hear at your listening position can be wildly different.” In short: where and how the speakers are set up is more important than the quality of the audio system itself.
Calibration should involve two separate processes. The first: mechanical. You want to physically move your main speakers, listening positions (where you’ll be sitting) and subwoofer(s) to their best locations. This can very quickly improve the sound quality of the audio system. An auto-cal system can do a good job if the speakers/sub and seats are intelligently positioned. However, you can’t calibrate a poorly laid-out system with equalization.
“Audio is an odd duck in that the only way to truly appreciate an improvement is to hear the difference,” Lemay said. As people, we have a natural ability to listen through distortion. It’s only when we are exposed to a really good system that we are aware of what we are missing. In that regard, there are a few things to listen for.
“One of the complaints I hear most is about dialogue intelligibility,” Pelz said. If you’re constantly rewinding to have to listen to audio again, that’s usually a dead giveaway. The next thing to listen for is the bass. Can you hear clear, distinct notes? Or is it all a muddy, boomy blur of sound? When listening to music, notes should not be inconsistent (meaning that they should sound like they are coming from the same place). If some notes fade away while others seem to “ring” longer, that’s usually a sign calibration is needed.
Calibrating small rooms, like your living room, is surprisingly more complex than calibrating larger venues. “The technical explanation is that large rooms do not distort the frequency response of speakers significantly,” Lemay said. “Small rooms have much more distortion because bass-frequency wavelengths do not fit inside the room. The subsequent folding of the bass sound waves causes severe resonance, which is the common ‘boomy’ or ‘ringing’ bass commonly heard in consumer theaters.” The good news is that these issues are solvable with proper speaker, subwoofer and listener placement.
Every system can benefit from some level of calibration, even if it’s just moving the speakers and furniture around. Keep seats away from walls and other boundaries, and make sure your center channel is in line with your main listening position (MLP). Your left and right speakers should be 45-60 degrees apart. “A simple rule of thumb would be to measure the distance from the MLP to your center channel,” Pelz said, “and then set the left and right speakers that same distance apart.”
When placing speakers and setting up listener positions, you’re looking to avoid placing the listener in what Lemay calls a “resonant null,” or “a cancellation point for one of the room’s prime resonant frequency modes.” Basically, it’s the position where sound doesn’t sound as good. Small rooms resonate loudly at several frequencies, which equalization cannot cancel out. The only solution is to move the listener out of the null, Lemay said.
“As people, we have a natural ability to listen through distortion. It’s only when we are exposed to a really good system that we are aware of what we are missing.”
Finding these nulls in small rooms, however, isn’t that difficult. Why? Because they occur in predictable locations. “The most severe [nulls] are the middle and 1/4-length and width positions. Don’t sit there,” Lemay said. These nulls can be remedied by placing the speakers in a smart location, which Lemay said is usually near the 1/4-width positions. “Using two subwoofers and smaller satellite speakers makes this solution much easier, and that’s the setup we recommend. Bass management is one of the most impactful developments for small rooms in the last 20 years; simply put, it’s the process of sending the bass (the bottom two octaves) to the subs, and sending the rest to the satellite speakers.”
The next step deals with the electronics, which is fairly simple. “Use the setup menus of your system,” Lemay said, “and make sure you have properly set speaker distance, time delay (distance) and matched speaker volumes.” The basic calibration menus will be in the surround-sound processor, or AVR. Even the most basic will have the ability to set crossover, distance (delay) and level matching of the speakers.
And in regards to simple room calibration, that’s about all you can do. “Unless the end user has access to test equipment, digital signal processors and such,” Lemay noted, “calibration stops there, aside from pushing the auto-magic button and running Audyssey or other flavor of room EQ.” For more advanced users, Lemay suggests checking out Room EQ Wizard (REW). “That very powerful free software, combined with a laptop and a test microphone, can give a user a tremendous amount of information about their room acoustics and frequency response.”
For any further calibration advice, both Lemay and Pelz advised consulting a professional. Lemay, who is also the principal instructor for THX’s professional training programs, suggests these simple send-off tips for anybody who is setting up a multi-channel audio system:
Use bass management — i.e., use a sub(s) and set your other speakers to “small” in the AVR menu.
Don’t put the sub in corner. Place it in the width center of the room if possible, or try the 1/4-length point.
Use two subs placed at the 1/4-width points if you have EQ, or place them at the opposing 1/4-length points on the side walls. (This one gets complicated in special cases.)
Place the seat or seats between the length center and 1/4-length points.
Make sure the left and right speakers are between 45 and 60 degrees apart as measured from the center or prime seat.
Use the same exact speaker for the front left, center and right channels.
Keep the center as close as possible to the same height as the right and left.
Room size is simple: the larger the better. This is because large rooms distort frequency response less than smaller rooms.
More speakers is good, but more subs is better. Lemay recommends using multiple subs — at least two. Four is ideal.
Rooms must be somewhat absorptive. The best rooms have plenty of fuzzy stuff — meaning carpet, cloth chairs, drapes, etc. (Glass, wood and stone make for a reverberant room.)
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