Subwoofers

Do You Need To Time-Align Your Subwoofers for Home Theater


You may have read the advice that your home theater subwoofers need to be time-aligned. For many, this is a curious statement as it assumes that you have more than one subwoofer (most people don’t) and that you’d know how to time-align them. What does it mean to time-align, what does it do for your home theater subwoofers, and should you do it? Let’s discuss.

What Is Time-Aligning?

As the name suggests, to time-align your home theater subwoofers is to ensure that any sounds that come from one also arrive from the second at the same time. “Where,” you might ask. At the primary listening position. The seat where you take your first room correction measurement.

But it is more than that. You also, according to pundits, need to time-align your home theater subwoofers to your mains. What are your mains? Your front left and right speakers of course! The idea is, again, fairly simple. You want the sounds that come from your front left and right speakers (the ones that are crossed over into your subwoofers) to arrive at the same time as your subwoofers. If not, the sound will be muddied or somehow inconsistent.

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What Does Time Alignment Do For You?

The concern, of course, is sound quality. If your subwoofers or your mains are not time-aligned, then the crossover will not work as intended. At frequencies where the crossover takes place, because of the misalignment, the mains and the subwoofers will start to cancel each other out instead of working together. Time-aligning your home theater subwoofers and your mains seek to avoid this. You want good bass! Surely this is something you should do!

The Science of Time-Alignment

Before you start ordering stuff from Amazon, let’s take a closer look at the science. As we’ve explained before, subwoofers are omnidirectional. This means that sounds that come from them do not fire out the front like in a normal speaker. Instead, they emanate in all directions.

Subwoofer frequencies are very long. At our recommended crossover frequency of 80Hz, a complete wave takes over 14 feet to resolve. Look at the placement of your subwoofer. Is there a boundary within 14 feet (don’t forget the ceiling)? Of course there is! This means that the room starts to affect the directionality of the bass long before it reaches your ear much less the measurement microphone. Any sound that you can actually perceive from your subwoofer will already have any time-alignment you’ve done canceled out by the room interactions!

Do You Need to Time-Align Your Home Theater Subwoofers?

The quick answer is “No.” The lower the frequencies, the more the room affects the sound. At 60Hz, the note takes almost 19 feet to resolve. At 20Hz, it is nearly 60 feet. Unless your home theater is a school gymnasium and you are sitting more than 60 feet from your subwoofers, time-aligning them is useless.

The simple fact is that your automatic room setup program in your AV receiver is doing a bit of time-aligning for you. That is what the distance settings are all about. They somewhat affect the timing of your speakers and subwoofers but, more importantly, they address the phase.

These subwoofers, for example, don’t need to be time-aligned with each other or the mains. No matter what the Internet might tell you.

So, where does the concept come from? In actuality, it comes from concerns with large and outdoor venues for live events. In these places, subwoofers may be placed on the ground while the speakers they are paired with are high up or very far away. Unlike in our home theaters where our subwoofers and our speakers are often feet apart, in these venues they are meters. This can cause some serious cancelation issues around the crossover point. This is just not the case in most modern home theaters.

If you want to get the best bass from your two subwoofers in your home theater, don’t worry about time-aligning them. Worry about putting them in an enclosed, rectangular room and placing them properly.


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