Perhaps you want to fit your subwoofers on both sides of your car trunk, meaning they will face each other. Or maybe you heard somewhere that facing subwoofers towards each other creates a richer bass tone.
Whatever the reason, if you care so much about sound quality, then it’s important to know how two subwoofers facing each other will impact its sound.
As a curious audio enthusiast, musician, and writer, I researched subwoofer placements, especially the effect of facing subwoofers towards each other. And here is what I found.
In short, yes. Subwoofers can face each other as long as both subwoofers are wired correctly. In fact, subwoofers play louder when they are facing each other. If one of the subwoofers is wired incorrectly, its output audio signal will be out of phase with the other subwoofer, and this can cause phasing issues.
Let’s talk in detail about what exactly happens when you are firing two subs facing each other. And I’ll follow that up with the potential problems with doing so.
Later in the article, I’ll give you some ideas on different ways to place your subwoofers to get the most out of them. Let’s get into it.
What happens with subwoofers facing each other?
Short answer — Constructive Interference.
But what exactly is constructive interference?
This is a concept in physics, and for those of you who took physics class on waves, you’re probably familiar with this concept. It’s not a challenging concept to understand, so I’ll keep it simple, short, and sweet.
Constructive interference occurs when two waves are in phase, and the amplitude of these waves combine to form a final amplitude that is the sum of both amplitudes. Here is constructive interference explained with a simple mathematical formula
Final Output Wave = Wave 1 + Wave 2.
Constructive interference doesn’t only happen with sound waves. It happens with all types of waves. Let’s talk about constructive interference when it comes to subwoofers.
When you connect two or more similar subwoofers to the same source, and all the wire connections are made correctly, all of the subwoofers will produce identical sound waves with the same loudness and are in phase.
When these subwoofers are facing each other, what happens is their sound waves interfere with each other in a positive way. Because they are in phase, their sound waves amplitude essentially adds up into one big sound wave.
So, if you place two subwoofers facing each other, you are essentially doubling the output sound volume.
As I mentioned earlier, as long as the wiring is done correctly, you shouldn’t have any issue with subwoofers facing each other.
Potential Problems With Subwoofers Facing Each Other
The only instance where two subwoofers facing each other becomes problematic is when the subwoofers are out of phase. What do I mean by this?
Here is a much simpler way to look at it. When two subwoofers are out of phase, although they are both playing the same sound wave, one is delayed. This means that the two sound waves don’t align perfectly. And there are varying degrees one sound wave can delay from the other.
But why would one subwoofer’s sound wave delay from the other when they are connected to the same source?
Well, when one of the subwoofer’s wire connections is reversed, this causes its signal to be out of phase with the other subwoofer that is properly connected. Here is how this happens.
When the positive (+) terminal on a subwoofer’s amp is connected to the negative (-) terminal on the subwoofer, and the negative (-) terminal on the amp is connected to the positive (+) terminal of the subwoofer, this reverses the polarity of the audio signal sent to the subwoofer. This flips the audio signal.
When this happens, and the two subwoofers are facing each other, their sound waves cancel each other out, and you’ll have much quieter sound output. This is known as destructive interference.
Here is a video demonstrating this concept.
However, the chances of this happening are quite low, even when the subwoofers are out of phase. That’s because the subwoofers will have to be very close to each other for the cancelation to be more profound. And you’ll probably not place the subwoofers too close together, facing toward each other.
And also, most subwoofers are omnidirectional — they transmit their sound waves in all directions instead of one direction.
There may be some form of sound cancelation when two subwoofers are facing each other and out of phase, but it won’t be enough to drastically reduce the sound quality and loudness of the subwoofers.
Do Subwoofers Sound Better Facing Each Other?
I’ve read a couple of times on audio forums that subwoofers sound much better facing each other. But is this true?
Subwoofers facing each other will sound louder; specifically, the loudness will be increased by 3dB. And humans perceive loudness as better sounding. However, there is no known proof that subwoofers actually sound better or have an improved sound quality when they face each other.
Quite a number of people have experimented with turning their subwoofers to face each other to see how it sounds. And many of them swear by the fact there is a noticeable difference in sound quality, and the sound improves tremendously when the subwoofers are facing each other.
Some also claim that there is a certain richness in the subwoofer’s tone when they are facing each other.
There is no denying the fact that the subwoofer’s sound will change. But many factors may account for this change, not necessarily because you turned the subs to face each other.
Firstly, the room acoustics play a major role in how a sound system and your subwoofers sound in general.
For instance, the difference in sound may be because the subwoofer’s sound waves are reflecting on the side walls a couple of times before it reaches the listener. It could also be because of different subwoofer positioning and the fact it is not firing directly at the listener.
These factors and a dozen more can be the reason for the difference in sound. And they may actually make the subwoofer sound better or worse.
The point I’m trying to make is, there is no audio physics or science or tests conducted that proves that subwoofers that are facing each other sound better and richer. However, they will sound louder, and that is a fact.
And I’m sure that’s the reason why people think they sound better. That’s because humans perceive loudness as better sounding.
Which Way Should a Subwoofer Face?
Although you may have no issues with your subwoofers facing each other, it’s certainly not ideal to do that. So which should a subwoofer face to get the best result?
Ideally, subwoofers need to face the listening area. And the subwoofer port must be away from the walls or corners. This will ensure the best sound quality from the subwoofers.
I know this can be quite challenging. That’s because our A/V equipment is usually close to a wall. The speakers and subwoofers will all be connected to the receiver, which is usually on a TV stand close to a wall.
However, I’ll advise you to find a longer speaker wire for your subwoofers. This way, you can move them away from the wall and corner.
You don’t want your subwoofer close to a wall or the corners because it can lead to a muddy bass tone or cause rumbling sounds that you definitely don’t want.
And most importantly, the subwoofers must face the listening position. That is where you’ll be sitting.
As I mentioned earlier, subwoofers are omnidirectional, meaning they transmit sound waves in all directions. However, the best listening position of a subwoofer is when they are facing you directly.
You may hear them just fine when you’re sitting on the left or right of the subwoofer, but you get the most from them when they are facing you directly.
Do Subwoofers Sound Better Facing Up?
Another way some car audio enthusiasts place their subwoofers is by facing them up. Just as facing the subwoofers each other, this is another way to save some space in your trunk. But do subwoofers actually sound better facing up?
Facing subwoofers upwards fills up the room with or car with sound waves which is felt and heard clearly. There is no risk of sound cancelation when the subwoofers are facing up. And overall, they sound good.
Many times, people prefer firing their subwoofers at the rear or the back. Not many people face their subwoofers up. However, they sound quite decent. It’s an excellent way to hear all the nuances in a sound wave produced by a subwoofer.
In summary, you can definitely face subwoofers towards each other without any issues. The final audio will be much louder.
Many people think there will be some form of sound cancelation. But that is only true when the speakers are out of phase. Once the speakers are connected properly, there won’t be any phase issues.
I’ll recommend experimenting with different subwoofer placements, such as facing the subwoofers up, towards each other, and even down and see what works best for you. If you found this helpful, do well to share.