We are going to talk about subwoofer phase control as well as how to incorporate multiple subwoofers into your system. So, beginning with phase, a lot of you with subwoofers have either noticed or have probably wondered about either a switch or knob located on the front or back of your powered subwoofer that is marked phase. 

For some subs this can be a simple toggle switch between zero and say, 180 degrees, whereas other subs may have it as a variable dial. If it’s a switch, you really only have two options, zero or 180. There are some subs with switches that have a 90 degree setting. And you can use the method I’m about to describe with the switch. You just won’t have as much room for playing around as those with subwoofers with a variable phase dial. 

So the easiest, most effective way that I have ever been shown, and it’s the way that I use to make sure that my subwoofer is in phase with the rest of my system is something that was shown to me by a very very smart man. But this is a tip that he uses, and he definitely knows what he’s talking about. And honestly when he showed it to me, it’s turned my whole world upside down when it comes to getting the most out of your subwoofer. 


So it’s really simple, it goes something like this; with your subwoofer in place, put yourself between the nearest main speaker and your sub. So let’s say our sub is located just off to the side of our right front speaker with the sub off to the side of our right front speaker, because we did a subwoofer crawl and we determined that that’s where it was supposed to go. Position yourself so that you create a kind of a stereo pair between your right front speaker, and your subwoofer. 

This would make the right front speaker, kind of like the left speaker and your subwoofer like the right front speaker. Now, sitting between them or between the speaker and the sub. If you can, you might need help for this but if you can grab the phase dial while listening to bass heavy music and slowly turn it clockwise. What’s going to happen or what you’re going to notice is that the bass is going to shift from sounding like it’s coming exclusively from your speaker versus exclusively from the subwoofer.


You’re literally going to hear the bass travel across the plane if you will, that exists between your right front speaker and your subwoofer. And as you turn the dial one way and you go back the other way, you’re literally gonna be able to hear the bass shift like that. So, where do you stop ? When the bass has a stereo image in front of you. So, you don’t want the bass to sound like it’s only coming from the right speaker versus only coming from the sub. That means that your sub is out of phase. You actually want to adjust the phase dial on the subwoofer until it appears to come from between the right front speaker and your subwoofer. That’s it! That’s how simple it is. 

And if you have a subwoofer with only a phase switch, you’re going to want to experiment with just the switch’s placement, to get as close to that ideal as possible. Now, if you want to incorporate two subs or multiple subs into your system, let’s just start with; again it’s very simple, you’re going to want to place those subwoofers in the best places in your room using the subwoofer crawl method from our previous post, you’re going to want to set the phase, using those methods.

However, you may have to then switch the phase on one of the subs, so that it’s not taking bass away from the equation, but rather, enhancing the bass. This is how you can tell how to do that; with both subs placed, and both subs connected, turn the second subwoofer off. Go to your receiver or processors level control or whatever menu you find on the speaker level Settings and select sub one.

Again if you only have one subwoofer output and you’re using a y cable, that’s fine, select the subwoofer channel and using an SPL meter at your listening position, measure the SPL of the single subwoofer and make a mental note or write it down, of what that number is. So let’s say for the sake of argument we’re taking a measurement of our first sub, and our first sub is measuring at 70 Db in our room. That’s fine, perfect. That’s where we want it to be.

Now, through that same test tone through that same test signal, if you’re using the “y” cable, just simply turn the second subwoofer on. You should see your subwoofers SPL in the room, increased by around three dB. If it goes up by three dB, the sub woofers are in phase with one another and that’s a good thing.

And then all you need to do is adjust the second subwoofer down a little so that your overall bass is back at 70 db, where we want it. However, if when you turn the second sub woofer on your decibels drop by three DB or so, then that second subwoofer is out of phase and it’s actually sucking bass from your system. 

That’s where you can simply go to either your phase toggle switch or your dial and make the opposite adjustment. If the second sub was set at zero, turn it to 180 and measure again. You should put the second subwoofer by doing that in phase with the first and be good to go. Now a lot of you probably think, “ Well I have a second subwoofer! Why do I want the overall decibel level to be the same ? Don’t I want to double my power and double my bass ?” 

All of this stuff, having two subwoofers is not about doubling anything. It’s actually about smoothing the bass response in your room over a broader location. That’s it. Having two subwoofers doesn’t mean that your system hits twice as hard. It just means that it has a more even bass response provided you’ve placed them properly and tuned them and gotten the phase correct.

It just means that you’re going to have a better bass response over a wider, call it seating area or a wider spot in your room. So, if people sit there and they tell you, “ I’ve got 10 subwoofers in my room! “ You can ask them why because chances are they’re under the impression that by adding subs they’re somehow, you know, got 10 times the bass, and they might if they have 10 times the bad placement. 

They might be compounding upon all these negative aspects which then they feel is bringing them some sort of performance. But in reality, it’s not about doubling anything, it’s about getting a broader response over a broader area when done right. So there you have it, there’s two,new quick, very simple free tips on how to make sure that your subwoofers are performing at their peak either if you have one or two or three or four. I hope this was informative.

Leave a Comment