My Second Subwoofer Killed My Bass

We’ve long been advocates for dual subwoofers. The experts agree that if you want more even bass across multiple seats in your room, dual subwoofers are the way to go. There are some restrictions. This advice works best in enclosed, rectangular rooms. The subs have to be the right size for your room. But, if you want even bass, dual subs are the way to go. So why is the first complaint we hear from people that buy a second subwoofer that they lost bass?

Why Your Single Sub Was Uneven

When you had one subwoofer, you were likely experiencing uneven bass. What does this mean? The bass waves bounce around your room and interact with each other as they pass through. Sometimes that makes certain frequencies louder. Sometimes that makes them much quieter. Even if you did the subwoofer crawl to place your single subwoofer, this will likely be the case.

When you ran your room correction program, the receiver was forced to take into account all these different volumes. It tried to knock down the overly loud frequencies as much as possible while not making those same frequencies too quiet at the other seats in your home theater. This is a tall order and likely didn’t work very well.

For example. Let’s say that you run your room correction and take five different measurements. If they all measure a 10dB increase at 60hz, the room correction doesn’t have a problem. It uses its FIR filters to cut the volume at 60Hz by 10dB and now the volume is equal across all seats. But if the main seat has a 10dB boost at 60Hz but the left seat has only a 5dB. And then the right seat has a -1dB cut…well, you see the problem. If it cuts the volume by 10dB, the main seat will be “perfect” but the left seat is at -5dB and the right seat is at -11dB. What it will likely do is cut it by -4dB or so trying to do the most good with the least harm.

That does mean at your main seat you are still experiencing a +5dB or so boost at 60Hz.

What the Second Subwoofer Did to your Bass

When you added your second subwoofer, your bass didn’t magically become more even. That’s a common misconception. What happened was that those three measurements we talked about above? They were more similar. So, the main seat might still be at +10dB but now the left and right seats were also near +10dB. This allows your room correction to get ALL the seats closer to the the optimal volume at all the frequencies.

To your ear, you’ve lost bass. The unevenness you were experiencing sounded “right” to you. Because it was all you knew. Now that you’ve added the second subwoofer, your brain is telling you that you have less bass. That is true. It is also true that you have more accurate bass.

How to Know You Have More Accurate Bass

The most common comment we hear from new dual subwoofer owners is that their subwoofers seemed to go away until there was a loud bass scene and then suddenly they started shaking the couch!

Yep. That’s what it should sound like.

When you have bass unevenness, your subwoofer was usually turned down overall by your receiver to adjust for the overly loud frequencies. Now that your bass is more even across the seats, your receiver can get your bass response flatter. This allows the overall volume to go up. The reason you are not hearing more bass all the time, is because you were never supposed to! There wasn’t that much bass in those frequencies you were hearing before. The interaction between your single subwoofer and your room made those frequencies overly loud.

This is a case where spending a little time with your system will readjust your “ear.” Grab a couple of dramatic scenes that you know have a lot of bass. Suddenly, not only do you have bass, but you have BASS! Louder, cleaner, lower…you are experiencing the movie as it was meant to be heard. Sure, you are missing out on some “bass” that was a result of the room, but that was never meant to be there anyhow! Enjoy your system knowing you now have accurate bass.

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