Subwoofers

Everything You Know About Bass in Home Theater is Wrong!


When you are shopping for a home theater subwoofer, you will be told that you want all the bass. ALL OF IT. What does that mean? Well, a subwoofer that does not play down to 20Hz, cannot play all the notes that a human can hear. But more than that. there are lower notes. Infrasonic bass that many deem important if not essential for your home theater. But is it? If the bass is too low to hear, why would you need it? Let’s discuss.

Extension to the MAX!

We’ve talked about how important extension is for your home theater subwoofer. The range of human hearing is from 20Hz to 20kHz. If you want the possibility of hearing all those notes, you need speakers that can reproduce them. But many subwoofers claim performance lower than 20Hz. These infrasonic bass notes are important in home theater, some say, because you can feel them. You may not hear them, but you can certainly feel them!

Super tweeters claim the same. They say that notes that are higher than what a human can hear are important because you can somehow sense them. We’ve railed against that notion as nonsense. But the subwoofer thing? That’s something we’ve generally agreed with…until now.

What’s Changed?

Science. Science has changed. No one that we know of is doing research into infrasonic bass in home theaters. Why? Because…who cares? If we want to buy subwoofers that play down to 1Hz…have at it. But that doesn’t mean research isn’t being done!

It is in research with elephants where we can glean some insight. Researchers were surprised to learn that elephants were sending out infrasonic sounds to each other. The reason is quite simple. Higher sounds are more easily absorbed or blocked by the forest foliage. These extremely low notes, however, travel much farther. In open areas, they could travel and be heard by other elephants up to 4 km away. In a dense forest, it was more like 800m. Either way, it was much farther than higher frequency sounds.

The key here is the researchers’ surprise. In this article where some of the early research was done, they specifically say:

“We were entirely unaware of many of these calls at the time they occurred. Others, though inaudible, generated a perceptible throbbing in the air.”

Are your ears this big? No? Then you can’t hear infrasonics!

Ha! See, They Could Feel the Bass!

Yes, yes, we figured you’d focus on that. But let’s look closer at the research. Basically, the notes ranged from 14 to 24 Hz, with durations of 10-15 seconds. This is with the nearest elephant 5 meters from the microphone. How loud were they measured? The sound pressure levels were 85 to 90 dB at 5 meters! That means that at one meter from the animal’s mouth they would have measured closer to 105 dB!

For those of you not familiar, that is freaking loud. Like reference volume loud. Loud enough that no one should be “entirely unaware” of any, much less many of these sounds.

When you are worried about infrasonic bass for your home theater, you have to ask yourself if you’ll actually experience any of it. These elephants have been yelling infrasonic sounds to each other from nearly 2.5 miles away and I’m guessing you’ve never noticed it in any of your trips to a zoo. These researchers, who obviously work with these animals regularly, certainly seemed surprised.

But If You Can Feel Anything, Isn’t That Worth It?

The researchers did say they could feel something. But what was it that they were feeling? As we’ve explained before, bass frequencies are hard for us to hear. The notes that the researchers were recording are what we’d call fundamentals. This is the loudest note. But when you play that note (pretend you are hitting a key on a piano), you don’t just get the fundamental. You also get the harmonics. These are higher sounds that are created along with the fundamentals. While these sounds aren’t necessarily louder, they are much easier for us to hear (and in this case feel).

Harmonics are multiples of the fundamental. So a 10Hz fundamental will have a harmonic at 20Hz (10*2), 30Hz (10*3), and so on. In home theater, our subwoofers may be playing the infrasonic bass, but what we are really hearing (and feeling) are the harmonics.

But Don’t I Need an Infrasonic Capable Subwoofer?

You’d think that in order to get those harmonics, you’d need the infrasonic fundamental. You’d be wrong. The thing is that the harmonics are already part of the recording! Whatever they used to make the infrasonic sound also created the harmonics.

It is also worth noting that any bass you could “feel” from an infrasonic source would be remarkably hard to pick out. Think of nearly every modern movie with low bass. Is there just a single note playing? Not likely! Instead, there are explosions and music and all sorts of other sounds going on. The researchers were working with elephants that were making only those very low sounds and they could rarely pick them out. Do you think you could really pick out the infrasonic subwoofer in a blind test?

Don’t Worry About Infrasonic Bass

If you are shopping for a subwoofer, you should be looking for one that will play down to 20Hz. That is the lowest note we can reliably hear as humans. When you do so, you will inevitably end up with a subwoofer that will play slightly lower. Down into the infrasonic bass range. Will you be able to “feel” these notes? We doubt it. But you can rest easy knowing that, if they are there, your subwoofer will play them.

Where we have a problem is when people start recommending larger subwoofers to people that don’t need them simply because they play even lower into the infrasonic range. In most home theaters, once you get a subwoofer that can pressurize the room, the infrasonics will take care of themselves. Buying the bigger subwoofer is a waste. And recommending a subwoofer simply because it plays lower into the infrasonic range is irresponsible. A sub needs to hit 20Hz. Anything lower won’t make a difference.


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