Big, bigger, biggest: subwoofers
We have a bit of thing with subwoofers. It’s because adding a subwoofer can be one of the most powerful upgrades you can make to your home theatre or stereo system. Yet, a lot of people are not convinced of their merits. With a good subwoofer it’s like you can feel the room breathing. I guess it’s one of those things you have to experience to realise. But also… one subwoofer is not the same as the next.
The best subwoofers add dimension, impact, excitement, and low-frequency extension without negatively affecting the overall accuracy and believability of your system’s sound. A big subwoofer can do this – and so can a small one. One of the misconceptions we want to address is that a bigger subwoofer is better. For someone who’s not familiar with acoustics, the reasons for this may not be readily apparent.
To explain why a small subwoofer might sound better in certain environments than a big subwoofer, it helps to understand what a subwoofer is, how subwoofers have evolved, and what elements make for great subwoofer performance. Let’s get back to basics first.
Subwoofer foundations
A subwoofer is a type of “woofer”; a low-frequency producing loudspeaker “driver” – designed to reproduce the very lowest sound frequencies, typically from 20 cycles per second (Hz) to 200 Hz. Subwoofers, as said, are a “subset” of woofers, which, when playing on normal speakers, typically produce frequencies from 60 Hz to 250 Hz.
It’s actually quite interesting to see how subwoofers have evolved over the years.
Subwoofers were invented in the 1960s. The first US Patent issued for a subwoofer was in 1964, for a device invented by Raymon Dones of El Cerrito, California that could reproduce distortion-free low frequencies down to 15 Hz and also be contained in a portable enclosure. Marketed in the Unites Stated under the trade name of “The Octavium”, Dones’ device ended up being used by some big-name recording artists in the 60s and 70s, including the Grateful Dead and the Pointer Sisters. Various other versions of the subwoofer came out after this and generally improved upon Dones’ design.
It would be decades though before the subwoofer became a common component of home speaker systems. That’s because, until the advent and proliferation of “home theatres” in the 1990s, the vast majority of home speaker systems were used for music, and these systems generally produced sound via pairs of large floorstanding (or tower) speakers, each tend to house two large (12- to 15-inch) woofers that could sufficiently provide a bass sound.
It wasn’t until the 90s, when audio systems expanded beyond tower speakers to include a small army of much smaller bookshelf or satellite speakers that subwoofers broke through. These smaller speakers could be more easily placed in a room to surround the listener and also relied on a subwoofer to provide a full bass sound as the smaller drivers couldn’t produce a low frequency output.
Elements that Make for Great Subwoofer Performance
So, let’s get back to why the biggest subwoofer may or may not the best choice for you.
Subwoofers can range in size from 3 inches (yes, that small!) to more than 15 inches.
Plain physics of speakers tells us that speakers work by fluctuating the air pressure in front of them via vibrations. In doing so, they convert electrical signals into acoustical energy, or sound. The lower the frequency, the longer the sound wave, which means bass waves are the longest of all sound waves.
The result of that is that drivers need to work that much harder to produce bass frequencies in volumes you can actually hear, which is why subwoofer drivers are so much bigger than regular woofers or tweeters. On a very basic level, it comes down to this: the bigger the driver, the easier it is to produce the long-wave frequencies.
Just like a big truck takes a lot longer to brake before it comes to a stop compared to a regular car, in the same way drivers measuring 15” normally speaking have less control and not as accurate as smaller subwoofers. A large driver/big subwoofer is certainly capable of incredible depth and output, but often it is at the expense of speed in transients and tonal accuracy. This means bass can potentially sound powerful yet bloated or “boomy” as opposed to controlled and detailed. There’s an incredible amount of nuance when it comes to low frequencies and a big subwoofer that just plays loud and deep may not render the details as well as a smaller subwoofer. Aha!
BUT, you can also create effortless and powerful bass by increasing the power, or wattage of the amplifier, so you don’t necessarily need the big subwoofer with the biggest driver to get the best bass, since a robust and sophisticated amplifier design is actually just as important. What we’re saying is that one subwoofer is not the same as the next. A lot depends on how well designed the subwoofer is. A smaller subwoofer may not go as deep as a bigger one, but it may perform better in producing detail plus it can compensate for its lack in size because of higher amplifier wattage. But then again, if a you design a big subwoofer really well, it may just change the cards on the table again.
There are some potential game changers that make the difference between a well-designed and a poorly designed subwoofer. These are the things to listen for:
Low-frequency “extension”, even at highest volumes
– A lot of subwoofers actually don’t have the ability to reproduce the deepest bass frequencies and try to make up for it by exaggerating the mid-bass frequencies. A truly great subwoofer will produce ALL the low frequencies, even those that are too low to be heard (and can only be felt) and it will be able to do this even at the highest volumes. Low-quality subwoofers cap their amplifiers’ volume output, which leads to the bass “disappearing” once the volume surpasses conversation level.
Accurate source content delivery –
Unless you’re at a live show, music and sound have to travel through various filters between the actual source – the instrument producing the sound – and the object (ie, your ear). On this journey, sound can get diminished, enhanced, altered, tweaked, or otherwise changed in some essential manner that takes away from the experience the musicians and the music producer intended. Even the untrained ear can hear the difference between boomy “one note” bass and a full bass sound that resonates inside your chest cavity. A great subwoofer, whether big of small, adds no sonic signature and is completely faithful to the source content, including starts and stops or what’s known as “transients”.
Seamless blending
Subwoofers should blend seamlessly with the other, speakers in your system, including the satellite and tower speakers, and never draw attention to the bass alone.
Why Your Subwoofer Doesn’t have to be the Same Brand as Your Speakers
Apart from size and the idea that a big subwoofer is better, another common misconception is that the best subwoofer match for a speaker is one made by the same manufacturer. Wrong! The reality is that all speakers have specific voicing characteristics which gives each model a distinct sound. In that respect, choosing the best speaker is, to some extent, a subjective decision based on your taste.
Similarly, you should choose a subwoofer to match your speakers, which to some extend is equally a subjective decision. That said, no matter what, you should always look for the key elements we mentioned above that make a great subwoofer. The manufacturer of your speakers is not by default a great subwoofer manufacturer. So don’t assume…
Our advice: Just Listen
As with any type of speaker you are selecting, let your ears be the judge. From strumming bass guitar riffs and drum beats to the most complex and demanding movie sound effects, a great subwoofer reveals deep layers of sound a speaker is simply not equipped to handle. And remember: While some subwoofers merely add bass, a truly great subwoofer elevates the listening experience in a unique and visceral way, be it a musical experience or a cinema experience.
We have long been advocates of SVS subwoofers. SVS helps out with subwoofer matching with their Merlin tool. Enter your speaker set-up and the tool will suggest an appropriate sub that works well with your speakers. It’s a good starting point for the obligatory listening test we talked about. Not gospel, obviously.
So, bottom line: Bigger is not necessarily better. A bigger subwoofer may have an easier to create big bass, but it is also a lot more difficult to control and actually sound good. That said, big subs like the SVS SB-16 or PB-16 or the SVS 4000’s are really big subs, but despite their size, they perform amazingly well. It’s one of the reasons why they receive so much praise. Whether a big subwoofer is the right choice for your system depends on the rest of your set-up and how well it blends with your speakers.
Sources: SVS, What Hifi, Audioholics, AVSforums