Which subwoofer is better-sealed or ported?

Which subwoofer type is better – sealed or ported? An ever returning and extremely popular discussion topic on the forums and blogs, there is no shortage of opinions on the subject. Add in a few die-hard myths and generalizations, and it’s no surprise this is one of the most commonly questions asked.

You might hear some people say that ported subwoofers are no good for music, and are only useful for delivering big sound effects, or conversely that sealed subwoofers are “musical”, but lack the depth to deliver the bass called for in today’s blockbusters. While some subwoofers may certainly fit these stereotypes, the truth is considerably more complex.

The strengths of each subwoofer type are discussed below, along with the recommended applications and listening environments which will result in optimal performance. 

SEALED SUBWOOFERS:

These are the simplest type of subwoofer to design and construct. As you all know, sealed subwoofers consist of a driver, an enclosure, and an amplifier; with the driver being responsible for 100% of the system’s output.

Because sealed subwoofers typically have a smaller overall cabinet size and footprint, they are much easier to integrate into the listening environment without upsetting the décor too much. This makes the sealed subwoofer a natural choice in living rooms used for mixed media.

On a physics level, the sealed air inside a properly designed sealed subwoofer acts like a shock absorber, smoothly modulating the subwoofer cone’s back and forth motion, so all the notes get produced evenly.

Each beat in a tight bass setup plays crisply, accurately and with no ringing after it hits. A sealed sub doesn’t roar, thunder, or boom. To many people that is exactly the appeal of a sealed sub, especially for music enthusiast who use their sub for critical music applications. The sealed sub sound is typically described as sounding tighter and more articulate, with less perceived overhang (a bass note continuing due to resonance after a bass sound has stopped).

One of the characteristics of a sealed sub is a shallower roll-off slope (reduction in volume of the lowermost frequencies) than a ported subwoofer. In other words, a sealed woofer takes more power to produce the same volume as a comparable ported sub.

The SVS sealed subwoofers at Rapallo address this with the use of sophisticated DSP equalization (digital signal processor); these are techniques used for improving the accuracy and reliability of digital communications. In this case, DSP cleverly takes advantage of the available ‘room gain’ in small to medium sized rooms by tweaking the frequency response and roll-off slope. All quite complicated, but the end result is much deeper in-room extension. Bingo!

This means that while sealed subs are typically recommended for listening to music, the SVS sealed subs are not necessarily to be excluded from action movies (assuming you play them in a smaller room of course, we wouldn’t recommend them for large rooms) thanks to the earlier described DSP.

After all, not everyone listens to movies at IMAX theatre levels. So, if the dynamic limits of the sealed subwoofer are well-matched to the room size and playback level, the result can be excellent performance on movies too.

PORTED SUBWOOFERS:

Where sealed subwoofers are relatively simple devices, ported subwoofers add a bit of complication to the mixture, i.e. the port.

In a ported sub, low frequency response is extended by the resonance of the port at a certain frequency (tuning frequency). The diameter and length of the port give it its tuning frequency. The lower the tune, the longer the port needs to be, and its length is proportional to its diameter; so the larger the port, the longer it has to be.

Add the need for sufficient port area to minimize chuffing (noise caused by turbulence as air enters and exits the port) to the equation and the ported subwoofer enclosure becomes a fairly substantial box. BIG is the word.

The result however is 2-4X more peak dynamic output in the 18-36 Hz octave compared to a sealed subwoofer. This makes the larger ported subs a natural choice for system applications with larger rooms (where less room gain is present) and where IMAX-like playback levels are high on the wish list, particularly on demanding Blu-ray action and sci-fi movies with big bass (LFE or low frequency effects) tracks.

But what about music?

One of the most persistent myths in the audio industry is that ported subwoofers perform poorly on music. This reputation was largely earned by the public suffering through decades of small, ported boom boxes so common in cheap systems purchased from brick&mortar retail outlets. Let’s get this out of the way: These subwoofers don’t sound bad on music because they are ported; they sound bad on music (and movies too) simply because they are bad subwoofers.

A lot of the pros in favour of sealed subs can be countered by good ported subwoofer design paying attention to how these ports are ‘played’. Good design (like ‘variable tune subwoofers’ for instance, using multiple ports) results in very deep tuning frequency, below the the typical music bandwidth where we are relative insensitive to the ‘buts’ and ‘ifs’ of ported subwoofers.

So, to sum it up: both sealed and ported subs have strengths and advantages, and which type of subwoofer is best for you depends on several variables. Room size, system usage, playback level, aesthetic considerations, available floor space and other limitations on overall subwoofer size which we shall not mention –  they all factor into the selection process.

Bottom line is that both types of subwoofers can deliver an outstanding, no-compromise listening experience on both music and movies, provided the selected subwoofer model is a great match to your specific requirements.

Sources: SVS, Audioholics, Crutchfield, AVSforum