The home audio and cinema industry has long been loaded with myths. A quick google search for the term myth and any topic related to audio is sure to generate thousands of hits. We at Audioholics find the information around bass myths to be as wrapped up in lore as the myths they intend to break. As such we have decided to throw our hat in the game and take on the top ten subwoofer and bass myths that we think really need to die already. Enjoy!

1) Myth: Sealed subs are faster sounding than ported subs.

Pursuing the Truth: While sealed subs have less group delay inherent in the design, EQ used to restore the response to flat adds some group delay back. Also, these marginal differences in group delay are not very audible, if audible at all. Far more important is the in-room frequency response.





Diagram 1 Diagram 2

In diagram 1, we see a simulation of a subwoofer driver in both a sealed and ported enclosure. The ported subwoofer does not use EQ to flatten the response but does include a high pass filter to protect the driver against over-excursion, and a low pass filter. The Sealed subwoofer has the same filters but also includes EQ to flatten the response. You can see that once you have done this the group delay of the two is very similar. However, simulations are not worth much if they don’t hold true in real life. In diagram 2 you can see the real-world measurements of the HSU VTF-15H Subwoofer in 1 port mode. This is a ported subwoofer setup in a way that would ensure the lowest group delay for a ported design. The sealed subwoofer is a JTR RS1, a brand new sealed subwoofer from JTR with state of the art drivers. This subwoofer has extremely flat and low group delay, and because of its extremely high excursion driver and dynamic limiters, it can avoid a high pass filter.

Note: The group delay of the RS1 and VTF15h are nearly identical down to 30hz. As you can see, in practice, there is no difference in group delay between ported and sealed subwoofers. The rise below 30hz is so low in frequency and our ears so insensitive, that it is highly unlikely to be audible.

Both subwoofers have just half a cycle or less of group delay down to 30hz, and the ported sub rises to just 1 cycle at 20hz, still below the 1.5 cycle sometimes cited as the limit of audibility.

2) Myth: The ultimate goal for bass is a room with no reflections since this eliminates modes. I know because my friend works in a studio and this is what they do.

Pursuing the Truth: Reflections are a good thing. An uneven response is a bad thing. While eliminating reflections does smooth out bass, taken to an extreme this will eliminate important reflections our brain uses to recognize the spaciousness or envelopment of the musical or cinema event. A primary goal of any high-fidelity system is to accurately reproduce all of the frequency-dependent spatial and temporal reverberation characteristics inherent in the original sound. The complete or near-complete removal of reflections would prevent the creation of a low-frequency reverberant field. This would reduce the accuracy of the system. Bass doesn’t sound real anymore. As for your studio friend, he is misinformed. Reflection free zones are only reflection-free down to a certain frequency, at some point the room’s dimensions dictate this behavior and the room would need to be very large to avoid reflections. Even anechoic chambers have reflections at low frequencies, no matter how deep the absorbing wedges are made. In the end, we both do not want and cannot absorb all low-frequency reflections. Instead, we should focus on enhancing the reverberant field at low frequencies by spatially averaging the excitation of modes to improve low-frequency spatial consistency through multiple subwoofers.

3) Myth: Placing a subwoofer close to you eliminates any room reflections.

Pursuing the Truth: Sitting on a subwoofer is great fun, don’t get me wrong. No matter where you place a subwoofer it will interact with the room. What this technique does is increase the amount of direct sound energy you hear (and feel) relative to the reflections in the room. While this leads to a smoother response near the listening area, as noted before, it sounds less realistic. This isn’t a desirable quality in a room. Further, it is still impossible to dramatically change the ratio of direct to reflected energy at low frequencies, even by sitting on top of a subwoofer.

4) Myth: Bass can be directional in a room, where you point the driver or port changes how it sounds.

Variation: The use of Cardioid or Dipole bass radiators increase the direct to reflected response and improves sound.





Pursuing the Truth: There are three issues to unpack here:

A) bass is largely omnidirectional with sealed or ported designs. The placement and orientation doesn’t impact sound due to any change in where the bass is directed. However, the position of a subwoofer or its proximity to the wall and floor can impact how it energizes modes or what cancellation affects you see. With more complex situations such as cardioid or dipole radiators, we do sometimes see differences in the energizing of modes with position, but we don’t, on average, see any overall differences in the coupling to modes. That is, two subs in the same location, one a dipole and one a monopole, will show differences in the bass response. But move the sub and the response still changes just as much. The actual ratio of direct to reflected energy doesn’t change, it can’t. The wavelengths are so long at such low frequencies that the perception of tone still will exceed multiple reflections within an average room. The time it takes to perceive tones below 100hz typically is longer than even the longest first reflections (length) in a normal room. This is why dipole and cardioid bass systems don’t tend to make a substantial (if any) difference in the quality of bass in a room.

B) Bass is also not particularly localizable by our brain. This is because the two methods the brain uses to detect sound source direction do not work well at low frequencies (the difference in time arrival to our ears and the difference in loudness between our ears or ITD and IAD). What we hear in a room is mostly reflected sound at low frequencies, very little of the total bass we hear is coming directly from the sub. Directional bass systems exist, such as H frame or other Cardioid systems. However, there is no good evidence that this increases direct to reflected energy or changes how modes are energized. When multiple low-frequency sources are put into a room, it doesn’t matter if it is directional or not, the end effect is the same. What you hear is still mostly reflections around the room. That’s a good thing, we want a largely reverberant field at low frequencies.

C) We sometimes recommend aiming the subwoofer driver at the wall, carpeted floor, or acoustic panel. We make similar recommendations for ports. This is not because aiming the subwoofer changes how it interacts with the room. Drivers and ports make higher frequency distortions and aiming them at a wall, carpeted floor, or acoustic panel can reduce the audibility of these noises.

5) Myth: I don’t need more than one subwoofer, I don’t listen very loud and my wife/children/neighbors would complain.





Pursing the Truth: Multiple subwoofers are not used to increase output or play louder necessarily and isn’t why Audioholics advocates for them. It evens out the activation of modes in a room and creates a smoother response with greater spatial consistency. In other words, the bass sounds better in more places where you would sit. One benefit of this is that it may reduce the volume of the bass that escapes the room in the event you are sitting in a null and had to turn up the bass. Multiple subwoofers spread throughout the room typically integrate in random phase and the total gain achieved is only a few decibels. However, I will argue that this increase is valuable since nobody likes a noisy subwoofer.

6) Myth: Subwoofers are for movies, music needs full-range speakers. Subwoofers just go boom boom boom.

Pursing the Truth: What utter nonsense. While full range speakers are great to have, subwoofers produce bass extremely well. In most cases better than the main speakers. The drivers are optimized to produce low frequencies with low distortion and high output. They have dedicated amplifiers and often DSP optimization. Main speakers are almost never in the optimal location for bass, which is typically near a wall. Also, multiple subwoofers throughout a room provides the smoothest bass, something a pair of speakers can’t achieve so easily. The reality is, subwoofers are the high-fidelity choice for good bass and few speakers can equal the quality of bass even a modest subwoofer can produce.

7) Myth: One better subwoofer is better than multiple cheaper subwoofers





Pursing the Truth: Maybe or maybe not. While this isn’t a popular thing to say, for the most part, all subwoofers will sound the same within their linear range. What dictates the audible differences in subwoofers tends to be differences in maximum output and extension (which are functions of extending the linear range). What this means is that a subwoofer that costs twice as much doesn’t sound better than one that costs half as much if both are operating only within their linear range. What does make a big difference, the biggest difference is the overall evenness of the bass response. The more consistent the temporal-spatial response is, which is best achieved through a more even spatial activation of modes, the better the sound. While EQ can flatten a response to a point, it primarily deals with peaks, not dips, and has its limits. Multiple subs often is a better option. Further, multiple subs will couple below around 30hz or so as in phase sources (if set up right) providing 6dB of gain, and as random phase sources above that point, providing about 3dB of gain.

8) Myth: Sealed subwoofers are better because ported subwoofers ring more in the room and sound boomy.





Pursuing the Truth: I call shenanigans. Nonsense again. If a ported subwoofer sounds boomy it’s either a poor design with a non-flat response or is poorly set up (which is not something inherent in ported designs). Well designed ported subs are just as tight and articulate as sealed subs. In many cases, the increased tightness some perceive from sealed subs is simply the fact that there is less bass coming from the bottom octaves in a sealed design. However, that is nothing more than a response issue and can be mimicked in a ported design. While there are poorly designed ported subwoofers, there are just as many poorly designed sealed subwoofers. This is not a point for comparison.

9) Myth: smaller subwoofers are faster than larger ones. Big subwoofers sound slow and inarticulate.





Pursuing the Truth: Larger woofers displace just as much air as small subwoofers by moving a lot less in and out. By minimizing the amount of in/out movement, the driver tends to behave in a more linear fashion. In general, the “speed” is a function of group delay. Larger subs do not have more group delay. However, larger subs do typically have lower distortion, can play louder, and can play deeper. There is no replacement for displacement. No turbos for subwoofers. On the other hand, to make small subwoofers linearly displace a lot of air, they often need very large motor systems with very big voicecoils. These large voicecoils can lead to more inductance and this can cause several response problems such as a peaking midbass, roll-off in the upper bass, inductance related distortion, and increased group delay (See figure 2 as an example of the effects of increased inductance on the response shape). This can be just as true of large woofers. To combat the effects of high inductance, specially designed linear motors can be made that include things like inductance rings or specially wound coils that lower inductance.

10) Myth: high-level speaker connections to a subwoofer is superior. You get better integration and time alignment.

Pursuing the Truth: Just a big No! This is nonsense. A high-level (Speaker level) connection is no different than a low level (RCA or XLR) connection. The time delay in an amplifier is minuscule and adding it then adds more time delay to the amplifier in the subwoofer. Why would that be good? Amplifiers often have higher noise and distortion than preamp outputs so this could make things sound worse. However, for the most part, there is no difference. The intuition that many use to justify this improving Integration lacks logic. Integration is and always will be about the crossover, level, phase, delay, and placement. The connection you use is of little consequence. Incidentally, connecting a subwoofer high-level or speaker level, negates the bass management in the AV receiver or processor and thus you'd have to activate the internal LPF of the subwoofer. Bass management is usually best done in the digital domain on the AV processor/receiver side, not at the subwoofer itself.

For more information, see: Bass Management Settings Made Simple

Top Ten Myths Debunked!

I am sure that some will take issue with the myths and truths we have discussed here. There is no shortage of opinions in our industry. We at Audioholics feel that the myths we have discussed are pervasive and the truths we have provided are accurate. We know that bass is very important to your music and movie enjoyment and we want our readers to be able to cut through all the bogus information to land on a truth-filled bass bliss. Further, many may note that the author of this article previously advocated for the superiority of sealed subwoofers over ported. Yet this article makes clear that the audible differences are small. I do believe that in a perfect world a sealed subwoofer is superior, but I also believe that in the real world, the audible differences are negligible and that ported designs can provide real advantages in low-frequency efficiency. We must be pragmatic. By following our many articles focused on bass optimization and choosing subwoofers based on our Bassaholics rating, we feel confident you won’t go wrong. Follow the advice of others and we make no promises where it may lead you.