Round Port Vs Slot Port

Round Port Vs Slot Port

The ports in the front of every subwoofer are one of the biggest arguments audiophiles find themselves getting involved in. The two most common of these ports come as a round or slot port. But which of the two ports is better?

To answer the first question, the ports are essentially added by subwoofer enclosure manufacturers to improve sound delivery. In addition, it also functions as a control for the sound output and resonant frequency.

In terms of the difference between round ports and slots ports, round ports have the lowest surface area per any given port area. On the other hand, for a slot port, the more square the port (the more equal the sides), the lower the wall surface area. 

round port and slot port comparison

The two ports produce different effects when they are the same size. But there is no obvious difference between both the slot port and the round port when the velocity of the air passing through the two is low. The difference thus starts getting obvious as the air velocity passing through each of them increases.

Although, when you choose the same frequency for the two of them, they will end up producing the same sound effect.

Feature Comparison

Here is a direct comparison between the two: 

Best sound compatibility

  • Slot ports are best for movie
  • Round ports are most ideal with music delivery.

Ease of Use

  • Slot ports are not an easy option to build.
  • Round ports are much easier and come in varieties of ready-made sizes.


  • Slot ports are known for taking up more space and volume.
  • Round Ports on the other hand takes less volume for the same size.

Noise Production

  • Slot ports tend to produce noise if they have a larger port area.
  • Round ports are also guilty of noise particularly if not properly sized.

Performance with low port air velocity

  • The two ports act normally and the same under this condition. If you ever have to decide which one to choose using this criterion, a round port will be best suited since they are easier to make.

Internal Surface Area

  • Slot ports have more internal Surface Area and the more their sides are, the lower the wall surface area.
  • Round ports generally have less internal Surface Area.


  • Slot ports have less efficiency due to the greater friction attributed to their large surface area.
  • Round ports are however more efficient since they have a lower surface area and lesser friction.

Performance with High Port Air Velocity

  • Slot ports perform a lot better because they can easily distribute noise across different frequencies.
  • Round ports are however bad with handling noise from high port air velocity.

Slot Port Review

This is a rectangular-shaped outlet on the speaker that is designed to control distortion caused by the bass energy leaving the speaker. You will find them on most movie-compatible speakers but this does not mean they can’t be on music woofers as well.

slot ports

One of the easiest ways to make a slot port is by adding an extra wood to the already and an opening to the end of the wood to complete the port. They are pretty good for dampening unwanted cone excursions just below the tuning frequency.

Should you choose this port? Here are some of the pros and cons that can help you make better choices.


  • Slot ports distribute the noise better due to their ability to distribute noise across different frequencies.
  • They add balance and strength to the speaker
  • Has a straightforward building process.


  • They are less efficient as a result of the high friction caused by the narrow duct.
  • They need to be in higher port velocity to perform better.

Round Port Review

Round ports are straightforward to make. They only require fittings that use a PVC pipe to form a circle. This makes them more efficient and reduces their volume. By common practice, you will find the round ports to be around 3 to 6 inches across by diameter.

Round ports

The port area is a major source of concern since the noise from these ports will be decided by its port area. That is, the bigger the surface area, the lower the chances of making noise. Here are some of the pros and cons of this port.


  • This is a lot easier to make since they only need PVC fitted in a pre-drilled box.
  • In any case, where the tune has been affected, it can be adjusted easily without making another box.
  • It is more portable and has better sound quality than the slot port.


  • The bass is not as nice as a slot port. The bass delivery is scattered.
  • Although it is easy to build, the cost of getting PVC is not always encouraging.
  • The loud sound does not guarantee quality music output.

Which Of The Two Ports Is Better?

The main issue here is that when deciding which is better it is based on a specific factor in mind.

For example, if a round port has a wrongly sized fitting, it will be annoying to use because of the noise. However, when the two ports are tuned to a specific frequency, they both perform the same.

Therefore, in the context of which is better between the two, the answer will be based on your preference and which you generally prefer.

How To Choose The Best Enclosure for Your Subwoofer

  1. The sound delivery

The first factor you should worry about is what kind of sound you want. A safe practice if you have the two available is to test them on the same level.

2. Velocity

This means that you should consider the highest peak of air for the port you will be choosing. This peak cannot be a narrow one for slotted ports as it can increase their friction. Generally, rounded ports are the favorites when the velocity is considered.

Best Enclosures You Can Get

You don’t always need to make it yourself, these are some of the best universal fits you can get for your subwoofer

What is An Aero Port?

These are ports you can easily use to readjust the tune of your enclosure whenever you feel it has detuned without having to make an entirely new box.

Larger or Smaller Ports, which is better?

A smaller ported enclosure might be the best you can get for yourself. Asides from the fact that they are mostly portable and can be moved easily, they also tend to achieve higher air velocity faster.


If you are a newbie that would love to try out any of these ports as a DIY, then slot ports are an easy take. This is because it is pretty straightforward and does not require you to get extra equipment. However, you might need to consider the quality you want to achieve or the effect you are looking for before you opt for any of the ports.