A port can be defined as a harbour or an area that is able to provide shelter to numerous boats and vessels (transferring people or cargo), and can also allow constant or periodic transaction of shipment.

In layman’s language, a port is a place to facilitate loading as well as unloading of vessels. Technically speaking it is a convergence point between freight circulation domains.

Ports are the inhibitors which begin the social and economic growth of a region by not only allowing trade but also by serving a hub for social activities.

These days, most of the ports (especially seaports) are well-equipped with specialized fixtures such as forklifts and gantry cranes to facilitate regular dealings of cargo.

Ports can of great significance to a nation, as it promotes the commercial welfare and the trade scenario. Ports can also be of military importance, as they are used to keep the warships before moving out to the battle scene.

Ports are also a major source of employment as a large number of workers are employed at the ports.

Credits: BMT Press Office

What Are Port Facilities?

The port can be a natural establishment or artificial construction, which provides a place for the loading and unloading of cargo. Ports can be for large seagoing ships and also for inland waterways such as rivers and lakes. The depth of the ports plays a vital role in allowing various types of ships to enter and dock at the port.

But nowadays along with its basic purpose, a port is equipped with certain other amenities and facilities. Different types of ports are equipped with different port facilities.

Some common port facilities provided by the most common sorts of ports throughout the world are as follows:

a) Special Warehouse: This is available on all the ports, for storing the shipment and for maintaining regular stock.

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• While it is most likely the case that slightly less turbulence will occur comparing slot port to a straight round one with longer ports this is at the cost of decreased backwave resonance. Because round ports will require a longer box it is far more likely to cause excitation of a backwave resonances in the passband compared to a slot port.

b) Port Reception: Reception has details of all the shipment scheduled and moreover it is a guide for the port facilities.

If port air velocity is fairly low there's basically no difference. So usually you'd make a round port because they're easier to make and comes in many ready-made sizes. If port air velocity is fairly high then a slot port is preferable as port noise will be distributed over a large number of frequencies instead of one frequency as with a round.

c) Other facilities: Some other essential facilities are also available at seaports namely hotels, restaurants, restrooms and eateries for the port visitors. Some of the ports are provided with medical facilities to the people present there, if there is no hospital in the vicinity it becomes obligatory for the port to provide with primary medical services.

d) Fishing facilities: Fishing ports allow its customer with fishing aids and amenities at the port.

e) Warm water facility: A greater revenue-generating warm water port provides warm water even in frosting winters.

f) Loading and Unloading Facility: It is the mandatory part of every port to allow loading and unloading of freight as well as people in a ship.

g) Infrastructure and Equipment’s: A port has piers, basins, stacking or storage areas, warehouses to store various ferry equipment. Each port is equipped with essential equipment for e.g. hauling equipment’s, draggers, cranes, trucks, loaders, etc.

h) Workshop: All the bigger and significant ports provide the facility of vessel workshop. It is the place where one can get spare parts and accessories of a vessel. Also, the vessels which have gone out of order are repaired and catered in the workshop.

What is Port Authority?

The Port Authority of any country is a government or semi-government public authority which builds, maintains and operates critical transportation and trade assets at the seaports.

In short, the seaport authority facilitates the management of millions of people working on the harbour and maintains or supervise vessel movement. The London Port Authority was the first port authority. It came into action in the year 1908.

Port Authority controls, legalizes and manages all the port and marine services, facilities and activities within the concerned country waters, it also includes management of vessel traffic, improvisation of navigational safety, and facilitation of security and environmental management at the port.

Organisation Of Port Authority:

Port authority comprises of following Departments:

1. Supervisory Board: It is the highest Department in port authority which supervises all the activities of subsequent departments.

2. Executive Board: This Department is the most important department of port authority as it actually makes and executes all the decisions regarding maintenance, control, security and managerial operations. It has two main components namely:

President and chief executive Officer: The main functions of President and Chief Executive Officer are as follows:

• Corporate Affairs and Corporate Strategies: They have to look after all the corporate affairs and make strategies regarding the improvement of corporate relations.
• Human Resources: They have to appoint crew members, labours at the port and work for their improvement by regular performance appraisal.
• Communication and External Affairs: They have to manage internal as well as external communication on port and work for enhancing International trade.
• Internal Audit: They have to maintain Internal Audit as well.
• Legal Department: They have to legalize trade and cater to all the legal matters.

The President and Chief executive Officer are to manage following sub-departments:

i) Executive Vice President and Chief Financial Officer and

ii) Vice President and Chief Operating Officer

i) Executive Vice President and Chief Financial Officer: They have to cater to all the matters related to Finance, Procurement, Digital Business Solution, Digital and Information technology, Innovation, etc. They also have to look after the Faculty Service Centre to manage working personnel and their services.

ii) Vice President and Chief Operating Officer: They head Harbor’s Master division and work primarily for Harbor Development. They manage all the assets and also work for environmental Management.

Types of Ports

Considering a variety of factors such as location, depth, purpose, and ship sizes, ports are classified into various types. Some of the main types are as follows:

Inland Ports

Inland ports are ports built on comparatively smaller water bodies such as rivers or lakes. They can either be for cargo purpose or for passengers or for both. Conventionally Inland Ports are constructed or naturally maintained ports at the coastline of small waterways like lake, river or estuaries and rarely seen at sea coasts too.

Some of these inland ports can have access to the sea with the help of a canal system. As such ports are built on inland waterways they usually behave like normal seaports but are not able to allow deep draft ship traffic.

Some of the inland ports can be also be specifically made for recreational purpose allowing only small-sized vessels or can be used just for ferrying people and fishing activities.

Inland ports are known for their quality to function in a smooth manner, unlike the clogged seaports. These ports can also sometimes be referred to as dry ports, and are similar to active intermodal hubs. The inland port at Montreal is the biggest of its kind.

Inland ports are conventionally maintained for quenching the needs of stocking and dispatching of cargo but sometimes these are also made open to passengers too. These are shallower than seaports so they don’t allow deep docking, but only docking to ferries is allowed at inland ports.

Inland transport services are used to connect these inland ports (generally called rail or road terminal) through marine terminals. For e.g. St. Lawrence Seaway is an important inland port.

Intermodal transportation and tanker ships are on their peak in the international market due to the development of Inland ports which are also referred to as Inland freight distribution ports, which are a hub for inland waterway trades mainly due to their congestion-free space availability and adequate capacity.

Inland terminal is the key connector for trading expeditions between two regions, not only for inbound traffic but also in serving outbound traffic. This port also has to handle various concerned logistic activities. Important functions of Inland ports are summarized below as:

• There should be well-established distribution centres for freight distribution
• Inland port Depots should be made available for ensuring proper storage of hulks and containers which can be later used in different voyages
• There should be well established logistic department to handle all logistics activities as well as to maintain inventory records
• There should be a proper warehouse to house spare parts of cargo and other machinery involved in the loading of cargo.

Fishing Ports

Fishing ports are mainly related to the commercial sphere as they participate in fishing. The fishing activities can also be treated as a mode of recreation. The existence of a fishing port entirely relies upon the availability of fishes in that region of the ocean. A fishing port can be an inland port or a seaport.

Often, fishing ports are marketable port which is generally used for recreational purposes or aesthetics. These are the ports which allow controlled and disciplined fishing to their customers. These are the highest revenue-generating ports when properly operational.

Unlike other types of ports, the fishing port has an operational loophole that is this port is operational when there are fish available in the port area or locality. In the scarcity of fish in the vicinity these ports become uneconomical.

Also, fishing ports require more maintenance works as compared to other ports so many are on the verge of closing. These are the ports with smaller depth because of the draught of the fishing vessel is limited to a short depth. A fishing port comprises:

• Hangers: These are the special area employed for the preservation of goods and products. Also, it houses the production as well as a storage area which produce and store necessary food or other items for the fish.
• Supply post: This is an important part of a fishing port and is responsible for satiating the fuel needs and freshwater demand by the ship.
• Operation and Administration building: This the main building in which plans are made for the voyage and fishing and management for all legal as well as health issues.
• Premises: It is the building which houses the deals in fish that is either purchase of fish or sale of fish.

Warm Water Ports

These are the ports in which the water is maintained at warmer temperature. The biggest advantage where a warm water port is concerned, is that the water does not freeze during the frosty winters. Therefore, it is free to operate all year round without a temporary shutdown during the freezing time. Such ports help to a great extent to boost the economy of the nation.

These ports have a significant role in the economic growth of the region where these are located.

Two such major revenue-generating ports are Valdez port of Alaska and Vostochny port of Russia. The main reasons for which warm water ports are considered important and due to which important developed countries of the world quest for establishing and acquiring more warm water ports are as follows:

i) It allows trade throughout the year, because in chilling winter when other ports deny their services, warm-water port is still operational and reach the import-export demand of the nation.

ii) These warm water ports made inland waterway trading possible in countries like Ethiopia.

iii) These are the main reason for the expansion of an empire around the globe.

A few notable examples may include Ukraine’s Odessa, Russia’s Vostochny Port and Murmansk Port, Japan’s Kushiro and Alaska’s Valdez.

Dry Ports

Dry ports are defined as inland terminals that can be interconnected with a seaport via road or rail transportation facilities, and they usually act as centres of multimodal logistics. A dry port proves useful in the trade of importing and exporting cargo and can help to lessen the inevitable congestion at a nearby seaport. Its functions are quite similar to that of a seaport, with the only difference that is not situated near the coastline.

These are specifically employed for transhipment of cargo to inland destinations. It is a trans-shipment port which is connected to a seaport and manages intermittent operation like billing and managing co-ordination between importer and exporters.

These ports serve the same purpose as the veins do in our body because these are used to connect importers and exporters from remote areas who cannot access to seaports for trading or other purposes. In India alone, there are nearly 300 to 330 dry ports and certainly, more are under development.

A dry port consists of all the necessary machinery to handle the constant clearance of shipment, like proper cargo-instrumentations, rail sidings, storehouses, and even container yards.

Sea Ports

Seaports are the most common types of ports around the world which are used for commercial shipping activities These ports are built on a sea location and enable the accommodation of both small and large vessels.

Numerous seaports are situated along the coastline and actively handle the ongoing cargo transactions. A seaport can be further categorized as a cargo port or cruise port. Some of the oldest seaports are still used for recreational and fishing purpose.

Special warehouses are also constructed to store the shipment and to maintain the regular stocking. Added facilities such as hotels, restaurants, port reception facilities, restrooms and eateries can also be made available to rouse the interest of the people visiting the port. Seaports form some of the biggest and busiest ports in the world.

Seaports are the most common type of ports and a major part of water transportation. These are further classified into three categories namely: Cruise Port; Port of call and Cargo port. These all are briefed as under:

i) Cruise Home Ports

This type of port specializes in dealing with the activities of cruise ships and provide the platform for the passengers to enter and disembark the cruises at the beginning and the end of the journeys, respectively. A cruise home port is also capable of providing the essential provisions required for a luxurious cruise voyage. The supplying may vary from fuel resources to fresh drinking water, wines, foods etc.

A typical cruise home port is always congested and is buzzing with people boarding or leaving the cruises.

These are the busiest sort of ports due to continuous boarding; loading; unloading activities. Also, all the formalities and arrangements for a safe voyage through cruises is pre-planned and executed by the port authority at the port.

In South Florida, Miami ports are considered as the modern cruise capital of the world. Also, Port Everglades and San Juan port of Florida and Puerto Rico respectively are also considered significant for their destination holiday cruises.

Some of the popular cruise homeports include Florida’s Port of Miami and Port Everglades, and Puerto Rico’s Port of San Juan.

ii) Port of call: Also known as the mid-way port, Port of call is somewhere midway on ship’s travel plan to accept fuel supply and stocking or unloading cargo.

Port of Callis a type of port which is paid a brief visit by a ship on the voyage. It is also used for carrying out essential repair works. Many passengers can also leave the vessel at a “port of call”.

It serves as a stopover port, in between the home ports of a particular vessel.

iii) Cargo Ports

As the name suggests, these ports act according to the cargo it manages and the amenities available differ from one port to the other. These are the special ports to handle cargo only. These ports are also known as “bulk ports”, “break bulk ports” or “container ports”.

The cargo ports involve many mechanical techniques to load or unload the shipment. A cargo port may be designed to deal with single, as well as multiple types of products.

Items such as liquid fuels, chemicals, food grains, timber, machines and motorcars, are transported to various places, employing the adeptness of a cargo port. Deep water ports are sometimes used along with those cargo ports which do not have sufficient depth to allow big ships.

Cargo like wood, liquid chemicals or fuel, food grains, automobiles, etc. are handled by Bulk ports whereas containerized cargo or cargo in containers is handled by the Container ports. Sometimes a third category is also added in this series which is all-in-one port this sort of port not only handle specific cargoes but can manage all sorts of cargoes on a single port.

Numerous operating terminals branch out from individual bulk ports and are assigned to maintain the various kinds of ship ladings. Stevedores are the companies which act as terminal operators and preside over the actions of the diverse operating terminals.

Difference Between Ports and Terminals

Ports are strategic geographical locations which are situated at the edge of ocean, seas, rivers, or lakes. These locations are then developed to inculcate facilities for loading and unloading of cargo ships. The facilities provided for a port depends on the purpose for which the port is being used.

Whereas a terminal is referred to as the set of facilities at a port where loading and unloading of cargo/container take place. Terminals are named on the basis of the type of cargo that can be handled by them. Some of the most common types of terminals are container terminal, bulk cargo terminal, LNG terminal etc.

Summary

In a nutshell, it can be concluded that in interstate or international trade ports are the key areas which ensure safety, security and reliability of voyage.

There are different sorts of ports as per the purpose they are used for, but the main parts of all the ports are same which are the port authority, administration and operation building, warehouses, a depot for containers and vessels, etc.

There are five major types of natural or man-made ports which are Inland port, fishing port, dry port, warm water port and seaport.

Among all these types of ports, seaports are the largest and busiest type of ports. This is due to the reason that seaport serves to both cargoes as well as passengers. So more facilities and equipment are available there which results in the employment of more personnel as a port authority.

But all the regions cannot access to seaports, these are connected to the dry port by means of either road or railways. These dry ports are further connected to seaports and serve as a mediator of trade to the remote importers or exporters.

Fishing ports are leisure commercial ports which are only to serve the fishing activities by the people for fun and enjoyment.

Inland ports are similar to seaports but with smaller capacity. When all these ports fail to serve transportation due to freezing of water in winters then only warm-water ports are still operational. So importance of warm water ports can never be out skirted. These are the only media to carry out international or national trade expeditions in winter.

Today all the countries quest to own more and more warm water ports.

Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendation on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared or used in any form without the permission of the author and Marine Insight.

The mysteries of ports

As simply as possible:

Ports deal with all the deep lows and give the woofer(s) an easier ride - tune them right and use a good geometry and there are no downsides. Tune them too high or too low and the tone won't be as good and the cab won't handle as much power. Make them too big and the cab will be huge (this hardly ever happens); make them too small and they'll stop working right as you play louder, killing your bottom end (this is a really common problem). We design, test, adjust, test, etc and make sure they're as good as can be.

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How do ports work?

There are a huge number of misconceptions about ports - here's some of them:

1. The ports relieve the pressure in the box and make it easier for the woofers to move
2. The ports push air out when the woofers move back and suck air in when the woofers move forwards
3. The ports 'fire' sound out in whichever direction they face - so rear ports need a wall behind them to bounce the sound back to you
4. Ported cabs sound boomier than sealed cabs

So let's address them one at a time:

1. The ports do not relieve the pressure at all - at frequencies more than an octave above the tuning frequency the ports act just like a solid wall and don't allow any air through. At frequencies within about an octave above the tuning frequency and a third of an octave below the tuning frequency, the port takes energy from the vibrating woofer and uses it to set the plug of air filling the port into vibrating back and forth motion. This reduces the amount the woofer is vibrating (the amplitude heading towards zero at the tuning frequency) thus hugely increasing the excursion limited power handling. The port is much better than the woofer at vibrating at these low frequencies (the woofer's motion is damped by the mechanical compliance and electrical/magnetic circuit) so at the tuning frequency it produces almost 100% of the sound, with its output diminishing to about 20% of the sound half an octave above the tuning frequency.
2. The only time where the ports are pushing air out when the woofers move back and sucking air in when the woofers are moving forwards is well below the tuning frequency - at this point the port has no useful function and in fact is detrimental as it makes the woofers think that they are not in a box at all but in free air - which causes the excursion to vastly increase but little sound come out as the positive woofer movement is mostly cancelled by the negative port air movement and vice versa. This is why it is critical to not tune a cab too high, and is one of the reasons why a lot of cabs (particularly small ones) struggle with low notes, especially at the bottom of the E and B (and lower) strings (overly high port tuning increases the mid-bass which is the only sort of bass ('fake' bass) that some cabs can do in quantity).
3. This might get a little deep - sound is a longitudinal wave which travels through the air in the form of pressure changes. When the wavelength is long relative to the size of the source and you're up close to it (the true nearfield) the wave is considered to be a pressure mode (you'll have felt this standing next to a subwoofer stack in a club or putting your head up against you bass cab). As you move further away from the source that pressure mode transforms into a velocity mode. Because the frequencies are long relative to the source size, the source has no ability to control their direction - they are emitted omnidirectionally. The wavelengths of the sounds coming from a loudspeaker port are huge compared to the size of the port and even our very large ports are small relative to the wavelength's emitted. This means that once the pressure wave just outside the port exit has transformed into a velocity wave, the output goes everywhere! Consequently, in the far-field the port output will sound the same whether the port is on the front/side/back/top/bottom/etc of the cab. The output will be different if there is a wall behind the cab but it will differ in the same way regardless of the port position/direction.
4. The reason ported cabs are deemed to have worse transient response than sealed cabs is because their transfer function is different. An 'ideal' ported cab has a 24dB/octave cut-off but an 'ideal' sealed cab has a 12dB/octave cut-off. The steeper cut-off rate causes the transient response to be less accurate - this can be proved mathematically and is true to all filters - the steeper the slope the greater rate of change of the phase shift and thus the greater the group delay. However, an 'ideal' ported cab isn't actually ideal! The way the generation three cabs are designed means that the LF roll-off is actually much closer to a 12dB/octave transfer function, which results in excellent transient response (in conjunction with the higher efficiency and power handling of a ported vs sealed cab).

The passive radiator - a speaker that think it's a tuned port

You may have seen loudspeakers which have 'passive radiators' or 'drone cones' - this is a woofer with no magnet and no voice coil, in other words just the cone mounted via flexible suspension onto a frame. Looking at one of these is the easiest way to understand ports. Let's say your woofer has a free-air resonant frequency of 35Hz and Q of 0.25. Once we put this woofer into an enclosure the air in the box acts as a spring, raising the resonant frequency of the cab by reducing its suspension compliance. The woofer now has a resonant frequency of 70Hz and Q of 0.5. (Q is how much a device wants to resonate at its resonant frequency: 0.707 is often considered the ideal balance of frequency and transient response, 0.5 is called 'critically damped' and has less bass response but better transient response, 1 is under-damped so gives more bass response but poor transient response). The problem with a resonance of 70Hz and Q of 0.5 is that it will sound thin in the lows.

How a passive radiator helps a simple cab perform better

If we take then a passive radiator with a free-air resonant frequency of 20Hz and Q of 0.3 and put it into the same box, its resonant frequency shifts to 40Hz and Q of 0.6. What then happens is at 100Hz the woofer is producing all the output but as you head down towards 80Hz the passive radiator starts to scavenge energy from the woofer and re-emit it itself. By 40Hz the passive radiator is taking most of the energy from the woofer and re-emitting it as sound. If the woofer was just on its own, although it would be taking in approximately the same about of electrical energy it would be losing most of that energy as heat and not creating a useful amount of sound down low.

Adding the passive radiator massively improves the conversion of electrical energy to sound energy at very low frequencies because it is a better low frequency resonant system than the woofer alone. The way the energy is transferred from woofer to passive radiator is that the passive radiator pushes back against the air in the enclosure, creating high pressure against the woofer around the PR's resonant frequency. This high pressure improves the transfer of energy into the air (this is what makes compression drivers and horns more efficient than normal dome tweeters), so more sound energy comes out of the woofer into the inside of the enclosure and then into and back out of the PR into the outside world.

Ports are not just a hole or tube that lets air in and out

Hopefully by thinking of a port as being like a passive radiator we can get away from the misconceptions of it blowing air out or sucking air in or of acting like a leak which reduces the back pressure in the box. As we've explained above, it actually increases the back pressure in the box at certain frequencies thus improving the efficiency of the system!

A subwoofer that's made of air?

So how does a port differ to a passive radiator? Instead of being a paper/cardboard/plastic/aluminium/etc membrane vibrating back and forth it is instead a mass of air doing the vibrating. In a perfect port in a simplified world this mass of air never changes - it is always the same lump of air which vibrates back and forth and thus creates vibrations in the outside air that you can hear. If you look at passive radiator design information you'll find that PRs should have approximately double the volume displacement of the woofers it is working with - so you'd pair a 10' woofer with two 10' PRs of equal excursion or a 12' woofer with a 15' PR of 30% greater excursion. This may seem a little strange - why would the PR that's helping out in the lows need to be able to move more air than the woofer which is driving it?!

Volume displacement requirements

Well the answer is that to produce a given SPL at 50Hz takes twice as much excursion as at 100Hz - this is obvious if you think about it because the woofer moves in one direction for twice as long at 50Hz so it travels twice as far outwards before it starts coming back in and then moves twice as far inwards before it starts going back out and so on. Our woofer reaches its peak excursion about 2/3 of an octave above the tuning frequency of our PR. At that point the PR is moving about 40% of the air and the woofer 60% - to put it another way, without the PR helping out the woofer would need to move about 65% more air.

Down at the tuning frequency the PR is moving about 90% of the air and the woofer 10%. So in the case of our hypothetical cab the PR doing 50% of the work at 56Hz, increasing to moving 90% of the air at 40Hz and then dropping back down to sharing half of the air movement requirements at 33Hz. This 33-56Hz region requires twice as much air be moved as the 66-112Hz region where the woofer is doing the lion's share of the work because it is an octave below. Hence the PR must have double the volume displacement of the woofer or the full ability of the woofer will not be able to be utilised.

Below the tuning frequency...

The key difference between a port and a PR is that at very low frequencies a port just acts a like a huge hole in the cab - basically it turns it into an open baffle design where the woofer back wave starts to cancel the front wave. A PR can obviously never act like a hole because it is a solid membrane - instead it acts like it is in free air itself and thus sucks energy out of the woofer at its free-air resonant frequency and produces out of phase output with the main woofer causing a distinct notch in response. When we see this plotted on a response graph this notch makes the roll-off of a PR appear steeper than with a port but it isn't really a change in transfer function so much as an additional function. Head lower in response and the port and PR response curve tend to converge and continue on the same slope together.

Why ports need to be big - not just little after-thought tubes stuck in the cab

Getting back to the ports, this large volume displacement requirement certainly doesn't go away. We don't want our port to be blowing air in and out, we want the air in the port to resonate in a controlled fashion and thus set the air in the room vibrating, creating extra bottom end. The larger the area of our port, the better it can do that because the shorter the distance the port air needs to oscillate back and forth. This is why our ports are big - so they work right!

Balancing area, length and volume

Unfortunately the larger the area of your port, the longer it needs to be to maintain the tuning frequency. This has two effects - firstly it makes the whole cab bigger, and secondly it can cause the port to be longer than the cab's depth or width and thus require a bend or kink (we can't practically use the height of the cab in a bass guitar cab because an upfiring port would be liable to have beer spilt into it and a downfiring port will vary in performance depending on the floor). These issues are why passive radiators are common in home cinema subwoofers - their very low tuning would require an incredibly long port, especially in the small enclosures they use. Putting a bend in a port tends to introduce unpredictable losses which reduce the port output and also lower the power level at which air noises due to turbulence (chuffing) will be heard.

Size matters!

The larger a cab, assuming a fixed port area, the shorter the port will be for the same tuning frequency. If we're running into port length/volume issues we investigate making the internal volume of the cab bigger and then seeing out that works out with are target response curve, sensitivity, port function, max SPL etc.

Optimisation for different purposes

The BB2 & BT2 are both designed to perform extremely well low down for any owners who use very big amps and heavy EQ boost at low frequencies, which is why the ports are so big. With the SC and ST the cabs are not tuned quite as low, nor the enclosures so large, nor do we encourage quite such large amps and therefore there is likely to be less port output at very low frequencies where air velocities are highest, hence they have less huge (but still large) port area.

Round Port Vs Slot Port For Splash

The SM's port area is smallest because a larger port would require a bend (thus defeating much of the benefit of a larger port) and would make the cab larger (thus defeating a key design feature of the SM - its tiny size!) However, a notable advantage of our tall slim ports is that as they approach their limits their relatively high perimeter to area ratio causes increasing linear frictional losses - this makes the port function quasi-aperiodic, keeping the bass response under control and avoiding obvious distortion from chuffing.

Impedance curve power compression

Not only do larger ports operating at lower velocity couple more effectively with the room, they also maintain the correct impedance curve seen by the amplifier. At the tuning frequency the impedance is at minimum and the amplifier delivers maximum power but when an undersized port exhibits overly high air velocities the impedance around the tuning frequency increases, so not only is the efficiency of the port dropping because of turbulence and frictional losses but also the amplifier is delivering less power.

One could say this is like trying to drive a car across a hot high altitude sandy desert (Atacama?) - you have less power from the engine because the air is less dense (high temperature and altitude = less oxygen to burn the fuel) and you can't put the power down effectively because the wheels are spinning the power away in the sand. If Barefaced made a car for that it would have turbocharging, 4WD, diff. locks and knobbly tyres!

Ports you can feel

Our ports are up the side of the front of our cabs because that is where you FEEL them best when you're standing up close playing bass. Once you're out in the far-field then it doesn't make any difference but there is definitely a physical benefit when you're on stage near your cab.

We don't use strongly flared ports because although that would allow us to reduce the port area and shrink the total cab size, when a flared port is pushed into turbulence the effective port length drastically shortens, thus raising the tuning frequency which causes a hump in response and more output in the mid-bass, and worse unloading and risk over over-excursion at low frequencies. This causes a negative spiral of even higher air velocities and more turbulence, distortion and compression. Heavily flared ports are great in more controlled environments but we do not see high SPL live sound as the right place for them.

Thermal power compression

Another key feature of our ports is their ability to help cool the cab. By running vertically up the cab they provide a path for the warm air to flow out of the upper sections and cool air to be drawn in through the lower sections. The power ratings you see on bass cabs are thermal ratings taken from the driver manufacturers' ratings, which are done in free air. Is a plywood boxed lined with damping material (which is always a good thermal insulator) the same as free air? Definitely not!

Round Port Vs Slot Port For Split

Our woofers use cast aluminium frames which help conduct heat out from the motor and our waveguides are also cast aluminium which do likewise with our HF drivers. By making our cabs as tall and slim as possible we encourage cooling convection currents within the cab and then our vertical ports do the rest to get that warm air out. This doesn't just help with the ultimate thermal power handling before driver destruction, this also reduces thermal power compression by keeping the voice coils cooler. Hot voice coils exhibit higher resistance which reduces the power your amplifier can deliver - this is what causes bassists to have to turn up their amp as a long gig progresses, and not only is this bad for tone it also increases the risk of premature driver death.

Round Port Vs Slot Port For Split Rail Fence

Double-duty bracing

The way our ports are constructed is integral to the stiffness and tone of our cabs with the box section of the port proving extremely rigid. Wherever possible the port dividers are positioned at unequal distances for two reasons:

1. Any flex in the enclosure walls will have unequal resonant frequencies - this keeps the tone as pure as possible at high SPL

2. Any standing waves in the port will have unequal resonant frequencies - this minimises the chance of there being significant detrimental midrange output from the ports.

We go a step further than merely ensuring these resonant frequencies are different - we've also tried to ensure that the harmonics are different too, only coinciding when you're a long way up into the harmonic series. Details, details, details...

Round Port Vs Slot Port For Splitter

Yes, we care a LOT about ports!