Porting.

[RichCresci]

What is the purpose/need to port a sub box?

 

[Tyson128]

Porting as it relates to speakers

Porting sets the lowest usable frequency for the speaker that you are using. Typically it varies with:
1) The size of the enclosure in liters or cubic feet.
2} The size of the speaker Figure of merit QTS factor in the speaker specifications (<.5)
3) The length and the diameter of the port cylinder.
Any frequency below the port freq will distort like crazy and can with high wattage blow your woofer. At frequency and with a tight properly damped box and crossover sounds magical.
Sealed enclosure may be a good solution if you don't want to be bothered with calulation and build your enclosure to its recommended size. By and large you can achieve good bass with less distortion, just not boomy
Other factors include:
Excusion of the speaker cone (More is better)
Power that the speaker can handle
The ability of the speaker to control its cone (magnet size and motor characteristics).
Keep in mind that unlike your stereo in the house where you are outside the box. Your car is kinda like being inside a box so you don't need as much power as you may think unless you want to be deaf.
There are plenty of sites to help you with you choices like DIY speaker building.
Hope this helps.

 

[RichCresci]

Thank you bunches.

 

[aznboi3644]

purpose of porting...some woofers are designed specifically for ported application while others are for sealed only.

Some are in the middle ground...But port opens up a whole new world to different types of enclosures

 

[Turdle]

IMO
Sealed boxes are best for SQ while ported work well for SPL

In theory, a sealed box will be tighter and more accurate, while a ported box will deliver higher sound levels at the expense of accuracy.

I prefer to listen to my music, rather than try to make others listen to my music, which is why I prefer a sealed enclosure.

 

[Beastb15]

Essentially ported boxes are used to increase the low frequency output. Ported boxes are more efficient (requiring less power for the same amount of output).

 

[aznboi3644]

Properly designed a ported enclosure will sound just as "tight" and musical as any sealed enclosure.

Sealed enclosures can also sound sloppy and muddy.

It is all about the design essentially

 

[Wagonized]

Anyone who claims they prefer the sound of sealed enclosures over ported because of the sound quality difference hasnt done a good head to head test with a well designed ported enclosure.

Ported enclosure will be louder though everytime, providing you dont design it completely wrong.

Then there are vented variations such as bandpasses which can be quite amazing sounding but very difficult and time consuming to tune to desired frequency range in a car environment. Bandpasses have the ability to be even more efficient than ported enclosures. Yet there are many many variations of the bandpass aswell to suit your needs. Nearly all of the loud competition vehicles in the world now are using bandpass enclosures if they have the room.

I personally built a 6th order bandpass for my 97 explorer using a single 15" shocker extreme motor with atomic apx recone on it. Ran approximately 5000 watts rms to the sub using a memphis mojo 4kw amp at 0.7 ohms using 2 northstar nsb90 spl batteries and a 300 amp alternator for power. The bandpass was by far the most versatile enclosure Ive ever had in my truck. From 36-62 hz it was over 150 db at the dash on the termlab and peaked at 151.7 with minimal tuning and only the single amp. If I really tuned the enclosure for SPL and poured on the power Im sure I couldve broken into the 155s with it. But the goal if this build was a box that played music amazingly, not SPL. The downfall of the enclosure was its size however. Im fairly sure it was 40 wide X 28 deep X 18" tall. The port sizes and lengths are all a secret however but heres what it looked like...if you're serious about you're sound and have some time to experiment definitely try a bandpass...4th order is easier though (sealed firing into ported)

 

[Beastb15]

^^^ I won't even begin to get into ABC and transmission line boxes

 

[BigBoom]

that's actually not too big of a box. i was expecting bigger before i read the dimensions and saw the pics. i would love to try to do a 4th or 6th order bandpass for my 18's, but the trial and error that goes into it doesnt sit well with me lol since i'm not too familiar in designing them. it'd get expensive buying lots of wood . the size for my 18's would be big as well. i dont mind building a wall, but i wanna keep my back seats. maybe i'll look for someone to help me with one sometime. that's a really good score off of 1 15" too. did you design that box yourself?

and to stay on topic lol, here's some nice information from digital designs website:
Efficiency is the easiest one word reason for choosing ported over a sealed box. Everything is better with a little efficiency sprinkled on it. Ask any motor builder what they would do to a motor if it were theirs and they'd say turbo charge it! What does turbo charging do for an engine? It raises the efficiency. Why not apply this same thing to your audio system. Making the most out of the air space you have for a subwoofer enclosure, is the first step in raising the efficiency of your system. This means that you will utilize this space in the most efficient manner possible.

Designing a ported a.k.a. vented enclosure will not only give you added output, but can give you more low-frequency extension. This means louder and lower! Since the speaker system is the least efficient part of the whole audio chain, would it not make sense to make it as efficient as possible? Of coarse it does.

MORE SOUND, BETTER BASS
(back to top)

This is why venting is basically free output, and free sound quality. Local shops tell you that a small sealed box is the best way to go? Hit up your local hi-end home audio store and find out how many of those $20,000.00 pairs of speakers are sealed designs. You won't find many. Think efficiency as you read up in the DD tutorial section, this will help you clear all of that smoke out of your eyes that most car audio manufacturers have been pumping all along.

HOW DOES A PORT WORK
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Think of a box port not as a vent in the terms of a venting path for air to travel into and out of a box, but rather as extra cone area that is propagating acoustic energy from the enclosure to the cabin. The air in a port is fixed; it is trapped within the confines of the port walls. When the cone moves there is a corresponding change to the pressure in the box, that pressure change then causes the trapped air in the port to move either forward or backward. It moves as a solid unit, just like a speaker cone does. When you build a properly vented enclosure, its kind of like a two for one special! Since the port is essentially another woofer!

 

[aznboi3644]

port is just a resonating mass of air...not another subwoofer.

Subwoofers play all frequencies...around the tuning of a ported enclosure the majority of the sound comes from the port and not from the subwoofer.

Efficiency is one thing...but a main thing is the bandwith...with ported you can have high efficiency way down low between 20-30Hz...or tune higher and have high efficiency for SPL.

Hoffmans Iron Law basically