Sealed Versus Ported
07-22-2004, 10:20 PM
#1
0 Watt CAFz'r
Thread Starter
Join Date: Jul 2004
Posts: 2
Our new Audio Answers is up on our website and we hope you find it useful. we will feature a new topic each week, below is our first article.
Hey all,
With this being my first article for this website, I have decided to touch base on a simple topic that a lot of enthusiasts don't completely understand..the ported vs. sealed misconception. Lots of enthusiasts argue the benefits of each every day, but they do so with uneducated facts. Here I won't give the advantages and disadvantages of each, rather just give facts as to what each does. This way one can draw their own conclusions as to which they would rather use.
For those who don't know what these are, here is a little refresher. The two most common enclosure types that are used in audio systems are ported (or vented) and sealed (or air-suspension or acoustic-suspension). A sealed enclosure is simply that where the entire enclosure is airtight, with no vents or holes of any kind. This is what you will commonly see people using, as they have not built their own and are using a pre-fabricated box. Sealed enclosures tightly regulate the suspension of the woofer, as the air inside the box is always trying to equal its pressure to that of the atmosphere.
Typically, the bigger the enclosure is, more low-end output is produced at the expense of the amount of power that can be allocated to the woofer. The larger box limits throw less, and excursion is increased. This results in an overall lower box Qtc (Q quotient), which is a more advanced topic I will discuss later.
The smaller a sealed enclosure is, the more controlled the woofer's stroke is. Driver excursion is limited, and response is generally more punchy. Because of this limit in excursion, more power can safely be allocated to the woofer through means of an amplifier.
A ported enclosure is that which is "tuned" to a specific frequency within the frequency range. This tune usually ranges anywhere from 25 Hz all the way up to 50 Hz, which is the optimal range for producing bass. This tuning is accomplished by means of a port, which acts as a bass reflex to amplify the sound produced. This port utilizes the rear sound waves that come out of the back of the subwoofer, thus effectively increasing output, among other things.
This kind of enclosure is tuned by adjusting the dimensions of the port in relation to the internal net volume of air inside the box. This change is affecting the way the port resists motion, thus tuning the box. Tuning a box in this way however, does limit the frequency range where the most output can be achieved. When the factors are put together, the rear waves from the subwoofer are delayed so that the front waves and the port waves are constructive and compliment each other.
Designing a useful ported enclosure is much more complicated than a sealed, so making one is usually only for experienced enthusiasts who have calculated the factors correctly. However, doing so can cause a large increase in output over the main frequency range of bass, usually 3-6 decibels.
Some people like to claim that one enclosure type is better than the other, but this is just not true. Both have their ups and downs and in-betweens.
For questions for Audio Answers email audioanswers@mycarjams.com
www.mycarjams.com
Hey all,
With this being my first article for this website, I have decided to touch base on a simple topic that a lot of enthusiasts don't completely understand..the ported vs. sealed misconception. Lots of enthusiasts argue the benefits of each every day, but they do so with uneducated facts. Here I won't give the advantages and disadvantages of each, rather just give facts as to what each does. This way one can draw their own conclusions as to which they would rather use.
For those who don't know what these are, here is a little refresher. The two most common enclosure types that are used in audio systems are ported (or vented) and sealed (or air-suspension or acoustic-suspension). A sealed enclosure is simply that where the entire enclosure is airtight, with no vents or holes of any kind. This is what you will commonly see people using, as they have not built their own and are using a pre-fabricated box. Sealed enclosures tightly regulate the suspension of the woofer, as the air inside the box is always trying to equal its pressure to that of the atmosphere.
Typically, the bigger the enclosure is, more low-end output is produced at the expense of the amount of power that can be allocated to the woofer. The larger box limits throw less, and excursion is increased. This results in an overall lower box Qtc (Q quotient), which is a more advanced topic I will discuss later.
The smaller a sealed enclosure is, the more controlled the woofer's stroke is. Driver excursion is limited, and response is generally more punchy. Because of this limit in excursion, more power can safely be allocated to the woofer through means of an amplifier.
A ported enclosure is that which is "tuned" to a specific frequency within the frequency range. This tune usually ranges anywhere from 25 Hz all the way up to 50 Hz, which is the optimal range for producing bass. This tuning is accomplished by means of a port, which acts as a bass reflex to amplify the sound produced. This port utilizes the rear sound waves that come out of the back of the subwoofer, thus effectively increasing output, among other things.
This kind of enclosure is tuned by adjusting the dimensions of the port in relation to the internal net volume of air inside the box. This change is affecting the way the port resists motion, thus tuning the box. Tuning a box in this way however, does limit the frequency range where the most output can be achieved. When the factors are put together, the rear waves from the subwoofer are delayed so that the front waves and the port waves are constructive and compliment each other.
Designing a useful ported enclosure is much more complicated than a sealed, so making one is usually only for experienced enthusiasts who have calculated the factors correctly. However, doing so can cause a large increase in output over the main frequency range of bass, usually 3-6 decibels.
Some people like to claim that one enclosure type is better than the other, but this is just not true. Both have their ups and downs and in-betweens.
For questions for Audio Answers email audioanswers@mycarjams.com
www.mycarjams.com
07-23-2004, 10:31 AM
#5
I thought that a port could give a maximum of 3db gain at tuning (rear wave can only meet at 90 degrees out or less -right ?)
I don't see an increase in effecieny with a larger box as an 'expense' to powerhandeling... unless you like power compression that is.... [img]tongue.gif[/img]
There was also no mention of increased thermal powerhandeling with larger/ported boxes....
I don't see an increase in effecieny with a larger box as an 'expense' to powerhandeling... unless you like power compression that is.... [img]tongue.gif[/img]
There was also no mention of increased thermal powerhandeling with larger/ported boxes....
07-23-2004, 12:46 PM
#6
Guest
Posts: n/a
^ We did some testing the other day in a car - the dude got over 4db "free" by adding a vent to his sealed enclosure (total misalignment too) [img]graemlins/thumb.gif[/img] We expect more once the enclosure is rebuilt specifically to the vented specs.
Man - a guy expresses an opinion on a topic and people pigeonhole him..
And technically the article there explains how both enclosures work but not the benefits and drawbacks of each [img]graemlins/dunno.gif[/img]
This is really a simple subject though: Vented kicks total ***. See? Simple. [img]graemlins/headbang.gif[/img]
Oh yeah - welcome to CCA dude!
Man - a guy expresses an opinion on a topic and people pigeonhole him..
And technically the article there explains how both enclosures work but not the benefits and drawbacks of each [img]graemlins/dunno.gif[/img]
This is really a simple subject though: Vented kicks total ***. See? Simple. [img]graemlins/headbang.gif[/img]
Oh yeah - welcome to CCA dude!
07-23-2004, 10:13 PM
#7
Goalie Man
Join Date: May 2003
Posts: 1,412
ok paul dont want an argument or even a rebuttle. iam very glad that you are an avid ported box design guy, but if you go to iascas or usaci web pages and count the number of sq cars with ported boxes as opposed to sealed, i think you will see that the difference is overwhelming sealed 79% vs ported 18% dont even ask why its not 100% there must have been one or two free air designs, or heavens forbid even a bandpass box. my point is ported designs are, without question, louder and can sound even resonably good in a car, but ported boxes have there place and its not in the small confines of a vehicle, now in a home or stadium, yah ported all the way. a good guy to talk to is doug gilroy . this guy is wicked smart and tought me tons.
07-24-2004, 12:03 AM
#8
^ So I understand you are dominating the "circuit" in USAC with your fantabulous Civic according to your Carsound posts. Strange though, I have yet to see it at all of the 2 shows that were around here. Got some pics? Maybe I missed it among the other Civics out there with a deck and 4 and a prefab box [img]graemlins/dunno.gif[/img]
07-24-2004, 08:51 AM
#10
Guest
Posts: n/a
Bandpass boxes have their application, and they can work very well if designed correctly.
Sealed boxes are ok if you have no space and a lot of power. Otherwise I don't see the point of crippling your system with the inferior performance they deliver [img]graemlins/dunno.gif[/img]
Sealed boxes are ok if you have no space and a lot of power. Otherwise I don't see the point of crippling your system with the inferior performance they deliver [img]graemlins/dunno.gif[/img]
