This week I’ll be talking about the two most common cabinet types: sealed and ported. Sealed is exactly as it sounds: a sealed box behind the driver. Ported is essentially a sealed box but with an open tube poking into the side. Remember, the cabinet behind the woofer only affects frequency response below 1kHz.
The pros of a sealed box is easy calculation and construction as well as delivering clean tight bass. They, however, don’t boost the sound level of the bass at all and are somewhat primitive, being one of the simplest of all enclosure types. Ported cabinets, however give a 3dB (essentially double the power) boost at a select frequency determined by the volume of the enclosure as well as the cross sectional area and length of the port. The port increases the volume at a particular frequency be basically resonating at that frequency in the same way a bottle resonates when you blow over it. People use this property to extend the bass response as seen in the graph below. The downsides of having a ported box is that they are physically larger than a sealed box and if designed incorrectly can easily produce a “boomy” rather than a tight bass.
One of the most egregious errors I see is when people drop any one woofer into any old box and slap it into a car. While still producing a ton of bass, the system will not perform anywhere close to as it could if everything was optimally designed. To determine the volume and port length of these enclosures, many online calculators are freely available and easy to use:
http://www.diyaudioandvideo.com/Calculator/Box/
Lastly, it’s important to note that not all drivers are suitable for a sealed enclosure and not all drivers are suitable for a ported enclosure. In order to behave predictably and perform well, they have to have a suitable EBP (see previous post). An EBP of between 0 and 50 will really only work in a sealed box and an EBP above 90 will really only work in a ported box (between these values can be either). Here’s an online calculator to figure out your EBP:
http://www.diyaudioandvideo.com/Calculator/SealedPorted/
Ported is by far the most common enclosure type on the market today; from cars to computer speakers to hometheatre systems to just about everything. They are pretty easy to design and they give some of the most satisfying results for effort put in.
hearthstone Decks reddit
Sealed/Ported Cabinet | Speaker Design
WOW! This is incredible Brian, although I don’t know much about speakers, this is truly impressive. Also, it is so neat to see the pictures of your progress, I am very interested to see how everything works out for you!
-Sarabeth