Test & measurement
Ever wondered why some speakers have a vent tube and some do not? Compared to closed-box speakers, which are almost airtight, bassreflex systems have an opening knows as a port or vent that is cut into the cabinet and mostly fille Show more
Ever wondered why some speakers have a vent tube and some do not? Compared to closed-box speakers, which are almost airtight, bassreflex systems have an opening knows as a port or vent that is cut into the cabinet and mostly filled with a bassreflex port tube. A bassreflex port is a tube that incorporates a port or vent into a so-called vented speaker. As opposed to a standard sealed- or closed-box speaker or an infinite baffle mounting, this port allows the sound from the backside of the diaphragm to maximize the system's performance at low frequencies. Here at SoundImports, you can buy bassreflex port tubes from our premium brands Goldwood, Monacor and Precision Sound!
Yes, keep in mind that there are two factors to consider when choosing the dimensions of the port to obtain a specific resonance frequency: the mass of the air inside the port and the compliance. You do not just pick any parameters for radius and length to reach the desired volume if the port needs to have 2l of capacity. It is necessary to consider compliance. Because air passes with less restriction through a large port, it is more compliant. This means that the port must be long enough to meet the compliance requirements. A small port, on the other hand, is less compliant and does not need to be as long. As a result, the port's radius and length are intertwined and must be matched appropriately to achieve the intended result.
There are some criteria you should consider when installing a bassreflex port tube. In general, one can say that the most excellent acoustic coupling is achieved when the bassreflex port is placed on the same side as the woofer. If this is no option, installing ports on the back or the side of the cabinet are perfect alternatives. However, it is recommended not to block the opening of any installed port. For the best performance, you should keep the bassreflex port tube one port diameter away from the sides and the back of the enclosure.
Nevertheless, it is essential to mention that the diameter of the opening of the port tube, the flange diameter and the length of the port tube itself are even more relevant than its instalment position. The size of your bassreflex port tube is easily calculatable, and you find the most common sizes here in our assortment!
Got a taste for it and feel like a new DIY project to install some bassreflex port tubes yourself? Check out our high-quality DIY-kits!