DNick454
10+ year member
Honda + Subs = Rattles :(
Basically, a transmission line enclosure is a ported box without the actual "volume". The sub fires direction into a long port. The port is tuned by making it a certain length. The most common is the quarter-length wave t-line.
Lets say you want to tune to 22Hz, the Fs of your woofer.
1. Take 1,130 (the speed of sound in Ft per second) and divide it by the tuning frequency you want, in this case, 22Hz. That gets you a length of 51.4 feet. Yeah... thats the FULL length of a 22Hz sine wave traveling through air.
2. No need to panic though, we're making a quarter wave t-line so you don't have to have a 51 foot long port:crazy: So divide that by 4. That gets you 12.8 feet of port for a 1/4 length t-line enclosure tuned to 22Hz.
3. So how big does the port area need to be? Well, it's supposed to be the size of the actual cone area. But you can get by with a little smaller. And ontop of that, a 8" woofer doesn't actually have 8" in diameter of cone. Including the surround and the gasket, the cone is closer to 7".
So 7/2=3.5
3.5 squared = 12.25
12.25*pie (mmm pie) = 38.465 sqaure inches.
38 square inches of port seem like alot for a single 8" driver, well yeah, but keep in mind there's no actual empty space used as a "volume" for the driver like a typical sealed or ported box.
More or less it's a giant long maze of a folded port.
Benefits: It will get loud off of VERY MINIMAL power. The driver has next to no resistance in a t-line enclosure since it is very free-breathing and unrestrictive. It also has a great transient response and doesn't drop off real quick like a typical low tuned ported enclosure.
