Design Theories: TL - Transmission Line
| TL - Transmission Line | |
| Basic Theory | |
| The driver is mounted in a type of acoustical labyrinth or long pipe commonly referred to as a transmission line. The length of this transmission line is usually somewhere between 4-8 feet and is dependent upon the Fs of the driver and the fill material used in the labyrinth. This t-line may have a tapered effect or maintain the same cross-sectional area throughout its length and may also contain various folds which help reduce the overall size of the enclosure. The length of the transmission line corresponds to the 1/4 wavelength of the resonant frequency of the driver. The t-line is almost always filled with various types of stuffing material which help reduce the speed of sound through the t-line allowing shorter line lengths while still achieving the proper tuning. For example, a transmission line for a given driver with an Fs of 25 Hz without any fill would need to be nearly three times longer than the same driver in a transmission line that was damped with 8kg/m^3 of wool. | |
| Advantages | |
| Transient response is considered equal to (and sometimes better than) a 2nd order sealed enclosure and is considered far superior to that of a vented enclosure. The cut-off rate is somewhat shallower than a typical sealed enclosure and may be as low as 10 dB/octave or lower. This results in improved deep bass performance. Less upper bass coloration due to reduced impedance peaks. A more pure, cleaner, and deeper bass. | |
| Disadvantages | |
| Difficult to design as well as build. A transmission line is every carpenter's nightmare. Extensive knowledge of wood working is required. Not all drivers will work well for a TL enclosures, yet there is no specific guideline for which drivers may work well. There are no concrete methods or formulas for designing TL's. It's mostly trial and error. Not recommended for the novice DIY'er. Enclosure size may be very large. | |
| Best Applications | |
| Where you've got a ton of room, a ton of time, and a ton of patience. TL's will work well basically wherever any of the other alignments would work. It's unique performance characteristics make it suitable for even the most serious audiophile. | |
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Source: www.danmarx.org
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