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<blockquote data-quote="PV Audio" data-source="post: 6514265" data-attributes="member: 554493"><p><strong>Continued from ABOVE</strong></p><p></p><p>The final considerations are the pipe diameter and where to put the woofer. In this case, you want the cross sectional area of the tube to be the radiating area, or Sd of your speaker. Why? Well, all that we're doing is taking whatever is coming off of the back wave, shifting its phase, and combining it with the front wave out front. You don't want anything bigger or smaller, as all you're trying to do is simulate having the backwave be another speaker that is in phase with what you already have. You can, if you want, taper from beginning to end starting with 1.5-2x Sd at the start and ending with Sd at the exit. You can also load the speaker with a slight chamber before it enters the tube, but that's up to you. What that does is creates an effective 1st order filter that again knocks down upper harmonic sounds as well. It's suggested by George Augspurger, a phenom in the field of TL design when he worked for JBL, that the volume of the chamber should only be about 1/3 of the total line volume. Most of these changes are either rules of thumbs or are subjective to the listener. To keep it simple, keep it uniform. //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif</p><p></p><p>For the location of the speaker in the tube, you've got a couple of choices. You can usually offset the speaker about 1/5 to 1/3 from the beginning of the tube if you want. The further away you move the speaker from the opening, however, the higher the rolloff frequency of the system. At 1/5 offset, that means you lose 20% of your bandwidth. While that might be desirable in some cases where the speaker has notorious breakup modes or simply poorly damped low frequency behavior, it usually isn't and you should put the cone at the beginning of the tube. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif</p><p></p><p>Well, that's about it! There's a fair bit more to TL theory than this, such as how to fold the tube, flaring it, tapering it, variations of the two, damping materials, stuffing density, and loads of other stuff that you really don't need to know to start designing your own TL. I hope this cleared TLs up! //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif</p><p></p><p>-Dave</p></blockquote><p></p>
[QUOTE="PV Audio, post: 6514265, member: 554493"] [B]Continued from ABOVE[/B] The final considerations are the pipe diameter and where to put the woofer. In this case, you want the cross sectional area of the tube to be the radiating area, or Sd of your speaker. Why? Well, all that we're doing is taking whatever is coming off of the back wave, shifting its phase, and combining it with the front wave out front. You don't want anything bigger or smaller, as all you're trying to do is simulate having the backwave be another speaker that is in phase with what you already have. You can, if you want, taper from beginning to end starting with 1.5-2x Sd at the start and ending with Sd at the exit. You can also load the speaker with a slight chamber before it enters the tube, but that's up to you. What that does is creates an effective 1st order filter that again knocks down upper harmonic sounds as well. It's suggested by George Augspurger, a phenom in the field of TL design when he worked for JBL, that the volume of the chamber should only be about 1/3 of the total line volume. Most of these changes are either rules of thumbs or are subjective to the listener. To keep it simple, keep it uniform. [IMG]//content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif[/IMG] For the location of the speaker in the tube, you've got a couple of choices. You can usually offset the speaker about 1/5 to 1/3 from the beginning of the tube if you want. The further away you move the speaker from the opening, however, the higher the rolloff frequency of the system. At 1/5 offset, that means you lose 20% of your bandwidth. While that might be desirable in some cases where the speaker has notorious breakup modes or simply poorly damped low frequency behavior, it usually isn't and you should put the cone at the beginning of the tube. [IMG]//content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif[/IMG] Well, that's about it! There's a fair bit more to TL theory than this, such as how to fold the tube, flaring it, tapering it, variations of the two, damping materials, stuffing density, and loads of other stuff that you really don't need to know to start designing your own TL. I hope this cleared TLs up! [IMG]//content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif[/IMG] -Dave [/QUOTE]
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