transmission line sub

Huh... :) (More on this comment later, but time doesn't allow at this moment.)It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

About the power handling...the rated power is basically cut in half...In a transmission line there isn't really much of a chamber behind the sub...just a column of air. In a TL the sub is basically IB/free air. The enclosure doesn't really do much to control the excursion...pretty much the only parts controlling the sub is the soft parts...basically the spider and the surround.

haemphyst wrote: Huh... :)

I said that because those are pretty close to the numbers I have always used for my TLs. 100 to 150% of Sd tapering to a terminus of around 50% of Sd.

aznboi3644 wrote: About the power handling...the rated power is basically cut in half...In a transmission line there isn't really much of a chamber behind the sub...just a column of air. In a TL the sub is basically IB/free air. The enclosure doesn't really do much to control the excursion...pretty much the only parts controlling the sub is the soft parts...basically the spider and the surround.

Not true at all. BELOW RESONANCE, it is, but that is true with ANY vented enclosure. The air in the line does just as much damping of the cone as does a sealed enclosure. I feed 1kW into mine, and the system is only rated 700 watts (and that's only because there are two woofers...) In a straight line, as I have seen you build, it DEFINITELY becomes significantly more difficult to control the driver's excursion.It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

ic...thanks for the clarification haem

Yep, haemphyst is right. The mass of air plus the restriction caused by the small'ish opening and and polyfill is enough to dampen the woofer. Below the resonant frequency the woofer will "unload" and like you say, only be restricted by the surround and spider materials. This is why I was so keen on choosing an amplifier with a subsonic filter just below my resonant frequency. And haemphyst, you seem to like the 3:1 ratios hmm? Sounds good to me! -JustinMalcom: "This is the captain. We have a...little problem with our engine sequence, so we may experience some slight turbulence and then...explode."

Jayne: "We're gonna explode? I don't wanna explode.

teenkertoy wrote: And haemphyst, you seem to like the 3:1 ratios hmm? Sounds good to me!

I'm actually building (or in the progress of) a TL for my car.  I'm actually going to be using about a 3 to 1 ratio as well.

It looks like you have a bit more work in the design of your TL.  Mine was not designed with the worksheet at all.  Hope yours turn out well.  I'd like to see pics when your done.  I know I'll hopefully be posting some pics when I'm done with mine as well.

Step the seventh: build enclosure striving for production quality Using excel, for no other reason than convenience, I began the layout of the enclosure. The picture is the internal dimensions, and each square is one inch. The blue line is the audio path, which came out to nearly 120" as planned. The height of the box internally is 10.5", just a bit larger than the woofer itself. Should be a tight fit! Home Depot was nice enough to cut the wood for me, but I would later find out their saw is not square, curses! Here the box is assembled and glued together, but the top will not fit because none of the top edges are square and will result in massive air leakage. A belt sander and a little while later though, everything was flush and ready to get the top glued on. I added some polyfill at this point, to get a constant density of 0.25 lb/ft^3. There is some screen door fabric inside the line to keep the fiber from spilling out the end. There are a dozen screws along the top surface that helped sandwich it and the vertical pieces together despite all the sanding. I knew it wouldn't be absolutely perfect and wanted to make sure it was touching on all surfaces. The salt and pepper carpet not only hides the screws but also make the box look like a real enclosure, I'm starting to become giddy at this point! Here's a tip for rolling the carpet over the edge and forming a tight inside corner, like in the photo: use a tool with a wheel on the end. I used one designed for tucking in the rubber rings on screen windows, and it made all the difference in the world. The carpet is coming along nicely, except I don't know how to make the seam where two edges meet look decent. The best I can do is put the seam on the bottom of the box. It's clearly visible in the photo, but doesn't look bad once it's turned over. She's done! She's also a bit overweight and I need help to move her haha. I can't help but notice the big empty space between the terminus and the woofer. I'd love to put a big Infinity logo there, but not sure exactly how to make one. Or maybe some abstract art, I'm just not sure. Oh well, a project for another day. Also, the amplifier arrived in the mail today. It was a steal! The guy selling it posted pictures with moderate "scratches" all over the face and sides. Turns out these are simply sticky gunk and cleaned off easily. Not that it matters though, since it'll be under my back seat and out of view. -JustinMalcom: "This is the captain. We have a...little problem with our engine sequence, so we may experience some slight turbulence and then...explode."

Jayne: "We're gonna explode? I don't wanna explode.

whiterob wrote: I'm actually building (or in the progress of) a TL for my car. I'm actually going to be using about a 3 to 1 ratio as well. It looks like you have a bit more work in the design of your TL. Mine was not designed with the worksheet at all. Hope yours turn out well. I'd like to see pics when your done. I know I'll hopefully be posting some pics when I'm done with mine as well.

Sweet! Please let me know when you get some photos posted. I'm really curious to learn which woofer and amp you chose too. It'll be fun to compare builds and results. -JustinMalcom: "This is the captain. We have a...little problem with our engine sequence, so we may experience some slight turbulence and then...explode."

Jayne: "We're gonna explode? I don't wanna explode.

   teenkertoy an infinity raised letter logo is simple, before carpeting the panel lay dynamat on the panel. Next get an infinity sticker-the size you want-  and stick that to the dynamat, then with an olfa knife carefully cut along the outline of the sticker going through the dynamat... peel excess dynamat off and cover. The best way i have found to do it................. vinyl and suede requires one layer of dynamat , but carpet is thicker so i put two layers of dynamat.  ....nice thread and nice box 

I'm excited FOR you, except I aim more towards .5 pounds per cubic foot... I think your Fs is going to be a bit higher than planned with that light a stuffing density. Until you know the results, be careful of unloading... It might happen higher than expected. I also stuff heavier toward the woofer, and taper the density toward the terminus end, and AVERAGE .5 pounds per cube, throughout the enclosure. (The way I would approach this would be (with your enclosure - with 4 sections) .75 for the first section, .5 for the second, .25 for the third, and nothing in the 4th...) This seems to offer the best overall response, with the best smoothing on the output. I can only thing that any minute turbulences (wind noises, if you will) induced by the stuffing isn't quite so audible with this method. Yes, I have found the 1:3 ratio really works well. I have also found that adding a few thin dowels across the line helps quite a bit in preventing stuffing "sag", but generally speaking, it's NOT a huge issue with poly-fill. Acousta-Stuff can settle a little bit, and benefits from this treatment. Long-fiber wool DEFINITELY needs the dowels, but LFW will also provide the BEST results acoustically speaking, at the greatest expense. That XA1000 is gonna be a perfect match, I'm thinking! VERY NICE WORK!!! I might be in SJ this weekend! I'll keep you posted! (And seeing yours, I may just be rebuilding mine, soon... Thanks. (Be sure you get the sarcasm there...)) 3 feet square, huh? My first one was that big; built for two Infinity Pro-12's, heavily stuffed, and damped with 300 pounds of sand! LOL Don't talk to ME about "overweight"! I like the idea of the Dynamat under the carpet... Very slick, boogeyman!It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."