Anybody built a transmission line subwoofer?

So, besides cars, I've been into home theater for a long time. My home theater is ever changing, always has been, always will. My next HT project is to build my next iteration of my subwoofers. I had one HUGE cabinet in the past, that gave way to a smaller one that housed the dedicated amp. Then I upgraded the amp, and separated out the drivers into two independent sub boxes. Now, I'm going to dabble in the scary realm of building my own transmission line boxes. I currently have 4 10", and 1 12" driver to play with. I'm thinking about possibly building one cabinet that houses two of the 10s, one side would be a transmission line tuned to about 25-30 Hz, the other in a sealed box tuned to somewhere north of that, not sure about that though.
Anyway, has anyone here built a T-line box before? Any thoughts?

I built my first set of speakers when I was 15. I've built sub boxes before, but not what you're talking about.

Make sure you do a build thread, I'd really like to see what you come up with.

can't say that i've done what you are looking to do, but i can say that a 15" Rockford Fosgate sub in a big sealed box sounds really cool when you plug it into a wall outlet... for a little while..

Watching.

Me too. I like big noise.

i dunno wtf you guys are talking about. the first thing that popped into my head was building a speaker out of 5/16 steel hard line. darn kids and your noise boxes.

I haven't found the formulas easy to come by, but they look to be an interesting project. Use some mad tyte Googlefoo and you should find your answer....

Parts-Express' forums might be some help.
http://techtalk.parts-express.com/

I've built transmission lines, and experimented with higher density abbreviated lines. There are some good online resources, but I still have some excellent general info, some from old copies of speaker builder magazine. You just can't beat a transmission line for incredible, effortless, boom free bass.

patgizz wrote: i dunno wtf you guys are talking about. the first thing that popped into my head was building a speaker out of 5/16 steel hard line. darn kids and your noise boxes.

I had a roommate who did all sorts of crazy E36 M3 with electrical stuff and speakers. At one point he bought a hearse and ten 12" subs to put in it, and he did subsonic experiments with this 24" sub that he got from who knows where. On the electrical side, he did a lot of stuff with 5/16 tube, making Tesla coils and other things that made my computer equipment go haywire.

If you look on YouTube, you can find people playing music with Tesla coils.

I did a little reading last night. Those look very interesting. Build it, make a thread.

Toyman01 wrote: I did a little reading last night. Those look very interesting. Build it, make a thread.

I've been interested in them for years, since I had a Fried Model F t-line sub. I think this is a winter project for sure.
The thought of being able to roll down to below 20Hz with none of the port noise associated with ported boxes is very attractive. Then there's the tuneability with stuffing....

Knurled wrote: If you look on YouTube, you can find people playing music with Tesla coils.

I have a friend who does this. He didn't build the coils, but he did compose the music as well as did some of the engineering work on the Continuum Controller he's using to play the coils.

https://www.youtube.com/watch?v=uYi6vUsEl4c

In reply to DrBoost:

My sub smoked the amp a couple of months ago and always did sound like crap, so building something is tempting. I've got a 10", two 12" and a 18" driver floating around here, but the boxes for them are huge. Can a t-line sub be smaller than a conventional sub of is it larger? Have you found any resources for figuring box sizes? The couple of books I have don't cover them.

Worth the watch.

https://www.youtube.com/watch?v=J6WDVeS10Eg

Edit: Here's part one.

https://www.youtube.com/watch?v=pF7N8u9u3rc

And a link to the paper he used in his design.

http://www.t-linespeakers.org/design/classic.html

EDIT: I see Toyman beat me to it.

http://www.quarter-wave.com/

http://www.t-linespeakers.org/

http://www.t-linespeakers.org/projects/links.html

These are good resources. Try not to over think the build, and be prepared to do a little tuning. The cabinet dimensions are not cast in stone, and there is some flexibility. I've had very good luck lining the front part of the cabinet with the pressed fiberglass 2' x 4' ceiling panels with the vinyl peeled off, and (although it's not supposed to work) loosely stuffing with fiberglass insulation. As far as the driver is concerned, I've had the best luck with higher Q's, in the .4 range, large surface areas (for the size), and decent Xmax. Lower Q's will work, but I would steer clear of anything lower than .3.

Thanks Zomby and Toyo for the links. I know there are no set-in-stone formulas, but the tunimg with batting makes it seem like it'd be fun.

It's starting to come back to me now. Start keeping an eye out for carded wool, and high quality polyester fill. The softer and fluffier the better. Both work far better than fibreglass which is a reactive, rather than a resistive fill.

Every time somebody talks about speakers I start looking at building a new project, then realize that I have enough parts accumulated (because of the fore mentioned) to keep me busy for a few years.

So I've been doing lots of reading and searching. It's kind of a black, or maybe grey art, this T-line designing stuff. Do you taper, do you fill, how much fill, where, etc.? But I have a decent understanding, enough to kick off the early design phase at least. If it's too big, it'll blow the W.A.F. to smitherines. W.A.F. is wife approval factor, one of the most critical parameters of speaker building (and project car aquisition) there is. I think I'm going to tune the t-line for somewhere south of 35 Hz so it'll reach down to stupid low frequencies. If it doesn't extend high enough, I'll build a 10 or 12 cabinet to fill in the upper low-end.

You have my attention.. build thread?

Yeah, I'm going to do a build thread for sure. I don't expect it'll be before the end of the year though.

Just a little update. I've been researching this a little here and a little there. I mentioned to my wife that I was going to build a new sub and that I might just make it replace the current TV stand. She liked that idea, but morphed it into building an entire built-in wall unit entertainment center thing.
So, it'll be a few phases. I'll do the sub and the lower cabinets at one time, the the upper cabinets/book shelves a few weeks later.
I have an idea of how long the line needs to be, and have a series of formulas that I think will help me chase the elusive interior volume/line length number.
When I build it, I'll start a build thread.

I just built a big sealed box for the parts express reference 18" driver, painted it black, and plopped it in our living room. Wife said "that looks cool!"

I got lucky with this one :D

Still have no idea what you guys are talking about. All I can picture is a speaker built into the transmission lines on a car.

FWIW, my Mazda has a subwoofer built into the spare tire. Yup. The spare tire.

I had to look up what a transmission line subwoofer was too. I had it confused with Near Field Line Arrays. Now I am thinking it would be cool to make an array with subwoofers...