Has anyone here built a transmission line sub enclosure? I posted a forum about houseboat subwoofers asking for something extremely loud. I actually soke with a JL rep and he gave me the specs for what he thought would be the loudest out in the open on top of the boat, its pretty loud but still has that bandpass sound to it. I built a 5th order bandpass sub box for 2 JL 15 W3's and it does pretty good but Im still looking for something more. I was hoping that I could build a tml box and be just as loud or louder and have a better frequency range and tonal quality. I looked through all the google searches and couldnt find any formulas on calculating line length, box size, air space etc. (atleast that I could understand). So can anyone give me some basic or extensive guidelines on designing/building them? I have a general knowledge on tml's (elementary though).Thanks in advance!

How about an infinite-baffle design? This could allow for bass both inside and outside the cabin.

Are you referring to mounting a sub to the deck of the boat and having both sides of the woofer exposed, Inside and out? I dont think this guy would be to keen on me cutting a large diameter hole in the deck of his 500k boat. Besides that, wouldnt I get better output from some type of an encosure? Thanks

This message was edited by DIRTE on 05/05/05 20:39 ET.

As you know opinions are like...well you know, everyone has one. Mine happens to be that transmission line designed speaker enclosures provide the most accurate reproduction of music (I don't know if I would personally persue a transmission line design enclosure for HT use, but you can always give it a shot) , but 1st you need the right driver, because not all drivers will work well in a transmission line enclosure, 2nd to get the box right for the driver it is a lot of trial and error, and it does not matter what box program you use, you can get close, but you still have to tune it "manually" no software (I.E. LEAP software) can get you "there". Choosing the design is also important, because their is no "one" transmission line design. I have a pair of transmission line designed speakers and love them very much, but as my "handle" says...Mr2Channel...I love music, and that is what I wanted them for...10" peerless woofer, 7 1/2" focal mid, and a Seas 400 tweeter, box built by a friend, and crossovers tweaked by Albert Von Schweikert himself....musical bliss to say the least(and yes I still have a turntable...). Here are a few links if you want to look into T-Line designs...

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

[Link: quarter-wave.com]

[Link: quarter-wave.com] this one should keep you busy for a while...

you will want one of these...

[Link: speakerbuilding.com]

[Link: linearx.com]

http://www.speakerbuilding.com/

Have fun with it, its alot of work, but worth it if you have the time to get it right!

my .02

Larry was kidding(I hope?!)

Basically, bandpass enclosures sound like crap!
From a 'musical' standpoint, anyway.
They are good for getting a peak output at the frequency that you set the port tuning at!
The frequency cuttoffs above and below the port frequencys can leave a lot of holes in general. Kind of like what Bose does!

THATS why I suggested a slot ported ,down firing enclosure for outdoor use.

By using a 'slot' port(a rectangular port with the same area as a round port) you won't get the port noise associated with a tube. You still get the 'boost' at the selected frquency and it's louder with less power.

By 'firing' it into the floor(I assume the 'outside' doesn't have a connecting wall to bounce off of!) You gain 3db output verses firing it out into the air!

Actually a transmission line requires surrounding walls to produce the same effect!

Low frequencies take a few feet(8 to 14) to produce the 'low end' that we perceive as bass! The more that you can 'bounce' it off of something, the better that it will sound!

A transmission line woofer produces accurate base, is very large(do to the required feet to produce a low frequency) And requires a TON of trial and error!
Nothing like building 5 or 6 enclosures, at the cost of 12 sheets of MDF, not counting labor, to get it CLOSE!

Trust me on this!

Been there, tried that!

DIRTE
As an experiment , try this;
Take your enclosure, support it off of the floor with a 2Xby(down firing) and check the output.

Now, imagine that it will produce ALL low end frequincys at the same level!

With the JL 15W3's, make the port about 35 to 45HZ, depending on the class of music the client listens to!
Keep in mind that everything below the port frequency will cause the woofer to 'unload'(flap hopelessly in the wind!)

Yes, I was.

I am with pilgram here. I have built boxes for open air jeeps and range rovers. One box I built for an open air jeep was so loud it cracked the front winshield and it you could hear it loud from over a quarter mile away. It was so loud it hurt your head not just your ears.

Any way I am talking insanely loud here. Louder than insane!

Oh yeah, and for those open air situations I would use a slotted box design where the woofers are in seperate sealed boxes all firing into a common slot that is about 3 inches tall in front of the woofer. The closer the woofers edge is to the edge of the front of the slot use a tighter slot. Like if the woofers are right up to the edge of the slot I would use a 1.75" slot about.

Also, if you can, make the baffle out of 2 pieces of .75" MDF instead of 1 or just add supports to right behind the woofer hole.

For the woofers you mentioned I would chose a sealed box at the middle range of recommended box sizes. seal off all edges of the slot except one.

I would actually consider lining up the two subs so they fire through a single slot opening that measures 15" wide by 3" tall. That is where all of the sound comes out of. The woofers should be in seperate or a single sealed enclosure with the cones firing towards the slot.

Depending on your amplifier, I would wire the woofers in parallel. You can series the Dual Voice Coils or Parallel them if your amp and alternator can handle 1 ohm mono loads.

So yeah, I looked at the info sheet and they say they want 2.125 cu ft sealed. I would do that per speaker both firing into a slot that has internal demensions of 3" tall x 16" wide x 40" or so long. The slot opening would be 3" x 16".

Then do it twice so you have 4 subs.

This message was edited by currentsupply on 05/06/05 14:18 ET.