TLine for 15" lvl 2.

[95Honda 486]

A T-line is exactly that. It is a line. Not a box, not a chamber, not a port. It is a line.

[Adrian_D 520]

Both look like ported boxes...

[3stagevtec 2]

A T-line is exactly that. It is a line. Not a box, not a chamber, not a port. It is a line.

the pic i posted above, with the RF sub.. will you consider that a line??

the builder kept the volume of the 'line' the same throughout its length.. he even accounted for the displacement of the driver in his design..

[Duke 0]

A T-line is exactly that. It is a line. Not a box, not a chamber, not a port. It is a line.

Yeah, thats true. There are alot of variations of T-Lines though... the chambered T-Line being one of them.

Yeah Adrian, it looks like a ported box as said many times before. Its not a "ported" box though.

[Duke 0]

A T-line is exactly that. It is a line. Not a box, not a chamber, not a port. It is a line.

the pic i posted above, with the RF sub.. will you consider that a line??

the builder kept the volume of the 'line' the same throughout its length.. he even accounted for the displacement of the driver in his design..

No he wouldn't consider that a line. Mine is very similar. Yours has a longer line length it appears and thats about it. They both have chambers. I don't understand the logic behind how they're thinking here. Its not hard to accept that there are different variations of DIFFERENT enclosures in existence. My box, and yours too probably, does not use a set volume of air, or a set surface area of port per cubic foot, or a standard "ported" tuning frequency. Mine was designed using various specs from the sub, and wavelength considerations/transmission line theories.

[95Honda 486]

A T-line assumes there is no chamber behind the driver, that is why round T-lines behave most predicably.

If you have a chamber, and then a hemolitz resonator attached to the chamber, it is a ported box.

T-line gets thrown around in car audio all the time. Just about everything described is in fact not though....

Don't get bent over it, it's just the way it is. Call it something else if you want, just don't call it a T-line, because it isn't one....

[Duke 0]

You're misunderstanding what I'm saying here. Yes, round T-Lines made with say, the sonotube stuff, are the direct definition of a T-Line. This box I have made is a variation of a T-Line using the same principles as a non chambered straight T-Line. This is not a bass reflex box, so I'm not going to call it one. Its a variation of a transmission line. Car audio T-Lines exist and they generally are designed to get the rear wave closer in phase with the front wave. I didn't just throw in a random volume of air for the chamber, random port area, and low tuned length... which is what most people tend to do. This box does not behave like a ported at all either. The woofer does not unload like crazy like it would if I threw it in say, 4 cubes/30hz. The output stays high down to the lowest common musical content and the excursion doesn't get out of hand. This box is designed around average wavelengths, the length from the port to the headrest, and a few T/S parameters. I'll refer to it as a wave box from now on...

Edited February 22, 2009 by Duke

[aznboi3644 2]

A T-line assumes there is no chamber behind the driver, that is why round T-lines behave most predicably.

If you have a chamber, and then a hemolitz resonator attached to the chamber, it is a ported box.

T-line gets thrown around in car audio all the time. Just about everything described is in fact not though....

Don't get bent over it, it's just the way it is. Call it something else if you want, just don't call it a T-line, because it isn't one....

dude you still don't get that this is a MLTL...if you really know anything about t-lines its called a MASS LOADED TRANSMISSION LINE...people have been building these for years. Its still a transmission line variant.

Don't get bent over it though...thats just the way things are. Call it a ported box is you want...but its a chambered t-line, mass loaded transmission line, or MLTL for short...just don't call it a ported box....because it isn't just a ported enclosure.

[SPLChris 0]

Kind of ironic that you made one of those, I had plans for a box with 1/4 wavelength "port." How did you figure how large to make the compressoin chamber?

[germandark 0]

this is interesting. flaming!

[Quentin Jarrell 671]

This is a side view of a quartewave transmission line enclosure. It has a compression chamber equal to the drivers' dispalcement to help flatten the response curve below the tuning of the enclosure. Normally a compression chamber is only used when the woofer has a weak motor and supension compared to the moving mass of the woofer. The throat is 1.5 the effective piston area of the woofers to get a db boost around the tuning frequency. Most home systems use a ratio of 1.7 to get a flatter curve. The line itself is 1/4 of (the speed of sound divided by the desired tuning frequency). Not 1/4 the wavelength of the desired tuning frequency itself. So if you wanted the box tuned to 35 hertz the line would need to be 8 feet not 8.75 feet. This is done so the rear sound from the sub is time aligned with the sound coming from the front of woofer at the desired tuning frequency.

And yes there are many types of hybrid transmission line enclosures because would be nearly impossible to stick a 8 to 10 foot long pipe in most people's living rooms. That is why we have folded designs.

[Duke 0]

Hey dude, thats an awesome box and some nice information! You got more pics? These two sentences are confusing me however. "The line itself is 1/4 of (the speed of sound divided by the desired tuning frequency). Not 1/4 the wavelength of the desired tuning frequency itself."

Here is the second box since the first one was a success.

Second box. The other piece of the port is also drying, just didn't take a fudgeing picture of it.

The first box in teh Assrango. Notice the imaginary line in pic 2... a glare off something?

Right at the window line.

Perkins.

[SPLChris 0]

So....the compression chamber isn't really necessary if the sub has a strong motor? But how do you find out how large to make the chamber anyways?

Duke, are those second enclosures line length the same as the first? What's the port area?

[Quentin Jarrell 671]

So....the compression chamber isn't really necessary if the sub has a strong motor? But how do you find out how large to make the chamber anyways?

Duke, are those second enclosures line length the same as the first? What's the port area?

Correct you don't need acompression chamber. It just helps woofer stay "tight" at high excursion by creating back pressure. Calculating the chamber is complicated. There is a lot of Trig and calculus involved. Normally, volume equal to the Qts of the sub is sufficent. But if you have a decent sub it is not needed.

What I attempted to explain about the length is: the port is equal the time is takes the desired sound wave to travel to the end of the port (or mounth). Not equal to the hertz itself.

So for 35 hertz it would be: 1108 feet/second divided by 35 cycles/second = 31.657 feet And because you will not fit a 31 foot long port in you house, or car for that matter you can divide it by 4 which will make the rear wave 90 degrees in phase with the woofer's front wave. It's not as efficient as a full transmission line but it will result in a lot more output thana regular ported enclosure.

I don't know everything about t-lines but I have built at least a hundred of them. And have figured most of it out by trial and error.

[SPLChris 0]

You're saying that a well designed TL will have more output than a bass reflex enclosure? Just want to make sure because I've always read mixed reviews before I started making sawdust. I have plans lying around for an expanding TL except I used a 2:1 throat area (throat area was half of the total Sd) and the mouth was as big as I could make it. I'll have to build that after I finish my 4th order BP

Sorry for the thread jack, this is just such an informative post.

[Duke 0]

I really don't want to divulge any of my methods as they may or may not work for someone else/another woofer. I'm really at noob status when it comes to designing enclosures, although this particular design worked as I had hoped, and then some.

Audibel Customs, anything else you can tell me about the chamber would be greatly appreciated as woofer cone control is high on my list but information is very scarce on this subject.

No worries about thread jacking here... I posted pictures of the enclosure, so that about completes my reason for this thread anyways... however, if we can get a bunch of useful info going in here about T-Lines and what not, thats cool.

[Quentin Jarrell 671]

For the moment don't worry about a compression chamber. For the most part any woofer in the car audio market should not need a compression chamber. Unless you are using a 8 inch woofer or a base level woofer you won't need one. The three thing to remember is:

throat area: (port area at the sub) should be around 1.5-1.7 to 1 ratio of the subs sd.

mouth area: (port area at the end of the port) should be equal to the subs SD

port length: should be tuned to the FS of the woofer.

And yes most t-lines are so efficient they are normally 8-12 DB louder than a normal ported enclosure.

[SPLChris 0]

Awesome. I always thought that if the mouth was large, you would get some added output. I'm probably wrong, though.

If you had a sub with a stiffer suspension, do you think a higher compression ratio could be used to get some more output?

[95Honda 486]

And yes most t-lines are so efficient they are normally 8-12 DB louder than a normal ported enclosure.

LOL....

OK, now this poop is really getting thick...

How many of you guys have actually built a stuffed 1/4 wave T-line and tuned (impedance curve) it?

[3stagevtec 2]

And yes most t-lines are so efficient they are normally 8-12 DB louder than a normal ported enclosure.

what a load of

[Quentin Jarrell 671]

And yes most t-lines are so efficient they are normally 8-12 DB louder than a normal ported enclosure.

what a load of

I did not mean it would make your car 10 db louder. Normal ported enclosures are less than 5% efficient. t/l and horn loaded enclosures can be upwards of 75% efficient. The free air response is 8-12 db louder than a ported enclosure. If you don't think it is true take a meter and put it a few feet in front of a ported box. Then take the same woofer and put it in a T/l and measure it.

People are getting upwards of 10and 12 Db boosts with bandpass enclosures. So why would this not be capible with an encosure like the t/l.

If it is not possible to get that much gain out of an enclosure please explain how Alan Dante hit over 180 with ONE WOOFER and it took Scott Owens 13 woofers to get close to 180.

You have all the right to say that it is all bull, but please add a little helpful information with your remarks that will help this guy out with his enclosure.

[3stagevtec 2]

if it's as easy as that, then Dante wouldn't be the only one hitting those figures.. i know tlines are pretty efficient, but you are over estimating their capability, and by alot imo..

a 3dB increase is comparable to doubling power...

a 10dB increase is comparable to a tenfold increase in power...

do you really believe that a tline could be that efficient??

[3stagevtec 2]

Normal ported enclosures are less than 5% efficient. t/l and horn loaded enclosures can be upwards of 75% efficient. The free air response is 8-12 db louder than a ported enclosure. If you don't think it is true take a meter and put it a few feet in front of a ported box. Then take the same woofer and put it in a T/l and measure it.

People are getting upwards of 10and 12 Db boosts with bandpass enclosures. So why would this not be capible with an encosure like the t/l.

where did you get those figures from?

[Quentin Jarrell 671]

Most of my basic knowledge comes from diyaudio.com, quarter-wave.com, loudspeaker cookbook, and a few other sites and books. My db figures are from actually metering different enclosures. And your right about it not being easy for Alan to hit those type of numbers. I totaly agree, he didn't just throw a box in his truck and hit a 180. It took him years to get where he is at. But he has one woofer and Scott had 13 woofers. Going by the normal guidelines in order for Alan to be as loud as Scott his woofer would have to have the same excursion as Scott's 13 woofers. And the normal power rule is out the window because Alan is running around 40,000 watts and Scott had 156,000. So considering that, we would have to assume that there is a way to get extreme amounts of db increase from an enclosure.

[95Honda 486]

Additionally, the last thing a traditional 1/4 wave T-line is known for is being super super efficient. In fact, a properly built 1/4 wave T-line is well dampened, with a flat response curve and efficiency at or just below a average 4th order vented aligment. It just has a much a shallower roll-off with a more efficiency in the last octave.....

This is why most "car audio T-lines" aren't... Alot of them are peaky 4th order vented alignments, some have horn loading mixed in, some even are acting as a banpas filter. Some (most) are undamped lines that people think are behaving like a T-line, but in fact if they even were, the cutoff would be an octave higher than they think.

I have been building speakers, alot of speakers, since the early 90s. I have build a lot of succesfull 1/4 wave lines. I have built a lot of unsuccessfull 1/4 wave lines. Some of them turned out to be low tuned, ported aligments when the Sd of the line became to small, there was too much airspace and not a proper feedpoint to the line, they were undamped or they were to short. I have measured many of these, I even have a buddy who used to own MLSSA in the mid 90s, I did some tuning with him on one of his t-lines and saw first hand how these things work. 1/4 wave lines must be dampened, especially at the lengths you guys are using, to be effective. How many of these lines actually get the proper dampening?