ported vs. transmission lines

[oldenglishD 0]

This kind of goes with myths and lies. Here I am trying to figure out why some insist on a port box for spl? Is there a specific reason why?

Some pros and Cons I know of for ported verses transmission lines.

Ported:

High spl output= pro

High x max =con

Loud bass output. Pro

Box size= pro or con

Transmission lines:

Loud bass output below 70 hertz. = pro

Reduced x-max =pro

High spl output the same as a ported. = pro

Large boxes =con

The reason I see the transmission line is better is x max is reduced so when you add 8,000 watt burp to a 2,500 watts rms sub the tinsel leads do not come apart as easily. The t lines can be tuned the same as a ported for high output. So why go ported? i was told this by some one that said glassing the inside of the box will increase output. just trying to straiten my self out on it

thanks: D

[porkchop 304]

you will find two large crowds on this subject.

your personal preferance and goals will begin to override all input toward the end of your research.

you will find, when done right, that either can deliver satisfaction to a specific set of goals.

size, that is a big one. ease of design and build, mentioned and considered alot.

sound, output, both style enclosures have been designed, built and documented as having great results.

bosting very enticeing numbers.

what one is right or wrong, there is where you will end up, personall preferance and goal.

i searched the net over, found so many facts and figures, extremly ellaborate builds, on both sides of the spectrum.....

with car audio, like the nich i happen to fall into, daily driver, hip hop and rap style music.... the ported is simple enough.

the thing on the x-max, i have read that, and with the same confident reviews, i have read that installing a sub into a t-line will reduce it' power handling.

i have been trying real hard to read up on the t/s specs and learn all their values....... when you begin to design a t-line..... man they all are present.

x-max has so many other values that intertwine, it can not truly be narrowed down to a general statement.

perhaps to one specifically designed enclosure and one specific subs specs, with a specific tunning and power, but not in everycase....

there is truth in the glass, but how much louder is what comes to play.....

we are talking about itin another thread, 10th's are indeed louder, just not to the ear.

why go ported? that is way to broad..... once again.... goals and personal preferance comes to play.

[oldenglishD 0]

Sorry as for goal it's spl. I just bought a mach5 audio spl 12 for the box it says 40-70 L at 38-40 hertz. and was wondering if it would do better in a line then a ported box but am unsure of it. I will be running it off a sae1200d for now till i can get a bigger amp maybe even two amps like the saz1000d strapped.

thanks for the reply D

[porkchop 304]

what vehicle are you doing the install in?

strictly spl?

i am not at the level to read it's specs and form an opinion yet.

i do know that there are programs out there that you can model your subwoofer in different enclosures and see how they would react.

i talked to a kid in 502, he was world champ in his single sub class....

perhaps you should look him up, benhemp.

he does not use models though, lots of testing.....lots of tweaking.

[REVpuggie 23]

testing and tweaking is the only right way ...with any box , box calculating programs are only a tool to get somtething close to what you're after .

not all woofers work in a QWTL , very low QTS (spl) woofers tend to work really well though butt not for burping only because the wavelength becomes to long till it gets to the meter and thus tuned too low

build and test both and keep the loudest one .

[oldenglishD 0]

thank you so much that is what i am thinking. the reason i am worried is it is a sae 1200d v.2 with the decrease x max in the 40 hz region would it require more power i quess the only way to find out is build and test like you say. if not i can find a bigger amp it may not be a sundown thought which will suck love sundown audio.

it is going in a ford x cab truck. it is almost as small as a honda crx.

[95Honda 486]

A true T-line will never be as efficient as a 4th order vented alignment.

If you have a T-line that is more efficient than a 4th order vented alignment, chances are it isn't a T-line.

The whole point of a T-line is to be very flat in amplitude response, it is about as good of a choice for SPL as a 2nd order sealed alignment.

[kirill007 52]

Not all woofers can be put in a TLine and sound good and loud.

Tlines have more control over the cone within it's tuned freqeuncy, but if u go below or above it, it drops faster then a ported box.

Tlines don't need as much power, because they are more efficient.

But the mechanical power handling drops, because if u go out of the tuned freqeuncy the excursion will be bigger.

@Honda:

A Tline or a quarter-wave enclosure is more efficient than a 4th order bandpass.(and certainly more efficient then a ported box)

You are tottally wrong about efficieny of a Tline, they are more efficient then a lot of other enclosures.(but not as good as a Horn enclosure)

Tlines aren't that flat if they aren't stuffed with polyfill.

A half-wave enclosure will be even peakier then a Tline, thus be louder at a certain freqeuncy.

(By the way, i have a Tline and i had a well designed ported box before and the Tline walks over a ported box without a doubt.)

[95Honda 486]

No.

But it doesn't matter what I say, lol....

[kirill007 52]

No.

But it doesn't matter what I say, lol....

Yes, I had both kind of enclosures, Tlines, normal ported, and 4th order bandpass.

The 4th order bandpass could get louder, because power handling is better then in a ported box, and Tline was waay more efficient then any of those boxes.

[oldenglishD 0]

No.

But it doesn't matter what I say, lol....

Yes, I had both kind of enclosures, Tlines, normal ported, and 4th order bandpass.

The 4th order bandpass could get louder, because power handling is better then in a ported box, and Tline was waay more efficient then any of those boxes.

so have i my ported old set up peaked 136 band pass about 137-138 db's and the t line about 142. of course it small subs peanuts if you will. thanks for the tip i was wondering if the watts would need less watts in a t line. answered one of my many questions.

[ABXX49 20]

No.

But it doesn't matter what I say, lol....

Yes, I had both kind of enclosures, Tlines, normal ported, and 4th order bandpass.

The 4th order bandpass could get louder, because power handling is better then in a ported box, and Tline was waay more efficient then any of those boxes.

I'm pretty sure for a T-line to be as efficient as a bass reflex design, the box has to be MUCH larger. How are you defining efficiency though?

[///M5 2,833]

The problem with a question like this is that it makes it obvious you shouldn't even think about it. If you sit down and truly look at the response and math of T-lines you'd never even ask. Add that to the fact that you won't ever nail the build on the first attempt it is surely not what you should use. Even if you didn't have to ask the question the answer you'd come up with would be to not bother as there is no benefit for you.

[95Honda 486]

I know, it is obvious from his (kirill007) 2nd post that he didn't understand that a 4th order vented box is not a bandpass (I never even mentioned bandpass) and that he completely missunderstands how a T-line works (look into the use of the word "tuning").

Pretty much everyone who believes this, and believes they have built a T-line (when in fact they have build a ported box with a huge port) will go on and on about it.....

The whole point of a T-line is NON-resonant behavior and flat response with an enhanced low end. A proper T-line will never be more efficient (except the last octave, in which case they accell, but this doesn't help car audio SPL in the least) than a proper 4th order vented alignment...

It is also appratent when someone post a picture of a "T-line" only to find that in fact, they have not built one at all.

But like I said before, it doesn't matter what I say, lol...

[Gioia69 30]

not trying to jack this thread or nothin, but can someone explain the difference between 4th order bandpass and 4th order vented? i read this whole thread and was confused because i thought they were the same thing lol. i thought it was a sub in an enclosure with one side sealed, and the other ported, ending in fairly flat response from like 30hz to 70hz or something (depending on tuning obviously). sorry, im a

[Soapbox 7]

I'm tuned in. Hopefully some of the knowledgeable ones will teach us a thing or 2. Why does the power handling go down? If it's the math show us the formula's for a true t-line.

[///M5 2,833]

I'm tuned in. Hopefully some of the knowledgeable ones will teach us a thing or 2. Why does the power handling go down? If it's the math show us the formula's for a true t-line.

The math? Haven't you designed a few? If so you should know it isn't trivial. I find this not so amusing that you are on here pushing members to build T-lines, you design one that causes a catastrophic failure of a driver, and still people follow along with your desires. Not sure which is worse your recommendations of them or the fact that people follow along and still want to build them. Chop take note, not the person you want designing you a T-line....

As for the math, what reading have you done and what do you need clarified?

[///M5 2,833]

not trying to jack this thread or nothin, but can someone explain the difference between 4th order bandpass and 4th order vented? i read this whole thread and was confused because i thought they were the same thing lol. i thought it was a sub in an enclosure with one side sealed, and the other ported, ending in fairly flat response from like 30hz to 70hz or something (depending on tuning obviously). sorry, im a

4th order ported = standard bass reflex design

4th order bandpass is when the driver is in the box and all sound comes from the port. A simple sealed enclosure with the driver firing into a ported one. Better transient response than 4th order vented, but a narrower passband.

[95Honda 486]

Aditionally, all the "order" refers to is the roll-off of the encloure. Standard vented box rolls of at an average rate of 24db/oct below F3. Hence 4th order. Add another 2nd order HP filter to the mix (like a SSF) and you now have a 6th order bass reflex aligment, which is what many people on this site are running for subwoofer alignments as we speak. They just probably never realized it.

And band pass that is 4th order has a vented chamber that has a roll-off of roughly 24db/oct above and below the F3 points.....

Seriously, alot of this stuff people are posting is pulled out of thier asses. And like M5 said, most of it causes more harm than good....

[REVpuggie 23]

Seriously, alot of this stuff people are posting is pulled out of thier asses. And like M5 said, most of it causes more harm than good....

Hope you weren't refering to me .

point taken that this is stuff that's not for everyone ,

butt if noone would attemt these kind of things progress would never be made .

I've got a box calculation program that alows me to tune horns and T-lines ,

and yes when you mess with length and the Sd of the beginning and end of the line ,altering powerhandling and response its is very possible it cant be called a T-line anymore , not saying it cant be done or cant lead to very loud enclosures (from experience).

oh one more note , when designing a box a T-line rarely wins from a backloaded horn design (calculated).

[95Honda 486]

If you didn't build something that wasn't a T-line, but called it one anyway, then no, I wasn't refering to you.

Also, this thread has nothing to do with stiffling creativity, it is meant to cut the BS and give people correct information, that is why we are here anyway, right?

[oldenglishD 0]

Seriously, alot of this stuff people are posting is pulled out of thier asses. And like M5 said, most of it causes more harm than good....

Hope you weren't refering to me .

point taken that this is stuff that's not for everyone ,

butt if noone would attemt these kind of things progress would never be made .

I've got a box calculation program that alows me to tune horns and T-lines ,

and yes when you mess with length and the Sd of the beginning and end of the line ,altering powerhandling and response its is very possible it cant be called a T-line anymore , not saying it cant be done or cant lead to very loud enclosures (from experience).

oh one more note , when designing a box a T-line rarely wins from a backloaded horn design (calculated).

ya i know about the horns too but it's just a little hard finding good info on them.

also all my books call it a tapered t line tapering it from 2.5 times sd to 1.25 times sd what the difference betwen minipulating the sd a bit and doing the same to port tung/ box size ? it's not like your not going to call a ported some thing else because you messed with it tuning/box sizefor the same alignment lol's so can you explain why it not a line or is it bs?

[95Honda 486]

It is simple. It is a T-line if it is a line and only a line. The Sd to cross-sectional ration doesn't come into play with this definition. It isn't a T-line if there is anything but a line involved. If it is a box, with a "T-line" attached to one part of the box, it isn't a T-line anymore, it is a bass reflex alignment with a big ass port.

Also, a T-line has a cutoff frequency determained by length, they don't have a tuning frequency. The longer the length and the heavier the stuffing, the lower the cutoff. They aren't resonators, they are tranmission lines that introduce phase shift.

[oldenglishD 0]

It is simple. It is a T-line if it is a line and only a line. The Sd to cross-sectional ration doesn't come into play with this definition. It isn't a T-line if there is anything but a line involved. If it is a box, with a "T-line" attached to one part of the box, it isn't a T-line anymore, it is a bass reflex alignment with a big ass port.

Also, a T-line has a cutoff frequency determained by length, they don't have a tuning frequency. The longer the length and the heavier the stuffing, the lower the cutoff. They aren't resonators, they are tranmission lines that introduce phase shift.

bull like i thought !

[Adrian_D 520]

Clarify a little what you called bs in your previous post...