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R/T Pimp
09-24-2007, 11:16 PM
Looking for some help with designing a t-line enclosure. I have a 2000 Dodge Interpid with 2 Massive DMX 12's for power I have 2 merlin md3ds strapped. Who is willing to help me out. All I have experience building is basic slot ported, square ported and round ported bass reflex enclosures for spl and daily. I really would like
to learn how to design and build t lines. All help is greatly appreciated.

UCF52
09-25-2007, 12:09 AM
I read this a while back, but IIRC it was a pretty good read.

http://www.stevemeadedesigns.com/board/index.php?showtopic=1828

80INCHES
09-25-2007, 12:10 AM
Looking for some help with designing a t-line enclosure. I have a 2000 Dodge Interpid with 2 Massive DMX 12's for power I have 2 merlin md3ds strapped. Who is willing to help me out. All I have experience building is basic slot ported, square ported and round ported bass reflex enclosures for spl and daily. I really would like
to learn how to design and build t lines. All help is greatly appreciated.

u dont have enuff room
and a t-line box in a car is impractial
just do a ported box 5.5 cubes tuned to 32hz with 70 sqaure inch port and u will be fine
80

joetama
09-25-2007, 12:11 AM
Nice read...

Megalomaniac
09-25-2007, 06:55 AM
I read this a while back, but IIRC it was a pretty good read.

http://www.stevemeadedesigns.com/board/index.php?showtopic=1828

its too simple(that thread) i even pm'd him he agreed there is a lot more to it then that. its just a starting point...

it gets very complicated designing one.


i want to make a tline for a single eu700 i have sitting here. i think i'll make my own thread...hint hint joetama

Fattony911
09-25-2007, 08:19 AM
i agree with wat 80 said, i had one for my 8 and it was big

joetama
09-25-2007, 11:47 AM
its too simple(that thread) i even pm'd him he agreed there is a lot more to it then that. its just a starting point...

it gets very complicated designing one.


i want to make a tline for a single eu700 i have sitting here. i think i'll make my own thread...hint hint joetama

Was that the question you were hinting about?

Megalomaniac
09-25-2007, 12:07 PM
ya

joetama
09-25-2007, 12:53 PM
Humph....

Immacomputer
09-25-2007, 01:40 PM
I read this a while back, but IIRC it was a pretty good read.

http://www.stevemeadedesigns.com/board/index.php?showtopic=1828

I wouldn't go buy that thread at all as it is way too dumbed down.

PM me with the sub's full parameters and the space you have available (max dimensions) and I'll see if I can help you out.

R/T Pimp
09-25-2007, 10:31 PM
cool I will take measurements and pm you.

joetama
09-25-2007, 10:54 PM
I've done some searching and have found it is hard to find good information on T-Lines...

Max_Power
09-25-2007, 10:59 PM
send themommyvan a pm. he had a xxx in a transmission line once.

joetama
09-25-2007, 11:17 PM
Just googled it and found a **** ton of info... Guess googling skills are better tonight than before...

Megalomaniac
09-25-2007, 11:47 PM
Just googled it and found a **** ton of info... Guess googling skills are better tonight than before...

whatcha google exactly?

joetama
09-25-2007, 11:49 PM
whatcha google exactly?

Transmission Line Design... :rolleyes:

Megalomaniac
09-26-2007, 12:18 AM
funny man :p:

Random1010
09-26-2007, 12:26 AM
im interested...

joetama
09-26-2007, 12:47 AM
funny man :p:

I'm serious...

twisztdauthorit
09-26-2007, 12:59 AM
http://img297.imageshack.us/img297/5914/0912071523yt0.jpg (http://img297.imageshack.us/my.php?image=0912071523yt0.jpg)
http://img341.imageshack.us/img341/3041/0912071615cr7.jpg (http://img341.imageshack.us/my.php?image=0912071615cr7.jpg)

sorry for the ****** pics, there off my camera. This was my t-line designed for 1x10"
Some calc got messed up and port was 2x as large so im gonna replace the 1x10" with two stronger ones. This is for my room and is tuned to 28hz i believe. first t-line and i used a tapered design because i spent days drawing out other ones but it just didn't work.

It is considerably louder and it hits 26-32 hz like a mofo. My clothes hangers start to rattle in my closet on the other side of the room.

So anyways this is just a cheapy lil 10 off around 120 watts.

The sub bottoms out way to much for me so i need a better handling sub for max potential.

I can take more pics if you like or measurements,

twisztdauthorit
09-26-2007, 01:22 PM
bump

joetama
09-26-2007, 01:26 PM
Aparently what I posted was wrong.

I posted it because no one else was posting much information. So, since I have no idea I will delete this and hope that the people who do know what they are doing, or say they know what they are doing will enlighten us...

Immacomputer
09-26-2007, 04:06 PM
Two basic rules...

Ready...

TL area should be equal to or a little greater than the Sd of the drivers.

TL length should be 1/4 the wavelength of the Fs...

Both of those rules are not good to follow and are way over generalized. That is just like saying:

Ported enclosures for 12" subs should be between 2-2.5 cubic feet.

Ported enclosures for 12" subs should be tuned between 32-35hz.

It's a terrible over generalization that may work out occasionally but will very rarely be optimal.

Megalomaniac
09-26-2007, 04:09 PM
Both of those rules are not good to follow and are way over generalized. That is just like saying:

Ported enclosures for 12" subs should be between 2-2.5 cubic feet.

Ported enclosures for 12" subs should be tuned between 32-35hz.

It's a terrible over generalization that may work out occasionally but will very rarely be optimal.

i replied to your pm last night bro

twisztdauthorit
09-26-2007, 04:33 PM
i agree with the 1/4 wavelength rule but i dunno bout the port area rule
I have read that your port area should be tapperd down to 1/2 to 3/4 of your speaker surface area to reduce some type of backbouncing waves or something.

joetama
09-26-2007, 04:42 PM
Both of those rules are not good to follow and are way over generalized. That is just like saying:

Ported enclosures for 12" subs should be between 2-2.5 cubic feet.

Ported enclosures for 12" subs should be tuned between 32-35hz.

It's a terrible over generalization that may work out occasionally but will very rarely be optimal.

That's why I called them Basic... :fyi:

Immacomputer
09-26-2007, 08:40 PM
But they do more harm than good. :fyi:

Spreading around information like that leads to people thinking they know what's going on when they really are just making a pipe organ chamber with a sub that drives it into resonance.

twisztdauthorit
09-26-2007, 08:55 PM
lets get some more info on these t-line boxes...

joetama
09-26-2007, 09:09 PM
But they do more harm than good. :fyi:

Spreading around information like that leads to people thinking they know what's going on when they really are just making a pipe organ chamber with a sub that drives it into resonance.

I admit that I don't know much about TL's. I'm doing reading and trying to understand them. Several places that I have found list these rules as 2 basic principles that make up a TL. Is that wrong?

buildmeabox
09-26-2007, 11:28 PM
I hope this helps.




I've always found transmission lines intriguing, not only because of their attributes, but also because for so long their design was cloaked in mystery and conjecture, rules of thumb, and sometimes outright bunk. The recent works of Martin King and Augspurger, among others, have removed the veil on proper design-or at least made it somewhat more transparent.

Although their design process can be tricky, transmission lines provide an alternative solution to some basic acoustical challenges. Half of a driver's acoustic energy radiates from the back of the cone. In a sealed design, an attempt is made to dissipate this unwanted energy by absorbing it in stuffing, but in many cases a significant amount of energy reenters the cone- delayed in time, and revealed as response peaks due to internal standing waves. All of these effects cause distortion of the original signal.

A transmission line functions by using this wasted and unwanted acoustic energy in a positive manner. By encouraging standing waves of a single low frequency, and providing an opening (or terminus) out of which these standing waves can escape, the bass response of the driver can be extended. At the same time, the transmission line reduces the energy that reenters the cone and causes distortion. I chose the classic tapered transmission line design for its characteristic nearly linear impedance, uncolored sound, good bass extension, and simplicity of construction.


The first thing I noticed on the TL build was the lack of stuffing, this is the second most important part of the TL, the first is keeping the box linear, the type of material and amount of material affect the sound.

Everything I've read about TL's performance is subjectively superior to that of both sealed and vented enclosures. But Vance Dickason stated in his "Loud Speaker Design Cook Book", "it is evident that TL group delay performance, which is a measure of transience, is very similar to a well-damped sealed box and as with a sealed box, superior to that of a vented enclosure". Martin Colloms, founder of Monitor Audio in England, believes the TL performance is no better than a properly constructed vented enclosure. It seems that everyone has their own opinion on the matter, less filling-tastes great. Currently I haven't seen any kind of 6th or 8th grade mathematically accurate design table as can be found/used for other box designs. You be the judge and audition the Bose Wave radio, its based of a TL design.

I hope this has shone some light, some of the info came from Vance Dickason's book and partsexpress.com projects page.

twisztdauthorit
09-26-2007, 11:42 PM
Martin Colloms, founder of Monitor Audio in England, believes the TL performance is no better than a properly constructed vented enclosure.

Hmm, I would like to see this topic debated. if i had the extra time and wood, i would love to try different designs and techniques.

I see the t-line as a more efficient version of a ported enclosure. Besides, Gotta love the huge port size!

twisztdauthorit
09-26-2007, 11:43 PM
Another thing im not sure about is the port size:

Is it supposed to be the same
Is it suppose to be smaller
or bigger?
then the surface area of the cone?

Immacomputer
09-27-2007, 12:26 PM
I admit that I don't know much about TL's. I'm doing reading and trying to understand them. Several places that I have found list these rules as 2 basic principles that make up a TL. Is that wrong?

Well, it's not that it's wrong, but way overgeneralized. The driver will be placed in an enclosure that still has a large air mass behind it. This will change its resonant frequency (Fs) like it does in a sealed enclosure. To get an idea of what the new Fs is, you need to calculate the sub in a sealed enclosure of equivalent airspace. Winisd Alpha will tell you this value. For some subs, an airspace as small as 2 cubes may give you the Fs of the driver in free-air while others may take massive enclosures.

As for determining cross sectional area of the line, you need to take in quite a few factors before you just pull anything out of your ***.

First, you need to know whether or not you're going to taper the line and by how much. This line taper ratio is very critical and will affect the final sound of the system. Then, you have to know how much stuffing you're going to use (or no stuffing at all). Then, you need to know the resistance factor for your sub which can be found based on the Qts of the driver being used. You will also need the peak value of the shape function, BL, Sd, and Re to calculate the optimal line area. If you take all these values and multiply them and then divide by BL^2, you will have a unitless value that will correspond to the ratio of taper you have chosen for the line. If you choose not to taper, then you multiply this number by the Sd of the driver and you get your final line area. Sometimes it's bigger, sometimes it's smaller.

Stuffing is important to really smooth out the impedance of the line and it's use will actually change the length that you need to get the proper tuning. It also helps break up higher order harmonics of the line tuning and can give you a more pure sound. Stuffing really helps in frequencies much higher than what it typically used for sub systems. In these ranges, you will have some serious issues with peaks and valleys in the frequency response due to standing waves and the line being out of phase with the sub. Stuffing isn't too critical when you're just dealing with sub bass frequencies but it will definitely help with the impedance smoothing.

Another important part of transmission lines is where to put the driver. Sometimes you can get away with putting it right at the closed end of the line and other times, this will hurt your sound. Off-setting the driver helps break up and suppress some of the upper order harmonics that would usually be heard. However, moving the driver further down the line will actually lessen your low frequency extension. It's all a bit of a compromise game.

T-Lines are very interesting and can sound very nice. They can get pretty large when working with larger drivers though and that makes them a little out of place in car audio. It can be done and it can work well but they won't be as at home as they would be in a nice large room. As far as output is concerned though, I think ported enclosures definitely have a one up but t-lines don't have as steep of a roll off after you go below tuning. Power handling is also reduced in a t-line but sensitivity is greatly increased.

Argh.. too much typing... go read for yourselves at www.quarter-wave.com and be prepared to follow some math.