Quarter Wave / T-Line tutorial-UPDATED

[Casparado]

Hey Triticum... could use a little more help for a second. Here's a quick and dirty hand drawn sketch of a T-Line to scale, and I am wondering how you would calculate the overall length of the line with a sub blocking the line in this way. Basically the sub needs almost 8 inches of mounting depth, but the port is only 4 inches wide, so to get a nearly flush mount, the sub blocks two levels of line, and creates an opening 3 times the size of the line. 

Where do I start measuring the line? Do I basically consider the area the sub takes up an enclosure, and only measure pure transmission line? 

based on these measurements (excluding the entire area the sub is in), I get about 116 inches, which is about what I am looking for to tune it around 30Hz with a 62in^2 port. 

Am I close??? 

I realize the sub is not exactly 1/3 the way down the line... it's closer to 1/4 (or more) down the line. Is this a bad design? This is going to be the first box I've built and I don't want to shoot myself in the foot with a poor layout. Any help is super appreciated! 

 

[Triticum Agricolam]

14 hours ago, 9264RANDY said:

Just do to space issues.  I wanted to get really clean bass.  I was thinking isobaric because it would minimize the enclosure size.

If space is a concern build a regular ported box, non-isobaric.  You will come out way ahead.  

[Triticum Agricolam]

14 hours ago, Casparado said:

Hey Triticum... could use a little more help for a second. Here's a quick and dirty hand drawn sketch of a T-Line to scale, and I am wondering how you would calculate the overall length of the line with a sub blocking the line in this way. Basically the sub needs almost 8 inches of mounting depth, but the port is only 4 inches wide, so to get a nearly flush mount, the sub blocks two levels of line, and creates an opening 3 times the size of the line. 

Where do I start measuring the line? Do I basically consider the area the sub takes up an enclosure, and only measure pure transmission line? 

based on these measurements (excluding the entire area the sub is in), I get about 116 inches, which is about what I am looking for to tune it around 30Hz with a 62in^2 port. 

Am I close??? 

I realize the sub is not exactly 1/3 the way down the line... it's closer to 1/4 (or more) down the line. Is this a bad design? This is going to be the first box I've built and I don't want to shoot myself in the foot with a poor layout. Any help is super appreciated!

I would measure the length down the center line, staying the same distance from the from the inside panel on that first corner as you do on the rest.  Like this:

Putting the sub 1/4 down the line length is better than leaving it at the end, but its better if you can get it a 1/3 of the way down.   If you can't you just do the best you can. 

The mounting depth issue is a common problem with T-lines, the best solution is to reverse mount your sub so the motor is on the outside of the box.  If you don't want to do that, what you did is the next best thing.  

[Marito]

On 12/31/2017 at 8:20 PM, MykeJ said:

Hi I have 2 dd608 subs and would like to build a t-line for them. I am not sure if I should even attempt it with these subs because of there QTS of 0.512 they have  a fs of 37.01. Because of the QTS should I go with a different box design? It is for a daily driver. 

 

Thanks for any help.

What box did you end up doing? Im interested in getting 3 of those subs

 

THX in advance

[BEEFKING69]

Does anyone on here build and ship boxes? Been reading through the thread and this T-line box has got me intrigued....I need a box for an american bass XR12 and now i think id like to have a T-line. I do not have the means or time to build one which is why im wondering if someone could build me one.

[fishchris1]

I guess this is still the official thread concerning T-line builds, and still quite active after 13 years ! That has to be some kind of record, huh ?

Anyway, I think I'm finally going to give a T-line a shot myself. 

I had always thought they would be too huge, and not suitable for larger subs..... Until I watched this video....

 

So the OP had showed how to calculate the T-line length.... 1130 divided by the frequency in Hz, divided by 4, and this tells you the length of the T-line length, in feet. Easy peasy. Then, the commonly accepted norm, is that the port area should be approximately the sq inches of the subwoofer being used.

 

So first, I got the bright idea to use two subs face to face (clamshell) in an isobaric setup, and I figured I could use the port area for a single sub...

 Until I watched the video above, and he actually said it cuts the port area in 1/2 of the 1 sub ! Or 1/4 of the pair ! This works out to only 75 sq inches of port area for my two 15"s, face to face. Crazy. Is there anyone here who doesn't believe this ? Or who has tried it, and it didn't work ?

Put it this way, I've pretty much finished this build for my two 15" Dayton's..... "On paper" that is  .....but of course I always get nervous, about spending all that time and labor.... Not so much the money, as this entire build shouldn't be much more that $100... Not much more than two sheets of 3/4" MDF..

I've had the subs in my closet for a few years now.

 

Who thinks this will never work ? Who thinks I should try it ?

Your thoughts ?

 

 

[Booger weldz]

On 12/18/2019 at 8:35 PM, fishchris1 said:

I guess this is still the official thread concerning T-line builds, and still quite active after 13 years ! That has to be some kind of record, huh ?

Anyway, I think I'm finally going to give a T-line a shot myself. 

I had always thought they would be too huge, and not suitable for larger subs..... Until I watched this video....

 

So the OP had showed how to calculate the T-line length.... 1130 divided by the frequency in Hz, divided by 4, and this tells you the length of the T-line length, in feet. Easy peasy. Then, the commonly accepted norm, is that the port area should be approximately the sq inches of the subwoofer being used.

 

So first, I got the bright idea to use two subs face to face (clamshell) in an isobaric setup, and I figured I could use the port area for a single sub...

 Until I watched the video above, and he actually said it cuts the port area in 1/2 of the 1 sub ! Or 1/4 of the pair ! This works out to only 75 sq inches of port area for my two 15"s, face to face. Crazy. Is there anyone here who doesn't believe this ? Or who has tried it, and it didn't work ?

Put it this way, I've pretty much finished this build for my two 15" Dayton's..... "On paper" that is  .....but of course I always get nervous, about spending all that time and labor.... Not so much the money, as this entire build shouldn't be much more that $100... Not much more than two sheets of 3/4" MDF..

I've had the subs in my closet for a few years now.

 

Who thinks this will never work ? Who thinks I should try it ?

Your thoughts ?

 

 

A 500cm2 line of 282cm (29-28hz tune) with a driver offset at 51cm you hover around 122db from 35-95hz assuming daytonaudiorss390ho4 at 800watts

 

at 1000cm2 CSA with 2 Daytons wired parallel its 128db. Not isobaric...

 

thats a 140 liter box and  a 280 respectively. 2.0 xpi curves...134/140db in 0.5xpi

 

Forget isobaric.

[CstrokerV]

I would just do an isobaric ported box see how you like it... the whole isobaric tline but get to cut the port in half doesn’t make sense to me u less he’s talking about it’s half of 2 subs I didn’t watch the video... noone likes that guy over hear he thinks he’s gods gift to boxes... I would search isobaric tlines and look for more articles if you want to try it 

[Booger weldz]

On 12/26/2019 at 2:21 AM, CstrokerV said:

I would just do an isobaric ported box see how you like it... the whole isobaric tline but get to cut the port in half doesn’t make sense to me u less he’s talking about it’s half of 2 subs I didn’t watch the video... noone likes that guy over hear he thinks he’s gods gift to boxes... I would search isobaric tlines and look for more articles if you want to try it 

The isobaric thing would help with lesser motored drivers, but that’s not so much an issue in this forum.  A really hardcore horn loaded PA style box might start showing car audio drivers bulky/heavy parts short comings or motor insufficiency (or both), but a typical mltl isn’t necessarily a problem and certainly not for the dayton reference series subwoofers, they’re really good!

[Fish Chris]

On 12/26/2019 at 2:21 AM, CstrokerV said:

I would just do an isobaric ported box see how you like it... the whole isobaric tline but get to cut the port in half doesn’t make sense to me u less he’s talking about it’s half of 2 subs I didn’t watch the video... noone likes that guy over hear he thinks he’s gods gift to boxes... I would search isobaric tlines and look for more articles if you want to try it 

Yea, for now I am just doing the ported isobaric.... but I'm still interested in a T-line at some point. I think that guy is great. He gets right to the point, and he talks in absolutes so I don't have to guess, or read between the lines. Even if he's wrong about some stuff, he sure sounds like he knows what he's talking about