[qObsession]

Hi, all...

I'm getting ready to build my first t-line enclosure (fingers crossed!). I think I'm okay on the calculations and overall design, but I'm not 100% sure where the port "begins" (on the end of the subwoofer). Below is a diagram of the box...

Would you start measuring the port's length at (a), (b), or (c)?

I would love to hear your thoughts. Thanks for the help!

 

[Grinder]

The answer is B (I think).

Here's a video on t-line design. At 7:05 Mark defines the center line as the Line Length:

 

[qObsession]

Thanks for your reply, Grinder. Yeah, it's Mark's video that inspired me to do the t-line... and how to calculate it. For anyone looking to learn more about equipment, fabrication, and installation, Mark's work is second to none, and I can't recommend his 'Car Audio Fabrication' YouTube channel enough. Thanks, Mark!

I watched the video again (thanks for the timestamp!!), and it's not entirely clear. He draws a quick schematic of the enclosure with the woofer (6:43), and when he says "this line here," it looks like it stops at the front edge of the driver, which would make (a) 'the correct answer.' But then (7:11), when he says 'that center line' (referring to the line length), he indicates with his pen that it goes to the middle of the woofer, in which case (b) would be 'the correct answer.'

I wish that ambiguity weren't there, because I'm happy to take anything Mark says as 'gospel.' haha Oh, and to make matters even more confusing, I posted this same thread on diyaudio and had two (the only two so far) respondents say that (c) is 'the right answer'!!

Maybe some others will chime in. Thanks, all!

 

[Grinder]

Thanks for your reply, Grinder. Yeah, it's Mark's video that inspired me to do the t-line... and how to calculate it. For anyone looking to learn more about equipment, fabrication, and installation, Mark's work is second to none, and I can't recommend his 'Car Audio Fabrication' YouTube channel enough. Thanks, Mark!

I watched the video again (thanks for the timestamp!!), and it's not entirely clear. He draws a quick schematic of the enclosure with the woofer (6:43), and when he says "this line here," it looks like it stops at the front edge of the driver, which would make (a) 'the correct answer.' But then (7:11), when he says 'that center line' (referring to the line length), he indicates with his pen that it goes to the middle of the woofer, in which case (b) would be 'the correct answer.'

I wish that ambiguity weren't there, because I'm happy to take anything Mark says as 'gospel.' haha Oh, and to make matters even more confusing, I posted this same thread on diyaudio and had two (the only two so far) respondents say that (c) is 'the right answer'!!

Maybe some others will chime in. Thanks, all!

I've been searching old threads here and elsewhere for going on two hours now, and have yet to find a definitive answer. I'm going to have to tap out on this for now and get back to what I was doing. If you find something, please report back.

 

[qObsession]

Yeah, I scoured the forum before posting (didn't want to duplicate), and I couldn't find anything either (which surprised me). Thanks for the time... and I'll let you know how it goes!

 

[Jroo]

I also believe it is b

 

[qObsession]

Ok, Jroo... duly noted. Thanks for chiming in!

 

[ckirocz28]

Hi, all...

I'm getting ready to build my first t-line enclosure (fingers crossed!). I think I'm okay on the calculations and overall design, but I'm not 100% sure where the port "begins" (on the end of the subwoofer). Below is a diagram of the box...

Would you start measuring the port's length at (a), (b), or (c)?

I would love to hear your thoughts. Thanks for the help!

I would expect if the basket were outside the box, C would be the proper spot; with the basket inside, A or B.

 

[qObsession]

That thought occurred to me, too, ckirocz. Thanks for weighing in!

 

[ckirocz28]

That thought occurred to me, too, ckirocz. Thanks for weighing in!

Maybe subtract the speaker displacement from the length of the port, then measure from that point.

 

[Focused4door]

IMHO, the best way to design a T-line is with Hornresp.

Hornresp takes a little time to get sorted out, but lots of tutorials online and lots of good tips to tweek a T-line. It is great for tapped horns and higher order boxes as well.

The Subwoofer DIY Page - Transmission Line Systems

 

[qObsession]

Yeah, Focused... thought about that--even downloaded Hornsrep. But I keep getting an error message that keeps it from opening... something about how it "cannot find font 'MS Sans Serif."

I've read that others have seen this message, but I can't rectify it!

Thanks for the info, amigo.

 

[chomba]

I believe its 'b'. Most mathematical models use the mid-point, or average of 'a+c', which is b.

 

[qObsession]

I believe its 'b'. Most mathematical models use the mid-point, or average of 'a+c', which is b.

Well, Chomba, as you can see, we've had a lot of back and forth about this. Everything considered, I was going to go with (b), so you've affirmed my choice! This was the kind of direct answer I was hoping for. haha Thanks so much!

 

[Focused4door]

Without modeling the answer is meaningless and the results somewhat unpredictable.

You could end up with a box with worse performance than a simple ported box, or low power handling. Or both.

If you model you can improve the design to get better results, and the goals you are trying to achieve.

 

[qObsession]

I get that, Focused--and agree. I haven't been able to download Hornresp, and I'm not sure I would know what I was doing even if I could. I thought about building this thing just to see what happens (maybe play with dampening afterward), knowing it's highly unlikely that it'll be optimal. My other thought was to just go with a more traditional design and save the headache (the t-line is so alluring, though!). haha Thanks for the info!