Transmission Line Subwoofer - Speaker Orientation/Placement

[lamsv]

I've been messing around with transmission line subwoofers over the winter. I have kept them very simple: Calculate total length needed using speakers Fs, figure out how to snake that length to fit within the constraints of my car. I've used several 6.5" and 8" speakers to accomplish this, with mostly fantastic results. I'm ready to step up to a higher power handling speaker though. Which brings me to one issue.

That past subs I've used where lower power handling, with shallow mounting depths. The shallow mounting depth helped with such small speakers, as the cross section area of the t-line has been very small (not much cone area with a 6.5" or an 8" speaker). The subs I have been eyeing to try next have vastly deeper mounting depths, and just won't fit inside a conventional t-line.

Below is a screen shot of (2) different configurations that would allow the installation of a deeper speaker. I've searched, but not really found the answer I'm after. In the case of the configurations below (speaker mounted into a small chamber that actually feeds the transmission line vs. firing the speaker into the transmission line, with a small open ended chamber to protect the speaker), is one better than the other? Does it really mater?

Thanks!

Click to read more...

 

[Jroo 10+ year member]

I would like to know as well

 

[NSTALN 10+ year member]

I’ll be following this thread. I’ve seen a few t-line designs with small chambers around the driver...I was always curious how that effects the performance and how the chamber is calculated.

 

[Buck 5,000+ posts]

You'd be fine either way. Just make sure you have the proper line surface area and the proper line length. You can have a deeper chamber for the sub to fit in, it'll still act like a t-line. I would just do whatever saves you space. You seem to have a good grasp on it.

This may be my OCD, I absolutely would never have a port exit right after a turn. I like to ensure my port's radiating surface has linear air coming out of it, not where the air is spinning like a vortex when it exits the port.

 

[Buck 5,000+ posts]

You can leave the 45's out too if makes the box smaller. 45's aren't that valuable in a port, IMO, in most situations. I would 100% leave out 45's if it meant getting a better layout or having more wiggle room.

 

[Buck 5,000+ posts]

On the first pic, if you make a chamber like that, do it tapered down in some fashion. Don't have it hit a 90 degree wall when it shrinks down to the port width. I would angle the larger chamber into a smooth transition into the line. And that chamber will act as line length as well. Just think about a tapered t-line or a reverse horn, if you will. Going from bigger airspace to smaller airspace means you get lower tuning. So I would keep that in mind. It's hard to get exact tuning, there's so many factors, but it may help you get as close as you can without actual physics modeling software

 

[lamsv]

Some great information. Thank you!

One of my experiments was a simple folded tapered t-line with a 6.5" DB Drive speaker. So, your suggestion to adding an angled wall to transition to the line itself is not lost on me.

I'm going to play around with the configuration so that I can get the exit of the line to occupy the entire length of one short side of the enclosure.

If anybody else has any insight, please don't hesitate to add to the conversation.

Updates from me won't be that often, but I will update this thread with what I eventually end up doing, and how it performs.

 

[Buck 5,000+ posts]

Yeah, I'd personally be interested in seeing some results in what you find.