Do TL lines need to be smoothly tapered?

[GuyPanico]

I'm spending a lot of time looking over posts on this site, and searching on the web basically feeding my brain with loudspeaker tech. Past couple days i've been focusing on transmission lines. I've learned a lot and think I have the basics down. I'm wondering though, if the taper needs to be a 'true' taper to work correctly. Or, if it could be incrimental. For example, 3ft of 12", 10" and 8" sonotube to produce a 9ft line? Would this create anomolies in the output? Or would it be treated as if it were a true 12" to 8" taper?

 

[Tweeker]

In a subwoofer line smooth response of the line at higher frequencies often isnt as important because your crossing over before them. This is why you can get away with (or want to for more dB) sticking the driver at the very end of the line.

 

[planet10]

It doesn't have to be... if you want to know how it will work, model it n the MJK worksheets.

dave

 

[GuyPanico]

I started playing with the worksheets. Way more information then I know what to do with. I'd have to say the thing that stands out most to me, is how important damping is. Finding the correct density is just as important as the form of the line itself.

Here's what I have thus far.

fs 25.5hz
vas 133.1L
re 4.16ohms
qes .28
qms 4.57
sd 510cm2

123" long
- 47" @ 1.5sd w/ .5lb stuffing
- 38" @ 1.09sd w/ .5lb stuffing
- 38" @ .44sd w/ .333lb stuffing

 

[planet10]

Here's what I have thus far

Usually there is no point building a line that doesn't do as well as the sealed reference.... try shortening the line & making it fatter.

dave

 

[Tweeker]

One thing you could do do make the taper smooth would be to glue 14/2 electrical cable along the inside, using more layer as you get closer to the narrower pipe.