TL sub design newb questions

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Hi folks,


I've been wanting to build a mono sub - mostly for music rather than HT - for some time now. Lately I've been leaning towards a TL, since there seem to be some compelling advantages over a simple ported design.



I came across this video describing the math for a "classic" TL design:
Transmission line speaker box math made easy - YouTube


This made sense to me, and I did the calculations based on the Dayton RSS265HO-44 driver:
https://solen.ca/wp-content/uploads/rss265ho44-3.pdf


I came up with a line length of about 103.75", but this is predicated on the area of the line being equal to the Sd of the driver, which isn't really practical since it takes some space to mount it. I understand it's possible to taper the line down to Sd, or should I calculate with a larger a larger line area?



But my main question is around stuffing. My understanding is that stuffing increases the effective line length, but also the effective "closed box equivalent" volume which in turn affects the resonant frequency of the driver in the line. So is it advisable to make the line shorter than the calculations would suggest, to account for stuffing?


But maybe the larger question is, is this still a valid method? I understand there are more modern models, but I'm not sure how to go about using them.


Anyway, apologies for all the "newbie" questions and I appreciate any advice. Thanks in advance.
 
Greets!

Well, the pioneer's way has its uses, just depends on the needs of the app and the kind of T/S specs it was designed for [horn drivers], but for the most technically correct that pares off any excess cab net volume [Vb] of other ways, use MJK's Classic TL design routine: https://web.archive.org/web/20130328134100/http://www.quarter-wave.com/TLs/Alignment_Tables.pdf

Otherwise............. using Hornresp's or similar SoS , do the 1/4 WL, then at whatever pipe area you choose, take its radius*0.613 and subtract this from the 1/4 WL = its 1/4 WL acoustic path length assuming its in free air and if bounded by a wall/whatever, then use the pipe end corrections here: https://www.diyaudio.com/forums/att...a_slotport-calc_omnes-audio_w8-670z_ml-tl-jpg

For best overall performance, use a 2:1 CR and for smoothest response with least stuffing use a ~L*0.349 or whatever driver offset offset MJK recommends.

GM
 
It still will be big, i did an MLTL sim for one of that series (could be this one, its on my home computer and i'm not home) and it was still a 155cm long pipe of 40x25cm with a 20x10cm taper of 15cm long for a 30Hz tuning... Reflex is is smaller and easier. But if you want a quarter wave design, an MLTL or TQWT could be it. But use the right math or the right sim software because it's easy to do it wrong ... Read the papers of Martin King to start (and be prepared to struggle with math on them ;) )
 
You might want to use the search engine for DIYaudio because I have asked about this in the past - just chuck in RSS265ho-44 and see what comes up.

For what it’s worth, I’d just do the spadework and learn how to use Horn Response software, or else, if you want a safer approach, check out Brian’s DIYsubwoofer.org site.

That way, you can sim the size of design you want to use, and Brian’s software spits out the panel cuts for you. It’s probably the safest way to get started.

Course, being a ****, I didn’t follow my own advise and ended up making a monster that I’m now having to deconstruct.

Also, check out the info on Brian’s Boom Unit. This is probably a v fine place to start for a reasonably compact TL that works and will get you a decent result for the space you might want to fill.

It is also a great way of learning how to use Horn Resp, as he guides you through what to do.
 
But my main question is around stuffing. My understanding is that stuffing increases the effective line length, but also the effective "closed box equivalent" volume which in turn affects the resonant frequency of the driver in the line. So is it advisable to make the line shorter than the calculations would suggest, to account for stuffing?


But maybe the larger question is, is this still a valid method? I understand there are more modern models, but I'm not sure how to go about using them.

Purpose of stuffing in a TL is to dampen the TL higher harmonics. Stuffing doesn't "lengthen" the effectiveline length or such.

The purpose of a TL line is to mass load to a frequency approximately same as that of the driver Fs, this achieving a flatter acoustic impedance curve and bass extension. There are two ways to decrease the TL length:
1) Tapering down the line and thus gradually increasing the mass loading
2) adding further mass by mass loading by introducing a short but significantly smaller cross-section tube at the end of the line aka mass loading proper
These two methods can be used as long as the peak port velocity doesn't cross 10 m/s or such. Otherwise you will hear "wheezing" at high amplitudes.

You can ask this question at Martin King's Transmission Line Facebook page, for better answers and help.
 
Mine is kind of based on the same design, only it has a 15-inch driver and the line uses pipe. I taper it by inserting smaller pipes in the final half. So a bit of a cheat taper. It's lightly stuffed because the HR result looked better that way.
 

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