Questions about transmission line speakers.

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aBitNerdy

Member
Joined 2018
Scottmoose said:
The best message here is: try not to get too hung up on definitions which are not universally applied in the same way. 'Transmission Line' itself as noted is a term that is often used by people to describe boxes that are functional opposites of each other. What is more important is that you understand what it is you are doing & the operating physics thereof.
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Got it. I will try to learn the underlying physics as much as possible. And I will try to read all the material on Martin King's website and others.
Yesterday I played a little bit with the math analyzing air in a closed-open pipe as a "heavy spring" using bulk modulus of air in conjunction with all the typical math for spring-mass systems. In the end I arrived at all the same harmonics as predicted by the quarter-wavelength rule. This was very insightful.
I think I will try to play with Hornresp too.
 
A

aBitNerdy

Member
Joined 2018
GM said:
Leonard Audio's TL program is good and more flexible plus generally easier to learn than Hornresp plus the latter can only do end/bottom location vents, though it can be approximated along the [ML]TL's length by using the 'path' delay feature in the Loudspeaker Wizard's 'chamber' window.

http://www.diyaudio.com/forums/soft...n-line-modelling-software-17.html#post5160274

Help File | Leonard Audio

GM
Click to expand...

Thanks. I've just installed this and going to try to use it. On the first looks it seems to be much more user-friendly than Akabak.
 
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aBitNerdy

Member
Joined 2018
Thanks everyone for your replies in this thread! I think I finally understand the fundamental difference between bass reflex and transmission line now. For now I decided to go on designing a bass reflex speaker as it seems much easier for my first speaker project. In the meanwhile I will continue reading about transmission lines and I'm hoping to design a transmission line speaker in the future when I have more solid understanding of it.
 
S

sujat

Member
Joined 2019
A few more basic questions in a student's mind!

Dear Stalwarts & Enthusiasts,

I couldn't find anything on the internet yet (or probably i missed recognising it on Martin King's wonderful site) to resolve a few conceptual questions on QW pipe design.

* When a driver is mounted in a QW pipe (or an open-ended terminated line of any geometry), the system resonance goes lower than the driver Fs (unlike in any other enclosure). On basis of this:

1. Is it safe to assume that the effective Mms that the driver's motor "sees" is greater than that as measured in free air and mentioned in the driver datasheet?

2. If yes, would the higher Mms also lower the high frequency extension as well as the sensitivity of a wide-band driver?

3. Does it have any indication that the column of air through the line/pipe acts as a constant load against the driver cone effectively helping control its excursion? Is this air column load effective only around the 1/4 wavelength tuning frequency, or consistent throughout the whole frequency band?

4. On basis of 3. above, for a given 8" driver, let us assume two boxes - a 54 litre simple closed box and a Tapered QW pipe with the same internal volume, i.e. 54 litres (with 1/4 wavelength tuning at approx. 45 hz.) - * Would the driver gain any advantage in the QW pipe (over the simple closed box) as far as its excursion-limited power handling in the lowermost operating frequency band is concerned (i.e. 100 hz and below)?

These questions have remained unresolved in my mind for a long time. I would be greatly thankful if anybody can shed some light on this.

Thanks in advance! 🙏
Sujat
 
picowallspeaker

picowallspeaker

Member
Joined 2007
Well, yes, viscosity of air and velocity of the particles allow to couple to the membrane till a certain frequency. Fundamental and harmonics make the rest, i.e. the mass loading of the cone by the column of air behind...er...what? I just wanted to write fundamental and harmonics, I like it!:boggled:
 
GM

GM

Member
Joined 2003
Right, this yields an acoustically lower tuning, so once the pipe's cross sectional area [CSA] is known, ideally need to shorten it: end correction = radius*0.613 and if you want to dial it completely in and/or just to make it as compact as practical, then have to factor in its room boundary gain, stuffing density, though it takes a proper TL/horn program such as Hornresp
or similar to sim a 'close enough' physical pipe length.

GM
 
M

mhenschel

Member
Joined 2019
As far as I know the genesis of the popular use of the term "transmission line" can be found in Arthur Bailey's first article on the subject in the October 1965 episode of Wireless World.

Bailey wrote:

"The only safe method of removing the rear cone sound energy is by transmitting it down an infinite transmission line. This is obviously impractical so the nearest approximation was examined."

His follow-up article used the term as the enclosure name pursuant to his particular design intent.

diyaudioprojects.com/.../Non-resonant-Loudspeaker-Enclosure-Design.pdf

diyaudioprojects.com/.../Transmission-Line-Loudspeaker-Enclosure.pdf

Of course before Bailey, Ben Olney described a lot of the notions on which Bailey founded his design. And after Bailey the objective of non- or minimal resonance as the primary objective was relegated to the corner by King et al.

As Scott pointed out the design intents included under the rubric "transmission line" have since come to include many other things. It's up to you to figure out what you want and pick the transmission line to get there.

Here's another interesting page to review.

Introduction and Historical Notes – Transmission Line Speakers
 
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mhenschel

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