This Video Made Me Miss You Guys (Transmission Line Speakers)

[Pogre]

So I'm still in love with my system and enjoying it. There haven't been any changes or upgrades since the last time I was here, which is actually a good thing. It means I'm still happy with everything! You guys didn't lead me wrong and I haven't had the upgrade itch for a long time. I just plain haven't been researching or looking for gear and sorta drifted away.

I do still love audio tho and watch plenty of videos (such as Paul McGowan's series on YouTube. More about him later... ), and when I stumbled across this one it totally made me think of you guys. This is the only place I know of where anyone would even vaguely be interested in something like this, lol. I learned a little about transmission line speakers too!

So yeah. Dude builds transmission line speakers and shows his testing process in a little anechoic chamber he built. He goes in depth about damping, comb filtering, etc.. It's not the most exciting fare, but a couple of you guys might appreciate it.

Enjoy

 

[Alex2507]

This is the only place I know of where anyone would even vaguely be interested in something like this

Like Twister pillow talk ...

 

[ryanosaur]

Great video. Thanks Pogre!
I've become fascinated with TLs. I am by no means an expert here, but want to share some of what I've learned. It is a different world! Couple thoughts as I'm watching this...

At the most basic level is a Straight Line: the cross section is the same area along the whole length.

Voigt Pipes, and other Flared Lines all begin with a closed end with a smaller cross-sectional area than the Terminus, or open end. Classic Voigt Pipes have a starting area of ZERO.

What I will refer to, for clarity, as a Tapered Line, is the opposite of a Flared Line: the closed end has a larger cross-sectional area than the Terminus. The Terminus will usually have an area of 1, and is determined by the T/S parameters of the driver and the specific tuning of the line, length, and other geometric and acoustic factors. The closed end will be in ratio to the Terminus area anywhere from 3:1 up 10:1, with a common ratio of 4.4:1.

You can Mass Load a Line by having a tuned port smaller than the cross sectional area of the open end of the line. (This is the design used in the Phil 3 from Dennis Murphy and Paul Kittinger.)

A few tidbits:
By putting the driver on the end of a tube, it is technically called rear-horn-loading.
When the driver is placed along the length of the line, then it becomes a transmission line.
Tapering the line yields the best "cancellation" of higher level harmonics and a shorter line at the cost of having a slightly higher F3, and lower terminus output.
Flaring the line yields a slightly lower F3 and higher terminus output, but the cost is more destructive harmonics inside the line, and the line is longer.
Straight lines are in between.
A Voigt pipe, with it's closed end area of ZERO creates many acoustic complication that can be solved partially by blocking it off and actually having a measurable area at the closed end.
Placement of the Driver along the length of the line influences the creation and excitation of different harmonics within the line. As an example, by placing the driver at a point about 1/3 along the line (at the anti-node of the third harmonic) you can almost completely cancel out that harmonic.
To Damp the Line, it is recommended to use about .5-.75# of Poly-Fill (or similar material) per Cubic Foot of Line Volume.

Some cool stuff to check out:
What is an ML-TL?
THOR: A D’Appolito Transmission Line | audioXpress
Transmission Line Speakers
Quarter Wavelength Loudspeaker Design
Designing a Mass Loaded Transmission Line speaker.
This one, an article by David Weems, is especially interesting as it is a Folded Voigt Pipe:
Tapered Quarter Wave Pipes

There are other sources with more info... And even a simple exposure to TLs is pretty fascinating. Admittedly, the more difficult part comes in understanding and practicing the geometry involved to maximize the acoustics. I still have a long way to go before I will be ready to design my own.

Best,
R

 

[shadyJ]

Audioholics will publish a review of a transmission line design speaker pretty soon, although it's not as sophisticated as many of the above mentioned designs.

 

[ryanosaur]

Audioholics will publish a review of a transmission line design speaker pretty soon, although it's not as sophisticated as many of the above mentioned designs.

Is this gonna be the Dayton?
(No means no.) (Maybe, or "can neither confirm nor deny" means... ... ...)
*wink, wink.

 

[shadyJ]

Is this gonna be the Dayton?
(No means no.) (Maybe, or "can neither confirm nor deny" means... ... ...)
*wink, wink.

 

[ryanosaur]

Nice... Don't worry... I won't tell.

 

[davidscott]

I believe my original DCM Time Windows were Transmission Line. Best sounding speakers I ever owned and I wish I never sold them.

 

[TLS Guy]

That Dayton does look to be a properly designed reverse tapered TL. So in this age it does not have a lot of company. Just make sure you get a good impedance plot, this will show if the damping is correct.

It is time for TLs to make a comeback. They were popular in the eighties with many of them based in the KEF B 139 driver.

Once I get settled I will have a smaller heated workshop, in floor heat in fact. I have sold all the machinery and boats that I used to be kept busy running.

So hopefully I will get time to develop cost effective designs. As far as I know there is only one bookshelf labyrinth available. It is from PMC, but third party measurements show its design and execution to be wide of the mark. I like to think I could do better. I have only designed one pair. I built them for my eldest sister four years younger than me when I was about twenty. My sister and her husband are still using them and refuse to part with them. I think in the age of HT a good bookshelf labyrinth speaker would be something people would like to build. So that would probably be first on my list for a research project.

 

[Alex2507]

I think in the age of HT a good bookshelf labyrinth speaker would be something people would like to build. So that would probably be first on my list for a research project.

That 10" TL sub sounds like something of interest as well.

Mains and centers tend to be out in plain sight so the always problematic finish often ends up screaming for store bought cabinets instead of the raw mdf diy'ers seem to deify. Flat packs for TLS Guy transmission lines and sealed front stages might be the next big thing. I wonder if your cabinet guy would be interested.

 

[TLS Guy]

That 10" TL sub sounds like something of interest as well.

Mains and centers tend to be out in plain sight so the always problematic finish often ends up screaming for store bought cabinets instead of the raw mdf diy'ers seem to deify. Flat packs for TLS Guy transmission lines and sealed front stages might be the next big thing. I wonder if your cabinet guy would be interested.

Well we don't know if it is any good yet! It will be at least 3 and a half months before I can listen to that system and do any measurements.

But yes, the cabinet guy is interested in producing flat packs. We have kept the board cutting data in the C & C machines computer in case that system is any good.

I think I will be building the crossovers this week. I will have to build them on our condo kitchen table though.

 

[Pogre]

That Dayton does look to be a properly designed reverse tapered TL. So in this age it does not have a lot of company. Just make sure you get a good impedance plot, this will show if the damping is correct.

It is time for TLs to make a comeback. They were popular in the eighties with many of them based in the KEF B 139 driver.

Once I get settled I will have a smaller heated workshop, in floor heat in fact. I have sold all the machinery and boats that I used to be kept busy running.

So hopefully I will get time to develop cost effective designs. As far as I know there is only one bookshelf labyrinth available. It is from PMC, but third party measurements show its design and execution to be wide of the mark. I like to think I could do better. I have only designed one pair. I built them for my eldest sister four years younger than me when I was about twenty. My sister and her husband are still using them and refuse to part with them. I think in the age of HT a good bookshelf labyrinth speaker would be something people would like to build. So that would probably be first on my list for a research project.

Yeah, honestly when I said the video reminded me of "you guys", you were at the top of the list, lol.

 

[Bucknekked]

Yeah, honestly when I said the video reminded me of "you guys", you were at the top of the list, lol.

Pogre
I believe my Salks are transmission line speakers. I am not certain, and there may be variations on a theme here, but I believe the basic design is a transmission line. I am not parting with mine anytime soon. Still love 'em

 

[shadyJ]

Pogre
I believe my Salks are transmission line speakers. I am not certain, and there may be variations on a theme here, but I believe the basic design is a transmission line. I am not parting with mine anytime soon. Still love 'em

Buck don't you have the Salk Song3As? I think those are ported with a slot vent.

 

[Bucknekked]

Buck don't you have the Salk Song3As? I think those are ported with a slot vent.

Shadyj
Yes, I do indeed have Songtowers. Here's what Salk says right on their website

Jim says its a 2 way transmission line. I am not an internals expert, so, I don't know if it accurate or what.

 

[shadyJ]

Shadyj
Yes, I do indeed have Songtowers. Here's what Salk says right on their website
View attachment 29937

Jim says its a 2 way transmission line. I am not an internals expert, so, I don't know if it accurate or what.

Oh I thought you had the Song3As, different speakers.

 

[KEW]

Shadyj
Yes, I do indeed have Songtowers. Here's what Salk says right on their website
View attachment 29937

Jim says its a 2 way transmission line. I am not an internals expert, so, I don't know if it accurate or what.

Seems like those are specifically classed as 1/4 wave (or was it 1/2 wave) transmission line speakers. Either way amazingly good bass for the size of the driver!

 

[ryanosaur]

Iirc, all of the 2-way Song and Veracity towers are transmission lines. If my understanding is correct, they are likely all 1/4 wave lines modeled by Paul Kittinger using Martin Kings program.

 

[TLS Guy]

Iirc, all of the 2-way Song and Veracity towers are transmission lines. If my understanding is correct, they are likely all 1/4 wave lines modeled by Paul Kittinger using Martin Kings program.

Yes, they are mass loaded lines. So they are hybrid pipe and Helmholtz resonator. So they are not damped like a true TL. You can tell that from the impedance curve, as they have two peaks of impedance and not one. Also roll off is 24 db per octave and not 12 db per octave. The advantage is a lower F3 than ported but with a smaller cabinet than a full TL would require. However they are not critically damped. If they were the tuned ported cabinet at the end of the pipe would not work. So the bass quality is different.

One last point, if a pipe is closed one end and open the other, it is a stopped pipe and is quarter wave. Its fundamental resonant frequency wave length is X 4 the length of the pipe. So that means quarter wave. The harmonics are odd multiples of the fundamental. If a pipe is open at both ends it is an open pipe. Its fundamental resonant wavelength is X 2 the length of the pipe. So it is half wave. The harmonics radiated are even multiples of the fundamental. These latter have no application in speaker design. Pipe organs however consist almost entirely of open pipes. There are ranks of closed bass pipes as you can make a 32 ft stop from a 16 ft pipe. These stops are generally labelled Gedeckt. However the harmonic content makes them sound not as pleasing as open 32 ft pipes. In speaker design placement of the driver helps suppress odd harmonic content which is less pleasing musically.

So a TL is a highly specialized stopped Gedeckt organ pipe. However an organ pipe resonates just one note in the rank and therefore high output, high Q is required.
A speaker on the other hand needs loading and assistance over a broader range of frequency. It also needs to be low Q. This is the reason for the taper to broaden resonance and this together with the critical damping lower Q. Although a TL is resonant it can be damped to the point where it sounds aresonant. This is not possible with a ported Helmholtz resonator, as it totally kills the resonance. So a properly designed TL has a much better and more natural bass quality than a ported enclosure. I have to really stress and emphasize the "properly designed", as there have been far too many commercial designs over the years that have not been. This has not helped make the case for TL loudspeakers.

 

[Bucknekked]

Yes, they are mass loaded lines. So they are hybrid pipe and Helmholtz resonator. So they are not damped like a true TL. You can tell that from the impedance curve, as they have two peaks of impedance and not one. .

TLS Guy
Glad to see you chime in on the transmission line details. I was also happy to see you agreed that the Salks are mass loaded lines. Beyond that, the dissertation on TL's was thoroughly over my head. I nodded accordingly and in an approving manner as I read it, but, if there were to be a quiz on the 2nd two paragraphs, I would probably not get a passing grade.

One of the things I love about the AH is the wealth information that's available. Even if some of the info is beyond my simple understanding of designs, I appreciate that there are members here who do understand it and can talk about it. I do love my Salks. Talking smack about their 1/4 wave TL design just helps me when visitors come over and they need a little techno talk. The speakers do the rest of the talking. Enjoyed your comment Mark.