https://www.t-linespeakers.org/download/Bailey_TLs_1.pdf
https://www.t-linespeakers.org/download/Bailey_TLs_2.pdf
Not the first TL. The earliest article i have is by Onley from 1937
https://www.t-linespeakers.org/download/Onley-acoustic-labyrinth.pdf
The title of the first article introduced some significant misunderstanding since it is possible to build such a line but the one he showed was not one of those. The second article has his triangular TL, the mathemetician in me wanted a smooth taper (turns out a stepped taper can have advantages), and came up with this idea, which Scott & i are revisiting. Starts with a modern design for the KEF B139 he used.
https://www.diyaudio.com/community/...ngular-transmission-line.403001/#post-7447205
Long haired sheep’s wool is very good, but yes moths, and it sags. You can mix it with some polyfluff so it stays in place.
The first bit has been shown to be untrue, but the latter part has some real-world stuffing data.
https://www.t-linespeakers.org/projects/tlB/appendix/bradbury/index.html
dave
There is no actual "glue" for polypropylene or polythene of PTFE. Chemically they look like waxes (no side-groups to bond to) and heat-welding or solvent-welding is needed - the latter is sold as a 'glue', but it works by dissolving the plastic (like polystyrene cement), so there's no going back if you screw-up!
Thanks for that clarification @Mark Tillotson - I've never needed to glue anything to PP or PTFE, but I just recall seeing on many glues that they mention that it cannot be used on these plastic types.
Wow! A huge treasure trove!! Thanks for this Dave.
Not sure if you actually seen genuine Dr Bailey's Long Fibre Wool from the backs of Yorkshire sheep. Arthur Bailey was a lecturer at Bradford University (Yorkshire). We (a proud Yorkshire company) sold a large transmission line stuffed with this. The fibres are looo.ooong, much longer than cheapo foreign (not from God's own county) wool , and it doesn't sag 🙂 Not sure if the Radfords used the proper stuff either.
Dunno what Miraflex or HoloFill are in the Bradbury paper, but in da previous Millenium, the Dacron stuffing everyone used was a LOT worse than DrBLFW or Fibreglass. We weren't so interested in reducing the speed of sound as we only did one TL.
Our main criteria was the Audible effect on a midrange mounted in a tube. which I described earlier. It's a quick and easy test and doesn't require Golden Pinnae either.
But I would have been lynched by the Factory girls if I had specified Fibreglass in any of my designs 😱
There was also an Open Cell Foam which was quite good but it was a SERIOUS fire hazard
Dave, I'm trolling through your TL pages with awe and resurrecting Jurassic memories. 😱
Is your favourite TL today, a TQWL, perhaps lightly damped?
I know a straight line needs the driver mounted at 1/3 but where do you place the driver in a tapered line?
I first played with a Baldock Paraline while still in school and have built a couple of other HFN designs in my youth. In my previous life, I would revisit TLs & TQWLs every few years but always went back to classic Reflex cabs. If you design drive units from scratch, many of the problems with ported boxes are solved.
One of my engineers, Roger Loughton, perhaps the best drive unit designer I know, went to Castle and did a couple of TQWLs for them ... but by that time, I was a beach bum
Excuse the off topic question ... and I know I should look up Martin's page but these days, I kunt reed orh rite 🙁
Is your favourite TL today, a TQWL, perhaps lightly damped?
I know a straight line needs the driver mounted at 1/3 but where do you place the driver in a tapered line?
I first played with a Baldock Paraline while still in school and have built a couple of other HFN designs in my youth. In my previous life, I would revisit TLs & TQWLs every few years but always went back to classic Reflex cabs. If you design drive units from scratch, many of the problems with ported boxes are solved.
One of my engineers, Roger Loughton, perhaps the best drive unit designer I know, went to Castle and did a couple of TQWLs for them ... but by that time, I was a beach bum
Excuse the off topic question ... and I know I should look up Martin's page but these days, I kunt reed orh rite 🙁
My favorites are the ones tha best suit the application.
Currenting listening to a tall, heacyily damped ML-TL. I started bt copying Radford S-90 and then started playing around.
One of my favorite design swas a folded-tapered, heavily damped tl. bud Purvine didn’t want to give them back, so we did a deal.
The midTLs i do are heavily tapered aperiodic.
I have to repopulate a lightly damped ML-Voigt.
I have 4 short end-loaded ML-TLs on the deck, moderate damping.
And i sort of put the Frigel-Horns as one of the designs on the boundaries of TL (quarter-wave) design space. Pensils ar epretty good. An ML-TL but a bit of a hybrid in terms of alignment (hevily damped).
TLS80s, Fried Hs have inhadited my space. DCM TimeWindows were lightly damped ML-TLs.
I know i have missed some.
dave
The practical effect is the the line can be shorter. Doh I kunt reed en rite, luking at Martin's pics, it appears the effective length can be nearly doubled. I've not seen as much ... maybe 40% extra length with optimum Fibreglass damping.
What colour was the DrBLFW? Bailey did the work for Radford but the company wasn't in Yorkshire, God's own county 🙂 DrBLFW was becoming VERY expensive & difficult to source in da late 70s, even in Yorkshire.
and a reality check. Though Dacron etc weren't as good as Fibreglass or DrBLFW, you just needed more depth in your midrange tube to get the same level of goodness 🙂
What is a ML-TL? I figured out TQWL is a Voight line. Is there a page that explains these multi letter acronyms?
The affect attributed to the reduction of sound was really the affect of the shape of a line that tapers smaller towards the terminus.
dave
A TL with a restricted terminus. ML=Mass Loading. The restricted terminus can be used to force the tuning lower than the natural quarter wavelength. As you shorten the line it becomes a hybrid and then progresses to a bass reflex. Almost every tower BR is actually an ML-TL.
It is Voigt. The expanding line means the line needs to be longer, and it is VERY beneficial to mass-load them.
dave
toldja I kunt reed, rite en spul 🙁
So http://p10hifi.net/TLS/projects/VTL-images/PP-B139-TL.gif isn't strictly a Voigt cos da hole is at the narrow end .... but a Paraline is cos it has the hole at the big end of the pipe?
Not even close to a Voigt. A fairly heavily tapered TL (terminus at the top) with the only trickery being the offset driver.
Paraline is a Vigt. Could be improved with mass-loading
dave
No aramid fibre wool addicts here? For midranges the stuff is quite affordable.
On the tapered line a page back: it’s easy to construct with just one panel diagonally placed between two bracing panels some 12 to 15cm apart. One needs those anyway in a 3-way design. Been there done that.
On the tapered line a page back: it’s easy to construct with just one panel diagonally placed between two bracing panels some 12 to 15cm apart. One needs those anyway in a 3-way design. Been there done that.
Doesn't the fact that the hole is much smaller than the big end of the Tapered Line count as ML ?
It does. But unlikely not near enuff.
You will see the same kind of slightly reduced ternimi in some vintage TLs, the IMF TLS80 i disassembled.
Here is a modern properly modeled ML-Voigt — for the original Alpair 10, like other enclosures the driver needs to be matched to the specific driver, althou they do tend to dominate so are more tolerant of changes in T/S. Same kind of terminus (not deep), it is much smaller proportionally. The most beneficial benefits is as a low pass filter.
dave
You will see the same kind of slightly reduced ternimi in some vintage TLs, the IMF TLS80 i disassembled.
Here is a modern properly modeled ML-Voigt — for the original Alpair 10, like other enclosures the driver needs to be matched to the specific driver, althou they do tend to dominate so are more tolerant of changes in T/S. Same kind of terminus (not deep), it is much smaller proportionally. The most beneficial benefits is as a low pass filter.
dave