Bud obviously didn't have modeling software like we do, so his designs were based on whatever the common ideas and theories were at the time. Then, there was a lot of post-build tweaking based primarily on lots of listening, leading to "fixes", perhaps like the stuffed vent in the Model R, resulting in whatever sound he thought was acceptable/good. We would presumably have done the same if we had been around back then.
Paul
Paul
Unfortunately true.
All we can do is try in our little corner to provide accurate information & correct nonsense when we see it.
His products came from the Radford/IMF school of design with some of his wacky ideas. And the product did evolve. When he first came out with the model M it had an LS3/5A style sattelite.
The design changed to a truncated pyramid after i showed him a picture of a modified sat some of our clients were building.
A piece of history. The R is using the same concepts the lead to Jordans ARU, the Dyna A25 vent, the ScanSpeak VarioVent, Mission [straws in the vent] and first seen by me in the early 70s when one of my gurus was playing with ideas.
dave
I've only been designing T-lines exclusively since 1991, and I'm, still learning especially, about bandpass, 5th order and aperiodic transmission lines. However, in my 32+ years of designing, I just want to address a few things that have been addressed by Scottmoose, and maybe add a few differences of opinion.
Wrong.
Don't make me use the "B-Word"
Wrong
And, wrong
'cause we can all stick the Bose Base Cannon in the trunk of our Mini's or Fiat 500's, can't we?
Folding the line is more a matter of convince.
Correct! With a linear or non-linear taper, you could do this, at the expense of efficiency.
Example (cough)
And here's the enclosures lack of efficiency.
Wrong.
It can taper down to a smaller terminus, have an area equal to the throat or expand ... but for why one would ant to design an expanding t-line is beyond me.
Wrong (see link below)!
Damping is a hornets nest of opinion. I rarely use the stuff. I simply design the line correctly!!!!
Define; "greatly reinforces content below 80Hz".
Wrong!
Depends on the designer!!!
Depends.
In car audio, no one uses Transmission Lines for SPL competitions, or hair tricks.
As for a "low efficiency" Is this good enough for ya?
Wrong
and
Wrong
I've never understood this misnome. For me, t-lines are by far and away the easiest enclosure to Design, and get a fairly good and results from a basic formula(s). I find, BR and BP, and their variants far harder to design than t-lines. And let's be honest, you don't need to be a rocket scientist to build a single fold t-line!
As for manufacturers, penny-pinching (5/8 MDF, cheap crossover's, $10,000 speakers with drivers from parts-express costing a much as a McDonald's Happy Meal) seems top be an accepted practice. I suspect the amount of wood used in the inclusion of a wave guide(s) would upset the 'Costing' department too much.
Blind/Double Blind Test
What region?
Again, depends on the Designer.
I have never said, and would never say T-lines are the 'b-all and end-all' of enclosure design. I find them easy to design, and the result can be amazing when done right. Therein lies the rub!
Wrong.
Don't make me use the "B-Word"
Wrong
And, wrong
'cause we can all stick the Bose Base Cannon in the trunk of our Mini's or Fiat 500's, can't we?
Folding the line is more a matter of convince.
Correct! With a linear or non-linear taper, you could do this, at the expense of efficiency.
Example (cough)
And here's the enclosures lack of efficiency.
Wrong.
It can taper down to a smaller terminus, have an area equal to the throat or expand ... but for why one would ant to design an expanding t-line is beyond me.
Wrong (see link below)!
Damping is a hornets nest of opinion. I rarely use the stuff. I simply design the line correctly!!!!
Define; "greatly reinforces content below 80Hz".
Wrong!
Depends on the designer!!!
Depends.
In car audio, no one uses Transmission Lines for SPL competitions, or hair tricks.
As for a "low efficiency" Is this good enough for ya?
Wrong
and
Wrong
I've never understood this misnome. For me, t-lines are by far and away the easiest enclosure to Design, and get a fairly good and results from a basic formula(s). I find, BR and BP, and their variants far harder to design than t-lines. And let's be honest, you don't need to be a rocket scientist to build a single fold t-line!
As for manufacturers, penny-pinching (5/8 MDF, cheap crossover's, $10,000 speakers with drivers from parts-express costing a much as a McDonald's Happy Meal) seems top be an accepted practice. I suspect the amount of wood used in the inclusion of a wave guide(s) would upset the 'Costing' department too much.
Blind/Double Blind Test
What region?
Again, depends on the Designer.
I have never said, and would never say T-lines are the 'b-all and end-all' of enclosure design. I find them easy to design, and the result can be amazing when done right. Therein lies the rub!
The TL has more design degrees of freedom than a reflex, so that makes them harder to design, or perhaps better to say a larger design space.
dave
Supposed to mean? Exactly what it says.
There are more things to consider in the design of a TL than a reflex, so more to juggle, more complex, harder to design properly.
dave
There are more things to consider in the design of a TL than a reflex, so more to juggle, more complex, harder to design properly.
dave
Not really!
6.5" subwoofer/midwoofer, 6.5" wide pipe of a certain Length. The longer the length, the lower the bass. Easy!
Here's the Blueman Group to demonstrate how a transmission line works.
Easy!
Yet show me how to design a dual bass reflex, or a 3rd, 5th or 6th order bandpass, or a series tuned, in a way that's as simple as the above video?
Actually, it's far from as simple as that -assuming a competent / high performance design is the goal.
For a start, Fp is a function of the axial length & geometry (taper), as well as the end-correction of the pipe. Then you have Vb, which depending on the desired alignment (more of which below) arguably offers more freedom than a regular vented box tends to. Next up, we have internal configuration, as this can be used as an additional acoustic low-pass if desired. Then we have general type of pipe geometry: what sort of TL? Is it an expanding (aka 'horn')? Is it a straight pipe? If it's either of those, are they mass-loaded, and if so, is the mass-loading element (duct, slot or similar) end-loaded or offset / tapped into the pipe at x location from the nominal termius / end? What proportions are used for that mass-loading element, and what are their individual balances of tradeoffs? Is it physically speaking a contracting pipe in its overall construction (which is inherently mass-loaded, degree depending on extent)? Is it a 1/2 wave pipe (not unknown, but uncommon) which is technically open at both ends, and related to, but not exactly the same as a closed cone / horn in terms of its resonant behaviour? Is the driver tapped into the pipe (any of them) at x distance from the throat, and if so, where since various positions provide various effects? Are any internal Helmholtz absorbers employed, and if they are -where and how? What acoustic damping material is used, what quantity and where is it employed in order to achieve the target alignment?
Which then brings us to alignment itself. What alignment is the object? Is it a maximally flat impedance design? Is it a high-gain design? Is it something in between? What operating BW is desired / targeted? Is it a max-gain with targeted BW design, max gain over its entire intended operating BW? Some other variation, or combination of features?
Those are a few aspects (certainly not all) -generally there is more to consider than a typical Helmholtz derived box.
For a start, Fp is a function of the axial length & geometry (taper), as well as the end-correction of the pipe. Then you have Vb, which depending on the desired alignment (more of which below) arguably offers more freedom than a regular vented box tends to. Next up, we have internal configuration, as this can be used as an additional acoustic low-pass if desired. Then we have general type of pipe geometry: what sort of TL? Is it an expanding (aka 'horn')? Is it a straight pipe? If it's either of those, are they mass-loaded, and if so, is the mass-loading element (duct, slot or similar) end-loaded or offset / tapped into the pipe at x location from the nominal termius / end? What proportions are used for that mass-loading element, and what are their individual balances of tradeoffs? Is it physically speaking a contracting pipe in its overall construction (which is inherently mass-loaded, degree depending on extent)? Is it a 1/2 wave pipe (not unknown, but uncommon) which is technically open at both ends, and related to, but not exactly the same as a closed cone / horn in terms of its resonant behaviour? Is the driver tapped into the pipe (any of them) at x distance from the throat, and if so, where since various positions provide various effects? Are any internal Helmholtz absorbers employed, and if they are -where and how? What acoustic damping material is used, what quantity and where is it employed in order to achieve the target alignment?
Which then brings us to alignment itself. What alignment is the object? Is it a maximally flat impedance design? Is it a high-gain design? Is it something in between? What operating BW is desired / targeted? Is it a max-gain with targeted BW design, max gain over its entire intended operating BW? Some other variation, or combination of features?
Those are a few aspects (certainly not all) -generally there is more to consider than a typical Helmholtz derived box.
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REALLY
A reflex assumes a shape not far from a sphere/cube, no dimensions significantly different from any others.
In a TL we add all sorts of variables that have to do with the shape of the box. Line length, line shape, line volume, driver placement, terminus placement, terminus restriction are additional design dimensions that need to be considered over a reflex.
And then damping. A reflex is typically lined, adding damping screws up the helmholz resonator. TLs can be lined like a reflex or all the way thru the spectrum to a heavily stuffed aperioidc TL.
A significant over simplification.
Technically a reflex, but not what most consider when you say reflex. They are bandpass boxes, ad dmore resonances, and i pretty much abandoned any consideration of these designs due to the compromises you have to make.
dave
There's a million variations and combinations of so called "TL" box designs, crossing over to using various other principles ie rear loaded horn, tapped horn w single or multiple driver taps, bandpass, TQWT, BR with oversized / slot loaded / tapered / variations thereof, expo reflex, DCR, etc etc etc. Its an endless list of combinations you can have, some of which are marketed as all sorts of trademarked and patented designs which end up being gimmicky marketing, as observed by that famous four letter "B" word I so loath.
Just using various degrees of dampening inside the line changes and shifts modes of operation and performance. Its very difficult to design a properly working, natural sounding TL which surpasses the neutrality of a well executed sealed box.
In my experience, using a damped tapered line to terminate a sealed box is the best method to achieve the cleanest and purest sounding low end possible. Just the ability of breaking up internal enclosure modes is the biggest advantage to using a reverse tapered line to kill the nasties of enclosure modes. To do any better, you'd have to go to a OB design which has its own set of issues.
Regardless of which type of TL you employ, the fundamental advantage of them is being able to tune and adapt them to almost any environment.
Some of the best bass I've heard in terms of musicality and textured detail was from a very large inverse tapered TL design using two 12" Isophon woofers per side in 34 ft line length. It took the designer several months of tuning and tweaking to get it right, but it was the most accurate and resolving low end I've ever experienced. The response was flat to 12 hz and the bass was so effortless and free from room modes without the use of elaborate room treatments.
Just using various degrees of dampening inside the line changes and shifts modes of operation and performance. Its very difficult to design a properly working, natural sounding TL which surpasses the neutrality of a well executed sealed box.
In my experience, using a damped tapered line to terminate a sealed box is the best method to achieve the cleanest and purest sounding low end possible. Just the ability of breaking up internal enclosure modes is the biggest advantage to using a reverse tapered line to kill the nasties of enclosure modes. To do any better, you'd have to go to a OB design which has its own set of issues.
Regardless of which type of TL you employ, the fundamental advantage of them is being able to tune and adapt them to almost any environment.
Some of the best bass I've heard in terms of musicality and textured detail was from a very large inverse tapered TL design using two 12" Isophon woofers per side in 34 ft line length. It took the designer several months of tuning and tweaking to get it right, but it was the most accurate and resolving low end I've ever experienced. The response was flat to 12 hz and the bass was so effortless and free from room modes without the use of elaborate room treatments.
Not hard, just that the laws of physics dictate that a high performance design requires the designer to take due care of all the factors involved, since if they don't, the results are either not of high quality, or a result of luck.
Perhaps you could share your fairly simple criteria to designing them that produces repeatable results to any desired alignment with minimal effort? I've spent nearly 25 years now (ye gods, it doesn't seem that long, and there are others here who have double that, with extras) designing quite literally several thousand TL variations & I thought I had a reasonable grasp of the operating behaviour, but there's always something new to learn, thank goodness.
Scott came on the scene when modern modelers appeared. I built my first TL in 1975. And quite a few since. Designing a TL is easy for me, i just ask Scott (not as easy for him, but he has a huge amount of experiecne and many, many successful TL designs.
dave
Apparently never heard of a conical, etc., BLH 🙁.......... resonance concepts, air columns
Defined as having a ~uniform particle density 😉