I didn't say he was, or he should. What I said was that he showed impulse responses (one of the first published measurements in fact), which is great, but based on his not-very-detailed comments, the vented enclosures he compared it to were poorly designed / implemented examples of the type. In other words, he was selective in his comparisons, likely by accident, but still introducing a positive bias into his data presentation. His TL design was certainly better than most contemporary alternatives in that regard (as a type, they tend to be, and he was absolutely correct in identifying that) but not necessarily quite as much as implied.
The point is that these things are relative & need to be kept in mind. Bailey's two WW articles are interesting, but the fact is they don't present any design method or repeatable guidelines, nor, to the best of my knowledge, did he ever claim they did. Yet they still regularly seem to be held up as such, which without taking anything from Arthur, isn't what he intended, and don't in fact do. To give a simple example: his TL was a good design & worked well. But it was designed for the drivers he had / used, and as soon as you moved away from that, his articles cease to be of much practical value to a designer, because no method, no analysis of line dimensions, geometry, damping, etc. or how any of these may relate to driver characteristics was made.
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I just think there's a distinct difference between trying to eliminate resonances and their effects (Bailey) and leveraging them -- which seems to be what the new models attempt to accomplish.
Why not call the Hegeman-Morrison enclosure a transmission line? Might as well.
This is mostly a semantic argument. But it seem to me it's a little unfair to dis Bailey's effort in comparison to quite differently-intenrioned designs just because it was decided to borrow the name.
Why not call the Hegeman-Morrison enclosure a transmission line? Might as well.
This is mostly a semantic argument. But it seem to me it's a little unfair to dis Bailey's effort in comparison to quite differently-intenrioned designs just because it was decided to borrow the name.
It is based on a "multi-tap/multi-tuning" sealed transmisson line enclosure. Meant to distribute/blunt standing waves to form at any specific frequency.
While Bailey took Only’s comcept of an aperidic chamber (the acoustic labyrinth) http://www.t-linespeakers.org/download/Onley-acoustic-labyrinth.pdf i doubt he ever saw Onley’s paper.
Bailey did advance the concept by showing that one could (mostly) keep the fundemental, in phase at the terminus and (mostly) kill the unwanted ones.
His was a bit of a sledgehammer approach.
The modern modelers have shown what driver offset, large pre-chambers, restricted terminus, — all used historically without knowing what they really did — the effect of what a taper really dows and how they affect the line harmonics.
Bright people took these modelers and went exploring. We have a much richer field of designs. Each designer has their preferences and experiecne. Paul Kitt does (mostly) heavily tapered traditional lines. Dr Scott is more likely to produce an ML-TL. Take a look at the MJK gallery and get an idea of some of the versatility,
dave
I have no complaint with the rich design field you guys till, just what you choose to call it and how you look at Bailey in your rearview mirror. I know you guys do brilliant work. If/when I build my next loudspeaker cabinet it'll likely be one of yours... not a transmission line.
To my way of thinking a "sealed transmission line" is an oxymoron since it is anything but a "non-resonant loudspeaker enclosure" that is designed with the intent of "removing the rear cone sound energy [ ] by transmitting it down an infinite transmission line"... or at least it's nearest approximation. Intent is important.
Again, my quibble is mostly semantic. We wouldn't be having this discussion if the scope of the advanced modelling had been honoured with a new named -- The General Theory of Loudspeaker Enclosures, piped (or at least longish), sealed, unsealed, resonant and non-resonant etc etc.... unwieldy that. I'm not good with names.
But you might be celebrating Bailey and his designs as the, perhaps sledgehammer, idea -- his transmission line -- that sparked all this creative diverse thought rather than claiming his as a pretty poor excuse for a Pensil or whatever.
To my way of thinking a "sealed transmission line" is an oxymoron since it is anything but a "non-resonant loudspeaker enclosure" that is designed with the intent of "removing the rear cone sound energy [ ] by transmitting it down an infinite transmission line"... or at least it's nearest approximation. Intent is important.
Again, my quibble is mostly semantic. We wouldn't be having this discussion if the scope of the advanced modelling had been honoured with a new named -- The General Theory of Loudspeaker Enclosures, piped (or at least longish), sealed, unsealed, resonant and non-resonant etc etc.... unwieldy that. I'm not good with names.
But you might be celebrating Bailey and his designs as the, perhaps sledgehammer, idea -- his transmission line -- that sparked all this creative diverse thought rather than claiming his as a pretty poor excuse for a Pensil or whatever.
It really is quarter-wave design, but the word TL has pretty much become TL=QW. While a (traditional TL) is a quarter wave design there are many QW designs that are not traditional TLs. We have a greater understanding how reflex, TL/QW, Voigt, Horn and their hybrids are related and part of the same design space.
Neville, Thiel/Small opened up vented design to the masses decades after those of the pioneers, Bailey introduced us to tranmisison lines and started serious exploraton, The modern analyticalk modelers opened the design space to the masses and some have really run with it.
There is still so much to be explored.
dave
as I said, a sort of general unified theory of everything. not really TLs or even QWs...
all the same for some reason the scene in Notting Hill when the chap comes into Hugh Grant's travel bookshop and asks for anything by Dickens or the new Grisham popped into my head. a book is a book after after all. and all men are Socrates.
(sorry, I don't mean to belabour this. I'm just off a frustrating and pointless discussion about resistor wattage. all I wanted to do was fill out the documents in the archive which always seem to be missed)
all the same for some reason the scene in Notting Hill when the chap comes into Hugh Grant's travel bookshop and asks for anything by Dickens or the new Grisham popped into my head. a book is a book after after all. and all men are Socrates.
(sorry, I don't mean to belabour this. I'm just off a frustrating and pointless discussion about resistor wattage. all I wanted to do was fill out the documents in the archive which always seem to be missed)
That's not actually the case.
a/ 'Models' are just that: models. You can do what you like with them. And
b/ Augpurger in particular generated alignment tables that do just that, if you read his AES paper. His two sets of alignments were in fact very much in the Bailey / Radford mold -the difference being that unlike Bailey, Bradbury et al, he provided data that can be used in design, and tables that allow people to consistently hit those alignments with a wide range of drive units if they didn't want / didn't need the added flexibility of buying his software. Martin King also provides a similar set of tables, based on a slightly different, but similar sort of alignment.
So I'm afraid the notion that regularly gets repeated (i.e. that Bailey was doing something 'different' to everybody afterward) isn't actually true. The truth is that if 'I' (or anyone else) want a near-aperiodic type of line, which is what his basically was -I design one. No big deal about that. As it happens, I provided one on another thread only a few days ago -oddly enough, with a confirmatory model in Augspurger's software, which I'd felt like giving an airing as I hadn't used it for a while.
Nobody is 'dis-ing' Bailey. What I'm pointing out is that he provided no consistently usable design data beyond one (arguably two) specific designs. He gave some interesting general information, and a decent quality contemporary project, but nowhere, in his Wireless World articles, will you find
- Analysis of line geometry and its effect on Fp (which is important for aperiodic lines just as for any other)
- Analysis of damping materials (same or a variety), necessary quantities to achieve desired results in different lines
- Relationships established between driver characteristics / requirements and the line design / proportions
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So what you're saying, basically, is that what Bailey concocted was an alignment. A design intent which, as you point out, is the first step. You can do what you want.
I agree.
it's also a different intent than Hegeman had when he bundled a bunch of tubes in a closed box and crafted a multi-resonant affair. A very different alignment.
Bailey called his alignment (or at least adopted the name) a transmission line. That doesn't make what Hegeman built a "TL" even if some of the enclosure behaviour falls under the rubric of general quarter wave theory and modeling.
The name goes with the intent.
You touched on this in your presentation back in 2018 (which was a good show by the way). I run into the same problem with my main passion, electoral reform: poor language gets in the way of meaningful discussion with little progress and often leads to unnecessary acrimony.
it's too bad Bailey didn't publish more on his empirical work... he obviously did a fair bit.
By the way, what did your aperiodic line wind up looking like?
I agree.
it's also a different intent than Hegeman had when he bundled a bunch of tubes in a closed box and crafted a multi-resonant affair. A very different alignment.
Bailey called his alignment (or at least adopted the name) a transmission line. That doesn't make what Hegeman built a "TL" even if some of the enclosure behaviour falls under the rubric of general quarter wave theory and modeling.
The name goes with the intent.
You touched on this in your presentation back in 2018 (which was a good show by the way). I run into the same problem with my main passion, electoral reform: poor language gets in the way of meaningful discussion with little progress and often leads to unnecessary acrimony.
it's too bad Bailey didn't publish more on his empirical work... he obviously did a fair bit.
By the way, what did your aperiodic line wind up looking like?
Inasmuch as every loudspeaker by default has an alignment of some kind, yes. However, it's important to understand that Arthur did not set any specific design or performance metrics in this regard. He had more generalised goals, but no precise targets.
Sort of. An alignment is an alignment, i.e. a specific set of criteria that something conforms to. 'Design intent' may include a specific alignment, but it may also (as in this case) be more generalised. There's nothing wrong with the latter, but it's not necessarily the same thing.
Yes, they are different forms of quarter-wave enclosures, with different objectives -I doubt anybody would suggest otherwise.
Certainly not by his objectives, although people are free to call it what they like of course (and do 😉 ).
'Transmission Line', as I and others like Dave have pointed out for decades, ended up being popularly adopted as a quick & dirty cover-all term to describe all manner of QW / HW enclosures, spanning the gamut from highly resonant types to max-flat impedance designs at the other end of the spectrum. Whether it's accurate or not is another matter. It's borrowed from electrical engineering, and since it's basically used to describe a structure long enough that wave behaviour needs to be accounted for / comes into effect (the actual details of the behaviour are immaterial as far as the name goes, providing it possesses that basic characteristic), it's not entirely unreasonable in this application. It's also not helped by the fact that Bailey titled his October '65 WW article 'A Non-resonant Loudspeaker enclosure design' and then proceeded to describe an enclosure that actually is resonant -albeit only mildly. Whether we like it or not though, we're never going to get shot of it. It's been used for too long, so all we can really do is be clear about the characteristrics and objectives for a given design or designs. The same can be said for plenty of others -'aperiodic' is a prime example, because what most people describe as an aperiodic enclosure is not technically aperiodic (as in 'without period') but a leaky sealed / resistively vented box. Again -the term has been around for too long & is too embedded in the 'popular' terminology now for us to get rid of it, so for the most part we just try to get on with it, and when necessary make clear what we're doing so everybody is on the same page. It's when we don't do that that problems tend to occur.
He appears to have done, judging from comments like 'a typical set of curves', so yes -it's a shame he didn't provide more. Possibly he had an eye to commercial applications, and however heavyweight it is / was in terms of the popular press, Wireless World isn't an academic journal (as well as having limited space!) so he may have felt the readers would be more interested in a practical project than the actual data. We're in '65 also of course, so while Novak / Beranek have continued to break down driver characteristics using filter theory, and Thiele has also published -the latter's time 'was not yet' and wouldn't really be until Small made further expansions, so it's to a point understandable why he didn't relate his line dimensions etc. to driver behaviour beyond the basket diameter / cone area references popular at this time.
'Near-aperiodic' rather than aperiodic. Just a continuation of my desktop / standmount labyrinth series (attached). When I design them it's to the alignment shown (this is a specific, repeatable alignment of my own -the frequencies & SPL vary of course depending on driver, but the actual alignment in terms of shape, behaviour etc. is consistant) which is quite similar to Augspurger's and Bailey's, but they're run as acoustical labyrinths with the lagging indicated in the sketch & notes, as most people want / require the higher gain with small drivers.
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"not by his metric"
...well he did the naming. that's the metric.
If anyone can call whatever anything they want then words don't mean much... welcome to Trump's world of alternative facts.
as far as the language goes, you're a recognized authority in some well-regarded circles. if you're rigorous then people will follow. Slowly perhaps but it will change.
For instance i wouldn't term an acoustic labyrinth a transmission line. It's another alignment that produces near-aperiodic results. But they're different.
This is all semantics but words are important. For those of us who are not well versed (Iean me), we only become "versed" if we are exposed to the right lyrics.
I appreciate the time you've spent on this discussion. Thanks.
...well he did the naming. that's the metric.
If anyone can call whatever anything they want then words don't mean much... welcome to Trump's world of alternative facts.
as far as the language goes, you're a recognized authority in some well-regarded circles. if you're rigorous then people will follow. Slowly perhaps but it will change.
For instance i wouldn't term an acoustic labyrinth a transmission line. It's another alignment that produces near-aperiodic results. But they're different.
This is all semantics but words are important. For those of us who are not well versed (Iean me), we only become "versed" if we are exposed to the right lyrics.
I appreciate the time you've spent on this discussion. Thanks.
I have strong opionions on that, but politics…
Language evolves, the term TL has, by use, evolved to cover a much broader range than originally intended. We can discuss that forever, but the real point is to design loudspeakers.
Vented modelers in the early days were pencil, paper, and slide rule, and we saw specific box alignments — once computer based modelers became prevalent it became obvious that it was a continuum of alignments and one didn’t have to target one of those alignments — i can’t recall any of the names, or care to, Scott can rattle some off.
MJK, and to a lesser extent pulled back the curtains to show how much more expansive this design space was than most ever imagined.
dave
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Me too. There are lots of people with strong feelings and opinions, many of which are biased into meaninglessness by the poor language that has become "standard". Most discussions are people talking past each other or circular and unproductive.
In other news:
lessor ---> lesser ?
expensive --> expansive ?
and the link is broken (I'd be interested...)
M
No need to explain. We all suffer under this automatic know it all technology to varying degrees.
Link?
Link?
In Post #31? I see it there, it is unfortunately a transparent gif so if you have black mode it may be hard to see.
dave
dave
OK. i looked again, it is a pdf not a gif, might not work on some mahines. You might have to Control-clik and download it.
dave
dave
Not so. As I pointed out, the term can be legitimately applied to other forms of quarter-wave enclosure. It's when people either aren't clear about what they're doing, or start thinking they have some kind of exclusive right to a term that problems start to occur. As far as the physics goes, and repeating what I said above, the term is borrowed from electrical engineering, and basically used to describe a structure sufficiently long that wave behaviour needs to be accounted for / comes into effect in its operating bandwidth. The actual details of the behaviour are immaterial as far as the name goes, providing it possesses that basic characteristic. So technically speaking it's a valid alternate name for quarter-wave (or half-wave) structures. And since Bailey's own line was mildly resonant -despite his title- the argument that the term 'must' only apply to critically / fully damped structures falls at that hurdle as well, since his wasn't.
I hope not -authority I ain't, thank goodness. There are others here and elsewhere who could legitimately call themselves that; none do as far as I know, and they have all the more respect from me because of that. To my way of thinking, what would be more useful is just an improved general understanding of the whole field.
Neither would I, in general.
It's a different, albeit very closely related type of enclosure, rather than a different type of alignment. All loudspeaker loads have an almost infinite range of possible alignments within their particular types or sub-types, some (many) of which may be equivalents, but acoustic[al] labyrinths and transmission lines aren't themselves actually 'alignments'. That simply describes a variable characteristic that they they possess.
Blimey, I'd forgotten that Seas / WD line. Well remembered, Dave! 🙂
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