Anybody ever heard about a Transmission Line with passive radiator termination?
I have access to a large woodshop and have been thinking about a TL. Still at the day-dream stage. I have a spare 12-inch woofer with matching passive radiator sitting idly nearby... devil finds use for idle drivers, eh.
Thanks.
B.
I have access to a large woodshop and have been thinking about a TL. Still at the day-dream stage. I have a spare 12-inch woofer with matching passive radiator sitting idly nearby... devil finds use for idle drivers, eh.
Thanks.
B.
Many thanks for your deep-dive into audio history. Yes, right company and their TL with passive radiator is the "Diapason". But I could find no posted details. Sad to read nonsense prose posing as profundity* and likely coming from somebody as old as me.
What do you mean by "ML-TL"?
Thanks.
B.
*on every speaker description, he waxes lyrical about Stokowski and the Chicago Sym Orch stereo broadcast. I could be mistaken, but sure sounds like dementia to me since the famous experiments were with Philadelphia.
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I see from your signature that you are interested in TL speakers.
Alas, after reading King's and Augspurger's papers, they seem to me to have come to few actionable conclusions different from the naive/obvious TL theory of yesteryear (except for the value of tapering the pipe). So I still don't know enough to make sense of your post. Grateful if you could explain your explanation.
B.
The mass-loading port tube (circled in red in the attachment) located at the exit of the transmission line in a ML-TL design, can be replaced by a passive radiator.
Attachments
That you much, David. The scales are beginning to fall from my eyes.
Don't you hate it when some idiot starts a thread without doing enough homework first. So as penitence, here's a little summary of TL to guide anybody who accidentally started reading this thread and got more confused by it:
Long, long ago, folks thought they'd attach a half-wave pipe to the back of a driver like an organ pipe in order to use that output productively and in phase with the driver front wave. Turns out there's no way to put that much bulky piping behind the driver and then plainly tumbling out a vent and get the result naive theory would expect. Or at least not particularly close. So much for TL hopes.
But if you don't fancy bass reflex boxes, you can use a long pipe in much the same way as a box Helmholtz resonator with various advantages and disadvantages. Simply by tapering the pipe from head to port, you can get it to resonate with the mass of air and presto-digito an overweight complex BR box-like performance; in that case, a quarter-wave is your choice. Or you can stick a tube or passive radiator on the end, again just like a BR box.
Luckily, you can adjust the tube - almost exactly as you would a BR box - and have it land in the wide range from "aperiodic" to leaky-box to over-stuffed sealed box character, rather rich choices. And funny, the "adjustment" is all in terms of handfuls of long-fibre wool (must be from English sheep, of course). Tricky since hands differ in size, a new fudge factor which Hornresp really should incorporate (as well as King's MatLab sims).
Less confused now? I hope so.
B.
Don't you hate it when some idiot starts a thread without doing enough homework first. So as penitence, here's a little summary of TL to guide anybody who accidentally started reading this thread and got more confused by it:
Long, long ago, folks thought they'd attach a half-wave pipe to the back of a driver like an organ pipe in order to use that output productively and in phase with the driver front wave. Turns out there's no way to put that much bulky piping behind the driver and then plainly tumbling out a vent and get the result naive theory would expect. Or at least not particularly close. So much for TL hopes.
But if you don't fancy bass reflex boxes, you can use a long pipe in much the same way as a box Helmholtz resonator with various advantages and disadvantages. Simply by tapering the pipe from head to port, you can get it to resonate with the mass of air and presto-digito an overweight complex BR box-like performance; in that case, a quarter-wave is your choice. Or you can stick a tube or passive radiator on the end, again just like a BR box.
Luckily, you can adjust the tube - almost exactly as you would a BR box - and have it land in the wide range from "aperiodic" to leaky-box to over-stuffed sealed box character, rather rich choices. And funny, the "adjustment" is all in terms of handfuls of long-fibre wool (must be from English sheep, of course). Tricky since hands differ in size, a new fudge factor which Hornresp really should incorporate (as well as King's MatLab sims).
Less confused now? I hope so.
B.
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So you go from wanting to build a TL, to making fun of people who want to build a TL, to making fun of people who write TL simulators? 
OTOH, I have heard some Shahinians - Compass or Starter and one of the pyramid models, can't remember which - they sounded nice in a big diffuse-reflective room.
OTOH, I have heard some Shahinians - Compass or Starter and one of the pyramid models, can't remember which - they sounded nice in a big diffuse-reflective room.
Yes, while the Shahinian speakers may have their adherents and have been around through decades of (opportunity for) development, their website prose really smells awful and has "fake-news" characteristics.So you go from wanting to build a TL, to making fun of people who want to build a TL, to making fun of people who write TL simulators?
OTOH, I have heard some Shahinians - Compass or Starter and one of the pyramid models, can't remember which - they sounded nice in a big diffuse-reflective room.
I said nothing critical about sims except to thank David. My joking about "handfuls" clearly was a riff all my own. In practice, the wool handfuls are quite precisely measured in quite precise specification and quite specific about where in the pipe it goes (and I think that is hilarious).
Nor did I say anything critical of those who wanted to build a TL except to say there are advantages and disadvantages relative to other resonant tuned boxes.
I did say the original theory is naive. A TL is not an organ pipe or, with respect to Augsberger, only partially much like a horn. I'll stick with that assessment.
My intuition is that TLs can be superior to resonant Helmholtz boxes because it allows more relevant audio dimensions to fiddle with (and with the right handfuls of wool). I suppose a very "aperiodic" BR and a well-stuffed TL are comparable.
B.
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The name "Helmholtz", one of my science heroes, is applied to all the stuff he studied as an adjective as well as coke-bottle type resonance as in a BR.
The problems with TLs, as I struggle to understand it*, it that they are hybridized from the get-go. Yes, an open pipe has some characteristics. But when you taper it or add a vent or port or tube or wool or bends or rough sides, it acts differently. For example, the speed of sound slows in ways that are challenging to predict. Thus the tuning and sonic behaviour changes.
Just because a deified "MJK" produced a picture out of theory (not measurements) doesn't mean that's how the TL behaves. But really pretty pictures.
I repeat, TLs look like a promising technology to me.
B.
*ooops, I never realized before yesterday that there are TL "true believers"..... kind of like the TH adherents found only at the DIYaudio sub forum
The problems with TLs, as I struggle to understand it*, it that they are hybridized from the get-go. Yes, an open pipe has some characteristics. But when you taper it or add a vent or port or tube or wool or bends or rough sides, it acts differently. For example, the speed of sound slows in ways that are challenging to predict. Thus the tuning and sonic behaviour changes.
Just because a deified "MJK" produced a picture out of theory (not measurements) doesn't mean that's how the TL behaves. But really pretty pictures.
I repeat, TLs look like a promising technology to me.
B.
*ooops, I never realized before yesterday that there are TL "true believers"..... kind of like the TH adherents found only at the DIYaudio sub forum
Wrong. Measurements are identical to the software simulation. Do you have a measurement to contradict this? Not likely.
Basic fact from scientific method: Theory is based on observing and measurements.
Software simulation and measurements may produce really pretty, but also a very ugly, hideous pictures (and sound) - it depends on your knowledge of loudspeakers.
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Taper affects where the harmonics show up, for a given fundamental, a line that tapers such that it gets smaller towards the terminus can be shorter, a line the tapers the other way has to be longer.
A restricted terminus (port) acts as another pole in the terminus low-pass function, and allows for a shorter line.
Damping (wool or other poly fluff) has been shown to not appreciably change the speed of sound.
Bends are not really seen at the frequencies of interest, but the increase in line cross-section if the bend does not have an angled bit added acts as an additional LP filter (a good thing).
Rough sides of any appreciable dimension (relative to the frequency involved) is not something well studied but would affect the cross-section.
Well i don’t know how much theory is involved, the shape is defined, a mesh added and ANSYS calculates what the air molecules do.
dave
Post containing nothing but vitriolic insults is against forum rules, not to mention common decency.
Care to provide an example of where I diss'ed "MJK"?
Granted, I think it is straaaaaaange for you to deify anybody with a "MJK" holy and solemn reference as you and others seem to glorify.... as if you believe "MJK" is some kind of exalted saint or leader of a cult.
B.
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There you go with the personal insults. He is not deifing Martin. Martin has earned much respect for being instrumental in leading us out of the wasteland as far as TL design goes.
dave
if I recall, if you were to design a TL with the pipe tuned to the f3 of a sealed box of the same overall volume, isn't it's behavior and rolloff similar to that of the sealed box?
haven't dug through Martin's site in eons and when he was publishing the bulk of his work and active in message boards and forums I was an 18 year old kid.....but I somehow recall the above from the "classic" TL model...
haven't dug through Martin's site in eons and when he was publishing the bulk of his work and active in message boards and forums I was an 18 year old kid.....but I somehow recall the above from the "classic" TL model...
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