You can disagree with the technical arguments. You can point out my mistakes. Please, do not resort to personal attack. 😡
Hi,
Poor understanding of the real physics. Poor and very biased descriptions
of the various TL options. Biased self justification in spades. No real idea
that the Bailey cannot be a 1/2 wave device, very poor basic TL theory.
Insisting LFW is the only way to do it properly, simply not true.
Insisting Bailey is right, when no-one agrees with you.
Insisting the Bailey TL is a unique solution.
No real useful advice to the OP.
Being good at maths means squat if the physics are wrong.
You can't blame someone that wants to assume your a pedantic troll.
rgds, sreten.
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Arthur Bailey and Leslie Bradbury provided very high quality test data in their articles. If those are not real physics, I don't know what it is. If you do not agree with with Bailey that the front and back waves in his tube are "in phase" (half wave) and the calculation of Bradbury's, show us yours.
If Bradbury's analysis and test data do not convince you that every type of fiber works differently in the TL tube, nothing else would. I am against anyone who changed Bradbury's equation to do misleading calculation that makes no sense to real physics. They never provided any test data to validate their calculation like Bradbury did.
Audio is just my hobby. I showed measurement of the Bailey TL I built. I do not have the kind of comprehensive data on LFW that Bradbury did. If you want to know the kind of physics I deal with daily, Google my name with my company's. They are in areas other than audio.
Where is your test and measurements? What makes you the authority of real physics?
Please, do not launch personal attack in this forum.
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Pillow stuffing, or BAF wadding is evidently poor at the bass end.
Correct me if I'm wrong, but a highly damped and labarynthine enclosure like the IMF TLS-80 must add a lot of delay with a long path for the bottom end at least. That dimpled foam must be a goodish idea for sheer resistiveness to airflow though.
I suppose we have various grades of transmission line, stretching from the IMF type through the quarter wave transmission line to the long reflex. Much the same thing according to Planet10.
They all have deep bass in spades. TBH, I get a bit confused about a floor pointing quarter wave or reflex, and a forward pointing IMF type.
As someone who doesn't know a lot about this, are you saying that transmission line is actually a quite shallow rolloff, whereas reflex is steep. So transmission line is quite fast and dynamic? Not my experience, TBH. Closed box is still the one that gets my feet tapping at the low end anyway. And I still like Steen Duelund's diagram even if it draws NO INTEREST WHATSOEVER from anyone here:
BTW, keilau, apologies but I can't quite get a grip on the possible sign error in the Complex number post you refer to. I'd guess that since heavy stuffing can produce a maximum 30% larger closed box in effect, the effect on a transmission line is to make it 30% longer, or deeper in effective bass performance.
As for whether it is quarter wave or half wave, I suppose that might depend on the orientation of the port. Surely a half wave port ought to be on the back of the speaker? IDK.
Correct me if I'm wrong, but a highly damped and labarynthine enclosure like the IMF TLS-80 must add a lot of delay with a long path for the bottom end at least. That dimpled foam must be a goodish idea for sheer resistiveness to airflow though.
I suppose we have various grades of transmission line, stretching from the IMF type through the quarter wave transmission line to the long reflex. Much the same thing according to Planet10.
They all have deep bass in spades. TBH, I get a bit confused about a floor pointing quarter wave or reflex, and a forward pointing IMF type.
As someone who doesn't know a lot about this, are you saying that transmission line is actually a quite shallow rolloff, whereas reflex is steep. So transmission line is quite fast and dynamic? Not my experience, TBH. Closed box is still the one that gets my feet tapping at the low end anyway. And I still like Steen Duelund's diagram even if it draws NO INTEREST WHATSOEVER from anyone here:
An externally hosted image should be here but it was not working when we last tested it.
BTW, keilau, apologies but I can't quite get a grip on the possible sign error in the Complex number post you refer to. I'd guess that since heavy stuffing can produce a maximum 30% larger closed box in effect, the effect on a transmission line is to make it 30% longer, or deeper in effective bass performance.
As for whether it is quarter wave or half wave, I suppose that might depend on the orientation of the port. Surely a half wave port ought to be on the back of the speaker? IDK.
Attachments
A 1/2 cycle the same as a BR. The back wave has to go far enuff to be in phase with the front.
At those frequencies everything is omnidirectional, so -- excluding boundary loading -- it makes no difference.
dave
It is unfortunate that the Bradbury paper is copy righted by Journal of Audio Engineer's Society and each download by non-member will cost $25. Below is the page of the Bradbury paper where a typo of the equation occurred.
Bradbury showed the computation results of air speed reduction and sound pressure attenuation in Figures 1 and 2. You will not get the numbers in these figures until you correct the size typo in equation 4. Once you do, bingo.
Because Bradbury presented his early calculation in parametric form, it may have caused additional confusion to the readers as I can see from comments by Martin King and Planet10. Instead of frequency, the early calculation was ploted using a wave number parameter, including packing density and drag coefficient. For a long fiber wool filling of 0.5 lb/cuft, you can get the frequency valve by multiplying the parameter (omega x P/lambda) by 14.4. From the Figure 1, you can see that the air speed is reduced by 1/2 at around 25 Hz. The actual reduction is a non-linear function of frequency. That makes the 2 meter Bailey tube a half wave length one at 25 Hz. Because the tube did not stretch in real physical length, it may be hard for some reader to accept calling a 2 meter tube half wave. From the attenuation plot in Figure 2, you can see that long fiber wool will present a very reactive loading to the woofer driver.
All the above results show that a long fiber wool reacts with sound wave very differently compared to other fibers. Bradbury did not include polyester in his analysis. I suspect that he knew that polyester had little reduction of air speed and poor attenuation in upper mid bass.
Because of these effect, it is technically correct for Martin King and Planet10 to call the polyester fill TL tube quarter wave and treat it as a resonance vented tube. Their design is based on completely different physics than the Bailey approach. It is just confusing to call both transmission line.
The fiber stuffing inside a closed box works differently again. The effect is mostly thermodynamics. Ken Kantor of the NHT fame did a fairly thorough research on various fiber while he was at AR.
http://auralization.blogspot.com/?zx=71b31d6d7a8c3d1a
I am afraid you cannot use closed box data to scale the Bailey transmission line effect. (One is thermodynamics, the other fluid dynamics.)
Hi,
The advanced nonsense above is just pathetic. If true, it would
be used enthusiastically by all and sundry after forty years.
Sadly it isn't true, and ploughing a lonely furrow is just sad.
There is only one set of physics that applies to all lines.
LFW does not change the game, why should it ?
rgds, sreten.
The advanced nonsense above is just pathetic. If true, it would
be used enthusiastically by all and sundry after forty years.
Sadly it isn't true, and ploughing a lonely furrow is just sad.
There is only one set of physics that applies to all lines.
LFW does not change the game, why should it ?
rgds, sreten.
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No, not all transmission line are created the same. If you build the Bailey transmission line, yes, "transmission line is actually a quite shallow rolloff, whereas reflex is steep. So transmission line is quite fast and dynamic".
George gpapag showed the impedance curves in post #21. I showed mine, both impedance and response curves, in post #22. In post #43, I showed the response curve from Bailey and several by Gary Galo. You can see they all have "quite shallow rolloff". Yes, the Bailey style transmission line are all "quite fast and dynamic" based on my listening test and others.
The above mentioned description does not necessary apply to those who build with a "quarter wave" plan. From what I can find on the net, those typically have the steeper rolloff of the bass reflex and a pronounced second bump in the impedance curve. Which one sounds better is NOT the discussion here, just their difference in measurable parameters.
BTW, who is BTH you called out in your post?
TBH= To be honest. Not BTH. 😀
I think I follow that, keilau. Damping the line gets you nearer closed box time response. But with nearer horn efficiency.
I'm not enough of carpenter to be doing this in the near future. But enjoying the thread.
It's actually a bit of a mirror image and inversion of Earl Geddes' damped horn tweeter. If you follow. 😎
I think I follow that, keilau. Damping the line gets you nearer closed box time response. But with nearer horn efficiency.
I'm not enough of carpenter to be doing this in the near future. But enjoying the thread.
It's actually a bit of a mirror image and inversion of Earl Geddes' damped horn tweeter. If you follow. 😎
Not exactly. Please, remember that I only quote Arthur Bailey and Leslie Bradbury in the objectlve, explanation and execution of the design. If you read the Bailey 1965 article, he wanted to get the driver loading (time response) of the infinite baffler and the efficiency of a bass reflex. It is the same direction as you described it, at different level.
The Bailey transmission line was very popular among the readers and editors of the Speaker Builder magazine in the 1970's. The articles on its page inspired me to build one pair. It was everything they said it was.
IMF founder Ian "Bud" Fried built a very successful business using the Bailey design. He later developed the foam filled enclosure and achieved the Bailey objective. I've heard the IMF model using the volume filled open cell foam and they sounded as the Long fiber wool one. Not sure how the later model using wall lined foam would have sounded. The IMF still have followers in the US.
IMF electronics
Most of IMF supporter hang around at the AudioKarma forum on speaker subgroup.
TBH, I like the closed box bass better than bass reflex and that's why I like the Bailey transmission line so much. But it is a very personal perference. Vented speaker in all forms are here to stay too.
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It should be noted that Byd did not found IMF or do any of the speaker design there. He was the US distributor.
dave
Yes, Bud Fried started with import business. His early credit included the Lowther corner horn and Quad Electrostatic.
stereophile said:
Irving M. Fried: 1920–2005 | Stereophile.com
As the legend goes. I do believe Bud Fried is a legendary figure in US audio history.
According to some of Bud Fried's former employees at his Philadelphia production facility, Bud is a very hands on speaker designer. (See posts by JimPA over at AudioKarma.)
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IMF = Irving M. ("Bud") Fried. Fried registered the IMF brand in 1961.
I met him only once when he came to Minnesota Audio Society to do a demonstration of his transmission line speaker products with several highend dealers from Minneapolis sometime in the 1970's. Yes, he was a little eccentric, but easy to talk to. I do not know him personally. But no one disputed that he got a golden ear and was a top notch speaker designer.
I don't know how accurate is the Stereophile memorial article on Bud Fried. But it seems to be consistent with the stories I heard over the years.
No, I do not know where Dave Planet10 got his information about Bud Fried.
Stereophile said:
I met him only once when he came to Minnesota Audio Society to do a demonstration of his transmission line speaker products with several highend dealers from Minneapolis sometime in the 1970's. Yes, he was a little eccentric, but easy to talk to. I do not know him personally. But no one disputed that he got a golden ear and was a top notch speaker designer.
I don't know how accurate is the Stereophile memorial article on Bud Fried. But it seems to be consistent with the stories I heard over the years.
No, I do not know where Dave Planet10 got his information about Bud Fried.
As a US company. He later gave the name to a small UK startup.
There was quite an exchange of information about this -- turns out much of what Bud claimed was marketing speak. Letters from the IMF founders are a major source. Bud did not design any IMFs or start the British company.
I will not diminish Bud's importance to hifi, he was a giant, I met him a couple times, and even believe he incorporated one of my design suggestions into his product line. I sold IMF and then Fried in the late 70s, and as i have stated owned TLS 80s & Fried Model H.
dave
Another important person to know about the commercialization of transmission line speaker is John Wright, the founder of TDL Electronics.
During the 1960s John Wright was involved with transducers at the front end of the hi-fi chain. His Audio & Design operation developed a well regarded pickup arm with mercury contacts to avoid lead-out wire torque, as well as the original vacuum record cleaning machine that is still made today under the Keith Monks brand.
The real business breakthrough, however, came around 1968, and at the other end of the hi-fi chain, when John’s large transmission line loudspeaker designs first appeared. Made by TDL with ELAC drivers, and marketed under the IMF Electronics brand, these monitors took advantage of the availability of high power transistor amplifiers to set a new ‘high-end’ benchmark, which helped raise the status and profile of British hi-fi speakers around the world. It was this combined Anglo-American company which produced the now legendary IMF Monitor, the first truly wide-band loudspeaker the world had seen, examples of which are still being used today.
In 1975, the English and American divisions of IMF parted ways and Bud Fried released speakers using the name "Fried." Among the speaker innovations under Fried's name were the Model H system, said to be the first modern satellite/subwoofer system; the Model M (1977), the first satellite/transmission-line subwoofer contained in a single unit; and the Super Monitor (1978) update of the IMF original. Bud's philosophy and speaker design legacy continue through Fried Products Corporation, a Pennsylvania corporation that was formed by a group of audiophiles including Bud Fried.
The above information are all from the page of "IMF People" at IMF Electronics.
IMF people - IMF electronics
During the 1960s John Wright was involved with transducers at the front end of the hi-fi chain. His Audio & Design operation developed a well regarded pickup arm with mercury contacts to avoid lead-out wire torque, as well as the original vacuum record cleaning machine that is still made today under the Keith Monks brand.
The real business breakthrough, however, came around 1968, and at the other end of the hi-fi chain, when John’s large transmission line loudspeaker designs first appeared. Made by TDL with ELAC drivers, and marketed under the IMF Electronics brand, these monitors took advantage of the availability of high power transistor amplifiers to set a new ‘high-end’ benchmark, which helped raise the status and profile of British hi-fi speakers around the world. It was this combined Anglo-American company which produced the now legendary IMF Monitor, the first truly wide-band loudspeaker the world had seen, examples of which are still being used today.
In 1975, the English and American divisions of IMF parted ways and Bud Fried released speakers using the name "Fried." Among the speaker innovations under Fried's name were the Model H system, said to be the first modern satellite/subwoofer system; the Model M (1977), the first satellite/transmission-line subwoofer contained in a single unit; and the Super Monitor (1978) update of the IMF original. Bud's philosophy and speaker design legacy continue through Fried Products Corporation, a Pennsylvania corporation that was formed by a group of audiophiles including Bud Fried.
The above information are all from the page of "IMF People" at IMF Electronics.
IMF people - IMF electronics
And one of the founders of IMF Elecrtonics in the UK (only the name came from Bud). Also the designer. TDL was a rebranded IMF.
dave
I wonder whether as a "total newbie", onkyponk feels that he has had his original question answered satisfactorily?
😉
A very pertinent reminder from surv1vOr about dealing with the query at hand.The specifications from KEF indicate that the B139,SP1044 is well suited to a vented enclosure of around 155 litre internal volume with an Fb of 25 Hz.Transmission line loading causes a delayed LF output signal which is colouration added to the original signal.Unfortunately constructors tend to avoid building to what the specifications indicate.Commercial reality can lead to an even worse compromise.Perhaps it would make more sense to arrive at a size of enclosure that would suit a listening room and then find a bass speaker that suits all the criteria demanded of it.After all, B139,s are old and spare parts unavailable.
I think the best recommendation is offer by George gpapag in post #29. George posted very details information on crossover and resultant performance using long fiber wool for stuffing in the post. onkyponk should be able to easily get the substitute crossover, stuffing material and other drivers from Falcon Acoustics in UK.
But onkyponk has his own idea and wants to lengthen the Bailey line by 30% to 2.6 meters instead of the original 2 meters design and make the line straight and no tapering. Tapering is in fact not necessary unless one wants to build a resonant vented line. His modular approach sounds like the Model H idea used by Bud Fried. (But different bass driver.)
Fried Model H
But it is easier to implement today. onkyponk should not need the huge coil for passive crossover at 100 Hz. Most modern preamp or surround processor have a subwoofer output. Many have adjustable frequency from somewhere between 60 to 200 Hz.
Hope that onkyponk will report back on his creation some time.
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I have never heard of TL loading having the delayed effect. Would you please explain why and provide a link to more detailed technical discussion on it.
I understand the advantage of time align all the drivers. But it is not the same as bass delay and coloration. I usually only heard that associated with horn loaded woofer.
On the contrary, Arthur Bailey showed that his TL design had very fast transient response to impulse signals, as compared to a bass reflex design.