Is the Daline concept outdated, are there better solutions nowadays?
I understand that this is a variation of a transmission line design. In that it's a speaker in an enclosure playing into a transmission line. Instead of being a simple enclosed or ported volume, the speaker opens into a folded transmission line.
What are it's perceived benefits / disadvantages?
Tip_80
Following on from this thread. Where I am trying to achieve full range sound with near wall placement.
I understand that this is a variation of a transmission line design. In that it's a speaker in an enclosure playing into a transmission line. Instead of being a simple enclosed or ported volume, the speaker opens into a folded transmission line.
What are it's perceived benefits / disadvantages?
Tip_80
Following on from this thread. Where I am trying to achieve full range sound with near wall placement.
It's another way of saying a TL / QW pipe with a filter chamber. They have little / no performance advantages compared to an equally well designed tapered line with an appropriate driver offset and many of the assumptions about them are erroneous. The low pass effect is fairly minimal in outright terms, as you'd expect if you think about the physics.
Broadband sound with near-wall placement needs a well-damped LF alignment (which can be achieved with a variety of enclosure types, though TLs are an obvious choice) and an appropriately designed FR / crossover. All quite achievable.
Broadband sound with near-wall placement needs a well-damped LF alignment (which can be achieved with a variety of enclosure types, though TLs are an obvious choice) and an appropriately designed FR / crossover. All quite achievable.
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Basically the shape of the LF response. Partly the Q factor. See attached.
This is same driver, two vented boxes for simplicity as I've got to go out in a minute, mathematical alignments assuming anechoic conditions. Yellow is maximally flat. In most cases you will have excessive LF output under most practical situations due to boundary gain. The blue trace is a more highly damped alignment which is more practical in many cases, especially near walls. A well-damped TL tends to provide a response shape similar to the latter (it has other attributes but we're focusing on LF response shape here). As you can see though you can achieve a nicely damped LF response with various box types (assuming the driver is capable of it), vented being the example here. Sealed is another. A Qtc there of 0.707 = maximally flat (lowest possible F3) Butterworth. But again, it may not be the most practical if you have an extended LF response & you may wish to go to a lower (more highly damped) Q.
This is same driver, two vented boxes for simplicity as I've got to go out in a minute, mathematical alignments assuming anechoic conditions. Yellow is maximally flat. In most cases you will have excessive LF output under most practical situations due to boundary gain. The blue trace is a more highly damped alignment which is more practical in many cases, especially near walls. A well-damped TL tends to provide a response shape similar to the latter (it has other attributes but we're focusing on LF response shape here). As you can see though you can achieve a nicely damped LF response with various box types (assuming the driver is capable of it), vented being the example here. Sealed is another. A Qtc there of 0.707 = maximally flat (lowest possible F3) Butterworth. But again, it may not be the most practical if you have an extended LF response & you may wish to go to a lower (more highly damped) Q.
Attachments
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Thank you - I also found this on the Nelson Pass website which is helpful.
“Personally we favor a well-done transmission line over a bass-reflex enclosure. The bass is tighter and less boomy, It also tends to extend deeper. Part of this effect comes from the actual lowering of the resonant frequency of the woofer due to the additional air mass it has to push in the pipe.”
PassDiy
So the benefits I’ve been hearing (I.e. very little bass boom compared be ported designs in near wall placement) of a transmission line are due to the damping effect of the cabinet and a reasonably low Qts value (0.35 for the HiVi F6 mid/bass driver in my IPL speaker).
I also found this great summary about transmission lines:
“BACKGROUND
A TL enclosure ideally is infinitely long and completely absorbs the backwave from the driver. Since this is not practical, a judiciously chosen finite length is used instead, and radiation emanating from the open end reinforces the direct output of the driver. The resonant behavior of the pipe serves to reduce cone motion at strategic frequencies. The absorption in the line increases with frequency, reducing or eliminating higher order resonances and further serving to damp the driver's fundamental resonance. In practice, this is found to be quite effective and the TL has earned for itself a reputation as a "non-resonant" enclosure [6]. The distinguishing feature of the TL is that unlike closed or vented boxes, it does not attempt to augment bass response with additional resonances.”
Transmission Line Speaker Calculation | Perry Marshall
So getting a speaker that works well at near wall placement is all about lowering the resonance of the speaker - something which transmission lines are good at.
“Personally we favor a well-done transmission line over a bass-reflex enclosure. The bass is tighter and less boomy, It also tends to extend deeper. Part of this effect comes from the actual lowering of the resonant frequency of the woofer due to the additional air mass it has to push in the pipe.”
PassDiy
So the benefits I’ve been hearing (I.e. very little bass boom compared be ported designs in near wall placement) of a transmission line are due to the damping effect of the cabinet and a reasonably low Qts value (0.35 for the HiVi F6 mid/bass driver in my IPL speaker).
I also found this great summary about transmission lines:
“BACKGROUND
A TL enclosure ideally is infinitely long and completely absorbs the backwave from the driver. Since this is not practical, a judiciously chosen finite length is used instead, and radiation emanating from the open end reinforces the direct output of the driver. The resonant behavior of the pipe serves to reduce cone motion at strategic frequencies. The absorption in the line increases with frequency, reducing or eliminating higher order resonances and further serving to damp the driver's fundamental resonance. In practice, this is found to be quite effective and the TL has earned for itself a reputation as a "non-resonant" enclosure [6]. The distinguishing feature of the TL is that unlike closed or vented boxes, it does not attempt to augment bass response with additional resonances.”
Transmission Line Speaker Calculation | Perry Marshall
So getting a speaker that works well at near wall placement is all about lowering the resonance of the speaker - something which transmission lines are good at.
It's not about 'lowering the resonance of the speaker' per se, it's simply about achieving a reasonably well-damped alignment. Some TLs possess this (the ones that are designed to, and those that do by accident 
). However, many sealed and vented box speakers do as well.
A couple of points about the Marshall piece you link to. Firstly it assumes a non-resonant variation; however, most boxes described as TLs are actually mildly - strongly resonant & in fact this is seen in his modelling. He also utilises Bradbury's aerodynamic drag assumptions for damping, which have since been shown incorrect (a pity, as it's a nice piece of maths -that said Bradbury himself noted the poor correlation of his theory to measured results at low frequencies). Nor did Marshall actually compare his model with measured data. So I would be a trifle cautious in using it. If you want proper TL data, Augspurger and Martin King have produced the best easily available works on the subject.
). However, many sealed and vented box speakers do as well.A couple of points about the Marshall piece you link to. Firstly it assumes a non-resonant variation; however, most boxes described as TLs are actually mildly - strongly resonant & in fact this is seen in his modelling. He also utilises Bradbury's aerodynamic drag assumptions for damping, which have since been shown incorrect (a pity, as it's a nice piece of maths -that said Bradbury himself noted the poor correlation of his theory to measured results at low frequencies). Nor did Marshall actually compare his model with measured data. So I would be a trifle cautious in using it. If you want proper TL data, Augspurger and Martin King have produced the best easily available works on the subject.
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A very dated and partially correct (in a small subset of TLs), and partially BS. Good reason to avoid this site.
Anyone interested in TLs needs to thoroughly go thru the material Here: Quarter Wavelength Loudspeaker Design
dave
Me too and I've been making speakers for 60 years.
Starting with a fairly straightforward problem - out of phase back radiation - there's an endless tower of complexity from the mathematical minded.
All you need to do is sequester rear radiation or engage the rear radiation without too much phase cancellation and, of course, without unduly impairing the front radiation ability of the driver.
Endless ways to do that, esp if you aren't a purist about it.
I'm working on a folded 18 foot Voigt pipe sub, with the outlet a further 6 feet from the driver.... kind of like the first posts in this thread.
B.
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