transmission lines and standing waves

The problem of standing waves in any speaker design is a serious consideration (though there are many ways to get around the problem), in a TL design it is no less critical.

Yet most TL designs are of the "box type" where the labyrinth may not have many right angles, it is nevertheless enclosed in a simple rectangular box with at least two parallel sides.

One way of reducing the standing waves in a regular speaker design is to design the enclosure so that there are no parallel sides.
Can this be done with/for a TL design, or is it redundant and otherwise too expensive?
 
You can, but it's not massively critical in an acoustic sense given that the wavelength of the lateral standing waves is short, relative to the primary longitudinal, and thus easily absorbed by the internal damping.

I also add on this that the back chamber of the speaker and the opening ,form an acoustic low pass filter. By this the high frequencies that will create standing waves do not enter the TL or the horn.
 
As in the reflections off the wall back to the cone & either passing through or modulating the moving components? Sure, this requires addressing & is one reason it's not a good idea to have walls in too close a proximity to the cone. By and large, except on very narrow boxes it's easy enough to address though given the wavelengths involved.

The eternal difficulty with working with either of Bailey's (very interesting / valuable) magazine writeups is that he raised a number of reasonable points but presented almost no hard data in the form of tabulated infomation, equations or measured graphs for wider analysis or use. So trying to apply some of his work in a general sense is problematic -the commentary on reflectors for example, which is fine within the context of what he was doing, but does not automatically apply when moving somewhat outside that. And so on.
 
Thank you for all your fine comments and insights. They have been a great help.

While there are many good design calculators out there which will help the designer with a TL design, given the details that exist for optimizing each configuration that may not be a part of the spread-sheet or other design calculator program, do you know of anyone who has maximized and then integrated the design details best?

I ask specifically because I am sure it is an arduous task that requires many years of experimentation, measurement and failed designs, something which I do not want to invest in. I do however want a good (experimentally and proven good by measurement) design for which I am willing to pay. Please advise. Thanks in advance.
 
Well, a QW / TL is no different to any other type of load in that it is designed to a specific criteria, for a specific drive unit, so there is no 'one size fits all'; there is and are significant variations in all of these things; in essence it depends what it is you are doing and why.

It also depends very much on how you define the term 'best'. 😉
 
I understand that the word best is loaded to which I would add: best for this speaker.
I have a pair of Philips 8" high impedance (400-800ohm) full range drivers for which I also have their T/S parameters. I would be interested in:
1) knowing their maximum (lowest) extension in a TL enclosure (high frequencies above 5khz will be crossed over);
2) the enclosure that would reduce distortions, increase efficiency;
3) building the design.
I understand that you do this commercially and with it can guarantee precision in your designs and applications.
Please advise.
 
Well, first up I should be very clear that I am on this forum as a fellow DIYer, no more.

Going though the first two points in order, and assuming for the sake of this post that it is suitable for any kind of vented loading:

1/ Depends on how you're classifying a TL enclosure; it's become an umbrella term that covers a range of different sub-types of enclosure. Ultimately in each case though it's mostly defined by the T/S data (as applicable with the driving amplifier).

2/ Efficiency only applies over the enclosure's operating BW, in the case of a TL variation the LF. Likewise, distortion depends on what distortion, specifically, is being referred to, but if it's driver distortion, then within limits the more efficient the LF load, then the less hard the driver is working & the lower its distortion.
 
The problem of standing waves in any speaker design is a serious consideration (though there are many ways to get around the problem), in a TL design it is no less critical.
Yet most TL designs are of the "box type" where the labyrinth may not have many right angles, it is nevertheless enclosed in a simple rectangular box with at least two parallel sides.
One way of reducing the standing waves in a regular speaker design is to design the enclosure so that there are no parallel sides.
Can this be done with/for a TL design, or is it redundant and otherwise too expensive?

It does not matter if the ends are "parallel" walls. All that matters is the length of the tube, and how it is terminated (open end vs. closed end). A closed end corresponds to a node of the standing wave (pressure maxiumum), whereas an open end corresponds to an "anti-node" (velocity maximum). Then it's just a matter of finding the wave length(s) that fit those node criteria.
 
While there are many good design calculators out there which will help the designer with a TL design

Ignoring Akabak, i only know of 3, and the best of those is pretty much NLA, another has no more support, and i rarely see people using the damping in HornResp so sims are very hard to interpret.

There are no on-line calculators that work.

dave
 
Could work, i haven’t seen many sims from it.

Does it allow for the addiiton of damping (recently added to HornResp, but the only sims i have seen that use it are from McBean himself as examples.)

I don’t use any of these since they are all PC, and Scott has so much experience with TLs and a large set of tools i just email him. He generates many boxes and i am always working on catch-up to get drawings done.

dave