Transmission line and loudspeakers

Martin King's MathCad worksheets. They only look frightening. Actually, they're quite easy to use; I'd advise sticking with the ML TQWT sheet to start off with. You just need to input the T/S parameters, and then play around with enclosure dimensions.

Remember:
So = the surface area of the closed end
Sm = the surface area of the end which has some form of opening in it. The rest, like line length, stuffing density and driver position are self-explanitory, and Martin's tutorial explanations are easy enough to follow, and very detailed.

There are 3 TL types you can try;
TQWT -narrow at the top, wide at the bottom (or end ofthe line)
Traditional -wide at the top, narrow at the bottom (ditto)
Straight -same size top and bottom.

Mass loading involves placing a port at the end of the line, like those used in reflex designs (that doesn't make these reflex cabinets though) -you can specify the dimensions here as well. Read the articles Bob Brines has written on this subject for more and some good starting values and guides. If you need any further help, sing out. There are simpler programs, but none will give the stunning results Martin's MathCad sheets provide.

Best
Scott

Is it possible to find a simple, really simple, software or program, without a lot of math or formulas, able to help in designing a transmission line box, having the T+S parameters of the speaker of course?

Click to expand...

Sure. I have a variety of MathCad worksheets and the free version of MathCad Explorer that can be downloaded from my site. The minimum effort required can be found in "TL Open End.mcd" where all you need is the cross-sectional area at each end, the length, and the stuffing density. If you take the next step up to "TL Offset Driver.mcd" you need to also specify the driver position. My TL alignment tables will provide an initial estimate of the areas and length for the TL that can be entered into the MathCad worksheets. Bob Brines also has some excellent recommendations for transmission line geometries on his site. All you need to do is iterate a little on the design inputs to see if you can improve on the calculated response. It is not that hard.

I don't know of anything that is more simplified then these recommendations that will ensure you get a TL design that works well. There is no rule of thumb design or simple Excel spreadsheet that provides a magic answer. For a TL enclosure, I think that at some point you need to do some calculations to produce a good design. Fortunately, all the math is programmed into the MathCad worksheets so all you have to do is enter input values and look at the plots.

Hi Martin,

I just wanted to ask- do you discuss group delay and transmission lines in anything on your site? I think I remember reading somewhere that the group delay is related to the slope of one of the graphs in your simulation pages.

Thanks in advance,

Joe

Hi Joe,

RPI to San Fran! My wife and I visited San Fran for almost two weeks before the kids, when we had a life and did nice vacations, and it was one of our favorite vacations. Great city and surrounding area.

Back to your question, I have added extra plots for both group delay and for air velocity in the port/terminus to the bottom of several of my worksheets in the past. If you need it for a particular worksheet I probably have it available and can send you a copy. Just let me know which worksheet, you can then copy the region and paste it into the other worksheets. Send me an e-mail off line if you are interested.