Designing a transmission line cabinet

Sean, you should get in contact with the transmission line guru, himself, Bud Fried. Although he is an irrascible type, and might spend all his energy dwelling on the top rather than front baffle, to me, it would be worth the effort.

The critical things about transmission line loading are the dimensions of the pipe(both length and diameter), damping the pipe(the most underappreciated, underrated, least understood facet of TL), and the exit of the tunnel. I have yet to tackle a TL project, but have always been interested from the periphery.

When a great deal came up on a pair of Frieds, I jumped on them. And, I hope to purchase another pair in the future. I am quite happy with the pair I own, although the speaker does not excel in any area outside of mid/high frequency response in my mind. The bass of my pair, a line tunnel, not a formal transmission line, is good but does not compare to my Coincident Troubass subwoofers, they are night and day.

Supposedly, the finest effort of Bud's in terms of TL design was his "coffin" sub(sorry, but I now cannot remember the model designation - D10 maybe - it'll come to me...). This was an old design, and I believe he offers the plans to those interested. In the more recent years of his company's existence, he did not produce ANYTHING on the scale of the coffin, though many seem to hold the Valhalla in high regard.

I would just be interested in anything he could throw my way. One of these days, I too, should contact him, and learn as much as I possibly can from one of the icons of loudspeaker design.

GOOD LUCK!

Sean, as you know, you can only calculate a reasonable starting point and work from there. Unless you have a pre-designed cabinet plan that is known to work for those drivers. One plan that could work with them would be the "Ace" cabinet. This is a "double Voigt Pipe" folded design, that was originally made for Lowthers. It had an up-firing Lowther with a 360 degree reflector mounted above it. If you made this design with a Walsh driver, it would not need the reflector, and would still have the omni pattern. The cool thing about the "Ace" cabinet, is that it has 2 different Voigt Pipe tunings inside it, that are tuned to coincide with each other at the "comb filter" frequencies, and do a good job of eliminating these dips and peaks at the F2, F3, F4 and so on. The cabinet is a folded design and is not real big, and is designed for the driver to be mounted on top. Bottom end is about 40Hz with a vented roll-off. Anther interesting thing about the Voigt Pipe design, is that it is not sensitive to individual driver parameters, but works as a combination of back-horn, t-line, and reflex, and seems to work with many different drivers, even different sized(like 4") drivers, with excellent results.It sounds like a perfect plan to me, for the Walsh. It is available from the Lowther America website, under "Cabinet Plans". Worth a look.