@roberjerman "Take a look at some of the old IMF’s (U.K.) and how they built their trans lines. TSL - 80’s. I’d just copy them!
That’s excellent advice. Bud (Irving M Fried / IMF) was a mentor of mine, and one of the most interesting and unique people in audio history. I have his own personal O subwoofers as part of his Valhalla (pyramidal C satellites with true transmission line midrange + TL subs) System that he gave me shortly before he passed on. Large, but manageable and not overly large cabinets, they would fit into most rooms that have mid - large sized loudspeakers. I have the plans for the O and D subwoofers around somewhere that I might be able to scare up if you’re that interested, they’re somewhere around 39" tall X 13" wide X 27" deep. He also produced even larger SM and the H (coffin) subwoofers, and I used to know where to find them on the web. There’s nothing about the design that any reasonable DIYer or someone with decent woodworking skills couldn’t handle. You can stuff (not overstuff) them with the ubiquitous open cell foam, though people also use a lot of other (wool, fiberglass, cotton or polyester batting) materials. I can scare the pants off most (literally) people, including myself, with a Dynaco ST70, though hefty solid state amps would obviously put out a lot more low-end grunt.
True transmission lines (TL) handily outperform both bass reflex / ported and sealed and aperiodic bass loading configurations. You get an incredible sense of the music (many use the term tuneful) compared with ported speakers, which was Bud’s (he also produced a poor man’s TL called the Line Tunnel which was a stuffed ported speaker used in many of the products, along with aperiodic loading in the Beta) motivation for using them. I’m not one who uses the "one note bass" description of ported loudspeakers, but I understand what people mean. The description I feel when comparing them is that ported speakers sound tremendously dirty and distorted next to a TL. They also portray a lot less sense of the box or restraint than sealed designs. It’s one of those things you don’t realize until you hear it in comparison to the other methodologies, and then you don’t forget it. I’ve heard so many people downplay the advantages of TL, but I think it’s simply a function of not actually experiencing it themselves, and underestimating it. I often wonder why more companies don’t sell such designs. That said, I don’t want to imply it’s something magical, mystical, or otherworldly, as it simply isn’t. But well-implemented TL is better than the other alignments. The downsides of transmission lines are the the added complexity, cost of construction, and people not really understanding them which others have raised, along with reduced efficiency compared with ported speakers.
As great as TL is for bass, it’s all the more advantageous for midrange loading. Bud and I often discussed how the music just flies out of the speakers in a way one likely never experienced otherwise
