DIY ?uestion


Greetings people,
     What are the arguments, pro and con, for transmission line speakers that: have channels with parallel walls, and those that progressively get wider, as in a horn?  I want to do a build with plans that show parallel walls, where I can alter them to create an ever widening channel within the same size container.  I am a newbie in this area of DIY speakers, and am sure there are opposing views.
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Thank you very much, @trelja. I made a lot of sawdust trying out different transmission line ideas in the late 70’s and 80’s.

You wrote:

"Bud Fried considered it critical importance to select a driver with as low a Qts specification as possible. Over the years, I’ve learned that’s exactly opposite of most opinions I find in the internet discussions, which recommend the opposite."

Must admit that I had better results with medium to high Qts woofers in transmission lines, but then I’m no Bud Fried!

Can you reveal anything else about what parameters Bud looked for? I used KEF B-139’s in most of my sixty-something transmission lines, but I’m sure the over-the-counter version’s parameters were not ideal. It’s x-lim was rather modest, as I found out the hard way.

I would love to know how to use a low Qts woofer in a transmission line. Low Qts = high motor strength = good midrange articulation, in general.

If you don’t think it would violate any confidentialities, I would be very interested in the plans for the D that you mentioned. I’d love to peek under the hood and see what the master did.

Very best wishes,

Duke

For TL theory that is backed up by measurements consider looking at the articles on my site.

www.quarter-wave.com

There is more bad information about TL's on the Internet than accurate information. The methods on my site have been used to design many TLs (100's probably) that have performed as predicted. The methods have been used by Salk Sound, Dennis Murphy, and a few other commercial TL manufacturers.
Thank you, Duke. Your experience with TL seems to mirror what I’ve read from most people apart from Bud.

Nothing proprietary at this point, most people don’t even remember who Bud Fried was. Anyway, I saw (Salk?) has been trying to resurrect the Fried name, but the products are far different than what Bud used to build. I can send you the plans for the C/6 satellites and D2 subwoofers. You can also have the crossover values from Bud’s C sats, if you want. I’m not sure if you feel comfortable with series crossovers, but even though most implement them as first order, you can alter a value called Zeta (ratio of cap to coil) to produce a steeper or more shallow rolloff than 6 dB/octave. 6 dB/octave has a Zeta value of 1.0, lower (say 0.8) values sound more forward and have a sharper rolloff, higher values (like 1.2) sound more relaxed and liquid and have a slower rolloff. Bud didn’t actually know Zeta per se, but it seemed he understood it from a practical means in terms of varying the cap to coil ratio. Bud’s crossovers are somewhat less than 1.0, and sound a bit more forward than I personally prefer.

I’ve met and received emails from more people over the years than I can remember, all with great stories about him. Most of them focus on either him writing 3 and 4 page handwritten letters to them multiple times in response to their letters or spending a couple of hours on the phone providing the same insight for those willing to pay for the call in the age of expensive long distance service. John Rutan of AudioConnection who often posts here loves to do a Bud Fried imitation that’s just like The Frog from Courageous Cat and Minute Mouse. Most don’t know Bud introduced Lowthers, Quads, Decca cartridges, Dynaudio / ScanSpeak, and other European products to America, quite impressive. I think there will never be another manufacturer like Bud.

Bud claimed to have had a real BAD experience with Focal. You may know he had a fondness for Europe coming out of his WWII service, and spent 1/4 - 1/3 of the year there. His side of the story is he went in pretty heavy with their impressive looking drivers in the early 90s, but told me the product received didn’t come close to what the product literature specified. They disagreed. While on one of his many travels through France, he claimed to have dropped in on them, and demanded a set of measurements be run in front of him to see who was right. Upon returning back home, no Fried ever used another Focal.

He wound up with Gefco for midrange and woofers, of Chicago, who are no longer in business. He claimed they produced the best drivers he ever used. They weren’t pretty (paper cones, stamped steel baskets) or seemingly advanced, but they made him happy. His own personal speakers use them, though a bit hot rodded. You can still find a few on eBay and the like. I have some, as well. For tweeters, he preferred the Hiquphon, and they’ve long featured him in their advertising. I agree they make good tweeters, but don’t think it’s wise in going with a tiny one man operation in Denmark that could ease to exist any day.

Obviously, Bud also believed in series crossovers, which he felt were the most important of the three things he believed in - the other two being TL and low Qts drivers. He didn’t develop the technology, and claimed to happen upon it during one of his meetings with Dynaudio. He was an intensely curious and outgoing person, and asked what the two sets of crossovers were, and what I’m certain was enough follow up questions to represent an actual conversation. Based on his account, they explained one set was a parallel network and the other series. He said, what’s the difference? Their answer, well, the series crossovers work and sound better (I realize that’s a subjective statement). Of course, next question, then why don’t you use them? Answer, everyone feels they’re too unusual. As for me, it took a while to get my head around them, as they seem exactly backwards with the coil seemingly on the tweeter leg and cap on the woofer leg. One day a light went off in my head, and they seemed simple and obvious. The signal either goes to the coil or the tweeter, and the cap or the woofer - ah, makes sense...
@trelja In addition to big, very LF TLs, I built a series of small TLs using 4" LF drivers. The first iteration used a higher Q driver that refused to deliver the calculated 56kHz roll-off until a bit of putty was added to the driver dust cap. The weight of the putty was calculated to drop the Q to be ≤ the .3 . This worked and effectively supported the benefits of a low Qts. That said, I am currently running a pair of big TLs that work down to 17Hz using Focal kevlar drivers with Qs around .55 but these are bi-amped and DSP controlled and never worked properly using passive second order x-overs without bottom-end compensation.

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