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In Reply to: RE: Stereophile Transmission Line Review posted by johns dad on January 30, 2015 at 18:09:54
...are much different than ports.
Bud Fried's speakers were the best example and highly regarded.
Many others made them - how about Klipsch Corner Horns.
Follow Ups:
Your point is well taken. What I should have said is that the end results, almost without fail, are the same with each design.
"Because the line is operating over several octaves with the drive unit, cone excursion is reduced, providing higher SPL’s and lower distortion levels, compared with reflex and infinite baffle designs."
-Wiki
Based on what?
Agreed although I refer to them as John Wright's speakers. After the Bailey article in Wireless World stimulated lots of DIY interest, JW had one in HiFiNews (linked below) describing the development of a commercial model (IMF) which greatly influenced me. I built several.The IMF was not the first commercial TLS as Arthur Radford had already produced a few and Stromberg-Carlson had marketed several similar "acoustic labyrinth" models here in the US. Currently, PMC markets such designs.
A later analysis in Wireless World demonstrated that the TLS was not more effective than a similar but simpler ported speaker but enthusiasts (such as I) have felt that the quality of the bass (whatever that is) was superior.
Lots of info on this can be found at: IMF
BTW, I was a proud owner of JW's "wireless" mercury contact unipivot arm that he marketed as the Audio+Design M9BA M9BA
Edits: 01/31/15
I think at the time it was easier to tune a line than a reflex by varying the damping to get bass control. But once Thiel/Small was published and especially with computer implementation of Thiel/Small control of the bass design became orders of magnitude better and lines weren't worth as much.
By the way, Bud Fried actually believed that the most important implementation of a transmission line was in the mid-range. The model G was a great example of this with a stuffed port bass design but a line for the mid-range and in the last version of the G the line was longer and folded and was an obvious improvement over the shorter front to back lines used in the 1st Gs.
I completely agree with you about the changes wrought by Theile/Small. After years of building TLs, I jumped on an article in "Audio" which offered a clear and logical series of equations for reflex design based on the Theile/Small work. I implemented them in a MS Basic program and never looked back.
As for the mid, he was right because it smoothly extended the FR and made the Xover design easier. KEF showed a prototype midrange with a dedicated flexible line. From Martin Colloms' book: "Covering a 250 Hz to 4 kHz range, this latter driver employed a 65 mm hemispherical dome formed in a rigid polystyrene/neoprene polymer, and was fitted with a double suspension and loaded by an 0.8 m pipe filled with long-fibre wool, for absorption."
I knew about the KEF mid line. They only built a few I think. It held up the completion of John Crabbe's second set of built in bass horns(down to 25 Hz) because he waited for it to be the mid-range. He finally gave up and adapted the mid/tweeter combo from the IMF monitor.
> It held up the completion of John Crabbe's second set of built in bass
> horns(down to 25 Hz) because he waited for it to be the mid-range. He
> finally gave up and adapted the mid/tweeter combo from the IMF monitor.
I was lucky enough to spend an evening listening to John Crabbe's bass
horn-based speakers before he sold the house. They did indeed sound fine.
But they were outclassed by a friend of John's. who had constructed a pair
of horizontal bass horns under the floor of his listening room, running the
full length of the room and venting under the main speakers.
John Atkinson
Editor, Stereophile
Thanks John.
Those were exciting times as one expected to see innovative products appear regularly. I miss that.
I loved them the first time I heard them.
E
T
According to Bud Fried Radford promised a lot for years(Bud was going to import his speakers)and produced very little which is where John Wright and IMF came in. Bud announced his line speaker for a show based on Radford's promises which fell through. John Wright suggested using a KEF Concerto kit(B139, B110, T27) and putting it into a transmission line box. As the speaker evolved the T27 was replaced with a Celestion HF1300/HF2000 tweeter/super tweeter combo seen on the classic IMF Monitor.
Too bad Bud would bend the technical truth in his salesmanship--the majority of the units he sold (not models in his line, units that were sold) were "inspired by" transmission line design, or "wanted to grow up to be" a transmission line. Only his top of the line speakers were full bass transmission lines, and I eventually had a pair built for me.
A fascinating variation on the TL theme was Dick Shahinian's ca. 1976 patent on terminating a transmission line with a weighted passive radiator. Obviously, that induces both a time lag and a potentially serious back-EMF problem.
Dick was his own worst enemy in that regard, sad to say. He wanted people to spend more money on his speakers and less on electronics so he would (reportedly, and reportedly also on his web site in the early days of his web site) tell people they could run his speakers on a Creek integrated amp.
Whereas the truth was more like, you needed best-in-class current delivery and damping factor to make the big Shahinian speakers sound as though they were worth the money. They never showed their speakers at CES with a Creek integrated that I recall... .
There is a new version of the Diapason, apparently. But it is expensive and AFAIK Shahinian does not have any US dealers, so I don't think it makes a lot of sense for me to request a review pair.
JM
Bud was a lot of fun if you understood that he used germs of truth to his advantage. But I will add that as a music lover he did understand good reproduction and many of his speakers exhibited that so long as you didn't take the reasons given as perfect gospel.
You're correct that only the larger speakers were true lines. All the others were 'line tunnels', a brilliant obfuscation. But I will add that the line tunnel was a very good loading method. It was a variation of the Dynaco A25 aperiodic loading also known as variovent. And in some ways if you look at its impedance curve it was nicer(less reactive) than a transmission line.
By the way IMF also tried a line with a passive radiator at the end in an attempt to shorten the line. They didn't like the results and ended up with a second active driver at the end in the ALS 40 speaker.
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