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In Reply to: RE: It was JA, answering his own question after hearing ESP Concert Grands at my place posted by John Marks on August 04, 2012 at 16:48:05
John,
Thanks for posting JA's sidebar. Very helpful.
I have an older pair of Proacs (Super Tablettes) which have a rear-facing port filled with drinking straws. Designer Stuart Tyler used the same approach on early versions of the Response 1 and 2, but later abandoned it on all of his speakers. What was Tyler trying to accomplish with the straws, and (if you have any idea) why did he change to a more convenetional open port design in later models?
Thanks in advance.
Follow Ups:
But that doesn't make much difference.
ProAc: The cocktail stirrers/straws (I think they were narrower than regular drinking straws) were a clever idea. The cumulative thickness of the sidewalls of the stirrers did not reduce the width of the port by much, so in terms of frequency reinforcement the port worked pretty much as if the stirrers/straws were not there, but!
The surface area of the insides of the straws was surprisingly large, and that much surface area presented friction resistance to the air moving in and out. I believe that the intent was to minimize "port noises" such as "chuffing," the characteristic sound as an organ pipe starts to speak. The straw approach can be regarded as an early "Variovent." Or not.
Also, by dividing the airflow into a multitude of narrow columns, the "vertical" magnitude of any turbulence within the port would be sharply limited. However, I am not sure how much turbulence there would be in the port of a speaker with a "woofer" as small as the Tablette's.
Why was this dropped? I have no idea. Perhaps the designer decided that developments such as radiusing the ends of ports, etc., gave an overall better result.
JM
The straws do act like a lossy variovent but probably allow bass reflex action as you state. A true variovent is not a bass reflex design as exhibited by a single resonance peak not two as for reflex and also by bass roll off like a closed box not like a reflex.
Thanks John. Sorry about the confusion over authorship. You're right about the size of the straws, definitely cocktail-sized. I appreciate the thoughtful, detailed reply.
tad
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