Terry Cain's BIB -why does it work and does anyone have those Fostex Craft Handbooks? - Page 521 - diyAudio
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Old 1st February 2013, 04:29 PM   #5201
xrk971 is online now xrk971  United States
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Originally Posted by B00B00 View Post
I agree. That being said, I don't think the enable pattern is supposed to dampen anything.
It makes the cabinet less... lossy???
How and why, who knows? I admit the science is beyond me.
I'm adding it here because I can and I can't see it doing any harm. I'll do before and after on the exterior of the cabinets once they are done but then again, that will be subjective.
I tried to take a crack at the physics-based reason behind why the dots reduce pressure losses on the BIB EnABLE thread. I used the golf ball dimple analogy and simple scaling arguments to show similar flow regimes between the two systems. Some people don't think there is "flow" of fluid in a speaker but I would ask them why the Mach number is used at speaker ports. It is oscillatory flow. It is like people who say AC current isn't current because it doesn't move anywhere like DC...
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Old 1st February 2013, 05:17 PM   #5202
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Originally Posted by xrk971 View Post
I tried to take a crack at the physics-based reason behind why the dots reduce pressure losses on the BIB EnABLE thread. I used the golf ball dimple analogy and simple scaling arguments to show similar flow regimes between the two systems. Some people don't think there is "flow" of fluid in a speaker but I would ask them why the Mach number is used at speaker ports. It is oscillatory flow. It is like people who say AC current isn't current because it doesn't move anywhere like DC...
I get what you are saying but the pure math behind it goes over my head
(as I originally posted the article about the golf ball in Race-Car Engineering.)
I intuit more than I understand at this level.

The question, a question that I have is: why not dimples? Would be real easy to make a die and bash it into the wood.

Sorry for the OT
and now back to our regularly scheduled program-
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Old 1st February 2013, 06:23 PM   #5203
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It may work, and someone out to give it a try. I think for lower speed flows, it helps to have a protrusion stick out into the flow - hence the bumps vs dimples.
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Old 1st February 2013, 10:47 PM   #5204
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I see this possibly having some effect on a driver cone that needs to be light fast and can't be damped otherwise. Just like the rings on some larger drivers or the star pattern on the Manger driver. But for everything else in the speaker, there are better methods to kill boundary layer and material resonances.
Frankly, I think it would be a pity to spoil the look of those fine old planks by plastering them in small ugly squares of plaster.
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Old 1st February 2013, 10:55 PM   #5205
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I agree that those weathered planks look great without dots. I don't think the enable dots are trying to dampen or kill resonances but to essentially reduce dynamic drag on all surfaces.
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Old 2nd February 2013, 10:24 PM   #5206
xrk971 is online now xrk971  United States
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The final photos of my FIB build and a sound clip are in the foam core thread.
Click the image to open in full size.
Foam Core Board Speaker Enclosures?
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Old 4th February 2013, 01:23 PM   #5207
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Wow... those look great xrk971. Congrats!

As for the plaster rectangles, those are for the inside of the baffles...
Outside, I will try tape first and then maybe some sort of discrete application of paint, varnish, I don't know... we'll see.

Progress on my end.
Click the image to open in full size.

-andré-
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Old 4th February 2013, 03:05 PM   #5208
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Thanks B00B00. Will you apply anything on top of plaster and wood to seal it and make sure it doesn't flake off or does it stick pretty well?
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Old 4th February 2013, 04:35 PM   #5209
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Interesting work so far.
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Old 4th February 2013, 06:12 PM   #5210
B00B00 is offline B00B00  Canada
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Thanks B00B00. Will you apply anything on top of plaster and wood to seal it and make sure it doesn't flake off or does it stick pretty well?
Oh it sticks all right... had to vigourously scrape with a putty knife and then sand to remove the offending rectangles. Fine instruments are often finished on the insides and it can apparently affect the sonic qualities of the instrument so I might put a light coat of polyurethane... it might seal the wood and keep it from expanding and contracting (or slow the process down). That being said, I get the impression it might make the inside of the cabinet livelier and that... I'm not sure I want.
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