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Old 25th January 2013, 05:41 PM   #1101
xrk971 is offline xrk971  United States
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Quote:
Originally Posted by surface tension View Post
Mmmm, you got me thinking about an in wall FIB with a 4" driver. Would that work? Approx. 48"x18"x3.5"
That sounds like a good wall hanging size. You will need to check if the driver height matches approx ear height depending on how high up you hanf it. Which driver were you thinking of?
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Old 25th January 2013, 06:15 PM   #1102
IG81 is offline IG81  Canada
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Originally Posted by xrk971 View Post
IG,
I am not familiar with a Karlson aperture design. Do you have internal photos or a plan drawing? It sounds like there is a large pressure wave at the aperture if it moves that much. Nice work!
You can find out some stuff on the old Job Ulfman website.

The Karlson Homepage

Googling "karlson speaker" for image results should also satisfy your curiosity.

There is indeed a lot of pressure in the front chamber especially at the very top of the aperture. Even 0.75" BB-ply wings have to be braced on anything larger than an 8" Karlson.

IG
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Old 25th January 2013, 08:32 PM   #1103
xrk971 is offline xrk971  United States
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IG,
Karlson aperture is very interacting and seems like it could be applied to a lot of concepts. Like a BIB... the purpose of the aperture does not depend on it not moving by several mm. It may be annoying but I don't think it affects sound as long as it doesn't rattle or buzz.

Last edited by xrk971; 25th January 2013 at 08:35 PM.
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Old 25th January 2013, 10:44 PM   #1104
IG81 is offline IG81  Canada
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The Karlson aperture is generally used to gradually terminate a pipe, in order to avoid reflections. It works quite well, especially if you look at the impedance plot of the Transylvania Power Company "The Tube" HF waveguide, there are your two main peaks and almost no signs of reflections.

IG
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Old 25th January 2013, 11:52 PM   #1105
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I thought about slowly terminating a transmission line using a narrow vent running along some percentage of the total line length many years ago. In early 2009 I experimented with foam-core prototypes using this idea around the same time U.S. Patent 8,351,630 was applied for. Then I heard about a guy named Karlson The effect I noticed (and liked) was a lack of strong standing wave influence similar to an open baffle.

There are actually several patents around this basic concept.
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Old 26th January 2013, 12:00 AM   #1106
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Originally Posted by cochleus View Post
I thought about slowly terminating a transmission line using a narrow vent running along some percentage of the total line length many years ago. In early 2009 I experimented with foam-core prototypes using this idea around the same time U.S. Patent 8,351,630 was applied for. Then I heard about a guy named Karlson The effect I noticed (and liked) was a lack of strong standing wave influence similar to an open baffle.

There are actually several patents around this basic concept.
Yes, it works well and lots of patents around. John Karlson was most active during the 50ies. He referenced much older patents, such as Swinyard, Fulmer... There were a handful of off-shoot licencees in the 70ies - it's a bit of a mess trying to patch up this history together. There are a few modern implementations if you know where to look, both DIY and commercial.

IG
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Old 26th January 2013, 12:01 AM   #1107
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I have seen similar things done by drilling series of holes of increasing dia as edge of pipe gets closer. It is all about matching impedance of pipe and room air. In the optical domain, a series of thin films is used to make antireflection coatings on lenses and windows. So what would happen if I put a Karlson slot on the end of a BIB? It would probably really smooth out those bumps that are in the simulations and make it less boomy. Easy enough to try in foam core
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Old 26th January 2013, 12:23 AM   #1108
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I first used this idea to treat the "back wave", a kind of transmission line. I never actually took any sound field pressure readings but merely cutting a slot (even a narrow one) seemed to eliminate the bass. Also, the cross-sectional area was tapered gradually along the length.
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Last edited by cochleus; 26th January 2013 at 12:27 AM.
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Old 26th January 2013, 03:24 AM   #1109
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Originally Posted by xrk971 View Post
... So what would happen if I put a Karlson slot on the end of a BIB?
iBIBk developement thread.

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Old 26th January 2013, 03:35 AM   #1110
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Thanks for pointing out the iBIBk thread Planet10. I scanned through it quickly and it seems that it is still at trial and error stage? Start small and expand as needed? This is perfect for foam core, I can even make a version with a frame with slot for inserting different Kslots to quickly do an A/B test of the sound.
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