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Strangest Box Material You used or Have Seen?
Strangest Box Material You used or Have Seen?
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Old 28th January 2018, 11:37 PM   #11
stephenmarklay is offline stephenmarklay  United States
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I had an idea for my next box and this cork may be a good thing to try;.. I want to build a free-standing Front and Rear Baffle. They will be bolted with a long enough bolt to give me the depth I need. That Baffle combo would have feet forming the part that sits on the stand.

The sides, top and bottom will “wrap around this frame but only between a visco-elastic seal like sorbathane.

The idea is that very little mechanical energy is allowed to transfer from the front and rear.

Instead of bolting the “wrap” I would figure out some form of strap system. I could just use some tie downs I have to prototype it.

I don’t even drink so this is a runners high
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Old 28th January 2018, 11:40 PM   #12
scottjoplin is offline scottjoplin  Wales
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Sorbothane is great stuff. I used sorbothane insoles cut up as feet for my U-frame subs, they were the only thing that cured the cabinet twisting at very low frequencies and high driver excursions
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Old 28th January 2018, 11:52 PM   #13
stephenmarklay is offline stephenmarklay  United States
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Some neat thoughts here.
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Old 29th January 2018, 01:01 AM   #14
Pano is offline Pano  United States
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Strangest Box Material You used or Have Seen?
I've covered speakers in shaggy faux fur, but that's not really a box material. Also done plaster with fiber, AKA "Staff". Nothing too exotic. I suppose we've all used a cardboard box.
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Old 29th January 2018, 01:02 AM   #15
planet10 is offline planet10  Canada
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Strangest Box Material You used or Have Seen?
Quote:
Originally Posted by stephenmarklay View Post
The BBC and UK company’s try to push it lower, out of the ears most sensitive, and critical range for speech and much of the vocal range from 2-5k. How high do you push it and what level of attenuation do you see?
I have a friend with Spendor BC-1 and a pair of LS3/5A. I can here them both resonanting down low. The BC1 makes them sound kind of romantic, the LS3/5A are downrightboxy sounding.

Since energy to excite resonances decreases as frequencies rise (above a certain point), if you can push them up above 500-1k they are unlikely to get excited. As well damping is related to the thickness of the material is much greater proportion of the wavelength, and with each transition from ply-to-ply acts as a damping mechanism, even if it does get going it is highly damped. Further we push for any potential resonances to have a highish Q. That means to get them going you have to have a lot of a tight (highish) frequency range pounding the panel for a long time… something rare in music. I get a lot of kickback on that last one, but it wors in practise.

dave
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Old 29th January 2018, 01:05 AM   #16
Sonce is offline Sonce  Macedonia
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Originally Posted by scottjoplin View Post
That's the opposite of my experience, fnar fnar
LOL
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Old 29th January 2018, 01:08 AM   #17
planet10 is offline planet10  Canada
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Strangest Box Material You used or Have Seen?
Quote:
Originally Posted by stephenmarklay View Post
The idea is that very little mechanical energy is allowed to transfer from the front and rear.
Opposite of what we do. The baffle is the weakest panel and the one you least want excited. If the back panel moves it is a lot less audible. We purposly transfer energy from the moving driver basket to the rear panel. As well as removing energy to a less critical panel, you also end up sharing the energy across much more panel meaning each one gets less energy (that same brace also sens energy to the top/bottom or sides as well). That points out one of the issues i have with KEFs tactic of gromment mounting the driver — it may remove energy from the cabinet, but it leaves it all in the basket decreasing the speakers DDR (Downward Dynamic Range — ability to reproduce small details).

dave
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Old 29th January 2018, 02:04 AM   #18
stephenmarklay is offline stephenmarklay  United States
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Quote:
Originally Posted by Pano View Post
I've covered speakers in shaggy faux fur, but that's not really a box material. Also done plaster with fiber, AKA "Staff". Nothing too exotic. I suppose we've all used a cardboard box.
Ok that shaggy faux fur is not a box but it makes me want to do this
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Old 29th January 2018, 02:13 AM   #19
stephenmarklay is offline stephenmarklay  United States
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Originally Posted by planet10 View Post
Opposite of what we do. The baffle is the weakest panel and the one you least want excited. If the back panel moves it is a lot less audible. We purposly transfer energy from the moving driver basket to the rear panel. As well as removing energy to a less critical panel, you also end up sharing the energy across much more panel meaning each one gets less energy (that same brace also sens energy to the top/bottom or sides as well). That points out one of the issues i have with KEFs tactic of gromment mounting the driver — it may remove energy from the cabinet, but it leaves it all in the basket decreasing the speakers DDR (Downward Dynamic Range — ability to reproduce small details).

dave

Interesting stuff here Dave. I like your thinking about moving to the rear. Never thought about that. The thing about the entire enclosure sharing makes sense too. However, one gotch (for the less experienced than you) is the vibration amplitude only needs to be small due to the relative larger area compared to the driver.

BTW I think Kef stopped grommeting drivers. They using a lot of constrained layer concepts etc.
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Old 29th January 2018, 02:27 AM   #20
planet10 is offline planet10  Canada
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Strangest Box Material You used or Have Seen?
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one gotch (for the less experienced than you) is the vibration amplitude only needs to be small due to the relative larger area compared to the driver.
If one is careful with the bracing, and one gets into a situation wher ethe panel resonantes (rare with music on my boxes) as long as the 2 subpanels are out of phase there is little output.

Constained damping works. But costs time & money. And if my cabinets don’t resonant then i see little point in guilding the lily.

Another trick is to load woofers in tightly coupled push-push so as to take advantage of active vibration cancelation… one gets dramatically lower box load. KEF does this in their Blades. As do a number of other makers.

dave
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