Unconventional & inexpensive bracing techniques - Page 2 - diyAudio
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Old 31st August 2005, 12:04 AM   #11
morbo is offline morbo  Canada
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Rademakers - thanks, I will likely try that!
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Old 31st August 2005, 01:05 AM   #12
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Quote:
Originally posted by morbo
I have a lot more time than money.
That breeds ingenuity.

Quote:
[i] but I have only a jigsaw [/B]
When I started, I took my allowance, went to the second hand shop and decided what was the best I could do for my $8.00. Guess what. You wouldn't believe the hours spent with a jigsaw and a straight edge.

That breeds patience.

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Originally posted by Rademakers
So I glued the bracings together from smaller pieces (like those pieces you can get for free). It will only cost you glue then.
1X2, 2X2, 2X4, it's all going to be there at your local scrap yard. They're happy not to have to pay for disposal.

That breeds humility.

See? Many of lifes greatest lessons can be learned from building the humble loudspeaker.

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Old 31st August 2005, 02:53 AM   #13
rcw is offline rcw  Australia
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Default bracing

In a AES apaper that goes back to 1972 Iverson published results that showed that most bracing used in loudspeaker enclosures is ineffective in achieving the primary purpose of replacing a single low frequencty panel resonance with two lower amplitude higher frequency ones.
The reason for this is that the brace must be a rigid boundary and most braces are not stiff enough to constitute a rigid boundary.
Steel is the stiffest of all common materials and even light steel sections are considerably stiffer than wood, so a steel section in very intimate contact by means of a rigid setting epoxy glue for instance, should at least in theory provide better bracing than a very much larger piece of wood in the same position.
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Old 31st August 2005, 08:00 AM   #14
Collo is offline Collo  Australia
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The photo was one I came across on the web some time ago.

Adding to what RCW says above, I would go for steel tubing, such as gal pipe, and epoxy it into position.
You could glue in a footplate to spread the load. Easier than going to the trouble of cutting threads, secured with a lock nut, and the whole lot epoxied anyway!
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Old 31st August 2005, 05:46 PM   #15
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wow, there is alot of really good info on this thread. I thought I already knew everything about bracing, but there is alot of stuff in this thread I had never heard of before.

bump
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Old 31st August 2005, 05:59 PM   #16
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would a length of pvc pipe do the trick as opposed to steel?
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Old 31st August 2005, 06:28 PM   #17
Ron E is offline Ron E  United States
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Pipe or stick bracing from wall to wall is not anywhere near as effective in raising panel resonant frequencies as even particle board shelf braces.
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Old 31st August 2005, 06:32 PM   #18
morbo is offline morbo  Canada
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thanks for that reference RCW, very handy, and very interesting considering how many people are using MDF for braces regularly. I wonder why there is not much interest in this aspect of box building?

Re: gluing the metal to the wood, does it have to be epoxy, or would say, a polyurethane glue (slightly flexible) work as well? And does anyone have any idea where to get the threaded tubing and 'footplates' as discussed here? I am assuming a plubming supply shop for tubing? but the footplate is a mystery to me...
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Old 31st August 2005, 08:25 PM   #19
morbo is offline morbo  Canada
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In case anyone was wondering, the braces at the building center look like this (different sizes):

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.
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Old 1st September 2005, 12:01 AM   #20
rcw is offline rcw  Australia
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Default bracing

Iversons data shows that panells that are glued and screwed into a box, along with glue block corner pieces have about 85% of the resonant frequency expected from an absolutely rigid boundary.
Typical bracing including cross bracing only increases panel resonant frequency by around 20%.
From this the closer to the ideal perfectly rigid boundary you approach the more effective the bracing. As mentioned only composite materials such as carbon and boron fibres are stiffer than steel, the only metal stiffer than it is beryllium, pvc pipe is not anything like as stiff.
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