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Old 15th June 2012, 04:35 PM   #1
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Default Bracing Zaph Style

I have read the Zaph subwoofer using 45 degree bracing seen here:

Google Image Result for http://oak.cats.ohiou.edu/~schneidw/audio/images/krutke_sub-bracing.jpg

In his write up he states that this bracing strategy is only good for symetrical cube enclosures. The reasoning seems sound, but I don't see why it couldn't be implimented in a non-cube enclosure.

It seems like an extremely easy and fast way to build bracing as an alternative to window bracing. I think in combination with a double baffle and a couple of cross braces of the same size it would be adequate.

What do you guys think?

I'm trying it on my next build and it will be mdf main structure, 2"x3" bracing and a hardwood outer baffle. It may not be as pretty on the inside, but I think it'll end up quite stiff.

Starting now:
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Old 15th June 2012, 04:39 PM   #2
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Oh yeah. This box will be 35"x26"x25" vented and will use twelve 45 degree braces and two cross braces along with the double baffle.

.....sorry about the disaster going on in my garage:-)
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Old 15th June 2012, 04:41 PM   #3
badman is offline badman  United States
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http://s42.photobucket.com/albums/e3...dio/Subwoofer/

I did something similar, though I used panels and cut out windows from the panels. Worked great.

Click the image to open in full size.
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Last edited by badman; 15th June 2012 at 04:48 PM.
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Old 16th June 2012, 12:55 AM   #4
tvrgeek is offline tvrgeek  United States
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The way I look at it, I am not trying to build a box to hold up an elephant. I use bracing to change the resonant frequency of the panels to raise them several octaves above the crossover. So I glue my sub braces along the panels, not between them. Then again, my subs are only about 60L, so the plywood ceramic composite I use is more than stiff enough. If you were building a box you could actually lift, like half inch ply, then maybe side to side would be an advantage. Far be it for me to argue with John's designs.
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Old 16th June 2012, 01:15 AM   #5
sreten is offline sreten  United Kingdom
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Hi,

You would be very hard pushed to argue its better than window bracing.
IMHO its very a poor bracing scheme, for mostly self evident reasons.
(i.e. get your thinking cap on and work out what it does / doesn't do.)

rgds, sreten.

FWIW its nowhere near as good as window bracing for assymetric
cabinets. For symmetrical cabinets it is equivalent as it has to be.
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Last edited by sreten; 16th June 2012 at 01:26 AM.
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Old 16th June 2012, 01:27 AM   #6
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+ 1 on sreten's comment

Quote:
If you were building a box you could actually lift, like half inch ply
We just did that. The box itself is quite light, add the 2 SDX10 woofers and it is not. An experiment to quantify the effectiveness of push-push and our typical bracing scheme.

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Old 16th June 2012, 10:31 AM   #7
tvrgeek is offline tvrgeek  United States
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Badman,
interesting cabinet. I suspect it works a lot like a 5 chamber box. It will be very interesting to see the results in an impedance and acoustic plot. Were the size of the holes specifically planned?

Dave,
I compared a push-pull with two in separate boxes. Just my own results, but I found the advantage of two cabinets in placement outweighed any perceived reduction in distortion in the push-pull. I don't push mine very hard though. Then there is the WAF issue.

The diagonal brace may be effective in reducing oil-caning of the sides, but what it does to transferring resonance is another question. I suspect that is what sreten is warning about. I might note, Linkwitz used a similar method in his sub. Testing is the only answer. Build it, load it, and with a mic and spectrum analyzer, tap all over the panels and see what the resonances are. Then do sweep tests. Whatever bracing method, I follow the general rule that they be asymmetrical.
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Old 16th June 2012, 12:27 PM   #8
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Quote:
Originally Posted by tvrgeek View Post
Badman,
interesting cabinet. I suspect it works a lot like a 5 chamber box. It will be very interesting to see the results in an impedance and acoustic plot. Were the size of the holes specifically planned?

Dave,
I compared a push-pull with two in separate boxes. Just my own results, but I found the advantage of two cabinets in placement outweighed any perceived reduction in distortion in the push-pull. I don't push mine very hard though. Then there is the WAF issue.

The diagonal brace may be effective in reducing oil-caning of the sides, but what it does to transferring resonance is another question. I suspect that is what sreten is warning about. I might note, Linkwitz used a similar method in his sub. Testing is the only answer. Build it, load it, and with a mic and spectrum analyzer, tap all over the panels and see what the resonances are. Then do sweep tests. Whatever bracing method, I follow the general rule that they be asymmetrical.
I will be using this in conjunction with cross bracing, similar to yh==the wooden dowel method, just more robust. I think it should take care of any structural issues (oil canning). I want this box to be as strong as possible as it will be permanent (it'll be sold with the house and built for a specific space in a basement alcove) and quite large. Weight will not be an issue; it's only getting moved once.

As far as panel resonances go, I think between the mdf/hardwood double baffle I should be good there, considering that panel will also be braced. What I hadn't considered is that this strategy may not control the other panel resonances adequately. I'm going to keep going on the build as is and check for panel resonances during testing.

If it is excessive are there strategies you can impliment after the build is done? I would think adding a couple of ribs (for lack of a better word) could help if need be.
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Old 16th June 2012, 05:16 PM   #9
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Quote:
Originally Posted by tvrgeek View Post
I compared a push-pull with two in separate boxes. Just my own results, but I found the advantage of two cabinets in placement outweighed any perceived reduction in distortion in the push-pull.
Mine are push-push. And i have 2 of them. Push-pull cancels even order harmonics, leaving the more objectionable 3rd in stark relief. A long time ago, i chatted with Nick McKinney. He figured that with well designed woofers, in paticular his, 2nd order distortion reduction would be minimal.

dave
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Old 16th June 2012, 05:20 PM   #10
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Quote:
Originally Posted by hooligan72 View Post
the mdf/hardwood double baffle I should be good there, considering that panel will also be braced. What I hadn't considered is that this strategy may not control the other panel resonances adequately.
One thing you could do to make your work more effective is to use good plywood and not MDF. Remember that, as a generalization, 1.25" MDF has equivalent stiffness to 0.75" Baltic Birch ply.

dave
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