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Old 4th March 2009, 01:35 AM   #1
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Default New designs for Curvy Bruce

Having developed a number of horns using CNC routing, I thought I'd play around with the Bruce design to get it curvy. Dave D has shared some material on this as well.

http://gallery.audioasylum.com/cgi/u...&w=1494&h=1339

http://gallery.audioasylum.com/cgi/u...&w=1447&h=1314

http://gallery.audioasylum.com/cgi/u...&w=1394&h=1326

The ribbing inside the comp chamber is purposely irregular.

Andrew
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Old 4th March 2009, 10:44 AM   #2
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Any chance you could post them here? Unfortunately, to access your links, one has to be a contributer to AA. Which I'm not. I rarely visit, & have never posted there. I've seen too many conversations descend into insult-hurling competitions, and as far as I'm concerned, I can do without that. Life is too short.
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Old 4th March 2009, 10:58 AM   #3
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Does this help?

http://gallery.audioasylum.com/cgi/w...&w=1494&h=1339

http://gallery.audioasylum.com/cgi/w...&w=1447&h=1314

If not, I'll have to get new photos because of the image size restrictions.
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Old 4th March 2009, 11:03 AM   #4
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Yes indeed. Thanks for that.
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Old 4th March 2009, 04:46 PM   #5
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(quotation from removed post also removed.)

These look good! I also prefer the second design shown out of the two gallery links you posted. Not totally keen on the legs at the back myself, I'd prefer a more or less solid block here, with mabye another hole through it?

A GIF filetype could be used for these and is more suitable than JPEG whilst being a little more efficient
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Old 4th March 2009, 08:39 PM   #6
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Look very nice I have to say (the speakers darling, the speakers ) -I like the 2nd one myself, with the straight legs (Nurse!) & circular brace.

The legs could be a possible issue; they'll need some cross-bracing at least just to make sure they're not vibrating too much. Still, nice work. I like them. Great artistry.

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Old 4th March 2009, 10:13 PM   #7
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I thought these sorts of posts were only seen on Audio Asylum?

One guy on that forum disclosed to me that they purposely use foul language as a tactic for the moderators to shut down a thread they don't like. Nice.

Anyway...

Thanks for the ideas on the comp chamber work. I'll try and get a new pic today.
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Old 4th March 2009, 10:39 PM   #8
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(quotes from removed posts also removed)

Quote:
Thanks for the ideas on the comp chamber work
Just as a general piece of information, a BLH doesn't really have a compression chamber per se, other than the room it is in. A low-pass filter chamber, yes, & the vast majority, including Bruce, can be regarded as variations on the bass reflex theme.

FWIW, the most effective place for the ribbing you mention would be on the side-walls, which are the largest parallel panels. It will still need some damping of course, but possibly a little less than the stock design.

Quote:
I'll try and get a new pic today.
More the better.
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Old 4th March 2009, 10:45 PM   #9
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Quote:
Originally posted by Scottmoose



FWIW, the most effective place for the ribbing you mention would be on the side-walls, which are the largest parallel panels. It will still need some damping of course, but possibly a little less than the stock design.



More the better.

Mmmmm. I was hoping to avoid that...given all the routing work is NOT on the sides. But, I'll work on something especially....probably using som sort of accousic foam in addition to the routered waves.

Thanks for the heads up on the wording of CC...I guess I'm using that wording because most people know what it is...still, sloppy.
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Old 5th March 2009, 03:34 AM   #10
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For the benefit of those having troubles viewing Andrew's images i have attached them in a more functional format.

Here are some constructive critism i sent to Andrew on these by email last night (edited to reflect what others have posted)
--------
Those are all kind of pretty -- but over the top to my eye. Issues i see:

1/ Even if you are using plywood, you have to keep in mind that the way you are cutting the wood is not playing to its strengths. For mdf i'd suggest a minimum of 40mm wall thickness, plywood could be a bit thinner,
2/ mdf will need to be finished inside and out with something that drys very stiff that soaks into at least the top couple mm. Still i doubt that will get rid of the mdfs negative energy storage (generally by the time this step is added it is cheaper & easier to start with ply or solid anyway). Another way to minimize mdf's issues (and solid wood for that matter) is to use more thin layers (ie something like 3-6 mm slices)
4/ Even with plywood, 20 mm is a minimum for side panels... we found in Maiko that this wasn't enuff and that is a 5" driver.
5/ (this echos Scott's comments) i like the direction you are taking with the inside of the BR chamber, but the variations are not large enuff to make a serious difference. Better to use all the available space and have large variations (on the order of 20-30% of the distance to the opposite wall) -- don't forget the sides either. Some bracing and variation there would be good too (and as the only expanse of parallel surfaces, by far the most important).
--------

It would be pretty easy to make the inside of the BR chamber quite complex. I'd use all the volume available to create a lattice of bracing and deflector/ripply surfaces. It would mean making all the layers in one half of the box different from each other (and then reflect a duplicate across the centre line -- top to bottom symmetry means you only need to work out 1/4 of the speaker volume. I'd also work in the very useful driver brace)

If Andrew is going to have a go at these, it behooves us to help him make the best one possible.

dave
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