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Multi-Way Conventional loudspeakers with crossovers

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Old 20th September 2012, 04:01 AM   #161
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You need to read up on the Raal foam because it does exactly the opposite of your assumption. Without the foam, the top two octaves are dispersed very narrow vertically. With the foam added, you get a much taller dispersion which would then bounce off of the top of that woofer hex tube and cause odd comb filtering. Kind of kills the whole idea of a free swinging driver.

See Goran's excellent measurements here:

www.audioexcite.com RAAL 140-15D
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Old 20th September 2012, 05:00 AM   #162
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Thanks Greg, I previously started reading that thread but I really didnít understand the results, but suffice to say you gleaned from it that the purpose of the pads is to increase vertical response not decrease it.
I will make sure that I plan as best I can to avoid any panels that would create a direct reflection. Just thinking what about lower (larger) hexagon that is sat on its edge, if I canít avoid having the tweeter close to a hex, having it angled away like that has to be better than a direct reflecting surface wouldnít it?
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Old 20th September 2012, 05:05 AM   #163
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Well, the basic info is on Raals site too...plus my own measurements follow Goran's very closely. It's Alexander's(owner of Raal) novel and simple approach to a common problem with ALL tall treble drivers, beaming in the top octaves. I'm thinking of trying my own larger pads to use with some Neo8 drivers I'm running as mid/tweeters.

Set at an angle would surely help some, but keep the creative wheels moving and maybe you'll come across something even better.
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Old 20th September 2012, 07:16 AM   #164
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Ok time for a new design... I call this one "the butt crack"
It's a modified version of the Slot Loaded Open Baffle.
Rounded front exit to smooth the sound transition. Closed in back to reduce baffle size.

Figure this would be fairly easy to make, two symetrical sheets of 10mm folded acrylic, glued at the centre back join (nice solid gluing point), and top and bottom plates...
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File Type: jpg Butt Crack.jpg (166.0 KB, 180 views)

Last edited by Silent Screamer; 20th September 2012 at 07:23 AM.
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Old 20th September 2012, 07:52 AM   #165
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And if you feel compelled to moon the sky you could try this...
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Last edited by Silent Screamer; 20th September 2012 at 07:56 AM.
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Old 20th September 2012, 08:32 AM   #166
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Being a little bit more serious now... It might take a bit more work but the front and sides could be done out of one piece and a separate top and bottom. Front slot would need to be machined post bend.
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Old 20th September 2012, 09:00 AM   #167
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You could also use some flexible MDF like this. You should glue two sheets together (slice against each other)
Click the image to open in full size.
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Old 20th September 2012, 10:45 AM   #168
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That flexible MDF would probably be an easy way to do a round tube..

But I do like the idea of using the clear acrylic. Just came back from the shopping centre and on the way out I spotted these.

Looked like 10mm so it gives me a good idea of how far it can be bent.
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File Type: jpg IMAG1006.jpg (167.4 KB, 57 views)
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Old 20th September 2012, 10:59 AM   #169
hajj is offline hajj  Lebanon
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Quote:
Originally Posted by Silent Screamer View Post
That flexible MDF would probably be an easy way to do a round tube..

But I do like the idea of using the clear acrylic. Just came back from the shopping centre and on the way out I spotted these.

Looked like 10mm so it gives me a good idea of how far it can be bent.

In the case of the bends shown, bear in mind that the acrylic is heated until it gets soft, and then bent at any angle needed.

The downside in your application is that the heated area will look wavy and distorted...
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Old 20th September 2012, 11:12 AM   #170
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The pictures of the acrylic in the shopping centre looked ok, and I was thinking of fairly large radius like in the Sketch Up pic, maybe several inch radius. would probably use bendy MDF to prototype.
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