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Old 15th December 2012, 11:40 PM   #41
xrk971 is online now xrk971  United States
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George,
I meant passive radiator as in similar to guitar body, not like actual non powered woofers tuned to enhance bass from driver. Yes, the vibrational modes are very complex, but can be modeled with FEA, especially if one has the Cornu in Solidworks model already. Not that I want to do this though... I have sandwiched a dense non drying putty ( plumbers' putty) between the foam core sheets and it is very quiet. Your tri-ply cardboard with silicone sounds good too. I took apart a hard disk drive once and noticed casing for the platters was a sandwich of stainless steel/sorbothane/stainless steel. You could tap it and only hear a dull thud. Earlier in the foam core thread I asked a question about using Dow Corning silicone dilatant (Silly Putty) as a smart material sandwiched between sheets of speaker cabinet walls but no one replied. I actually have a 2 lb chunk of that putty to play with...

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Old 15th December 2012, 11:43 PM   #42
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OK, I've got one made! Big gloopy mess of red and black hot glue, but it all stays in place. I used enough hot glue to seal up the edges, any more would be redundant. Gorilla glue for the top.

Will make another tomorrow.
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Old 15th December 2012, 11:45 PM   #43
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Pano,
Congrats on getting this far. You have colored hot glue?
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Old 15th December 2012, 11:45 PM   #44
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Great news Pano.
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Old 15th December 2012, 11:57 PM   #45
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Thanks guys!

Yes, I have red and black hot glue sticks. The big ones. The black really takes some heat to melt, the red flows a little better. Found them online somewhere years ago. I think there was glitter and day-glow, too.
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Old 16th December 2012, 04:14 PM   #46
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I suppose I should get the other one built today - busy week ahead. Want to hear the little fellows in stereo.

One thing I will NOT be doing is using Gorilla Glue again. The gorillas can take their damn glue and go back to the Belgian Congo, for all I care. What a mess! Got all over everything, including the speaker face and my hands. Fortunately I had a can of carburetor cleaner handy which takes it off my sticky hands. Only thing I've found that does.

Anyway. It sounds pretty good, if definitely mid-bass heavy. I'm guessing a big peak circa 100Hz, but will measure to be sure. It's a cool design, but I think needs some tweaking to get a good tonal balance.
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Old 16th December 2012, 04:22 PM   #47
xrk971 is online now xrk971  United States
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Thanks for the warning with Gorilla glue. Congrats on getting first sound. Which size did you make and what driver are you using? The stuffing is real important. Need dense pack in main driver cavity. I have some in the throats but loosely applied there. Cal noticed peak at 120 Hz too I think.

Oh, and please post sounds when you get a chance. I know you know how to do this Pano...

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Old 16th December 2012, 05:50 PM   #48
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I did the 20" size with the 3.5" Vifa.

Gorilla glue is OK (but messy) for small jobs. I regularly use it for gluing plastic to metal - works great. My problem with this big job yesterday was that the G.G. had thickened up in the bottle and completely clogged the nozzle. Nothing I could do would make it flow thru the nozzle. As I was already into the process, I had to remove the nozzle and dish it out with a stick. What a mess! Got all into the stuffing, as well. Yuck. G.G. does foam and fill gaps, bit it also runs down the sides no matter how you apply it. I have never used the new white gorilla glue.

I lightly stuffed the beginnings of the spiral and did some stuffing behind the driver. Sounds like more is called for. I will experiment. I have pillow stuffing, which is not very good for speakers. Might try fiberglass or cotton rags.

Yes, I'll post recordings and measurements.
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Old 16th December 2012, 07:51 PM   #49
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Quote:
Originally Posted by xrk971 View Post
Bose does have a spiral horn patent
U.S Patent 6,648,098
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Old 16th December 2012, 08:30 PM   #50
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Looks very similar, in a simpler way.
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