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Old 17th January 2013, 01:43 PM   #1071
xrk971 is offline xrk971  United States
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You probably can guess what my answer will be: Hot melt glue. It sticks to metal very well -try scraping it off after it hardens to test. Plastic will depend on type. If it is the slippery HDPE or LDPE (high/low density polyethylene), you may need to roughen plastic with sandpaper for durable bond. For ABS, PVC, it sticks very well. For polypropylene (the stuff that they make storage bins out of), it sticks very well, but sand paper first to make sure it stays.

Silicone caulking or latex caulking will work well, but is soft and springy.

Liquid nails will work well.

Good luck!
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Old 17th January 2013, 02:45 PM   #1072
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You guys have fun. I'll be away from a computer till the 25th. Heading to Maui for our annual trip to see Dad.
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Old 17th January 2013, 03:46 PM   #1073
bcmbob is offline bcmbob  United States
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Well that does it !! Last Sunday my son informed me that his friend had several tickets for the NFC championship game in Atlanta (he lives there), but he had no plans to send me one - along with boarding pass. Now you are going to Maui without even a thought that I might like to go along. I just don't understand.

Oh Well, Enjoy the trip and give your Dad a peck on the cheek for all of us back here shoveling snow.
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Last edited by bcmbob; 17th January 2013 at 03:51 PM.
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Old 17th January 2013, 05:58 PM   #1074
xrk971 is offline xrk971  United States
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Have a good trip Cal! Aloha
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Old 18th January 2013, 04:00 AM   #1075
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Quote:
Originally Posted by Cal Weldon View Post
You guys have fun. I'll be away from a computer till the 25th. Heading to Maui for our annual trip to see Dad.
That's just rubbing it in Cal.
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Old 19th January 2013, 02:04 AM   #1076
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Quote:
Originally Posted by bcmbob View Post
Well that does it !! Last Sunday my son informed me that his friend had several tickets for the NFC championship game in Atlanta (he lives there), but he had no plans to send me one - along with boarding pass. Now you are going to Maui without even a thought that I might like to go along. I just don't understand.

Oh Well, Enjoy the trip and give your Dad a peck on the cheek for all of us back here shoveling snow.
Lol!
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Old 19th January 2013, 02:55 AM   #1077
xrk971 is offline xrk971  United States
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I believe Sootboots is the first to make a simple sealed box for a great 2 way FAST system. Thread is here SB 8 inch woofer sounds great on its own.
Congrats Sootboots!
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Old 19th January 2013, 02:59 AM   #1078
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I am flattered but it was suggestions from the forum that landed me here. Without you all I would be stuck listening to the Costco cardboard specials! All joking aside, the foam core route is an excellent way to experiment and a bit of fun as well. The best part is you can have a few beer while you are making them, unlike working with MDF and a table saw.

John
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Old 19th January 2013, 06:05 AM   #1079
Carlp is offline Carlp  United States
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So I built my first foam core speaker today based on reading this thread. Thanks to all for the contributions.

I used a 5" fullrange el cheapo driver ($2) with an Fs <50Hz, Qts of ~0.3. I originally bought them to try out some boxes for an el cheapo home theater, but never got around to doing that. I built a Golden Ratio box with mid dimension as the speaker baffle (wider than it is deep), with speaker offset and port (approx 6x11x17 for a 0.75 cu ft box). I'll try another with the driver and port mounted on the smallest dimension. Perhaps obviously, I'm a speaker newbie.

A few observations FWIW:

1) It's a great technique to prototype, but I for one won't live with them as a final build. Too much cabinet resonance and too hard to get a well sealed box. Maybe it's the cabinet resonance that makes some projects seem to have so much bass?

2) I've never had great success using hot glue, but, still, hot gluing any seam over 10" seems prone to failure unless you work v quickly (otherwise, the glue starts to set as it cools, and the joint is prone to failure). In any case, it's possible to get a joint this way, but be prepared for failure. And you DO need to hold it for a bit for it to set. This may have been exacerbated by the fact that I used old and warped foam core panels that had been used for a display for a low-budget non-profit I used to work with, and required several hands to flatten out warps as the glue set.

3) I tried contact cement on a few joints to try to get a quick strong bonding alternative to hot glue. While it worked pretty well, it DID melt the foam in the core a bit, which also weakens the joint and affects the structure a bit. Still, the joint is pretty strong and the bonding is very quick, so maybe it's a decent alternative fastening technique. Work in a well ventilated area...

4) If you try contact cement, try cutting the panels 1/8 inch (0.3cm) or so heavy (at each joint) and clamp strongly when assembling to compress the extra size. A 7" wide panel becomes about 7.25" before gluing.

Despite my various complaints, I probably will adopt this as a prototype system as the cost (materials and time) is quite low. My idea of prototyping is to do a quick build and get an idea of how it will sound before investing in a full build. While an accurate sense of how a speaker will sound will require a more careful build, I think I can eventually develop a general sense of performance in a foam core box that I can use to predict performance in a wooden box...

We'll see, but I'll certainly try more with foam core.
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Old 19th January 2013, 07:13 AM   #1080
bcmbob is offline bcmbob  United States
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Just a note. I agree it is fun to experiment with the foam board, but we should remember that the spiral/spacing on the Cornu is somewhat unique to the rigidity of that design. Where the air pressures are highest (near the throat) - the unsupported areas are the smallest. Not till the second half of the horn is there any real chance of flexing. I haven't built a Cornu or anything else with foam core only, but I wouldn't expect as good a result without that spiral combined with the stiffness of at least 1/4" plywood walls. IMHO, there is a little magic in the match up of the foam and the spiral that would be difficult to get from any other design using the same materials.

My Two Cents
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