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Old 12th November 2012, 11:31 PM   #11
sreten is offline sreten  United Kingdom
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Hi,

For laminates the core isn't really the issue. Layered cardboard
varnished with polyurethane is very strong and light, and some
cheap furniture (storage boxes mainly) is made this way.

For paper foam board I'd suggest a varnish layer on the outside and
when its very near dry adding a layer of heavy duty aluminium foil.

Or varnish and let it dry, then add the foil with contact adhesive.

rgds, sreten.
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Old 12th November 2012, 11:38 PM   #12
xrk971 is online now xrk971  United States
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What's the aluminum foil for? I have thought about layering with a thick viscous material for damping if needed. Plumbers putty in strips in between sheets of foam board or cardboard might work? My first back loaded horns were cardboard.
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Old 12th November 2012, 11:45 PM   #13
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by xrk971 View Post
What's the aluminum foil for?
Hi, Make such a laminate and you'll soon work out what it does, rgds, sreten.

Outside dual foil layers stiffen softer laminates by a very large amount.
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Old 13th November 2012, 02:14 AM   #14
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Cardboard is Fugly
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Old 14th November 2012, 08:42 AM   #15
xrk971 is online now xrk971  United States
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Has anyone considered or tried using a 'smart' material like a non-newtonian liquid (cornstarch and water) as damping material in speakers? It responds by stiffening up like a hard solid when subjected to rapid time-varying shear stress. Silly putty (or Dow Corning 3179 dilitant compound) is a nice silicone based version of this type of material. It can be made to solid-like properties by combining with polyurethane foam so that it doesn't flow like a liquid under gravity, a commercially made material called D3O uses 3179 as the core ingredient in armor pads for crash protection. A laminate of thinner MDF or aluminum and D3O would be an interesting cabinet material. It would preferentially absorb higher frequencies and can be tuned by varying composition. A simple DIY test with silly putty would be interesting though.
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Old 18th November 2012, 10:01 AM   #16
xrk971 is online now xrk971  United States
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Default Wall hanging stereo TL's finished

I finally installed the VifaTC9FD's into the wall hanging 'picture' speakers. I hooked it up to the Lepai amp and iPod and tested with a variety of tracks. They sound fantastic, I mean really good. The bass is really nice, and the mids and highs have really good detail. The biggest surprise was the imaging given that they are mounted only about 2 feet apart in the same box as a stereo set. It is my first full range point source speaker and I just can't get over how good a pair of tiny 3.5 inch $12 dollar speakers and a box made of foam core paper and old pillow stuffing can sound. I am a true believer in full range drivers and TL's now. I am hearing details and sounds that I never knew were there before. The Vifa drivers are super in case anyone else hasn't heard them. Here is a photo of the new speaker propped onto some stools for testing. I need to have them decorated and put a picture frame wire for hanging on the back.
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Old 18th November 2012, 10:33 AM   #17
xrk971 is online now xrk971  United States
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Default Back loaded horn bookshelf speaker

My next project for the Vifa TC9FD is a back loaded horn. This design is tuned for about 70 Hz based on a 48 in path length. I am using the plumbers putty in a sandwich between foam core for the front baffle to reduce any high frequencies that may re-radiate from the front. The enclosure is 5 in wide by 10 in deep by 15 in tall, as usual, the size is chosen to maximize cuts based on 20 x30 foam core stock. I am lightly stuffing some bends to clean out the highs from leaking thru. The driver chamber is heavily stuffed and has a throat area equal to the driver piston area, the expansion is modest, only about 5.7 to 1 but that is all the room I had in a bookshelf design. I pre installed some lamp cord straight thru - no binding posts for these cheapy projects.
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Old 18th November 2012, 01:42 PM   #18
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Experimental foam-core backloaded exponential with 1:9 flare ready for side and bottom
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Old 19th November 2012, 12:50 AM   #19
xrk971 is online now xrk971  United States
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Quote:
Originally Posted by cochleus View Post
Experimental foam-core backloaded exponential with 1:9 flare ready for side and bottom
Which way does your driver point? Is this foamcore board?
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Old 19th November 2012, 08:44 PM   #20
von Ah is offline von Ah  United States
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I love this thread! Great work that must be great fun.
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