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Old 10th November 2004, 04:38 PM   #11
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Quote:
Originally posted by Nuuk


If people use open baffles, how can anything be 'too porous'?

And you are also assuming that the polystyrene is the only material used.

Yes Nuuk, I overlooked the open baffle. Thanks for pointing out my ineptness.

Polystyrene is the base material to which others are added?

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Old 10th November 2004, 04:41 PM   #12
Nuuk is offline Nuuk  United Kingdom
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I thought molten plastic was like treacle, it may take several layers of pouring and sorting through only plastic that melts, but it should be possible to make a fair polystyrene product
Never heat up plastic materials unless you know exactly what you are doing. Many of them will produce toxic fumes!
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Old 10th November 2004, 04:46 PM   #13
Nuuk is offline Nuuk  United Kingdom
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Quote:
Thanks for pointing out my ineptness.
That wasn't my intention Cal!

Quote:
Polystyrene is the base material to which others are added?
Yes, paper or foil can be laminated to the polystyrene. If you make a paper mache covering, it will be quite hard and can then be painted too.

I have heard of people using kitchen foil between two thin layers of polystyrene but not tried it myself (yet).

One of the best pairs of speakers that I have yet heard were made from polystyrene/paper. The sound was absolutely fantastic, with some of the qualities that I get from OB's now. I intend to explore that avenue again when I get time.
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Old 10th November 2004, 04:47 PM   #14
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I agree with Nuuk. Especially the "Never" part he put in bold.

Plastics can be very dangerous.

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Old 10th November 2004, 04:51 PM   #15
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All right Nuuk!

Paper Mache speakers

To go along with the plaster of Paris amplifier

I better go to work

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Old 10th November 2004, 08:12 PM   #16
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To go along with the plaster of Paris amplifier
And don't forget the polystyrene caps!
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Old 11th November 2004, 12:03 AM   #17
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careful about the working voltage, or they will become expanded polystyrene caps!
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Old 11th November 2004, 01:27 AM   #18
Magura is offline Magura  Denmark
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Hey!!!!!

You gotta get a grip before you hurt yourself.

1) Polystyrene will produce hefty gasses when heated in open air, which might burn or worse.

2) the result would be useless, in particular because polystyrene needs to be dried before molten to not end up like a brittle sponge (potentially explosive).

3) Sorting plastics by category is fairly easy, but within each category, say polystyrene or whatever, there are several sub categories, which are in no way compatible.


Molten thermo-plastics are in no way a DIY topic, it takes a lot of knowledge and experience to get anything usefull even if injection molded, let alone other methods


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Old 11th November 2004, 01:31 AM   #19
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Just to make it absolutely clear....

Let's say you accidentally get a piece of POM in your mix....it will 100% sure blow, not maybe or perhaps. I've seen that happen even with injection molding equipment, not a pretty sight.


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Old 11th November 2004, 02:56 AM   #20
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Along the lines of what Nuuk mentioned above, I made a pair of cabinets from molded polyester casting resin. The design was similar to the dynaudio gemini. I used 2 morel MW 142 drivers with vifa D26AG35 tweeters.

Martin Columns wrote about the potential of plastic cabinets which gave me the impetus to try it.

Some comments about moulding plastic and DIY speakers:
1. It's all about the mould. Every second spent on the mould is worth hours later
2. You must use casting resin if there is any thickness to your cabinet walls. The heat of regular resin curing can generate a lot of heat and can interfere with the chemical processes involved in curing plastic. If the problem is too severe it can cause the finished plastic to be too brittle and weak.
3. Load up the resin with a filler - it reduces the amout of resin needed and depending on the choice of filler can increase strength, or damping or reduce weight
4. you can put tint in the resin to make finishing a snap
5. buy the resin in large quantities from an industrial supplier - I bought a 5 gallon bucket of resin for a little more than the cost of one gallon of resin from Canadian tire. Your yellow pages (subject indexed) phone book should have several suppliers listed.
6. Make your baffle out of some other material, as plastic doesn't have the necessary strength to hold threads under pressure
7. Do it outside - I made the speakers in a garage, and even with the garage door closed and new weather stripping on the door to the house, the smell came right in and lingered for months.
8. If you play your cards right you can create a pair of skins of another material and simply use the plastic to fill the void. If done right you can side step the mould, but then you need to worry about finishing.

Just my .02 I hope the above is useful to you guys
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