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Lightweight carbon fibre dual 8" 18/36V BUILD

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Keivn.Pawlus View Drop Down
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    Posted: 30 September 2017 at 9:43pm
Hello!  

I always found the problem with my battery-powered speakers is that they are to heavy and therefore barely get used. This time I will build one light-weight in carbon fibre.

http://forumbilder.se/G9KCU/20170930-142346 -

http://forumbilder.se/G9KCU/20170930-154539 -
http://forumbilder.se/G9KCU/20170930-180734 -
http://forumbilder.se/G9KCU/20170930-203641 -

I have some old Philips 8" drivers that I know sounds good in a sealed cabinet in this size. I will cut two holes for the tweeter also, but im not sure witsch tweeter yet. Or if anyone could recommend some sensitive 8" I¨ll be very happy to hear about it (maybe neodym?)  :) 

I¨m going to make a slot for two 18v 5ah Makita batteries on the back. The speaker will be powered with a TA2020 for now, and in the future maybe some 36v amplifier. But I need to do some more research on 36v amplifiers first. I must connect some diodes in serie with the battery to get the voltage down to something like 14v so I dont fry the TA2020, maybe not the most efficient solution.

First I build a template that I will make a mould of, so I can make it of carbon fibre later. I¨m aware that carbon does¨t have the best acoustic properties(similar to metal) , but if it will be light and used I¨m happy.

Lots and lots of sanding... OuchLOL


Edited by Keivn.Pawlus - 30 September 2017 at 9:52pm
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bitSmasher View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bitSmasher Quote  Post ReplyReply Direct Link To This Post Posted: 01 October 2017 at 1:46am
Nice concept- just yesterday I resolved myself to try an 18v powered TPA3116 using a Ryobi battery... need to hunt down old/broken tools to repurpose for the battery socket
"Battery Acid Sound System" blog hopefully happening in 2017
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hemisphere Quote  Post ReplyReply Direct Link To This Post Posted: 01 October 2017 at 7:40pm
Have I missed something in the images? I can see a square of something that looks like carbon fibre but the rest seems like wood. Or is it foamcore?

Edit: Oh, I see. it's a mould is it?

How are you planning to do the walls? Most of the fibreglass and carbon fibre cabinets I've seen recently have had an XPS foam core with a thin skin of glass or carbon on the surface. That gives the best strength to weight ratio and is also the cheapest way to do it. It's a challenge to get the structure looking neat in the end but the one I built sounds great and is light as a feather. Something like 9kg loaded with 2x12 and a CD+Horn.


Edited by Hemisphere - 01 October 2017 at 7:44pm
Phase 1: Post on Speakerplans
Phase 2: ?????
Phase 3: Profit!
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Keivn.Pawlus View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Keivn.Pawlus Quote  Post ReplyReply Direct Link To This Post Posted: 01 October 2017 at 9:23pm
Thanks, this is the first time I work with carbon. So I hope it goes well 

I think i will mill some rails for the battery out of some plastic. Do you know how long you could run the  TPA3116 with your Ryobi battery? 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Keivn.Pawlus Quote  Post ReplyReply Direct Link To This Post Posted: 01 October 2017 at 9:29pm
Originally posted by Hemisphere Hemisphere wrote:

Have I missed something in the images? I can see a square of something that looks like carbon fibre but the rest seems like wood. Or is it foamcore?

Edit: Oh, I see. it's a mould is it?

How are you planning to do the walls? Most of the fibreglass and carbon fibre cabinets I've seen recently have had an XPS foam core with a thin skin of glass or carbon on the surface. That gives the best strength to weight ratio and is also the cheapest way to do it. It's a challenge to get the structure looking neat in the end but the one I built sounds great and is light as a feather. Something like 9kg loaded with 2x12 and a CD+Horn.

What you see is a mix of kevlar and carbon fibre. I have not started yet with the carbon fibre part, now I just build the mould. 

Wow, 9kg is neat Wink I will make the walls with 3-4 layers of carbon, then I will have 10mm foam and end up with a couple of layers on the inside.

I have decided to go with the Eighteensound 8NMB420 & Beyma CP 12/N now
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Keivn.Pawlus Quote  Post ReplyReply Direct Link To This Post Posted: 14 October 2017 at 10:28pm
Today I was finished with the "original" and I have now started to make a mould out of this in glassfibre.

I have also done some milling for the battery rails.


http://postimg.org/image/10d81lqlzf/ -

http://postimg.org/image/9h7ml98657/ -

http://postimg.org/image/874pexr9ez/ -

http://postimg.org/image/5fvn6v4xnf/ -

http://postimg.org/image/1sdc56js63/ -


Edited by Keivn.Pawlus - 14 October 2017 at 10:41pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SouthwestCNC Quote  Post ReplyReply Direct Link To This Post Posted: 14 October 2017 at 10:39pm
Nice work! looks like your going to need to get your head inside it to lay it up
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Keivn.Pawlus Quote  Post ReplyReply Direct Link To This Post Posted: 14 October 2017 at 10:55pm
Originally posted by SouthwestCNC SouthwestCNC wrote:

Nice work! looks like your going to need to get your head inside it to lay it up

Thanks, yes probablyLOL  If it looks possible I think I will try with vacuum injection for an easier lay up
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Keivn.Pawlus Quote  Post ReplyReply Direct Link To This Post Posted: 15 October 2017 at 2:03pm
Now I've come this far. 

http://postimg.org/image/1s6ppv1fyz/ -

http://postimg.org/image/1vqbnkvszf/ -

http://postimg.org/image/35t8twfi0r/ -

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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 15 October 2017 at 2:22pm
weight for weight, is a carbon fibre panel actually any stiffer than a wooden one? the main advantage of carbon fibre is that you can easily make curved shapes that are inherently rigid. you can also do this by laminating thin ply but with fibreglass you can curve in two dimensions at once.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote davey t Quote  Post ReplyReply Direct Link To This Post Posted: 23 October 2017 at 1:17pm
exactly.. if you want to save weight and increase rigidity, you should make a sphere/cylinder/hemisphere etc. Or at least use curved panels. What you've made will require lots of bracing

Good work though... good work
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hemisphere Quote  Post ReplyReply Direct Link To This Post Posted: 29 October 2017 at 6:09pm
I notice you mention 10mm foam and 3/4 layers of carbon - you might want to reconsider this for future builds.

The science of layered glass/carbon and foam composite structures is that the rigidity is mostly determined by the thickness of the foam. I saw a chart which illustrated this once and it's a steep exponential curve. 20mm is several times stronger than 10mm despite costing and weighing almost the same. You could save a layer or two of carbon or comfortably substitute cheaper and easier to work with glass by using more substantial foam.

Also you probably want it to have as many layers inside as out or the panel flex will be uneven. 3 in 3 out would certainly be preferable to 2 in 4 out.

Edited by Hemisphere - 29 October 2017 at 6:17pm
Phase 1: Post on Speakerplans
Phase 2: ?????
Phase 3: Profit!
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