SBL Posted August 10, 2013 Posted August 10, 2013 (edited) A few of the guys on here suggested I should start my own thread for this build. So here it is I previously have worked in the composite business and very much enjoyed it for the most part. After a while it begins to take its toll, whether it's because of the health hazards or the repetitiveness I decided to take a break from it. But I miss it, so decided to have a crack at doing some full composite enclosures for some loud speakers. To repeat what I said previously in the "What are you building" thread this is largely an experimental concept for me and I'm not sure if it has ever been properly attempted. So in the interest of experimenting and to see just what is possible with exotic composite materials. Here we GO! To mould anything from composites, whether it be carbon, fiberglass, Kevlar etc there are usually 3 main steps: 1. Making the plug 2. Making the moulds & tooling 3. Making the finished part, in this case the speaker enclosure Currently I am working on the plug. Once finished it will be the exact same size and shape as the finished enclosures. I will use the plug to make moulds from. So far I'm about 1/3 they way through finishing the plug. It was made from about 32, 12mm MDF cutouts that were routed with a single template. Glued together with quality wood glue. A few of the pieces cut out and held together with a clamp. There's no glue holding them together yet. I just have a habit of misplacing things so thought this would keep them all together Some woodglue holding the stack together now. From memory it's a 'Fuller' branded glue, I'll have to check but it's good stuff. Note the whole thing was put in a low temperature, low humidity oven (about 45degC, <20% humidity) This pulls most of the moisture out of the wood. This is VERY important for composite work. Humidity is your biggest enemy when working with composites. It has a habit of getting into fabrics and the resin often causing problems that you would much rather not have! 24hrs later, I pulled the whole lot out of the oven and gave it a quick go over with an orbital sander. This just takes off the rough edges left by the router. I wanted to get the wood sealed as soon as possible to limit moisture uptake while im working on the plug. It was sealed with some low viscosity laminating resin, very expensive but works excellent. This will limit the amount of moisture drawn into the MDF and stop the edges from expanding. Next day, pulled out the orbital sander again and went to work. All the bright spots are flush, the darker spots are still recessed. A few more coats of resin will be needed and possibly some filler to get a perfectly smooth finish. Second coat of resin on there. The second coat is back in the low temp oven again to cure. This particular resin does not dry very well at room temperature and requires an elevated temp cure, sometimes up to 110DegC!. Will need a large oven for large speakers! This is where I am at the moment. Tomorrow I will do some more sanding and another coat. I'm sure this being an Audio community some are probably wondering what drivers I'll be going for. I'm still rather undecided and welcome any opinions regarding driver choice. I'm looking at doing my first 3 way that will F3 around 100Hz, then fill the bottom octaves with an active woofer. Keep in mind I only have about 12L to play with. The water drop cabinet shape does take up a lot of extra volume that I could have had if I went with the standard rectangular prism shape. I'm looking at multiple drivers from the Scanspeak Discovery line. Again undecided on whether I'll go active or passive with the crossovers. Leaning towards active at this point. The D2608 http://www.essentialaudio.com.au/contents/en-us/p937_Scan_Speak_D2608-913000_Discovery_Tweeter_Loudspeaker.html The 8ohm version of the 10F driver. I would link to the 8ohm on Madisound but I always seem to have issues with their website http://www.essentialaudio.com.au/contents/en-us/p940_Scan_Speak_10F4424G00_Discovery_Midrange_Loudspeaker.html The 18w midwoofer http://www.essentialaudio.com.au/contents/en-us/p948_Scan_Speak_18W8434G00_Discovery_Midwoofer_Loudspeaker.html Plenty more to come. Edited August 10, 2013 by SlowBarless 1
Atlas Gouverneur Posted August 10, 2013 Posted August 10, 2013 Im not quite following what your doing. Is the Plug the pattern, and from that you will make a mold? Though interesting shape!
shaky Posted August 10, 2013 Posted August 10, 2013 A build thread!! Off to a great start. I am looking forward to seeing the progress on this one. Keep going but don't forget the updates.
SBL Posted August 10, 2013 Author Posted August 10, 2013 Im not quite following what your doing. Is the Plug the pattern, and from that you will make a mold? Though interesting shape! That's exactly right atty. The plug will be exactly the same shape, size and surface finish as the moulds will be. So it's very important to accurately make the plug and finish it to a high standard. If you don't the moulds be bad and the final part will be bad. As an example. This is a propeller I made a while ago for a model aircraft. The top photo is what I used as a plug. I made moulds off this plug and used the moulds to produce the propeller in the bottom photo. I'm sure as this build progresses everything will become much clearer
SBL Posted August 10, 2013 Author Posted August 10, 2013 Though interesting shape! I'm hoping the lack of parallel sides will do something positive for internal reflections. I've read a lot of mixed opinions on whether or not it's really worth it though. For what I'm doing though, it's easier to mould a nice curved shape rather then a normal box
Upfront Posted August 10, 2013 Posted August 10, 2013 I've subscribed. Keep the info coming mate! Linc
L J T Posted August 11, 2013 Posted August 11, 2013 Looking good. The construction of your plug is how I constructed my last pair of speakers Are you going to rebate the drivers? Curious to see how these come together. SB Acoustics make some drivers that perform and model very well also. 1
davewantsmoore Posted August 11, 2013 Posted August 11, 2013 I'm hoping the lack of parallel sides will do something positive for internal reflections. I've read a lot of mixed opinions on whether or not it's really worth it though. For what I'm doing though, it's easier to mould a nice curved shape rather then a normal box Worth it more for strength / vibration, rather than reflections IMO 1
SBL Posted August 11, 2013 Author Posted August 11, 2013 Looking good. The construction of your plug is how I constructed my last pair of speakers Are you going to rebate the drivers? Curious to see how these come together. SB Acoustics make some drivers that perform and model very well also. The drivers will be recessed, the faceplate of the drivers will be nice and flush with the cabinet. The "template cut, stack n' glue" method of speaker construction I definitely see potential in. I think they require a little more work to finish though, but the possibilities are really endless as far as shape goes. 1
GregWormald Posted August 11, 2013 Posted August 11, 2013 Nice work. I would have thought that choosing the drivers would be a part of getting the volume of the cabinets right, but I guess you can always "fill in" if the cabinets are a bit big. I'm looking forward to seeing the progress. Greg
SBL Posted August 11, 2013 Author Posted August 11, 2013 Nice work. I would have thought that choosing the drivers would be a part of getting the volume of the cabinets right, but I guess you can always "fill in" if the cabinets are a bit big. I'm looking forward to seeing the progress. Greg It's a bit difficult to know for sure what the volume of the enclosures will be, at least until I build them and measure. It's going to be a bit of trial and error. There are calculations to determine the strength properties of a laminate and thus determine how thick the walls need to be. But that's a bit beyond me and there are a lot of variables to consider. I am fairly confident that I will have enough internal volume to do what I would like to do with them. If they come in a bit oversized I will simply make the walls thicker which will reduce the internal volume to where it needs to be. I'm not going to order any drivers till I know for sure how much volume I have to play with. I know it seems bit backwards to build the enclosures without knowing for sure what the internal volume will be. But that's how things are for this project. I hope to find an optimum wall thickness for certain sized cabinets so if I choose to build future speakers this way I can know for sure what my internal volume will be before I start working on the enclosure. Just encase I've confused anyone with why the internal volume is dependant on the wall thickness... The enclosures will be made in 'negative moulds' this means the outer dimensions are fixed, but the internal dimensions are not. So the thicker the walls are the less internal volume you end up with. Essentially I will be building the enclosures from the outside-in. Just wait till I start talking about "painting in the moulds" first layer of paint goes on last and last layer goes on first, it gets pretty complicated I understand there will be bit of confusion about exactly what I am doing. But I'll try my best to answer any questions.
Nada Posted August 11, 2013 Posted August 11, 2013 (edited) Im already planning your next project. How about something curvy as a plug like: Oh look - someone's already made a mould. Im sure they wont mind you doing the same.... Edited August 11, 2013 by Nada
SBL Posted August 11, 2013 Author Posted August 11, 2013 Little steps B&W really went with the full snail on that one I do like the tapering tubes though 1
SBL Posted August 11, 2013 Author Posted August 11, 2013 Front of the plug is all sealed up, gaps filled and very shiny. But will be sanded back another time to prep for paint. The sides will get the same treatment over the next few days. Tomorrow I'll start Woking on the top peice and the speaker stand, all of which will be moulded to.
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