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Advice on building some SPL sub boxes

acarmody

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My dad loves an opportunity to play around with his woodworking tools.

My port flare mold.
snc00284.jpg
 

holdenboy

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Excellent!!!!

Does he wanna make me one....or maybe a 10" version? (pay ofcourse)


Those are really great, whats the outside diameter?
 

acarmody

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The diameter is 220mm at the bottom. The pipe is basically 160mm wide on the outside and the curve is 30mm radius. I was just going off what these guys recommended, Heat Moulded Port Flares .

While I have got him busy for the next few weekends in building my sub box, this is as large as his small lathe could handle. There was only about 1" clearance between the wood and the lathe. Sorry Holdenboy.

Also I was reading through this article Technical - Beginners Guide to SPL, Competing & Testing - Mobile Electronics Australia , and they mentioned using bricks to reduce the box volume. Could I make this box a bit bigger, say extra 20mm depth, and use bricks to reduce the volume for the comp and take them out for everyday use. Just thinking of how to have my cake and eat it too.

Also I checked out some prices for the rubber couplings, cheapest was Tradelink at $37.50 each,:bang:, so I'm going to see if I can just get some rubber from Bunnings or Clark Rubber and some 150-170mm hose clamps and make my own.
 
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acarmody

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Ok so my first attempt didn't go so well, pretty obvious what happened, I heated the pipe above the mould.

snc00285d.jpg


Second attempt went a bit better, I may even use this in the box, obviously my mold isn't exactly square, but its no more then a couple of millimeters off, just that one side has a slightly steeper curve then the other, shouldn't affect anything should it?

snc00286x.jpg
snc00287.jpg


And yes I will clean it before it goes in.
 

holdenboy

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No worries about the moulds.....i'd still be keen for a 6" one like yours, im sure i could make him some $$$ if he wants to make a few at a time?

That second one is a better flare than ive ever had to play with ;)

If you want, you can make a single port, just flare the inner one and cut it down to be smaller than the outer one, cut the hole just big enough for the inner flare to fit through....then the outer flare has a 5-10mm gap for mounting (Hope that makes sense).
 

acarmody

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I asked him about the molds, he says he can make some if you want, but not for at least over a month, possibly longer, shipping would be a bitch though. You can have mine when I'm finished with it if you want. I was going to make mine like this, Moulds for DIY Port Flares, but he wanted to get out of the house for a couple of hours so he went and made me my mold.

Also I found my rubber couplings, Reece and Tradelink both want about $37 each, the lady at Bunnings told me about another joint 1.5 blocks from Tradelink, end result is I got 2 Fernco rubber couplings for $17 each, bargain.

EDIT: You will be pleased to know that I have done some thinking and I have decided to stop asking questions about making a bigger box. I have thought about how I already turn down the bass quite often will just sealed box and these ported boxes will be what, 30-40% louder anyway.;)
 
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acarmody

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I have my 4 flares done, now I just have to cut them down to size. I made a bit of a mess that I better clean up before my dad sees, :). And a little bit of sealant will close the gap between the pipes, only 1-2mm anyway.

snc00291v.jpg
snc00289a.jpg
 

acarmody

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Hmmm I just measured up the diameter of the pipe at the flare, 230mm, damn, so the flares are close to 35mm each, no problem, but the box is only 400mm high, on the outside, so 350mm inside, damn. Could I offset the ports, so make one stick 2" further out than the other? That way the flares will overlap, but it shouldn't be much air-flow restriction. I'll remeasure up the boot and see if I can wedge a slightly taller box in.

Also the ports should be 400mm long, or 435mm tip-to-tip?

EDIT: Hmmm I may end up having to sit the ports directly up against the top and the bottom of the box, so I will have to get rid of the inside flare (either sand it off or try to remould it to straight again), but only the section against the walls.So there will be say 300 degrees of flare on each port. Once on the outside the flares can overlap the 25mm for the roof and floor of the box. I'll have another go at measuring stuff up. But can the sub driver screw into the end joint? As in the sub mounting screws go in the baffle and into the side panel, or should I keep it in just the baffle?
 
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holdenboy

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Firstly, it'll probably be 10x louder than a sealed setup using the same sub/s.....12db is equivalent to 10x isnt it?, because yeah....it'll probably be 12db louder ;)
Secondly, you will need enough room for loading between the subs and the tailights. Also need to have enough room for the sound waves to get back past the box and into the cabin (good for SPL). So those measurements are the maximum I would go. I also wouldnt go with one port sticking out 2" and the other flush, it'll cause a few loading problems like that. Can you mount them diagonally / offset in the middle of the baffle? each sub goes as far away from another as possible (each side of the baffle), do you have enough room then?

Usually you wanna measure the "un flared" length of the port, or near enough (i think 1/3rd of the flare counts, thats it). So if the flares come out 35mm, it'll need to be 470mm in total length......sorry, forgot to mention that.

Heres the design im thinking about:
Box-1.jpg


Same dimensions we agreed upon....just the ports can either be flush mounted into the baffle or like in the side on pic half internal / external.....my port i used was all external, i found it much better for SPL actually, although i never tested it on a Termlab.
 

acarmody

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Firstly, it'll probably be 10x louder than a sealed setup using the same sub/s.....12db is equivalent to 10x isnt it?, because yeah....it'll probably be 12db louder ;)

Bloody hell, I hope your kidding.



I have spent about 4 hours trying to work out different ways to make this fit, including diagonal, but damn me I will make it work somehow, no way I'm not using these ports I spent so long on.

Now if I screw these subs into the very end of the box so that the mounting screws actually go through the front into the side wall, and if the port flares overlap the sub itself, not necessarily the cone, just the frame, I should be able to fit it. The only problem I can see is that there will be very little wood between where the sub screws into and the port cutout, but if I add a brace like in the picture below it should be strong enough to support the sub. Basically the sub screws into the baffle and then into this brace, so really the brace is holding the sub up.

box1ch.jpg
 
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