Unconventional Speaker Design - thread carried over from multiway forum - Page 4 - diyAudio
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Old 14th October 2012, 01:58 PM   #31
a.wayne is offline a.wayne  United States
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Quote:
Originally Posted by DYNABLASTERTUNERS View Post
It can be a theoreticaly myth, because many guys that built spheres haven't notice any resonance...
The flip side , many guys who build them haven't noticed any sonic improvement either ..

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Old 14th October 2012, 04:15 PM   #32
philipc is offline philipc  South Africa
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Quote:
I leave the rings in this polygonal shape, or sand it into a perfect semicircle?
You can sand it down to a perfect semi circle if you have about a gazillion hours spare, but I wouldn't do it, the sound won't be affected in this application. When you get to the baffle you can round the edges, this will have a far greater effect than the shape of the blocks inside/outside
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Old 15th October 2012, 10:41 AM   #33
morgoe is offline morgoe  Australia
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Speakers came today. Look awesome. Gotta get an amp for them.. suggestions, for something cheapish? I've got a decent one lying around, but its quite big. I could always just put it under the desk.

I'm going to cut and glue my D's tomorrow, unless someone can give me a reason not to. Also, I think just glue, not screws. Screws will just be from the top and bottom.
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Old 15th October 2012, 11:37 AM   #34
philipc is offline philipc  South Africa
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No need for screws, 99% of commercial speakers out there only use glue (except for the driver mounting screws)
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Old 18th October 2012, 09:26 AM   #35
morgoe is offline morgoe  Australia
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Update:
Click the image to open in full size.

I didn't cut the D's after all, because the original thicknessing on the wood was not totally accurate, so some planks shortened from 44mm to like 40mm at points. Now they're all about 38mm - I'll glue 5 planks together, then trim off the excess.

Unfortunately one of the wood planks had cracked a bit. Not sure if that was there originally or developed in the shitty storage room I was using. I've used that plank entirely for the top panel, as I figured it would matter least there. Unfortunately I don't have enough wood to totally discard that plank.

I would appreciate any advice as to how to do this vent. I honestly have no idea how to do the calculations (the volume of my box is slightly different to the plan, and the driver itself is slightly different too). Along with calculations I'm not sure how to fit the vent into this oddly shaped box. I'm going to upload a blueprint as to what all the measurements are ASAP.

edit:Blueprint (not to scale, but measurements are good - within a few mm):
Click the image to open in full size.
Volume is around 2.7L.
Speaker is http://www.fountek.net/products.asp?id=52.

I don't mean to palm this off onto you guys, but the reality is I have very little idea what I'm doing, and only a week and a half left to do it (while struggling to pass my other subjects). I'll try to find out the details on my own, but I'd really appreciate any help with this.
I'm planning to stick with the 10mm horizontal vent described in the original diagram, unless there's a good reason not to. This does get a little difficult when it comes to the sides of the box. My wood is 18mm thick, and this'll mean it'll have to fit alongside TWO of the semicircles, which alternate, so it'll have to be really weirdly cut. Does the vent have to be flush with the sides? I assume so.

Last edited by morgoe; 18th October 2012 at 09:44 AM.
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Old 20th October 2012, 09:26 PM   #36
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With your baffle (flat) face planks oriented vertically, like in your photo, they won't expand (not warp) vertically. The wood fibers don't get any longer. But the rest of your cab will expand vertically. So I would recommend running the baffle planks horizontally as in your "world's worst" plan diagram.

I don't know how this vent is constructed, but you may be able to tune it by changing the length. What was the original volume supposed to be? And it was designed for this specific speaker originally?
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Old 20th October 2012, 11:28 PM   #37
morgoe is offline morgoe  Australia
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Unfortunately it's all cut and glued already. I do wish I'd gone with them horizontally, but the original thicknessing of the wood was not accurate on the wood I have left - dipped in by 2-3mm here and there, so I didn't really have a choice. Also, now I'm screwing into the endgrain. Ugh.

If the warping is going to be a HUGE issue, I could slice the planks horizontally and glue them back together? I'd rather not though, I don't have much time left.

The original plan is here, using an FR88EX. I have an FR89EX, which is extremely similar. The volume of both the diagram and mine is around 2.7L. I was planning to use the "alternate vent 10mm high, width of box" described
Click the image to open in full size.
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Old 22nd October 2012, 09:13 AM   #38
morgoe is offline morgoe  Australia
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Will a circular tube be alright as an alternate vent? To get the same area it'd be a 36mm circle cut out. Can I then just use plastic (76mm long, as in the diagram) for the tube? Or do I need to make this vent out of wood? And where does it go, can I put it roughly at the bottom, or does the position of the vent matter a lot?
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Old 24th October 2012, 12:48 AM   #39
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I don't think the location of the vent matters much. A tubular vent with the same cross-sectional area a similar length should work just fine. However the handiest thing to use will be some PVC or ABS pipe, and it only comes in certain sizes. However if your numbers are right, 1 1/2 inch ID (inside diameter) pipe is nearly perfect. (36 mm=1.524") There is an "end correction" to the equations for determining duct lengths that is different for unflanged and flanged ducts- they're all "flanged" on the outside of the box, assuming they are flush, but the pipe just sticking out into the internal space is a different situation than the triangle wooden duct illustrated, so the duct length may vary. However, tuning is easily accomplished by trial and error using different lengths of PVC pipe. This may well account for the differences between the specified driver and the one you are using as well. Consider going with a PVC duct so you can tune it by trial and error. When you get the flattest response, or the one you prefer, you're done tuning.

As for the wood movement issue with the baffle- lots more stable to have the wood all moving together, i.e. grain oriented the same way. Someone told me recently that the ancient Egyptians used to use swelling wood to split stones. It can easily break itself, depending on the environmental humidity variations. Finishing both the inner and outer services will help the wood not to take on much moisture. It'll last long enough for you to get through your class. It's just how many more seasons it lasts that's in question.

Good luck!
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Old 24th October 2012, 01:16 AM   #40
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Originally Posted by tapehead ted View Post
I don't think the location of the vent matters much.
Actually in the ML/BR the vent needs to be at the bottom. Which side or in the bottom it does not matter.

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