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Old 28th April 2006, 10:14 AM   #1
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Lightbulb Making Subwoofer - need expert help

My friend and I and planning on making a large subwoofer this summer. I am currently a fabricator and own my own machine shop as well as owning just about every tool made and several welders. The reason we want to make the subwoofer is because we are looking for a very large subwoofer to not only stand out but to allow low frequency respone. It will be designed to be about 20-24in in diameter and be fit to take the entire trunk of a hatchback camaro when in the box. We were thinking of making a fiberglass, maybe carbon fiber, cone and use a soft rubber tube cut in half and coiled around the cone to form the suspension. The spider/frame will probably be made with machined aluminium. We currently have about 4000w of amps available probably close to 1500-1800RMS. I have some preliminary designs but the real problem right now is finding information out about the best voice coil setup for this size and power, as well as magnet size an design. Its no big deal if it doesnt work well but we would like to try to make a decent design. So I thought I'd bounce a few ideas off of you guys to see your opinions. Thanks for any responses. Here a a few questions.

1. What is the best shape for the cone?
2. Is this suspension idea good?
3. What kind of magnet will we need?
4. How is the electromagnet properly constructed?
5. What shape should it be.
6. What gauge wire should be used?
7. How many wraps/what is the wrap pattern?

BTW this website inspired us
http://neurosis.mit.edu/mjolnir/
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Old 28th April 2006, 02:23 PM   #2
simon5 is offline simon5  Canada
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I know you want to build it, but do you know about Precision Devices?
http://www.precisiondevices.co.uk/showdetails.asp?id=17
http://www.precisiondevices.co.uk/showdetails.asp?id=16

If you want that much power handling, use a 6 inches diameter voicecoil.

Best shape for a cone is the "cone" shape IMO, for strength.

You can use any magnet, Ceramic, Ferrite, but it will be heavy. Neodymium is light and expensive.

Shape? Round is better for subwoofer drivers.

Machined aluminium is a bit overkill for a suspension, usually they use some kind of treated fabric. For the frame, it's a nice idea.

Might interest you :
http://www.vikash.info/audio/transducer_design/
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Old 28th April 2006, 08:06 PM   #3
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Sorry when I said spider I meant frame. It will be an aluminium frame, standard rubber spider. 6in coil, I was thinking maybe 2 X 4in coils, would that be better? Im still unsure if we want to try finding a coil and going from there or if we want to build our own. Are they're anymore resources exact driver design.
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Old 28th April 2006, 10:00 PM   #4
simon5 is offline simon5  Canada
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2x 4 inches coils, you mean a dual voice coil design? That doesn't increase the powerhandling much, it only help to play with the impedance. It also can be used to use a smaller wire but more turns and still have an acceptable final impedance.

If you have a nice design, a single or dual 4 inches voicecoil could be ok. If it's nicely vented and all.

You could also do dual 6 inches voicecoil, that would be great hehehe!

The coil is the easy part to build. Hardest part is doing the magnet circuit. You want to concentrate the magnetic field in the gap, to have as much linear throw possible. You want also a "tight" gap but since you own a machine shop, it's not a problem for you.

If you look at the link I posted, you'll see that you need to use tools like a Finite Element Analysis tool, FEMM.
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Old 28th April 2006, 10:51 PM   #5
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Here's a 25" driver with an interesting cone material.
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Old 29th April 2006, 05:24 PM   #6
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Well I'm having a few problems with the design. I can't think of anything I can use that will work for the spider, since a premade one is pretty much out of the question for this project (unless you guys know of something that will work). I heard ferrofluid can be used as a lateral locator when put in the speaker airgap and extra coils used to locate the speaker vertically. Is this true, is it too much work to be worth the effort? Any other ideas for making a spider that will work well? Also what AWG wire should be used for the coil, would thicker wire and more wraps or thinner wire and less wraps be better? I was thinking the thicker the wire the better because it can handle more power right, albeit at the cost of more coils?
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Old 4th May 2006, 05:33 AM   #7
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can anyone give some help here
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Old 4th May 2006, 07:02 AM   #8
AndrewT is offline AndrewT  Scotland
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Hi,
that Vicash site shows a lot of detail.

There is a site with details for building an electromagnet for a large driver (about 30inch). This is a project in progress. Again quite a lot of detail and machining shapes are given. For a 6inch coil the machining will be enormous, I suspect 12 to 14inch diameter.

A single layer coil poses the problem of bringing the wire from the far end of the coil back to the front lead out wires. Dual layer and all even layered coils avoid this problem.

Multilayer coils give a lot of flexibility in designing the voice coil and become mandatory if you want a large BL factor.
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Old 8th May 2006, 07:58 PM   #9
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whats the website?
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Old 8th May 2006, 08:19 PM   #10
Relax is offline Relax  United States
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If you really want to look at making a large linear throw woofer, this thread is for you:

DIY Parthenon
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