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Old 16th September 2012, 08:58 AM   #1
morgoe is offline morgoe  Australia
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Default Unconventional speaker design - would this sound any good?

Hi there, I was directed onto this forum by a friend of mine who built a guitar cabinet a while back. He said you guys were really helpful.

Basically, as part of an object design class at uni, I'm making a speaker. Unfortunately, because we're being graded on our woodworking skills, a 'simple' speaker box isn't good enough. I'm trying to come up with an alternative speaker design, and this is what I've come up with. I'm new to making speakers but I've got a strong background in audio engineering so I know a little about acoustics.

Click the image to open in full size.
Click the image to open in full size.

Basically, the sides of the speaker box are loads of little bars connected at slight angles. The idea is to have the sound bounce away every which way, and never form a mode. I'd have the top, front and bottom panels made of a solid panel of MDF, and then cut up a long piece of MDF into a ton of bars, maybe 10x10x40mm. Then cut various angles at the end of these to join them together.

Do you think this will sound good, or should I totally scrap this and come up with a new idea? I can imagine getting the corners solid will be quite hard, but otherwise I think it should be reasonable.
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Old 16th September 2012, 09:16 AM   #2
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You'll find that the length and angle of the blocks has to be a significant fraction of the wavelength to have much effect, so I doubt what you've shown will do much below midrange, but as a piece of industrial design I think that's really funky. I'd be tempted to use hardwood rather than MDF though as finishing will be much easier.
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Old 16th September 2012, 09:33 AM   #3
morgoe is offline morgoe  Australia
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Quote:
Originally Posted by pinkmouse View Post
You'll find that the length and angle of the blocks has to be a significant fraction of the wavelength to have much effect, so I doubt what you've shown will do much below midrange, but as a piece of industrial design I think that's really funky. I'd be tempted to use hardwood rather than MDF though as finishing will be much easier.
Yeah, with it being so small its not going to affect the lowend much.

I'm curious that you've suggested hardwood. I'm actually not allowed to use MDF at the university workshop for OHS reasons, but it seems to be so heavily encouraged everywhere I read that I thought I'd go with it anyway. What hardwood would you recommend?
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Old 16th September 2012, 09:41 AM   #4
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I like MDF and use lots of it, but it is a pain to get a good finish on the "endgrain", lots of sealing and sanding required, and with your design that would get very fiddly very quickly. As for hardwoods, just about anything with a fairly tight and even grain should work well. I'd see what you can get hold of locally for a reasonable price and like the look of. You could even use a mixture of types and with a clear finish, get a very nice pattern.
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Old 16th September 2012, 09:48 AM   #5
morgoe is offline morgoe  Australia
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I actually managed to pick up a few pre-veneered blocks of MDF second-hand (another requirement of the uni course is to use second-hand or recyclable materials). It would not be too hard to cut them like I've shown and preserve the veneer. The variety of vaneers would also look quite nice I think.

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Old 16th September 2012, 10:27 AM   #6
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MDF is preferred over hardwoods by many for speakers because hardwoods tend to resonate, and in large panels they can warp or crack (if not humidified properly). With your construction method, however, that shouldn't be a problem, and I agree with pinkmouse hardwoods (or softwoods) would finish better.
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Old 16th September 2012, 11:04 AM   #7
Jay is offline Jay  Indonesia
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I believe that this is for Art & Design class (not Acoustics). I know that "functions" is always a criteria in object design. But may be your teacher wouldn't care much if the box design will improve anything at all? In speaker design, crossover is everything. You can find many expensive speakers with perfectly square box, showing the subjective importance of the box.
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Old 16th September 2012, 12:07 PM   #8
ODougbo is offline ODougbo  United States
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To me it looks like a lot of work - without much gain. Also far from a golden ratio, this looks to be to boxy.

It would next to impossible to finish with stain/paint would need a super thick coat of something. E.g. truck bedliner coating(s).
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Old 16th September 2012, 12:18 PM   #9
tvrgeek is offline tvrgeek  United States
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I like the art of it.

Now, a little about acoustics: It is not the flats of the sides that are the problem, it is the edge where the baffle meets the sides. The modes will be the sum of all distances to an edge. The small variations the offset blocks provide won't sum much different from just an offset driver. I am making the assumption you will recess the baffle so the blocks form the edge. It looks cool, but will work no different from a sharp edge box and may actually be worse. For practicality, ( that design part) it will be fragile with all those sharp edges to bet bumped. MDF is very soft.

The plain truth is, a sphere is the correct shape. Any edge is bad. I have seen so many spheres where they cause the driver frame to stick out and the result is horrible, it is pathetic. For practical design, a box with 3/4 to 1 inch radius works quite well. For art and design, not so great. The magic is industrial design where art, design and engineering meet.

I half way agree with Jay. The crossover is the most important part. But, I disagree in that my last three builds confirmed how important baffle design is. I was surprised to find that rounding over all 12 edges was an improvement from the front four by quite a bit.

You sure can find many expensive speakers with square edges. Expensive and good have no relationship. You will find the good speakers all deal with diffraction.

BTW, it looks like you just picked dimensions and driver positions by eye. Download "The Edge" free software to see how varying the dimensions and positions change the diffraction. When getting into crossover design, you will find the closer the tweeter is to the woofer, usually the better.

Back to the art. Keeping with the blocks, why are you just building a box? Think about some wavy irregular sensuous shapes. Don't worry too much about sealing the insides, you can always line it with recycled cloth saturated with glue, tar, resin, anything that meets the class requirements.

Keep us posted.
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Old 16th September 2012, 12:21 PM   #10
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This one is in danish but with lots of pictures. It's beautifull and requires some woodworking skills.
HIFI4ALL Forum: Mine små nye babyer

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