Unconventional speaker design - would this sound any good?

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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.

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An externally hosted image should be here but it was not working when we last tested it.


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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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.
 
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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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.
 
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.
 
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.
 
This one is in danish but with lots of pictures. It's beautifull and requires some woodworking skills.
HIFI4ALL Forum: Mine små nye babyer

2006-08-22_083420_IMG_0075.jpg
 
You may find this useful:

QRD diffusers: Technical Overview

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.

Great news about the MDF, if I can stay away from I'd love to. I'll check out that link, thanks.


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?

Unfortunately not.. I did say that the majority of the work would be in the research and science behind it all, but no dice. I do only have about 6 weeks to complete this in - not a lot of time at all, especially considering I have very little idea what I'm doing, both acoustically and woodworkingly. At some point I'm just going to have to go for it.


I like the art of it.
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Keep us posted.

Lots of good points in here. I need to do a LOT more research before I can reply in some half-intelligent way. One thing I could stray away from is the box. Perhaps a kind of U shaped cylinder could work?


This one is in danish but with lots of pictures. It's beautifull and requires some woodworking skills.
Looks amazing but the skills required for that are WAY past what I have.




Thanks everyone, I'll bump this later on when I have some more to say/show.
 
People use "diffraction patterns" to attenuate reflections inside of loudspeaker boxes:
morgoe1.jpg
morgoe2.jpg
The shallow patterns above are meant for a midrange driver. For a bass driver you would need a wider distribution of "block depth" inside the box. I could imagine to use block depth differences at the outside as a kind of design element, and (much larger) block depth differences at the inside as an acoustic element. See below a square cutout of a side wall (left outside, right inside):
morgoe3.gif

Rudolf
 
What tools/shop do you have to work with?

More info you can give the better, what speakers are you planing on using?





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.
 
People use "diffraction patterns" to attenuate reflections inside of loudspeaker boxes:

The shallow patterns above are meant for a midrange driver. For a bass driver you would need a wider distribution of "block depth" inside the box. I could imagine to use block depth differences at the outside as a kind of design element, and (much larger) block depth differences at the inside as an acoustic element. See below a square cutout of a side wall (left outside, right inside):


Rudolf

Refection and diffraction do not attenuate. To attenuate you stuff. All this looks like nothing a simple non parallel wall would do ans the sizes look like they would only have any effect at very high frequencies. Irrevelant for a midrange.

People do all sorts of things, like jump out of perfectly good airplanes. It does not make it a good idea.
 
Take a look at the True Audio web where he has much of Olson's work on diffraction posted. I think you can go someplace with the blocks. Think about the "Danish" shape but done with bricks and the initial baffle to sided a smooth radius. You could do that with just coarse sandpaper and a block. If you can cut the blocks and the baffle, you can do about anything

True Audio TechTopics: Diffraction Loss
 
OD', Back to too small of a sphere to make the frame to baffle smooth problem. Tweeter size at best. Was talking to NonSuch about using a beach ball as a fiberglass form. You could flatten one side to make the baffle and still get a nice radius.

A good idea to think about a full range as learning to do a crossover for a design class is quite an undertaking. Been at at for 35 years and just getting a handle on it. Just don't pick the 125! Maybe the 105 in an egg made of the blocks. Rear port. No BSC needed. Why don't we do one? If it works we could do a Louther.
 
Could build a U shape box, form with 3/4" ply and build box up with layers of 1/8 Birch bending ply. Clamp/glue and then belt sand.

Back to the OP, if you need speakers and assuming you're on a budget, get out there and look for yard sale speakers.

Now Now TVR, pour little 125wk, that's a heck of a driver.
 
With your little pieces of wood, your overall shape isn't restricted to a box. You could cut small flat wood rings or squares to mount the drivers in and construct the baffle connected to them (as well as all the other walls) by irregularly stacking and gluing the small pieces into other shapes such as an egg shape (though a chunky one). If glued well enough, you could take a belt sander to the outside to smooth sharp edges. Fill the gaps between pieces and seal the box with bar-top epoxy coating. It would be a unique shape and an argument could be made for good acoustic performance.
 
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