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Old 2nd May 2007, 03:06 PM   #1
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Question Spherical Arrays...?

So Make magazine just posted a blog article about Spherical Arrays, with links to a DIY instructable.
Make blog article

Doing a "spherical" search on diyaudio, I came up with nothing except a few spherical enclosures for single drivers, nothing like the array concept.

Has anyone played with this? Any thoughts?
It might be fun to pack in a handful of full-range drivers, or mix mids and tweets, and hang one of these from the kitchen ceiling if the sound's decent.

Click the image to open in full size.

(Maybe this post should be in alternative technologies? mods, feel free to move it as necessary.)

Adding info sources as I research:
http://www.arts.rpi.edu/crb/Activities/SenSA.htm
http://www.music.columbia.edu/%7Edan...ices/more.html
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Old 2nd May 2007, 03:18 PM   #2
Zarathu is offline Zarathu  United States
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Default Need to learn about nearfield line arrays

You need to learn about how nearfield line arrays are built for use in homes. Read Dr. James Griffin's white paper on Near Field Line Array Design.

http://www.audiodiycentral.com/awpapers.shtml

After reading this, you can decide whether what you want to build will work.

Zarathu
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Old 2nd May 2007, 03:25 PM   #3
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I'm well acquainted with line arrays.
This is a totally different beast that I'm trying to find more info on.

And it's not "what I want to build," it's something some other people have built and I couldn't find anything on these boards about, so I got curious.
(It's unclear if you even read my post or just responded due to the usage of the word "array" in the title.)

Here's a commercial variant: http://electrotap.com/hemisphere/
They used Polk coaxial car speakers... http://www.polkaudio.com/caraudio/specs/db525/
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Old 2nd May 2007, 03:34 PM   #4
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The idea behind these things is to make an omnidirectional speaker. It will be omnidirectional for low frequencies. At high frequencies, it will be this thing that squirts several beams of high frequency sound in different directions, not even close to omnidirectional.

Who knows, in the right environment it might sound OK, but I wouldn't bet on it being hi-fi. In a kitchen full of hard, reflective surfaces, almost anything will sound about the same.

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Old 2nd May 2007, 03:40 PM   #5
Zarathu is offline Zarathu  United States
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Default I know exactly what you are talking about

Spherical arrays have been looked at during the 1950's and 1960's, which is a time which I remember, but is probably way before you were born.

They generally don't work because of the violation of the principles set forward in Jim Griffins paper, most notably center to center distance, as well as producing an incoherent sound image.

Bose put together an array called the 901. The diffusion of sound works for some but not for many.

I know exactly what you are talking about. My assumption is that people want to build high quality speakers to put in a house to listen music with an exact realism of the actual performance.

One has to consider what kind of sound image is going to be produced by speakers which beam the sound every which way, what kind room would have to be used to get a coherent image. Additionally, this looks like it has to be a one way(as opposed to a 2-way or three-way speaker system). As such the high frequencies are likely to be missing.

If it was a viable option you'd see it somewhere. Speaker design has been around since the 1940's. I've been involved since the late 1960's. This option was looked at and discarded many times over the period. And since the late 70's no one talks about it for some of the reasons I've posted and for many others.

Kind regards,

Zarathu
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Old 2nd May 2007, 03:54 PM   #6
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Default Re: I know exactly what you are talking about

Quote:
Originally posted by Zarathu
I know exactly what you are talking about. My assumption is that people want to build high quality speakers to put in a house to listen music with an exact realism of the actual performance.
Ok, from that perspective, these would in fact suck. I agree 100%

But if you check out the links above there are people doing interesting things with them, from for instance a music PA perspective. They're definitely not designed for sitting in front of and listening to two-channel stereo music, they're three dimensional for a 3d space and it looks like they do some interesting things.
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Old 2nd May 2007, 04:05 PM   #7
Zarathu is offline Zarathu  United States
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Default In that case....

In that case, all normal bets are off.

I should think that quite a bit of them would be needed. I don't agree with the message in the one web site that shows a spherical as useful. I can't imagine it as being anything other than diffuse Muzak sound.

There is an article in the Current Scientific American mag, about using direct beaming sound in outside venues where only one person hears it but now one else does. I should thing that a technology like that would be more useful than this "Where to heck is that coming from" technology.

My opinion though.

Zarathu
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Old 2nd May 2007, 04:19 PM   #8
rdf is offline rdf  Canada
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Default Re: Re: I know exactly what you are talking about

Though horizontally omni only, the mbl 101 E garners raves from all quarters so you're right to keep an open mind on the concept. The one ~spherical commercial speaker I recall was the dodecahedron Design Acoustics D-12 from the Seventies which used a cluster of cheap and cheerful small drivers in the Bose mold. It's possible true omnis haven't found commercial success because of the very high difficulty and cost of manufacture. It's an interesting design question. You can bet though true omnis won't tolerate indifferent speaker placement. Unless you have the domestic real estate to place them well out into the room and the option to damp the first ceiling bounce I would seriously reconsider anything more complex than a simple design study.
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Old 2nd May 2007, 04:34 PM   #9
Aengus is offline Aengus  Canada
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rdf said:

Quote:
Though horizontally omni only, the mbl 101 E...
There's also the Linkwitz Pluto.

Aengus
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Old 2nd May 2007, 06:22 PM   #10
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FWIW, I've done a couple of horizontal omni or partial omni DIY projects. Actually, one is still in the single speaker/prototype version. They don't seem to be as fussy as one woould think as far as room placment. I have mine centered about 3' from the front wall and 3-4' from the sidewalls and they work very well, IMO.

Also, since the drivers are coincident vertically, they are kept in phase, whereas with spherical arrays there would be lots of phase cancellation problems, I would think.

Here are a couple of pics of my omni projects from recent DIY gathering. It's a speaker type I see very little of posted on DIY forums and there are seemingly no designs out there you can build from, other than the Ohm F variant, I guess.

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