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Old 29th August 2006, 09:39 AM   #1
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Default Wide polar pattern speakers via Diffusors

has anyone made any attempt at widening the polar pattern of speakers built using Quadratic-Residue or Primitive-Root type diffusors before (These are found in hte master handbook of acoustics among other things)
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Old 29th August 2006, 12:06 PM   #2
Tenson is offline Tenson  United Kingdom
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Using them in what way? What are you thinking of?
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Old 29th August 2006, 12:07 PM   #3
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mount a driver and one in such a way that the driver fires into it perhaps, the diffusor would only have to work when the woofer starts beaming It just popped into my head earlier today
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Old 11th May 2012, 09:01 AM   #4
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Quote:
Originally Posted by noodle_snacks View Post
mount a driver and one in such a way that the driver fires into it perhaps, the diffusor would only have to work when the woofer starts beaming It just popped into my head earlier today
In these cases they are refered to as Acoustic Lenses, and yes, Bang and Olufsen has done it in their Beolab 5 for example.

Click the image to open in full size.

And i've seen at least one DIY speaker following the same principle. the horizontal polar was impressive - just a big, green rectangle
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Old 11th May 2012, 10:37 AM   #5
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I've played a little with surround speakers bouncing off a diffusor. It did spread the sound source a little. Using a QRD diffuser would guarantee a fractured impulse response. You might do better with a cylindrical spreader for a cleaner impulse response.

David
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Old 11th May 2012, 12:40 PM   #6
Tenson is offline Tenson  United Kingdom
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I'm not sure a clean impulse is really a goal to aim for in a speaker designed for ultra-wide dispersion. Adding reflections from the room that will be naturally diffused anyway, will make for a messy impulse.

If you do want to go that route I suppose a di-pole with only the rear wave diffused would be a good way to get it. Clean impulse from the front wave followed by diffused sound from the back.
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Old 11th May 2012, 07:47 PM   #7
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Duevel Bella Luna Omni-Directional Floor-Standing Speakers

ONE REVIEW:
"Several things immediately struck me during my extended listening sessions. The first is that the Bella Lunas set the image much farther back than my reference Talon Khorus X Mk. II. There's a wonderful depth to the soundstage, with a huge amount of air surrounding voices and the stage as a whole. It's not clear to me how much of this is actually on the recording, but the effect is both captivating and musical.

The sound, too, is surprisingly full. I did not expect the image to have the weight of the twice as expensive, double woofer/single tweeter/single super-tweeter Khorus X, but it did have a surprising amount of bass extension. I did not in the least feel deprived of bass with this speaker.

The treble was another story. Because the Bella Luna design is omni-directional, it does not have the pinpoint treble impact of conventional speakers. It's not as if treble is not present, or high extension is lacking, but impact on high is far less immediate than I'm accustomed to. This was especially apparent listening to opera segments that progressed from solo or ensemble singing to orchestral interludes. Soprano voices, horns, piccolos and cymbals lacked the cutting edge I had expected to hear.

Listening to Bella Luna is analogous to moving from an optimal front and center seat in a concert hall to one considerably farther back. Up close, treble is very direct and brilliant, as is the bass. Move back 15 or 20 rows, or ascend to the second balcony and you lose the brilliant immediacy and detail on high. Bass, on the other hand, remains strong. (Sometimes, in fact, the bass seems stronger as you move back due to the extra resonance of the hall that reaches your ears.) In place of treble directness and in your face highs one discovers a newfound warmth and glow. Many prefer to sit farther back or in the balcony precisely because they love this resonant glow so much. This mid- and far-hall perspective is what you hear with the Bella Luna."

Omni-Directionality:
The Bella Luna's omni-directionality is everything it's claimed to be. As I moved around my large living room, the image did change in size and character, but I never had the sense that I was "outside the soundstage" or that the imaging perspective was all mixed up. Rather, the music remained as a piece no matter where I stood. It's a wonderful experience to move around without losing a sense of air, depth, and coherency. Omni-directionality makes the Duevel Bella Luna a great speaker for both serious and casual listening.

Designer Markus Duevel would argue that the pinpoint imaging of conventional speakers is unnatural, and that reproduction of recorded sound benefits from an omni-directional presentation. Whatever the truth of that statement, it must be noted that live, un-amplified music is never produced through speakers, regardless of design, and that it does radiate from a set, rather pinpoint source. A voice sounds very different heard from a singer's front than from the rear, while it sounds the same everywhere in the room through the Bella Lunas.

In short, omni-directional speakers are a phenomenon in and of themselves. Their sound, IMHO, is neither inherently more or less natural in character than that of conventional speakers. It's simply different.

Speaker preference is ultimately a matter of taste. The Bella Luna's highs and image are far less in your face than through the speakers I'm accustomed to. But that does not render their presentation inherently less musical. On the contrary, the extra benefits of omni-directionality will, for many music lovers, take precedence. "
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