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Old 18th November 2014, 02:24 AM   #1
gmad is offline gmad  United States
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Default Hypercube Loudspeakers

Hello,

I would like to share some information and personal experience about hypercube loudspeakers. Firslty, this design (or discovery) was patented in 1980 by Matthew R. Kennedy and Thomas R. Weiss and has since gone into the public domain. Information can be found at the following addresses:

Matthew R. Kennedy

Random Distributionz


I have been in touch over the past several months with Mathew Kennedy and he has given me much encouragement and advice about building this enclosure. You can find the results of my independent research on Matthew's blog

Futiquity

The shape we are dealing with here is a square-truncation rhombic dodecahedron. The basic premise of this design is that being the inside out projection of a tesseract or hypercube, the enclosure essentially inverts the rear wave from the driver while supporting (and subtly resonating with) a wide range of standing waves. The enclosure becomes an extension of the driver, essentially increasing it's surface area. Based on my personal experience (as well as that of the inventors), this enclosure demonstrates the following advantages compared to a sealed box of equivalent volume:

-flatter frequency response

-near omnidirectional or wide cardioid dispersion

-increased efficiency across the range of the driver (upwards of 3 db)

-faster decay or improved transient response especially in the lower portion of the spectrum

-lower harmonic distortion (6db less in my findings)

I'm very excited about this design and I believe it to be a genuine breakthrough. I hope this is the beginning of a long dialogue about hypercube speakers.

--Greg
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Old 18th November 2014, 02:37 AM   #2
rayma is offline rayma  United States
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Quote:
Originally Posted by gmad View Post

I would like to share some information and personal experience about hypercube loudspeakers. Firslty, this design (or discovery) was patented in 1980
by Matthew R. Kennedy and Thomas R. Weiss and has since gone into the public domain.
I'm very excited about this design and I believe it to be a genuine breakthrough. I hope this is the beginning of a long dialogue about hypercube speakers.

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Does the crossover use flux capacitors?
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Old 18th November 2014, 03:17 AM   #3
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Certainly the non-parallel walls reduces issies with internal resonance.

To get 3 dB more out of the speaker, the box has to invert the back radiation phase and reradiate it in its entireity. That the back of a speaker will not have the same FR as the front creates an issue with the exact doubling of the system's output. And, at this time, i cannot see how the box inverts the output with flat FR.

In the 1st link, the author clearly does not understand how T/S parameters are used in box design -- unless aspect ratio is is sufficiently high that 1/4 wave resonance has to be considered, box shape is immaterial.

I willbe interesting to see the results of your experiments.

dave
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Old 18th November 2014, 09:28 AM   #4
xrk971 is offline xrk971  United States
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I don't see how this is going to be any different than a spherical speaker enclosure. The fact that there are small sides and angles may contribute a bit to the edge diffraction, but the overall shape at larger wavelengths (lower frequencies) will appear similar to a sphere. If you made the whole thing out of very lightweight material like foam core or tonewood, it can re-radiate, and would essentially act like a giant spherical passive radiator of mid frequencies. It might have interesting ambience but might sound colored and not flat.

The angled small panels will be stiffer like a buckyball but reduction of internal resonances is like a sphere. In the second link measurements are shown and clearly, there is less rippling but that is a lot in part due to lack of hard edges diffraction at the baffle step. In the hyper cube there is a strong resonance at 1.7khz that wasn't there in the regular box.

Second link quotes G.M., if same GM as diyAudio - then we have good basis to trust how it works as well as listening impressions.

Last edited by xrk971; 18th November 2014 at 09:39 AM.
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Old 18th November 2014, 09:33 AM   #5
Colin is offline Colin  United Kingdom
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I'm not sure how the Hypercube was patentable. Similar ideas for non-parallel wall enclosures have been in the literature for decades. Wireless World did one with a KEF system in the late 1970s and commented that it reduced a hollow sound from the cabinet (the author didn't, however, claim that it was insanely great).

Carl Pinfold's Musician speaker (Liverpool University) used a non-regular shape inside the enclosure to break up reflections. He called it a sound splasher and that was published in a number of magazines.
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Last edited by Colin; 18th November 2014 at 09:34 AM. Reason: foiling autocorrect's bid for world domination
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Old 18th November 2014, 02:35 PM   #6
gmad is offline gmad  United States
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Hi Dave,

If you'd like I could measure FR from the rear of the enclosure. I could do this with the driver mounted inside out as well. I believe my measurements show that there is something special about this shape since there is no foam inside and it's outperforming a sealed box of equivalent volume with both thicker panels and foam stuffing. --Greg
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Old 18th November 2014, 02:40 PM   #7
gmad is offline gmad  United States
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Hi xrk971,

I think the difference between a rhombic dodecahedron and a sphere is that the pyramids that make up the former support a wide range of standing waves. There is a resonance at 1.55k with my personal pair that I made (using acrylic) which I can hear while knocking on the enclosure. I found this can be easily eliminated by placing open-cell foam inside the enclosure (at the expense of increased directivity). I personally like the sound of my hypercubes better with no foam inside and that is what my measurements reflect. Also, I am indeed the G.M. (Greg Madama) who is quoted on the blog but I'm not sure how this validates or invalidates my subjective or objective observations. --Greg
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Old 18th November 2014, 03:07 PM   #8
gmad is offline gmad  United States
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Hi xrk971,

I think I may have misunderstood part of your post. I am not (nor have I ever been) GM on diyAudio.
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Old 18th November 2014, 03:20 PM   #9
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Old 18th November 2014, 03:51 PM   #10
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Looks very interesting to me. I was planning, for sometime, to build clear sphere enclosure but would like to try hypercube.

Any sw calculators to calculate sides from a given volume?

Without a simple one I don't think there will be much experimenting in diy community.
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