Hypercube Loudspeakers

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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 Matthew 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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Moderator
Joined 2011
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.

-

Does the crossover use flux capacitors?
 
frugal-phile™
Joined 2001
Paid Member
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
 
Founder of XSA-Labs
Joined 2012
Paid Member
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.
 
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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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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
 
Hi Ticovski,

You should find instructions by following the second link from my first post. I know this is going to cause a lot of eyeball rolling but internal volume seems to be less of a factor with this shape. I can't comment personally on that since I have only made one pair. I followed the advice of the inventors and just made it as small as possible.
--Greg
 
-flatter frequency response

FR is a function of the driver across the majority of its BW, notwithstanding box alignment and edge diffraction, for which latter a sphere is optimal per Olson unless a true IB is available (good luck in this universe).

-near omnidirectional or wide cardioid dispersion

As above.

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

A remarkable feat, given that efficiency (η0) is rated in percentage, not decibels. ;) To significantly alter efficiency across the entire audible BW the box must severely affect the suspension compliance, to say nothing of the resonant profile of the cone substrate. If this is the case, it should immediately be binned and substituted for something competently designed. Sensitivity will of course not increase except in line with what would be expected from vented or sealed loading of a given type / alignment and diffraction behaviour.

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

Relative to which enclosures of identical Vb, alignment and damping? Transient response is directly related to BW covered. Impulse response / group delay is a function of box Q &c.

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

Relative to which enclosures of identical Vb, alignment and damping?
 
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Being generous, I like to think it's a joke. If it's not a joke, then it is of course utter quackery of the first order. This for example is priceless:

Given equal mass and equal energy we could only hypothesize (with apologies to Newton & Einstein) that the either:

The rate at which time passes in the vicinity of the enclosure differed over a radius from the center of the enclosure (which could potentially do interesting things to the speed of light's status as an inviolable constant).

- OR -

The material of the woofer cone lost its inertia but not its mass(weight = mass in a 1G field). (and Newton spins in his grave with relativistic radial velocity).
 
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Hi Scott,

I hope you won't give up on this so soon. I have observed increased SPL with the hypercubes relative to the equivalent volume sealed box. With the 64hz distortion test I performed I had to reduce the signal level slightly (~1db) being sent to the amplifier when powering the hypercube in order to match the SPL of the sealed box. The test data that was published was done with the mic closer to the drivers than the pictures show (~2" from the phase plug vs. ~6" in the pics). I am assuming right now that the difference in efficiency will be slightly more when measured from a bit further away. The hypercube speaker is made from 6mm acrylic and is unstuffed. The sealed box is made from 12mm plywood and has open-cell foam inside. The two enclosures are of equivalent volume and happen to be almost exactly the recommended sealed volume (Q of 0.7). --Greg
 
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