Graham Holliman Velocity Coupled Infra Bass Speaker? - Page 25 - diyAudio
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Old 9th July 2011, 12:09 AM   #241
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does it work? shure... fog horns work also
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Old 9th July 2011, 01:20 AM   #242
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The only part that confuses me, like I said, is the "details at level A-A" part because in the top part of the diagram X' and X' are shown at the bottoms of the openings while in the bottom diagram they are placed in the center of the bowtie wings.

Click the image to open in full size.
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Old 9th July 2011, 01:54 AM   #243
tb46 is offline tb46  United States
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Hi Upstate NY low life,

Post #242: "The only part that confuses me..."

What you are calling the "bowtie wings" is the first section of the horn that is part of this design.

The driver energizes a way undersized bifurcated (split?) horn that is composed of the horizontal sections (the bowtie), and of the vertical sections (left and right of the box "V"), all horn sections are marked "X' ". The driver is coupled to the horn through a throat chamber with a throat opening called "Y". At the throat a Helmholtz resonator is also coupled to the begining of the horn; the resonator consists of volume "V" and opening "X". The drawing indicates that the back of the driver is left open to the room.

I doubt very much that there is any difference in principle between the box in the patent drawing, and the RobWells drawing in Post #162; just a different layout, and obviously the RobWells enclosure is designed for a different (modern?) driver.

From the general description above you should be able to develop an AkAbak model for this design. You could start by entering the horn data into Hornresp, and exporting the data as an AkAbak script file. Then you could add the resonator box to the AkAbak script, as well as respective electronic low cut, and high cut filters. That would give you a model with which you could evaluate the operation of the Graham Holliman enclosure with modern drivers.

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Last edited by tb46; 9th July 2011 at 01:56 AM.
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Old 9th July 2011, 02:33 AM   #244
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Okay, I think I see now. So the dotted lines are a widening horn channel that connects the top of the resonator to the top plate. So in reality there is no space there as it is shown in the top diagram?

And acutally, in response to "way undersized," I believe Holliman stated that it is not acting as a horn, but rather a slowly tapering port? I know there is some precise description of the cruciality of the angle of the port and that it should be as long and slow as possible. I think I understand it. Yeah, it's just a long, lightly tapered bass port designed to lower the tuning frequency of the entire unit as the frequency of the resonator itself is rather high. Perhaps tapered to reduce port noise? Which doesn't seem possible as docile as the driver action is... maybe to act as a hybrid between a port and a horn, acting mainly as a port but with slight horn-y attributes. Actually, wait a minute. Holliman claims the design to be effective over a wide range of frequencies (though 8-25 Hz doesn't sound wide, it's in fact over 3 octaves), and actually becoming more efficient as the frequency decreases (similar to a rotary?), and I know the unique port (not horn) has everything to do with this ability.

I made that diagram BTW, because the first one was so rough. Now it will be easier for people in the future trying to find it. Share the power that is knowledge.
File:Graham Holliman Velocity-Coupled Infra Bass speaker design.jpg - Wikipedia, the free encyclopedia

Last edited by Upstate NY low life; 9th July 2011 at 02:43 AM.
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Old 9th July 2011, 03:08 AM   #245
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Quote:
Originally Posted by Upstate NY low life View Post
Holliman claims the design to be effective over a wide range of frequencies (though 8-25 Hz doesn't sound wide, it's in fact over 3 octaves).........
You're apparently thinking harmonic structure. Octave spreads are a 2:1 ratio [exponential], so this is only ~10*log10[25/8]/3.01 = ~1.644 octaves. A 3 octave spread would be 8-16-32-64 Hz [rounded off].

GM
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Old 9th July 2011, 03:20 AM   #246
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YWhoops, I'm sorry, you're right. I knew that it just slipped my mind. However, it still is as much as a two+ octave range as I believe it was actually stated to start at 6 Hz. I've noticed that on this and other "infrasonic patents" different frequencies are given throughout. And, in fact, the response can go well above 25 Hz, it's just not recommended because it is not suitable for it and a traditional subwoofer should start at 25 Hz. I have an idea it would sound terrible at audible bass frequencies, anyway. I'm excited about building this. I'd like it to be the largest one suggested, to go for good response down to 5 Hz. Then I could brag that I've got flat response all the way from 5 to 25 (Hz to kHz)
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Old 9th July 2011, 03:35 AM   #247
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For sure, an interesting variant of a double bass reflex [DBR]. Looking forward to a review, though seems like bass shakers would be a better choice overall.

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Old 9th July 2011, 04:13 AM   #248
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I don't think so.

And the build should be pretty easy. But I do not have specific instructions for the 18 inch, original one. I should use MDF, even marine grade plywood has plywood characteristics I don't like. And one layer of 3/4 should actually be fine, for this thing is so docile in a way that it shouldn't matter. I find that mid bass frequencies are actually the hardest as far as enclosure resonance, while sub bass frequencies are harshest for enclosure flex, which is essentially just slower resonance. I guess it's sort of a phenomenon that ultra low frequencies stop having this problem. I'm sure it's only because they rely on low power and high efficiency, because no driver is meant to put them out at high power.

The South African also has some chicken scratch diagrams showing some are shapes I don't quite understand. He also has "standing wave control inserts" that must be intended for the resonating chamber which I don't understand. But mainly, take a look at this image:

Nevermind LOL. It's just the feet. Their the most intricate part there is, they're supposed to have a nice curve to them. Screw that.

Everything else being said, and finally feeling like I've got a full grip on this and am over the surprises (like the feet, fearing that diagram was an inside-y part was meant to have a perfect curve that unless done right would muck it all right up :/), what do you guys make of the varying sizes and their relationship between one another for the different driver/box sizes? I maintain that they simply cannot all perform similarly in the same ULF range, and I would like to go full tilt and extrapolate what the 18 inch size should be (and use double thickness-1.5", I won't stop till it kills me ) but I am not sure I should venture out when the design seems to necessitate some amount of precision. The South African, as well as a story by another guy who had auditioned one that by description sounded like it was a 10 or a 12, both testified to the nauseating effects of the apparatus, but I don't want to take any chance that I build it and it's a flop. Being aware of phasing issues and having several unique spaces to try it in (though none are well sealed, I should be able get some desired result even if I extrapolate for an 18. As far as the woofer, I already have the aforementioned Peavy 18 in mind, which if proves to be insufficient, is only a few hundred bucks so it's not a huge deal, and will be more than useful for other things. Not probably considering the exotic Focal 18. Any driver recomendations by you guys would be appreciated. If you know of a superb 15 I'd be steered to go with that design.

Last edited by Upstate NY low life; 9th July 2011 at 04:27 AM.
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Old 9th July 2011, 05:40 AM   #249
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I am undergoing final calculations, am thouroughly past misunderstandings and surprises, have figured the rough total box volume of the 15 to be about nine cubic feet, which isn't as big as I thought. When I heard the one guys story read "large box about 5 feet long and maybe 2 1/2 feet wide" I thought it was huge.

Pretty simple with just this table and this diagram:
All sizes | Graham Holliman instructions | Flickr - Photo Sharing!
^^
See how much better that is than the prehistoric image hosters you were using before that are now all gone?

Geez, it looks too easy!

Only, where and what is measurement "M," which is supposed to be 6.5 inches on the 15 and 4 on the 10, is that the total distance between the inside of C and the outside of A? That should not be necessary to specify as the thickness of the other pieces defines that...but that's what I'm guessing because the only place I think I see it is written sideways and being intesected by a line in the small cross section diagram...

Another thing is it doesn't say at what points along piece C to put standing wave inserts K, although it looks like there is a 22 scribled in there, this can't be possible; however, I do belive the South African said their placement is not critical, only that they are there. Although it seems like for spl a standing wave would be desired because it would give it a peak, which at 5-20 Hz could be interesting...

Also note how B is shown thinner than A in the diagram meaning that really, since they're doubled up, there is no need for B to be that thick. Actually the part of B that is directly under the driver is the part where Holliman specified absolutely no flex is acceptable and should be made of mica or some odd metal/rock or something. I wonder how much of an effect thickenss would have, the two mouths are not acting as ports to any critical degree, however the larger one into the resonating tub is cut at 45 degrees as if precision matters. If I were to double up walls it would be the outside walls I guess, I could double up F and C and slowly taper them toward the mouth and compensate by adding 1.5 inches to the outer dimensions (I'll already have to adjust this for using 3/4 MDF vs 1 inch marine plywood, who knows how this will affect it, and.... then agian I truly don't believe doubling should be necessary becuase of it's efficiency which is the whole point to it. Oh, which leads to another question, should I just use (the very expensive) 1 inch marine plywood? Per equal thickness, which is stiffer/better/less resonant, HQ plywood or average MDF? What about High Density Fiberboard? And acutally it's hard to find anything in one inch. One time I asked for one inch MDF and they looked at me like I was crazy. They actually looked it up and found out they could order it but it was phenominally expensive. God to answer all my questions I'll have to build about 10 of 'em!

Holliman (actually when I say Holliman I'm not sure what is original and what is the South African saying it) stressed the importance of the slow curve of the long port, which makes me think the diagram shows the battens being much too sharp in comparison to the final taper which is much less, which could make it like a horn. Perhaps this is not to scale.
^^
That is largely me talking to my self as a reference, my main questions for you guys are:
a). A good driver and b). what material to use

With the super high efficiency, if I were to go with an extrapolated 18 inch version, I could probably use my garbage Pyle 18, as this was intended to be operated in only the two digits of watts range. I honestly think the driver itself should amount to jack nothing in the performance of this instrument.

Also, I do conclude that this is all legitimate and that the South African't 22 page PDF is not hearsay and this not a Jonny one note boombox and those grainy diagrams are clearly scans of the original and the whole introduction sounds English, as well as the instructions for the decorative feet

Last edited by Upstate NY low life; 9th July 2011 at 06:09 AM.
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Old 9th July 2011, 05:08 PM   #250
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Don't you guys think it would be better if the inside part (tub shaped resonator) would be better off rectangular and let the outside walls angle out, resulting in the entire unit having a trapezoid shape instead of the inside part? Also, and I should have known this, the South African figured the standing wave control insterts to be spaced equidistantly, 1/4 from the ends and 1/2 from each other. But what's confusing is that you can see what looks like 22, 64, then 28 written between the inserts.
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