Can hear turbulence from the motor and fans? how does it compare with FR, and how does it's sonics rival an ordinary driver at say 50Hz?
Atlas ?
Yes i also feel sure it was an RA driver, and looking once again at the Wilmslow Audio design brochure i have for it, i noticed that Ryan Reynolds from South Africa who uploaded the PDF of the WADB, missed out a photo. This shows what looks like to me having bought & used RA drivers in the past, an RA driver being used by GH.
I can't see any mention of an actual in depth parts list in the WADB though, apart from the wood sizes etc ! I guess you had to contact them directly for more details/prices etc ?
Yes i also feel sure it was an RA driver, and looking once again at the Wilmslow Audio design brochure i have for it, i noticed that Ryan Reynolds from South Africa who uploaded the PDF of the WADB, missed out a photo. This shows what looks like to me having bought & used RA drivers in the past, an RA driver being used by GH.
I can't see any mention of an actual in depth parts list in the WADB though, apart from the wood sizes etc ! I guess you had to contact them directly for more details/prices etc ?
Okay, so you have the actual brochure? Can you scan it? Is there anything else it has that the PDF doesn't? And the pictures on the PDF are grainy, if by any chance you could do a better job it would be most helpful.
Another thing that worries me is that on the AVforums thread (besides the fact that the link to the zip called "PLANS" is gone) the guy says he remembers it as being about 5 feet long and about 2.5 feet wide, where as with the instructions I have from the PDF even the 18 inch size (just the 15 inch size divided by two times three) the width would only be about 2 feet. This tells me for sure that the original was large, there is no reason I couldn't make it as large as I wanted to as long as I kept the resonator and ports/horns in proportion so that the tuning was the same. I have gotten it all figured out for the relative 18 inch size, plus with double 3/4 inch layers instead of one inch, which is hard to find in anything around here. I plan on starting with MDF, because it's easier to work with (rounding, sanding, chamfering, etc), cheap, and will be smooth for the inside, which I think is important, but since MDF flexes so much a layer of 3/4 any plywood on the outside will do, then with some kind of finish. I'm not a big fan of box stuffing and carpet lining, but when do you guys find that to be an advantage over a smooth interior? Such as maybe for the resonator "tub." Obviously the ports/horns can not be lined and it's crucial that they are as smooth as possible. Maybe they should even have a finish on them. The instructions stress the importance of detail in the rounded corners and the curved fillet.
Considering the detail and intracacy and expense required for all the gear, the fact that it was scaled down to a "wimpy" 10 inch size and people would have been quite cross if all they got was a slight wind sound, I can't see any reason why, done right, this won't be more than satisfactory in a proper size.
Another thing that worries me is that on the AVforums thread (besides the fact that the link to the zip called "PLANS" is gone) the guy says he remembers it as being about 5 feet long and about 2.5 feet wide, where as with the instructions I have from the PDF even the 18 inch size (just the 15 inch size divided by two times three) the width would only be about 2 feet. This tells me for sure that the original was large, there is no reason I couldn't make it as large as I wanted to as long as I kept the resonator and ports/horns in proportion so that the tuning was the same. I have gotten it all figured out for the relative 18 inch size, plus with double 3/4 inch layers instead of one inch, which is hard to find in anything around here. I plan on starting with MDF, because it's easier to work with (rounding, sanding, chamfering, etc), cheap, and will be smooth for the inside, which I think is important, but since MDF flexes so much a layer of 3/4 any plywood on the outside will do, then with some kind of finish. I'm not a big fan of box stuffing and carpet lining, but when do you guys find that to be an advantage over a smooth interior? Such as maybe for the resonator "tub." Obviously the ports/horns can not be lined and it's crucial that they are as smooth as possible. Maybe they should even have a finish on them. The instructions stress the importance of detail in the rounded corners and the curved fillet.
Considering the detail and intracacy and expense required for all the gear, the fact that it was scaled down to a "wimpy" 10 inch size and people would have been quite cross if all they got was a slight wind sound, I can't see any reason why, done right, this won't be more than satisfactory in a proper size.
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You talking to me ?
@ Upstate NY low life
I guess you are
I don't have a scanner here, but i've uploaded the PDF Ryan Reynolds scan for you & anyone else who might be interested.
The Graham-Holliman Velocity-Coupled Infra-Bass Speaker.pdf
Please note the extra missing info i posted the other day.
@ Upstate NY low life
I guess you are
I don't have a scanner here, but i've uploaded the PDF Ryan Reynolds scan for you & anyone else who might be interested.
The Graham-Holliman Velocity-Coupled Infra-Bass Speaker.pdf
Please note the extra missing info i posted the other day.
My comment is not intended to put you off your project. I do think that if your current system had flat response to even 40 Hz you would be less likely to be looking down this path. If your current speakers had the same output level at 40 Hz as they do at 500Hz I think you would be very pleased. Either way if you want to achieve infrasonic response I should think that you would want to fill the holes else where in your speakers output.
Give the long number of years that this design has been about yet has not gained acceptance it does beg the question that perhaps it is not all that good a design.
With Horn Response you can design a tapped horn or other design which will perform as designed. This seems a lot of work for results which may not be there. While I am sure the GH design can grunt it does look to be a very limited band design.
Please carry on and try it out and document your work as one way or the other it will be of value to those who have expressed interest. best regards Moray James.
Give the long number of years that this design has been about yet has not gained acceptance it does beg the question that perhaps it is not all that good a design.
With Horn Response you can design a tapped horn or other design which will perform as designed. This seems a lot of work for results which may not be there. While I am sure the GH design can grunt it does look to be a very limited band design.
Please carry on and try it out and document your work as one way or the other it will be of value to those who have expressed interest. best regards Moray James.
I wonder if it can be tweaked to extend the bandwidth?
e.g. damping material in the chamber may lower the resonance Q and subsequently widen the bandwidth.
Also, maybe the design can be tweaked to add another chamber with a different resonance point.
All in all, an interesting design that I think I may try out, once I understand the parameters a bit better (why the need for the "shroud", for example, or can this be replaced with a simple 4th order BP system with a large vented cavity tuned to a very low frequency to achieve similar results).
brian,
The problem i see using common tuning for this design is the driver is being used as a air pump, you could use compressed air to drive this thing and it would work. It has more in common with a pipe-organ flute than a modern subwoofer. I have a funny feeling that amplitude of the signal will have more effect on tuning than frequency. Like overblowing a flute. ref: Flute
The problem i see using common tuning for this design is the driver is being used as a air pump, you could use compressed air to drive this thing and it would work. It has more in common with a pipe-organ flute than a modern subwoofer. I have a funny feeling that amplitude of the signal will have more effect on tuning than frequency. Like overblowing a flute. ref: Flute
With the back of the speaker is left open, it would of course need to be wired in reverse polarity to not cancel the main speaker’s bass response.
Lower frequencies require longer excursion, so more (velocity -coupled) air is blown in to the whistle at lower frequencies, adding an AM (amplitude modulated ) resonant low frequency addition to the direct output of the “sub”.
Kind of like adding a single pipe organ tone at various levels to the music being played.
Depending on the music being played, it may even be in the right key.
When the whistle is overblown, the pitch would change a bit too, adding to the fun.
You would be able to get different accompaniment just by changing the volume level.
I was wrong in calling it a Johnny one note cabinet, it may add a few different, musically unrelated low notes to the recorded music
.
i'm uploading a vid to photobucket now, one moment. 30-60hz sweep
http://s963.photobucket.com/albums/ae111/revboden/?action=view¤t=DSCF3772.mp4
http://s963.photobucket.com/albums/ae111/revboden/?action=view¤t=DSCF3772.mp4
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Coupling etc critical !
One of the seemingly important things that the GH device relied on to work correctly, from what i gathered anyway, was close coupling of the driver plate hole to the port hole entrance of the tuned box.
Also the driver plate was designed to be Very thin.
Any deviations from his original design will naturally produce different results. These may be better or worse !
Thinking about it further now, it "appears" to me that the Flute etc comparison "might" be justified in some ways. And the tuned box along with the side ports help to amplify the effect.
What's especially interesting to me, is the GH claimed inverse of rolloff down to Very low frequencies, as apposed to other methods which lose gain.
One of the seemingly important things that the GH device relied on to work correctly, from what i gathered anyway, was close coupling of the driver plate hole to the port hole entrance of the tuned box.
Also the driver plate was designed to be Very thin.
Any deviations from his original design will naturally produce different results. These may be better or worse !
Thinking about it further now, it "appears" to me that the Flute etc comparison "might" be justified in some ways. And the tuned box along with the side ports help to amplify the effect.
What's especially interesting to me, is the GH claimed inverse of rolloff down to Very low frequencies, as apposed to other methods which lose gain.
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more vid's added this time with a thinner plate (1/4in) and an actual jug
DSCF3777.mp4 video by revboden - Photobucket
DSCF3777.mp4 video by revboden - Photobucket