Mr. Bill, reporting back for duty! 
I'm in publishing, and my workload follows a monthly cycle, ergo I disappear from life for a couple weeks around the turn of every month, and I occasionally return having forgotten my own name.
Now what were we talking about--some kind of nonlethal crowd control, or sumthin?...
I'm in publishing, and my workload follows a monthly cycle, ergo I disappear from life for a couple weeks around the turn of every month, and I occasionally return having forgotten my own name.
Now what were we talking about--some kind of nonlethal crowd control, or sumthin?...
The silence of the crickets is deafening
I hereby resurect this thread to declare that I have come to a BIG decision>>>>>>>
We need something to show for all this yammering. So I propose a simple start. I will knock some holes into six pieces of steel plate 1" thick and we will start from there. The return paths can be bolted or welded as needed. Magnets will be coming soon. I've found some huge 2' by 2"y 0.25" neo chunks for $18 each??? Any ideas? How many or how much can be a point of discusion when there is something to put them on. The voice coil wire is a problem that I'm still working on. I can get it but it's allways to much of the stuff. I don't need a roll of miles just around 500 ' would work fine.
I've found the heavy walled pipe that I talked about away back when and It will be in my possesion by the end of the month of march. Funding is goin towards a new van at the moment.
Mark
I hereby resurect this thread to declare that I have come to a BIG decision>>>>>>>
We need something to show for all this yammering. So I propose a simple start. I will knock some holes into six pieces of steel plate 1" thick and we will start from there. The return paths can be bolted or welded as needed. Magnets will be coming soon. I've found some huge 2' by 2"y 0.25" neo chunks for $18 each??? Any ideas? How many or how much can be a point of discusion when there is something to put them on. The voice coil wire is a problem that I'm still working on. I can get it but it's allways to much of the stuff. I don't need a roll of miles just around 500 ' would work fine.
I've found the heavy walled pipe that I talked about away back when and It will be in my possesion by the end of the month of march. Funding is goin towards a new van at the moment.
Mark
I move that we ask Planet10 nicely for a dedicated forum for DIY driver discussion, as it seems to come up qith some frequency, and I have some questions about it that I'd like to ask, that are not related to this thread at all.
FEA analysis
I do a lot of structural analysis for a living and would be up for doing some finite element analysis (FEA ) in my spare time after work for this project if we could all agree on some basic requirements or goals. I have to admit that I haven't read this thread through completely, so I apologize if things have been nicely summarized somewhere.
Anyway, this is what I'd need to know...
1) I need to know the maximum cone/panel acceleration to apply as a body load. So, how much output are you looking for at each frequency? Or perhaps figure out what the max cone excursion as a function of frequency. There's lots of ways to skin a cat, but eventually I'll need the max panel acceleration at the end of the day. (i.e. obviously a cone moving +/- 3" at 10 Hz is much less stressful on a cone than +/- 3" at 100 Hz)
2) Ballpark panel area desired
3) Frequency range of the... um, er beast (i.e. 10 - 60 Hz)
4) Maximum acceptable mass
5) I'm not sure if the air pressure loading is significant or not. I suspect that it's more the inertia of the cone/panel than anything. If it is significant I'd need to know what sort of air pressure this beast will see.
I think I could get started with that. I could do a few quick trade studies first. i.e. -- cone vs. flat sandwich panel. I suspect we could run into more of a bigger picture trade study, such as a smaller/lighter panel w/ larger xmax, vs. a larger/heavier panel w/ lower xmax. Perhaps if the motor gets sorted out then that helps to narrow things down.
So does anyone want to take a shot at some goals/requirements?
- Robert
I do a lot of structural analysis for a living and would be up for doing some finite element analysis (FEA ) in my spare time after work for this project if we could all agree on some basic requirements or goals. I have to admit that I haven't read this thread through completely, so I apologize if things have been nicely summarized somewhere.
Anyway, this is what I'd need to know...
1) I need to know the maximum cone/panel acceleration to apply as a body load. So, how much output are you looking for at each frequency? Or perhaps figure out what the max cone excursion as a function of frequency. There's lots of ways to skin a cat, but eventually I'll need the max panel acceleration at the end of the day. (i.e. obviously a cone moving +/- 3" at 10 Hz is much less stressful on a cone than +/- 3" at 100 Hz)
2) Ballpark panel area desired
3) Frequency range of the... um, er beast (i.e. 10 - 60 Hz)
4) Maximum acceptable mass
5) I'm not sure if the air pressure loading is significant or not. I suspect that it's more the inertia of the cone/panel than anything. If it is significant I'd need to know what sort of air pressure this beast will see.
I think I could get started with that. I could do a few quick trade studies first. i.e. -- cone vs. flat sandwich panel. I suspect we could run into more of a bigger picture trade study, such as a smaller/lighter panel w/ larger xmax, vs. a larger/heavier panel w/ lower xmax. Perhaps if the motor gets sorted out then that helps to narrow things down.
So does anyone want to take a shot at some goals/requirements?
- Robert
The goal, IIRC, is 120 dB maximum SPL down to 10hz. I don't know how to calculate excursion or acceleration given those parameters.
The diaphragm we had in mind varied from 24" to 48" depending on who you ask, and application varies from just sitting on the floor, to infinite baffle. (IB is my personal favorite, oh yeah. No dipole rolloff for me, no sir!
)
Fs was expected to be around 6 hz, again IIRC.
The diaphragm we had in mind varied from 24" to 48" depending on who you ask, and application varies from just sitting on the floor, to infinite baffle. (IB is my personal favorite, oh yeah. No dipole rolloff for me, no sir!
)Fs was expected to be around 6 hz, again IIRC.
A shot across the bow
Mr. Batdorf9
The size is 36" by 36"
Frequency range in question is approx on low end of 16 hz to around 80 hz on the upper end which will be limited by the inductance of the voice coil which will be substantial.
Air pressure load is real think of this in terms of an operating driver. At rest to full excursion in 1/80th of a second. Full excursion meaning 160mm. The load is monmentary but significant. There will have to be some deflection but how much??
The chosen method of construction so far is a foam carbon fiber sandwhich. The carbon fiber will be approximately 0.40" on each side. The foam core will be 1/4" or 6mm. If a curve in the panel will help I'm game.
l l
l l
l=====l
l l
l l
Quciky drawing of the monster as a dipole which is the preffered method of construction. The vertical plates are the diaphrams. The bunch of equals signs are the voice coil former that will be the means of power transmission. The motor itself so far is a six gap dual voice coil behemoth.
The rst of the thread is quite tidy and not full of to much fluff. Give it a read.
Mark
Mr. Batdorf9
The size is 36" by 36"
Frequency range in question is approx on low end of 16 hz to around 80 hz on the upper end which will be limited by the inductance of the voice coil which will be substantial.
Air pressure load is real think of this in terms of an operating driver. At rest to full excursion in 1/80th of a second. Full excursion meaning 160mm. The load is monmentary but significant. There will have to be some deflection but how much??
The chosen method of construction so far is a foam carbon fiber sandwhich. The carbon fiber will be approximately 0.40" on each side. The foam core will be 1/4" or 6mm. If a curve in the panel will help I'm game.
l l
l l
l=====l
l l
l l
Quciky drawing of the monster as a dipole which is the preffered method of construction. The vertical plates are the diaphrams. The bunch of equals signs are the voice coil former that will be the means of power transmission. The motor itself so far is a six gap dual voice coil behemoth.
The rst of the thread is quite tidy and not full of to much fluff. Give it a read.
Mark
Hi mwmkravchenko:
I'm basically stalking a bunch of audio forums soaking up as much knowledge as I can. I'm also working through The Loudspeaker Design Cookbook and Testing Loudspeakers. My current obsession is driver design – especially unusual designs. This thread seemed to be heading toward a rather impressive final product.
Did you punch holes in a steel plate? I’d love to see some pictures of the prototype(s) taking on form.
BTW, Thanks to Dan Wiggins for his openness and wisdom. I met him briefly at the 2004 CES – heck of a nice man.
-Casey Walsh
I'm basically stalking a bunch of audio forums soaking up as much knowledge as I can. I'm also working through The Loudspeaker Design Cookbook and Testing Loudspeakers. My current obsession is driver design – especially unusual designs. This thread seemed to be heading toward a rather impressive final product.
Did you punch holes in a steel plate? I’d love to see some pictures of the prototype(s) taking on form.
BTW, Thanks to Dan Wiggins for his openness and wisdom. I met him briefly at the 2004 CES – heck of a nice man.
-Casey Walsh
Hold the phone No message to the pope Holes are not miraculous!!
My shop is in a state of extreme dismay. My folks have sold their house and mine has become the warehouse for all the senior Kravchenko's stuff. The good news is that they have purchased land and are building anew. The bad news is that a garage to store the stuff will only exist by the end of may or early june. So no holes to be punched yet. But I'm working on slaging my machinists buddy shop for a weekend. I just have to work for him for a while to pay for the free machine time that I'm getting. Mutual back scratching. I'll keep posting as soon as I have some pics.
MArk
My shop is in a state of extreme dismay. My folks have sold their house and mine has become the warehouse for all the senior Kravchenko's stuff. The good news is that they have purchased land and are building anew. The bad news is that a garage to store the stuff will only exist by the end of may or early june. So no holes to be punched yet. But I'm working on slaging my machinists buddy shop for a weekend. I just have to work for him for a while to pay for the free machine time that I'm getting. Mutual back scratching. I'll keep posting as soon as I have some pics.
MArk
Re: A shot across the bow
Hi Mark:
I completely understand the concept of extreme shop dismay! I'd post a picture of my shop, but I don't want to scare the bjeepers out of everyone.
I just tore apart one of the flat-diaphragm woofers I had in my big-ol’-pile-of-dead-woofers. This on is from Precision Power, but I’ve also got a couple Audiobahn ones with aluminum composite honeycomb panels for diaphragms. Here are some pics of the innards of the Precision Power unit:
http://photonlogic.com/IMG_2188.JPG
http://photonlogic.com/IMG_2191.JPG
http://photonlogic.com/IMG_2192.JPG
http://photonlogic.com/IMG_2193.JPG
They did use a flat composite panel, but the ratio of the voice coil former to the surface area of the panel is rather large compared to what has been presented in this thread. Also, the ratio of the panel thickness to the panel surface area is much larger than what has been proposed for the DIY Parthenon. It seems that we should either scale-up our ratios, use a frustro-conical or other strength-enhancing structure, or add tethering similar to the sketch below. Note that this could make a very effective jousting machine
.
Disclaimer: I am NOT a mechanical engineer
.
-Casey Walsh
Hi Mark:
I completely understand the concept of extreme shop dismay! I'd post a picture of my shop, but I don't want to scare the bjeepers out of everyone.
mwmkravchenko said:
I just tore apart one of the flat-diaphragm woofers I had in my big-ol’-pile-of-dead-woofers. This on is from Precision Power, but I’ve also got a couple Audiobahn ones with aluminum composite honeycomb panels for diaphragms. Here are some pics of the innards of the Precision Power unit:
http://photonlogic.com/IMG_2188.JPG
http://photonlogic.com/IMG_2191.JPG
http://photonlogic.com/IMG_2192.JPG
http://photonlogic.com/IMG_2193.JPG
They did use a flat composite panel, but the ratio of the voice coil former to the surface area of the panel is rather large compared to what has been presented in this thread. Also, the ratio of the panel thickness to the panel surface area is much larger than what has been proposed for the DIY Parthenon. It seems that we should either scale-up our ratios, use a frustro-conical or other strength-enhancing structure, or add tethering similar to the sketch below. Note that this could make a very effective jousting machine
.An externally hosted image should be here but it was not working when we last tested it.
Disclaimer: I am NOT a mechanical engineer
.-Casey Walsh
Here you have true linear cone travel. This driver has no "rest" point, thus the elimination og harmonic distortion at low frequencies. The explanation is in Norwegian, but I'll try to explain:
Both the rubber/silicone surroud and spider is made of a cone-shaped broad flat silicone. This cones inner diameter is fasten to the membrane/voice coil. and the outer diameter is fasten to the basket.
This will result in:
0 Hz free air resonance frequency
0 Qms
0 Qts
At full excursion:
Br.
Vidar
Both the rubber/silicone surroud and spider is made of a cone-shaped broad flat silicone. This cones inner diameter is fasten to the membrane/voice coil. and the outer diameter is fasten to the basket.
This will result in:
0 Hz free air resonance frequency
0 Qms
0 Qts
An externally hosted image should be here but it was not working when we last tested it.
At full excursion:
An externally hosted image should be here but it was not working when we last tested it.
Br.
Vidar
Antiresonat, that is a very nice idea, but it would require an infinite amount of compliance from the suspension system. This is impossible in reality.
A nice goal would be to get as high compliance on the axis of movement as possible, but this is probably antithetical to the suspension functioning as it should, to prevent voice coil rubbing.
A nice goal would be to get as high compliance on the axis of movement as possible, but this is probably antithetical to the suspension functioning as it should, to prevent voice coil rubbing.
Fun stuff! 
I'm not able to justify building a real Parthenon knockoff right now, but I have plans to build a couple square-diaphragm dipoles around a couple Aura 1808 motors I have lying around. Just looking for voice coils this week...
I'm not able to justify building a real Parthenon knockoff right now, but I have plans to build a couple square-diaphragm dipoles around a couple Aura 1808 motors I have lying around. Just looking for voice coils this week...
Hi Folks!
I’m quite excited to see that this thread might be resurrected. I am also building a large subwoofer with square diaphragms, only mine is a bipole with two opposing 18” x 18” square (w/rounded corners), ½” thick aluminum honeycomb core laminated panels. I already have all the raw materials (including custom-made NIB magnets) and have most of the machining done for the 1018-steel motor assemblies. It has eight motors – four for each diaphragm. I’ll try and get some pictures posted of this work-in-progress soon.
Hey, Bill F.: Can you post some pics of those 1808 motors and perhaps sketches of what you have in mind? Also, I was thinking it might be good to prod each other along by starting a new threat entitled something like “
Battle of the Planars ”. Whaddya think?
-Casey Walsh
I’m quite excited to see that this thread might be resurrected. I am also building a large subwoofer with square diaphragms, only mine is a bipole with two opposing 18” x 18” square (w/rounded corners), ½” thick aluminum honeycomb core laminated panels. I already have all the raw materials (including custom-made NIB magnets) and have most of the machining done for the 1018-steel motor assemblies. It has eight motors – four for each diaphragm. I’ll try and get some pictures posted of this work-in-progress soon.
Hey, Bill F.: Can you post some pics of those 1808 motors and perhaps sketches of what you have in mind? Also, I was thinking it might be good to prod each other along by starting a new threat entitled something like “
Battle of the Planars ”. Whaddya think?-Casey Walsh
Hey Casey,
Props to you for taking the plunge into driver DIYing! Sounds like an interesting idea. Love to see some pics. I'll share a little about mine, too, but since it'll use a unique suspension I've had on the drawing board a couple years, I won't be able to show the susp. parts--might want to apply for a patent first.
I've actually got 4 Aura motors at hand, so I've been giving the giant-diaphragm multiple-motor concept some thought, too. My most hairbrained scheme so far involves 3 or four motors driving the perimeter of a vacuum-tensioned diaphragm maybe 4 feet in dia.--a giant free-air driver to mount in a wall. Surround/suspension would be one or more spliced inflated innertubes.
BTW, can you point me to a good source for aluminum honeycomb? I'd like to play with some of that, too.
Props to you for taking the plunge into driver DIYing! Sounds like an interesting idea. Love to see some pics. I'll share a little about mine, too, but since it'll use a unique suspension I've had on the drawing board a couple years, I won't be able to show the susp. parts--might want to apply for a patent first.
I've actually got 4 Aura motors at hand, so I've been giving the giant-diaphragm multiple-motor concept some thought, too. My most hairbrained scheme so far involves 3 or four motors driving the perimeter of a vacuum-tensioned diaphragm maybe 4 feet in dia.--a giant free-air driver to mount in a wall. Surround/suspension would be one or more spliced inflated innertubes.
BTW, can you point me to a good source for aluminum honeycomb? I'd like to play with some of that, too.
Hi Bill:
Patent? Did you say patent? Cool! But I’ve got to warn you that this puppy I’m building is in fact a prototype for a patent that I have pending which includes an “highly-compliant half-roll surround supported by air (gas) pressure differential.” I checked uspto.gov this morning and it hasn’t been published yet, but I’ll let you know when it has. One of the detailed embodiments (and claims) includes a vacuum-tensioned membrane (no surround needed) for the diaphragm. BTW, do you too have a big-ol’ bald spot on the top of your head from thinking too much? Mine seems to be growing quickly!
What I found with inner-tubes is that they have widely-varying thickness within any given tube. Plus, for long surrounds (large diaphragms), they do add considerable mass. I ultimately went with rip-stop nylon for strength plus a layer of thin nitrile on the higher-pressur side for air-tightness. It’s a very low-loss and highly compliant combination. Just remember to wrap the nitrile around the rip-stop on the edges for sealing.
I obtained the honeycomb core material for the prototype from McMaster-Carr (http://www.mcmaster.com/). For earlier prototypes I got some sample material directly from Bellcomb (http://www.bellcomb.com/).
-Casey Walsh
Patent? Did you say patent? Cool! But I’ve got to warn you that this puppy I’m building is in fact a prototype for a patent that I have pending which includes an “highly-compliant half-roll surround supported by air (gas) pressure differential.” I checked uspto.gov this morning and it hasn’t been published yet, but I’ll let you know when it has. One of the detailed embodiments (and claims) includes a vacuum-tensioned membrane (no surround needed) for the diaphragm. BTW, do you too have a big-ol’ bald spot on the top of your head from thinking too much? Mine seems to be growing quickly!
What I found with inner-tubes is that they have widely-varying thickness within any given tube. Plus, for long surrounds (large diaphragms), they do add considerable mass. I ultimately went with rip-stop nylon for strength plus a layer of thin nitrile on the higher-pressur side for air-tightness. It’s a very low-loss and highly compliant combination. Just remember to wrap the nitrile around the rip-stop on the edges for sealing.
I obtained the honeycomb core material for the prototype from McMaster-Carr (http://www.mcmaster.com/). For earlier prototypes I got some sample material directly from Bellcomb (http://www.bellcomb.com/).
-Casey Walsh
So you're patenting my inflated tube surround idea from post #1? Are you gonna cut me into the profits? 😉 Just kidding. Good luck to you. I am even more impressed that you're not only DIYing drivers, you're investing in them too.
I'd like to see your take on the idea--what's your patent app. number so I can watch for it?
Back when I was thinking about it, I decided a pressure or vacuum-stabilized surround was generally too complicated/expensive to implement commercially. Perhaps you've made a breakthrough on that point?
rubberized nylon sounds good to me...
Don't worry--the previously-mentioned suspension I'd like to patent doesn't involve pressure stabilization of any kind.
LOL! You nailed me--I'm sittin' here feeling a constant draft from above! They say great minds think alike...maybe they dress alike, too...
Thanks for the honeycomb link. The 2" phenolic/paper looks about right for a big flat diaphragm.
The patent application number is 10/342,743 filed on 1/14/2003. I doubt that the initially published document will have all of the revisions and embellishments that are in the works, but the basic ideas are there. No real breakthroughs on maintaining the vacuum other than minimizing the surface area of any articulated membranes, use of low-permeability rubber, and including a small, automatic OEM vacuum pump for long-term corrections needed due to the slow-but-guaranteed ingress of air (it’s a powered subwoofer design).
Assuming this patent pans-out, the idealist in me wants to follow in the footsteps of Dan Wiggins and Nelson Pass by encouraging non-commercial use of this (or my other forthcoming) patents.
BTW, I acquired several 2’ x 4’ sheets of 1”-thick cardboard honeycomb-core material free from an office furniture broker. They use it to protect the more expensive furniture during transit, then it gets recycled along with the other cardboard. Fun stuff to experiment with.
Now back to the Parthenon…
These NIB magnets are great! I had a bunch custom made (in China – long lead time) for my prototypes. I used FEMM to maximize the B content normal to the voice coil motion and to keep the out-of-gap fields symmetrical. (Yes, if this puppy works, I WILL buy a license for FEMM!) I’m sure there are people much more proficient with FEMM than I, but I’d be willing to model any axisymmetric ideas we come up with.
Let’s get this party started…
Assuming this patent pans-out, the idealist in me wants to follow in the footsteps of Dan Wiggins and Nelson Pass by encouraging non-commercial use of this (or my other forthcoming) patents.
BTW, I acquired several 2’ x 4’ sheets of 1”-thick cardboard honeycomb-core material free from an office furniture broker. They use it to protect the more expensive furniture during transit, then it gets recycled along with the other cardboard. Fun stuff to experiment with.
Now back to the Parthenon…
These NIB magnets are great! I had a bunch custom made (in China – long lead time) for my prototypes. I used FEMM to maximize the B content normal to the voice coil motion and to keep the out-of-gap fields symmetrical. (Yes, if this puppy works, I WILL buy a license for FEMM!) I’m sure there are people much more proficient with FEMM than I, but I’d be willing to model any axisymmetric ideas we come up with.
Let’s get this party started…
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