Hello all,
First time posting after a long time lurking. I am a trained artist who is not so engineering inclined. I'm making a spherical enclosure for my 8" Audio Nirvana out of porcelain. I would like to use constrained layer dampening, which will consist of an outer layer of clay, a layer of green glue and a third layer I'm not set on. My original inclination was to use lead (1/8") as it is easy to cast to the required shape; however, it would be very heavy. I'm also considering using an acrylic resin as I can obtain it at a significant discount.
I have two questions:
What is the best material for my third layer?
Is constrained layer dampening the best solution?
Thank you in advance.
First time posting after a long time lurking. I am a trained artist who is not so engineering inclined. I'm making a spherical enclosure for my 8" Audio Nirvana out of porcelain. I would like to use constrained layer dampening, which will consist of an outer layer of clay, a layer of green glue and a third layer I'm not set on. My original inclination was to use lead (1/8") as it is easy to cast to the required shape; however, it would be very heavy. I'm also considering using an acrylic resin as I can obtain it at a significant discount.
I have two questions:
What is the best material for my third layer?
Is constrained layer dampening the best solution?
Thank you in advance.
As a 'trained artist' I assume throwing a pot is within your grasp, yes?
Okay, the reason why is that I have been playing with different spherical shapes for mid and FR drivers for some years and there's no real clear answer because the results depend on the amount of damping material that's fitted inside the chamber that varies with the type of driver, etc, etc - a lot of variables here.
I have done quite a bit of work constrained layers inside my prototype ceramic spheres with lead, rubber, cane basket weave, suspended shell, cones, etc and most of them just don't achieve much of anything - the lead killed the sound, surprisingly enough - never did figure out why.
Most recent version is a extended teardrop shape with the long 'tail' filled with damping material that increases in density towards to internal point - called a tapered resistance
This just leaves 2 things to tackle, the internal standing wave (1 main one as same radius all around) and the vibration of the chamber wall.
The second is pretty simple with additional internal ribs to 'brace up' the walls - best done by hand so not uniform around perimeter (it also means this sort of chamber has to be made in 2 parts, front half sphere/rear half + tail) and strapped together
Okay, the reason why is that I have been playing with different spherical shapes for mid and FR drivers for some years and there's no real clear answer because the results depend on the amount of damping material that's fitted inside the chamber that varies with the type of driver, etc, etc - a lot of variables here.
I have done quite a bit of work constrained layers inside my prototype ceramic spheres with lead, rubber, cane basket weave, suspended shell, cones, etc and most of them just don't achieve much of anything - the lead killed the sound, surprisingly enough - never did figure out why.
Most recent version is a extended teardrop shape with the long 'tail' filled with damping material that increases in density towards to internal point - called a tapered resistance
This just leaves 2 things to tackle, the internal standing wave (1 main one as same radius all around) and the vibration of the chamber wall.
The second is pretty simple with additional internal ribs to 'brace up' the walls - best done by hand so not uniform around perimeter (it also means this sort of chamber has to be made in 2 parts, front half sphere/rear half + tail) and strapped together
OOps, got posted before ready...
The business of internal standing wave - there is a scheme to make up a X brace from light ply and then add the damping at the intersection of the X (looking from front of 'chamber' that is.
If you bought the AN Classic 8 and want the frequency to go down to say, 40Hz, you'll possibly require a sphere internal volume of about 45 litres - you can get the plans from 'Commonsense' that'll tell you the required volume, port size, etc and you can adapt the size of your chamber accordingly - the port will need some attention as they're normally quite short, sometimes just the thickness of the baffle (3/4", for example) so your wall thickness at this point will have to be the same 3/4".
I too have a pair of the AN Classic 8" FR driver awaiting the 'breakin" period - I use the spheroid chamber about 1 cu ft (27litre) but the driver is only required to produce 125Hz and higher - the bass is done by a separate 15" driver.
Altho I didn't addmuch to clear up the question of Constrained Layer damping and such things, perhaps my ramblings are of some use to you.
The business of internal standing wave - there is a scheme to make up a X brace from light ply and then add the damping at the intersection of the X (looking from front of 'chamber' that is.
If you bought the AN Classic 8 and want the frequency to go down to say, 40Hz, you'll possibly require a sphere internal volume of about 45 litres - you can get the plans from 'Commonsense' that'll tell you the required volume, port size, etc and you can adapt the size of your chamber accordingly - the port will need some attention as they're normally quite short, sometimes just the thickness of the baffle (3/4", for example) so your wall thickness at this point will have to be the same 3/4".
I too have a pair of the AN Classic 8" FR driver awaiting the 'breakin" period - I use the spheroid chamber about 1 cu ft (27litre) but the driver is only required to produce 125Hz and higher - the bass is done by a separate 15" driver.
Altho I didn't addmuch to clear up the question of Constrained Layer damping and such things, perhaps my ramblings are of some use to you.
Thank you for the responses! Indeed, I thought to make the outside layer out of aluminum originally; however, the cost was outside of my budget. Getting custom shapes spun is pricey!
James, I find your input invaluable. By going with bracing I can experiment with damping. I think I'll go that direction. What benefit would I gain by bracing the driver? I've seen it done in some of the Planet-10 Fonken designs.
Yes, I went to art school, but never really took to the wheel. I will be slip casting the clay.
James, I find your input invaluable. By going with bracing I can experiment with damping. I think I'll go that direction. What benefit would I gain by bracing the driver? I've seen it done in some of the Planet-10 Fonken designs.
Yes, I went to art school, but never really took to the wheel. I will be slip casting the clay.
there are a number of steel bowls that'll do the outside 'skin' quite nicely - quite a few circular and half types of lamp shades - I got some cheap 16" ones from Amazon awhile back.
Aah, the rear of the driver - glad that you asked - on the Fostex ones, Dave has done this to reduce the metal frame vibrations and reduce the freq response peak/dip caused by the gap between magnet and frame
With the AN, it's much stronger and the frame not subject to same things, but I think maybe some damping on the frame would be beneficial - easy to try.
What I will be doing is to cover the magnet with a strong plastic sleeve - thinking of using a 'cut down' fishing buoy, those yellow ones, to fit right over the rear of the magnet and form a semi circular 'ball' around the magnet to the frame - it's not bad 'as is', but when I've done this in the past, has made quite a difference in the freq response, esp when cranking up the volume a bit.
I've had good results with adding supports to the driver but mostly with the bigger bass drivers - it also stiffens up the chamber - I think it depends on just how big (cubic feet) the chamber is and what freq/power/music you're intending.
Aah, the rear of the driver - glad that you asked - on the Fostex ones, Dave has done this to reduce the metal frame vibrations and reduce the freq response peak/dip caused by the gap between magnet and frame
With the AN, it's much stronger and the frame not subject to same things, but I think maybe some damping on the frame would be beneficial - easy to try.
What I will be doing is to cover the magnet with a strong plastic sleeve - thinking of using a 'cut down' fishing buoy, those yellow ones, to fit right over the rear of the magnet and form a semi circular 'ball' around the magnet to the frame - it's not bad 'as is', but when I've done this in the past, has made quite a difference in the freq response, esp when cranking up the volume a bit.
I've had good results with adding supports to the driver but mostly with the bigger bass drivers - it also stiffens up the chamber - I think it depends on just how big (cubic feet) the chamber is and what freq/power/music you're intending.
If your goal is spherical shape for best audio quality then that is wrong shape. It has major resonances that have nothing to do with wall damping. It's basically a system with one infinite parallel wall. You will have a massive peak at the fundamental spherical resonant frequency. No amount of CLD will help that. If your goal is un-colored sound, recently I have found that a simple 3-sided pyramid or obelisk (a tall pyramid) is the most effective shape. I call it the Dagger and you can look at how clean and uncolored the resulting response is here.
http://www.diyaudio.com/forums/full-range/273524-10f-8424-rs225-8-fast-ref-monitor.html
It uses minimal materials (4 walls vs 6 of a rectangular prism), has no parallel walls, can be made to look interesting. Can even be made of ceramics or clay. I also use CLD on my Dagger with soft liquid nails glue and second layer of wall material.
More info here:
http://www.diyaudio.com/forums/full-range/268037-fast-tl-8.html#post4192688
http://www.diyaudio.com/forums/full-range/273524-10f-8424-rs225-8-fast-ref-monitor.html
It uses minimal materials (4 walls vs 6 of a rectangular prism), has no parallel walls, can be made to look interesting. Can even be made of ceramics or clay. I also use CLD on my Dagger with soft liquid nails glue and second layer of wall material.
More info here:
http://www.diyaudio.com/forums/full-range/268037-fast-tl-8.html#post4192688
The first part is true, the second part not true when done right as it damps the fundamental, which in turn more rapidly decays its harmonics same as it does with a CLD parallel wall.
Even if it didn't, the spherical shape positively affects the drivers's radiation pattern enough to justify it and the additional internal damping it requires.
GM
Even if it didn't, the spherical shape positively affects the drivers's radiation pattern enough to justify it and the additional internal damping it requires.
GM
Yes, sphere has low or no baffle diffraction effects, and I guess CLD does damp the primary sphere resonance, if, the CLD damping is in the right bandwidth as that sphere resonance which is sometimes in the 1.5 to 2 kHz range. At last in my experience, with CLD, I think works best in the lower 10's to 100's Hz range. I did not see much improvement for kHz stuff.
paper mache - here's printer ink mixed with damar
An externally hosted image should be here but it was not working when we last tested it.
The funny thing is that it was even scarier before he painted it! It looked like the chicken from Eraserhead. 
RE spherical enclosures:
Realistically, simply pressing a layer of modeling clay into the insides of the spheres when they are done should dampen the ringing sufficiently. Compound curves are inherently very stiff.
A greater problem is the infinite parallel surface effect. I've build many speakers in my DIY years, and certainly some of them were failures and got scrapped. However, the one that stands out as being BY FAR the most horrible was a spherical cabinet for a full range. The internal (air) ringing was so great I couldn't even listen to it for 10 minutes. Even fully stuffed it was intolerable.
Any theoretical gains in external diffraction behavior are not worth it IMO. If you have the skills, a squashed golden ratio ovoid shape is infinitely better. IOW, you are better off with something like Freddy's pinhead than a true sphere.
RE spherical enclosures:
Realistically, simply pressing a layer of modeling clay into the insides of the spheres when they are done should dampen the ringing sufficiently. Compound curves are inherently very stiff.
A greater problem is the infinite parallel surface effect. I've build many speakers in my DIY years, and certainly some of them were failures and got scrapped. However, the one that stands out as being BY FAR the most horrible was a spherical cabinet for a full range. The internal (air) ringing was so great I couldn't even listen to it for 10 minutes. Even fully stuffed it was intolerable.
Any theoretical gains in external diffraction behavior are not worth it IMO. If you have the skills, a squashed golden ratio ovoid shape is infinitely better. IOW, you are better off with something like Freddy's pinhead than a true sphere.
I agree that the spherical ringing of the air mass is very audible. But go figure how Gallo manages to sell stuff like the greatest thing since ferrite magnets.
Compact Satellite Speakers - Anthony Gallo Acoustics
Compact Satellite Speakers - Anthony Gallo Acoustics
Why not do something like XRK's reference monitor? Sphere on the outside (instead of a box), dagger on the inside. I thought that as soon as I saw it. Seems like the best of both worlds to me. I could see a volume problem at that point, huge sphere to get a big enough dagger. Then you could have the dagger stick out the back of the sphere. Blend the two shapes together and end up with a teardrop.
Good idea, and you may end up with something like the mid on a B&W 801/802:
or Xrk's way using foam core and XPS foam:
Any number of really good quality hifi speakers are built using the spherical form and the reason is that there are a quite a few benefits not realised with 'normal' cabinets and the problems of internal 'standing waves and resonances' created have been solved by a variety of baffles, damping and diffusors some time ago.
The 'extended' sphere is perhaps the most enduring - the 'teardrop' shape has been around for half a century and the Nautilus mids are a more recent version - the "egg" shape is a perennial shape, quite common these days in plastic construction
I'm not sure what is this "spherical ringing of the air mass" and the "infinite parallel surface effect" - is this some 'boundary effect' as theorised by Michael Green or something?
Greg, what is this "a squashed golden ratio ovoid"? A drawing/photo perhaps ...
The big problem with spherical and similar types of chambers is the difficulty in building them - unfortunately, not as simple as it looks at first glance. Most of the information about these design has been lost before the internet although much of it is still available but just not easy to access it - big names like the Gallo, Cabasse, B&W (maybe) Jordan, Overkill, and the well known series of Epsilons - many more - pretty good speakers mostly, and quite a few studio & mastering monitors (few inexpensive items).
Fast is generally known as "FR Assisted Subwoofer" (<80Hz) although many have extended this to about <120Hz and called this "FR with Assisted Bass Driver" - I think a Xover point above 200Hz follows a different set of design protocols, but maybe not ..
To use 'wedge' and cone chamber designs is generally pretty good procedure in my experience and quite common in PA (professional Audio) - the trick is to use graduated damping known as tapered acoustical resistance' where the damping increases as the pressure increases and the damping remains same density but just gets 'thicker' is high velocity regions (directly behind driver, for example)
Perimeter and Diameter resonances/standing waves are reduced/eliminated by chassis ribbing and internal baffles/diffusers, circular traps, etc - it's nearly all there on the 'net' but you have to look hard (and sometimes pay) for it.
Spherical surfaces are still subject to this 'baffle step' radiating effect but it's 'much reduced' - it's not regarded as a 'problem' to be solved generally, but a great 'side benefits' of the spherical shape in the improvements available in stereo image/depth, etc especially when coupled with room acoustic diffusers.
All the best ...
The 'extended' sphere is perhaps the most enduring - the 'teardrop' shape has been around for half a century and the Nautilus mids are a more recent version - the "egg" shape is a perennial shape, quite common these days in plastic construction
I'm not sure what is this "spherical ringing of the air mass" and the "infinite parallel surface effect" - is this some 'boundary effect' as theorised by Michael Green or something?
Greg, what is this "a squashed golden ratio ovoid"? A drawing/photo perhaps ...
The big problem with spherical and similar types of chambers is the difficulty in building them - unfortunately, not as simple as it looks at first glance. Most of the information about these design has been lost before the internet although much of it is still available but just not easy to access it - big names like the Gallo, Cabasse, B&W (maybe) Jordan, Overkill, and the well known series of Epsilons - many more - pretty good speakers mostly, and quite a few studio & mastering monitors (few inexpensive items).
Fast is generally known as "FR Assisted Subwoofer" (<80Hz) although many have extended this to about <120Hz and called this "FR with Assisted Bass Driver" - I think a Xover point above 200Hz follows a different set of design protocols, but maybe not ..
To use 'wedge' and cone chamber designs is generally pretty good procedure in my experience and quite common in PA (professional Audio) - the trick is to use graduated damping known as tapered acoustical resistance' where the damping increases as the pressure increases and the damping remains same density but just gets 'thicker' is high velocity regions (directly behind driver, for example)
Perimeter and Diameter resonances/standing waves are reduced/eliminated by chassis ribbing and internal baffles/diffusers, circular traps, etc - it's nearly all there on the 'net' but you have to look hard (and sometimes pay) for it.
Spherical surfaces are still subject to this 'baffle step' radiating effect but it's 'much reduced' - it's not regarded as a 'problem' to be solved generally, but a great 'side benefits' of the spherical shape in the improvements available in stereo image/depth, etc especially when coupled with room acoustic diffusers.
All the best ...
To be completely honest I hoped that the sphere would make a good marriage of form/function. I'm much more knowledgable about visual design than speaker design. I feel like I can make a very friendly and appealing object out of a sphere. I read that there are benefits to such a shape. It appears to me that a sphere can work if matched with the proper driver and damped correctly. If I've learned anything reading these forums it's that there's no such thing as a free lunch. I'm willing to live with compromises.
James, if I read you correctly you have had good results with the Audio Nirvana Super 8. Am I correct?
James, if I read you correctly you have had good results with the Audio Nirvana Super 8. Am I correct?
I'm still going thru the 'break-in' period and not setup in the main system yet - another couple of days to go - it's a very even sound and the dynamics and transient response seems to be improving as they break in - they appear to be far easier to manage than the Coral beta8s, Lowthers and Fostex's, by these early indications anyway.
I'm still unsure what type of amp to use - from the 'Commonsense' website, it seems that the 845 valve amp should be a good match, but also looking at a hybrid circlotron design too - another might be the F5 amp (V-juma) with the Aikido preamp - we'll see ...
With the spherical shape should come a recommendation Jim Smith's "Get Better Sound" and one of the introductions to "Room Acoustics" and "diy diffusors" - if you're going to the trouble to build spherical chambers, getting better room coupling is just another part of the exercise, and not particularly difficult to do, surprisingly enough, once you get used to the different terminology.
I'm still unsure what type of amp to use - from the 'Commonsense' website, it seems that the 845 valve amp should be a good match, but also looking at a hybrid circlotron design too - another might be the F5 amp (V-juma) with the Aikido preamp - we'll see ...
With the spherical shape should come a recommendation Jim Smith's "Get Better Sound" and one of the introductions to "Room Acoustics" and "diy diffusors" - if you're going to the trouble to build spherical chambers, getting better room coupling is just another part of the exercise, and not particularly difficult to do, surprisingly enough, once you get used to the different terminology.
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