I think we are all talking about the same product when we use the term MDF, but here in Austraia "chipboard" is usually made from coarse pinechips, a material that is as much hole as wood; very stiff for its mass and with smooth outer facing and less material in the centre of the sheets it tens to be fragile but stiff.
Used for a lot of ikea furniture for esample
http://www.design-technology.org/chipboard.htmt of interior furniture and cupboards
I think it would help if common terms were consistent between countries but thats life
regards Ted
Used for a lot of ikea furniture for esample
http://www.design-technology.org/chipboard.htmt of interior furniture and cupboards
I think it would help if common terms were consistent between countries but thats life
regards Ted
Moondog55 said:
Actually MDF is a very loose term for a wide range & quality of material. One of the problems with MDF is consistency.
dave
Carbon fibre.
I am going to throw another building material into the what to build out of fire; carbon fibre.
I am building a 3 way TL system that uses 2 7" woofers (AudioTechnology), a 3" dome mid (ATC) and a 1" ring radiator tweeter (ScanSpeak). In order to fit all these drivers together on the front baffle and have enough stiffness/strength to hold it all together, I was going to epoxy a sandwich of 19mm BB (on the front), 1.5mm carbon fibre, and 13mm BB. I figured this sandwich will be pretty much bulletproof, very stiff and strong, will kill resonances by having different thicknesses of materials, etc. What do you think?
Has anyone here used carbon fibre before? I know lots of people get scared off because you generally need epoxy to glue it together and epoxy can be expensive, smelly and messy. Any suggestions?
For those that are interested I found some very good info at http://www.robotcombat.com/marketplace_carbonfiber.html.
My thanks, in advance,
John
I am going to throw another building material into the what to build out of fire; carbon fibre.
I am building a 3 way TL system that uses 2 7" woofers (AudioTechnology), a 3" dome mid (ATC) and a 1" ring radiator tweeter (ScanSpeak). In order to fit all these drivers together on the front baffle and have enough stiffness/strength to hold it all together, I was going to epoxy a sandwich of 19mm BB (on the front), 1.5mm carbon fibre, and 13mm BB. I figured this sandwich will be pretty much bulletproof, very stiff and strong, will kill resonances by having different thicknesses of materials, etc. What do you think?
Has anyone here used carbon fibre before? I know lots of people get scared off because you generally need epoxy to glue it together and epoxy can be expensive, smelly and messy. Any suggestions?
For those that are interested I found some very good info at http://www.robotcombat.com/marketplace_carbonfiber.html.
My thanks, in advance,
John
CF/foam/CF
I had considered this but I need to be able to countersink the drivers and I have some concerns with being able to tighten screws into foam. Maybe it's just a phobia from someone who has always worked with wood; using CF is a big enough step for me for now. My next pair of speakers may well be built using a CF shell.
I had considered this but I need to be able to countersink the drivers and I have some concerns with being able to tighten screws into foam. Maybe it's just a phobia from someone who has always worked with wood; using CF is a big enough step for me for now. My next pair of speakers may well be built using a CF shell.
Re: Carbon fibre.
I haven't tried that specifically but i know it should work... perhaps not optimum use of the materials, but you are charting territory not traversed much yet.
This is much like my laminating both sides of my HDF panels with Formica.
Jonathan Carr (Lyra/Connoisur (sp)) suggested fiberglassing both sides of the plywood panels in an earlier discussion on panels.
And i currently am "sponsoring" an experiment where very dry cedar will be partially impregnated with epoxy.
dave
vincentrubble said:
I haven't tried that specifically but i know it should work... perhaps not optimum use of the materials, but you are charting territory not traversed much yet.
This is much like my laminating both sides of my HDF panels with Formica.
Jonathan Carr (Lyra/Connoisur (sp)) suggested fiberglassing both sides of the plywood panels in an earlier discussion on panels.
And i currently am "sponsoring" an experiment where very dry cedar will be partially impregnated with epoxy.
dave
Re: Carbon fibre.
John,
I can't see any practical advantage in using this material. It's an added expense, for no return.
Resonances will not be killed by the construction of unequal layers. If you are thinking constrained layer damping, that's not it. Layers need a lossy medium between that will allow the inner layer to flex against the outer layer. Solid attachment means they will act as one.
How many high end speakers are made from fiberglass? Fiberglass is just a step down from carbon fiber.
vincentrubble said:
John,
I can't see any practical advantage in using this material. It's an added expense, for no return.
Resonances will not be killed by the construction of unequal layers. If you are thinking constrained layer damping, that's not it. Layers need a lossy medium between that will allow the inner layer to flex against the outer layer. Solid attachment means they will act as one.
How many high end speakers are made from fiberglass? Fiberglass is just a step down from carbon fiber.
If we just want to reduce the vibration from being transmitted to outside world. double box (box within box) can reduce this do ridiculous amount. probably using different material for inner and outer box could be used to "tune" the desired result.
Lossy material
Sorry I have a stupid question; what is a lossy material? Is this like a lead sheet?
Thanks,
John
Sorry I have a stupid question; what is a lossy material? Is this like a lead sheet?
Thanks,
John
Lossy material = flexible. Types of glue that do not conpletely harden, ashphalt, silicone rubber. Join the layers, but allow for independant movement.
Re: Re: Carbon fibre.
In a structural sandwich system, a thin top and bottom layer is attached to a core material. The core material may be strucurally weak on its own, but with the addition of these layers, deflection strenght is increased. The strenght of these layers is along thier axis, they resist stretching.
When force is applied to the panel, the nearest layer is in compression, the farthest is in tension.
The potential benefits are negated when used on an extremely rigid material like HDF.
planet10 said:
In a structural sandwich system, a thin top and bottom layer is attached to a core material. The core material may be strucurally weak on its own, but with the addition of these layers, deflection strenght is increased. The strenght of these layers is along thier axis, they resist stretching.
When force is applied to the panel, the nearest layer is in compression, the farthest is in tension.
The potential benefits are negated when used on an extremely rigid material like HDF.
Attachments
Re: Re: Re: Carbon fibre.
Now that you have shot down Dave's building methods and my considered methods, perhaps you could suggest a few of your own that you consider worth trying. It's always interesting to see how others build.
Thanks,
John
MJL21193 said:
Now that you have shot down Dave's building methods and my considered methods, perhaps you could suggest a few of your own that you consider worth trying. It's always interesting to see how others build.
Thanks,
John
Re: Re: Re: Carbon fibre.
Why are the benefits negated? This whole principle combined with the extra strength added by having a variety of grain directions is the reason that many consider plywood to be structurally more sound than solid wood or mdf.
Thanks,
John
MJL21193 said:
Why are the benefits negated? This whole principle combined with the extra strength added by having a variety of grain directions is the reason that many consider plywood to be structurally more sound than solid wood or mdf.
Thanks,
John
Re: Re: Carbon fibre.
John is completely off-base if he thinks your technique won't have benefit. Even better if you sandwiched the outside (ie 1 piece of 18mm BB in a carbon fibre sandwich would probably be better but not as practical for construction (you do have to attach the panel to the rest of the box.
Using dissimilar thickness layers is a well recognized technique.
Not many. Carbon Fibre is a whole nother thing to fibreglass (akin to the difference between cardboard & MDF)... dramatically stiffer. Wilson Benesch use a lot of carbon fibre.
dave
John is completely off-base if he thinks your technique won't have benefit. Even better if you sandwiched the outside (ie 1 piece of 18mm BB in a carbon fibre sandwich would probably be better but not as practical for construction (you do have to attach the panel to the rest of the box.
Using dissimilar thickness layers is a well recognized technique.
MJL21193 said:
Not many. Carbon Fibre is a whole nother thing to fibreglass (akin to the difference between cardboard & MDF)... dramatically stiffer. Wilson Benesch use a lot of carbon fibre.
dave
Re: Re: Re: Carbon fibre.
If you are talking non-woven scrim and polyester resin I will agree.
If you talking roving and epoxy resin, you are dealing with something one step down from carbon fiber.
planet10 said:
If you are talking non-woven scrim and polyester resin I will agree.
If you talking roving and epoxy resin, you are dealing with something one step down from carbon fiber.
Re: Re: Re: Carbon fibre.
You end up with a solid-plasticvery stiff outside skin with a highly damped interior, and the transition between the extremes is very chaotic.
Intelectually it seems a very good building material -- particularily for shapes. This is the proof of concept experiment.
dave
MJL21193 said:
You end up with a solid-plasticvery stiff outside skin with a highly damped interior, and the transition between the extremes is very chaotic.
Intelectually it seems a very good building material -- particularily for shapes. This is the proof of concept experiment.
dave
Re: Re: Re: Carbon fibre.
Thanks Dave. This was my line of thinking too. There seem to be alot of Johns around here so I will henceforth call myself Vince to avoid confusion.
planet10 said:
Thanks Dave. This was my line of thinking too. There seem to be alot of Johns around here so I will henceforth call myself Vince to avoid confusion.
Re: Re: Re: Re: Carbon fibre.
Dave used to me critiquing his methods.
The sandwich method to increase stiffness works VERY well. It's a structural system that depends on each part playing it's role. The outer layers have to resist stretching or crumpleing under tension or compression. The core needs to be just strong enough to link the two layers.
The typical hollow slab door in a lot of houses is a good example of sandwich construction. The core is a cardboard honeycomb link the front and back which are thin plywood.
Perhaps to use carbon fiber more effectively, you could form a sandwich panel by putting it on both sides of a core (such as plywood).
In the end, even though you would have carbon fiber bragging rights, the results may not be worth the effort.
vincentrubble said:
Dave used to me critiquing his methods.
The sandwich method to increase stiffness works VERY well. It's a structural system that depends on each part playing it's role. The outer layers have to resist stretching or crumpleing under tension or compression. The core needs to be just strong enough to link the two layers.
The typical hollow slab door in a lot of houses is a good example of sandwich construction. The core is a cardboard honeycomb link the front and back which are thin plywood.
Perhaps to use carbon fiber more effectively, you could form a sandwich panel by putting it on both sides of a core (such as plywood).
In the end, even though you would have carbon fiber bragging rights, the results may not be worth the effort.