Hi,
I have several questions for whose answers I would be grateful.
How do you laminate them?
In what form was the lead and how was it attached?
Thanks,
eStatic
BobeM said:
I have several questions for whose answers I would be grateful.
How do you laminate them?
In what form was the lead and how was it attached?
Thanks,
eStatic
Hi eStatic
I would agree with you that oak is really rewarding and a pleasure to work with. Of course, it is not as simple as MDF but far more satisfying.
I line the inside of the cabinets with adhesive lead which comes in rolls of various widths, then tack it for double strength. Its normal use is for lead flashing on tile and slate roofs, as a waterproof barrier. In the UK it is readily available from all good DIY outlets.
Adding the lead can either be done to sheet wood or once the cabinet is nearly complete. The result is a panel that appears to be accoustically dead.
Good luck
BobeM
I would agree with you that oak is really rewarding and a pleasure to work with. Of course, it is not as simple as MDF but far more satisfying.
I line the inside of the cabinets with adhesive lead which comes in rolls of various widths, then tack it for double strength. Its normal use is for lead flashing on tile and slate roofs, as a waterproof barrier. In the UK it is readily available from all good DIY outlets.
Adding the lead can either be done to sheet wood or once the cabinet is nearly complete. The result is a panel that appears to be accoustically dead.
Good luck
BobeM
Coulomb said:
Assuming that the gain of the whole system was 1 (taking into account the losses of the speaker and microphone and the gain of the amp) then the time delay caused by the distance between the microphone and the speaker would cause an echo effect rather than a cancelling effect - also the distance between the other speaker and the microphone would cause a secondary delay of the newly introduced signal and the feedback loop would cause the system to oscillate! The very thing you were trying to cure in the first place!
Ever heard what happens when you put a mic in front of the speaker that it's driving? Called howl round or squeal - and isn't nice.
I’ve seen plywood separate from a 12” driver it was suppose to be top quality wood.
And chipboard is just a joke in my opinion MDF is the best over all.
And chipboard is just a joke in my opinion MDF is the best over all.
For acoustically inert enclosure material try this:
http://www.precisionacousticlabs.com/::www.precisionacousticlabs.com:products.html
http://www.precisionacousticlabs.com/::www.precisionacousticlabs.com:products.html
While it's perfectly valid for a musician to use a speaker as a musical instrument in some sense while he is creating music, when I listen to the resulting composition through another loudspeaker, I want the least modification of that performance possible by that speaker - to consider *it* as a musical instrument is not at all valid or desirable.
I've built speakers using MDF usually but I really want to use real wood for my next speakers. First of all there are so many different types of wood. And to generaly think of wood as being a 'highly resonant' material is obvious non-sense. Sure it has a resonant point, but so does MDF and everthing else, including our sometimes thick skulls.
The only thing I worry about when it comes to wood is warping or shrinking. It's probably mindless paranoia but i would't want to damage an expensive driver. I don't know how strong the warping can be... are some woods strong enough to bend driver baskets as they warp?
Any wood experts???
The only thing I worry about when it comes to wood is warping or shrinking. It's probably mindless paranoia but i would't want to damage an expensive driver. I don't know how strong the warping can be... are some woods strong enough to bend driver baskets as they warp?
Any wood experts???
It seems unlikely that any movement will cause damage to the drivers. More likely some cracking, splitting, or humidity-caused movement will compromise the cabinet seal, fit or finish. Bear in mind, the larger the board, especially across the grain, the greater the movement. A twelve inch wide tight-grained, hardwood board will move at least an eighth of an inch in typical humidity swings indoors. Plan for it.
To avoid warping, use only well dried, or aged, straight grained wood and seal all sides.
To avoid warping, use only well dried, or aged, straight grained wood and seal all sides.
You could use hardwood plywood to bypass some deficiencies of the real wood. The finish on the outside is the same, it's stronger and stiffer.
Not being an expert, but having done some research, avoid pure hardwoods and go with something like plywoods, etc. The glued layers tend to cancel resonance. The exterior looks the same, so the aesthetic goal is preserved, and veneers can be more easily added to the smooth surfaces.. My 70s era Yamaha speakers are made with very thick plywood/no mdf that I can tell, and are very low resonance, not to mention beautiful.
Linkwitz uses plywood for his Orions - can't aregue with that, but they are open baffle anyway. Another option, mentioned in another reply, is to use mdf layered with thin plywood (on the outside) - this reduces cost and you get a "best of both worlds" result. Layering different materials, which is what plywood is anyway, has a good damping effect. Remember that your boxes can really never be too thick - just remember to build outward to preserve inner volume, and be careful of overall baffle width.
So you can build with both thick mdf and plywood if you want - I've seen many builders do the "box within a box" design, with an inner mdf box essentially "suspended" inside a plywood box, using bitumen or other materials in between. This is seen in bass units and subwoofers most often.
I am thinking of trying this approach to one small experimental project, but using a layer of asphalt damping sheets (Parts Express, etc.) for the layer in between the two boxes. Perhaps other might have some opinions on this.
Linkwitz uses plywood for his Orions - can't aregue with that, but they are open baffle anyway. Another option, mentioned in another reply, is to use mdf layered with thin plywood (on the outside) - this reduces cost and you get a "best of both worlds" result. Layering different materials, which is what plywood is anyway, has a good damping effect. Remember that your boxes can really never be too thick - just remember to build outward to preserve inner volume, and be careful of overall baffle width.
So you can build with both thick mdf and plywood if you want - I've seen many builders do the "box within a box" design, with an inner mdf box essentially "suspended" inside a plywood box, using bitumen or other materials in between. This is seen in bass units and subwoofers most often.
I am thinking of trying this approach to one small experimental project, but using a layer of asphalt damping sheets (Parts Express, etc.) for the layer in between the two boxes. Perhaps other might have some opinions on this.
My results have been good with using interior hardwood (oak) 1" x 3" bracing glued and screwed on edge & for taller cabinets plywood internal bracing 'ribs' joining the front, back & sides every foot or two of height.
MDF may sound better than cheap 23/32" 5 ply plywood with its voids, but my impression is that void free 11 or 13 layer birch veneer plywood is sonically preferable to either, partly because of its internal damping characteristics. Plus, the birch veneer is often good looking enough to stain and finish.
MDF may sound better than cheap 23/32" 5 ply plywood with its voids, but my impression is that void free 11 or 13 layer birch veneer plywood is sonically preferable to either, partly because of its internal damping characteristics. Plus, the birch veneer is often good looking enough to stain and finish.
You have all missed the point!
I just spent a lot of time reading this old thread, and I'll be damned if I don't post a response.
A lot of talk about resonances, strength, dampening, etc., but all off base.
Resonances and harmonics:
It is somewhat simplistic or misleading (although useful) to describe any material per se as having any particular resonance signature, or sound, of its own. A material's particular resonances are dominated by what shape it is given. This is not to say that different materials of the same shape sound exactly alike (they obviously don't, as different materials have different harmonic signatures), but that it is mostly its shape, or its proportions, which determines what something sounds like. Think of a brass tuning fork. It is shaped to ring at a particular note, its resonant frequency. This fundamental note (in air) depends entirely on the effective length of its legs. This note can be altered somewhat by altering its mass (by drilling holes in it, for example) and varying how it is stressed (like squeezing it), but these are just different ways of altering its harmonic signature. (The holes also changed the shape and thus added different harmonics, and squeezing it would have dampened, or absorbed, certain harmonics more than others.) If you made the tuning fork from a different material, say steel, it would still have the same (extremely close) resonant frequency, but you would be able to tell it apart because it has a different harmonic signature. Just like you (and voice recognition software) can tell people's voices apart.
When you make a speaker box from sheet material, you have to suffer with the fundamental resonances which result mostly from the dimensions of its sides. By bracing it or tensioning it, you can make it look more like several smaller panels, but you add the resonances of the extra parts. By choosing a different material, you can change the harmonic signature. All of these excitations comprise the coloration of the box. An open-baffle speaker can reduce this coloration by a large degree as there are many fewer sides, but the baffle itself still remains...
Strength:
A speaker box doesn't need strength as such beyond that needed to uphold its own weight (aside from withstanding the stresses of air pressure and mounting the driver) . What it needs is mass for the impulses of the cone to react against through the basket. Rigidity can to some degree make up for mass, in that the impulses can be distributed to all parts (all the mass) of the box, but these shock waves can only travel at the speed of sound of the material, and there will be some delay. More mass around the speaker mounting area is better.
Dampening:
For the purposes of speaker boxes, dampening is accomplished through internal friction of the material. Materials can have good inherent dampening. I believe MDF has fairly good inherent dampening, which is why it sounds pretty dead, relatively speaking, when you knock on it. A sheet of rubber is a lot deader, though. Other materials thought of as dead, or inert, like concrete, aren't well dampened at all. It's just that most concrete you run into is in such massive, grounded pieces that it takes a lot of impact to hear it ring. Lead seems well dampened because its soft, as well as heavy. And you can't dampen something by just adding weight to it. This just results in moving the resonances down in frequency, sometimes a welcome result.
A speaker enclosure carved from a pile of wet sand wouldn't have any strength and have no specific fundamental resonances, but it would be massive AND dead, almost the ideal speaker box...
Gotta go! Dinner's ready. Hope I could clear up some concepts...
Tosh
I just spent a lot of time reading this old thread, and I'll be damned if I don't post a response.
A lot of talk about resonances, strength, dampening, etc., but all off base.
Resonances and harmonics:
It is somewhat simplistic or misleading (although useful) to describe any material per se as having any particular resonance signature, or sound, of its own. A material's particular resonances are dominated by what shape it is given. This is not to say that different materials of the same shape sound exactly alike (they obviously don't, as different materials have different harmonic signatures), but that it is mostly its shape, or its proportions, which determines what something sounds like. Think of a brass tuning fork. It is shaped to ring at a particular note, its resonant frequency. This fundamental note (in air) depends entirely on the effective length of its legs. This note can be altered somewhat by altering its mass (by drilling holes in it, for example) and varying how it is stressed (like squeezing it), but these are just different ways of altering its harmonic signature. (The holes also changed the shape and thus added different harmonics, and squeezing it would have dampened, or absorbed, certain harmonics more than others.) If you made the tuning fork from a different material, say steel, it would still have the same (extremely close) resonant frequency, but you would be able to tell it apart because it has a different harmonic signature. Just like you (and voice recognition software) can tell people's voices apart.
When you make a speaker box from sheet material, you have to suffer with the fundamental resonances which result mostly from the dimensions of its sides. By bracing it or tensioning it, you can make it look more like several smaller panels, but you add the resonances of the extra parts. By choosing a different material, you can change the harmonic signature. All of these excitations comprise the coloration of the box. An open-baffle speaker can reduce this coloration by a large degree as there are many fewer sides, but the baffle itself still remains...
Strength:
A speaker box doesn't need strength as such beyond that needed to uphold its own weight (aside from withstanding the stresses of air pressure and mounting the driver) . What it needs is mass for the impulses of the cone to react against through the basket. Rigidity can to some degree make up for mass, in that the impulses can be distributed to all parts (all the mass) of the box, but these shock waves can only travel at the speed of sound of the material, and there will be some delay. More mass around the speaker mounting area is better.
Dampening:
For the purposes of speaker boxes, dampening is accomplished through internal friction of the material. Materials can have good inherent dampening. I believe MDF has fairly good inherent dampening, which is why it sounds pretty dead, relatively speaking, when you knock on it. A sheet of rubber is a lot deader, though. Other materials thought of as dead, or inert, like concrete, aren't well dampened at all. It's just that most concrete you run into is in such massive, grounded pieces that it takes a lot of impact to hear it ring. Lead seems well dampened because its soft, as well as heavy. And you can't dampen something by just adding weight to it. This just results in moving the resonances down in frequency, sometimes a welcome result.
A speaker enclosure carved from a pile of wet sand wouldn't have any strength and have no specific fundamental resonances, but it would be massive AND dead, almost the ideal speaker box...
Gotta go! Dinner's ready. Hope I could clear up some concepts...
Tosh
Re: You have all missed the point!
First of all, it 'damping' not 'dampening'. Dampening it to get something moist. Next, the shape of an object AND the material determine the resonance. Two identical shaped tuning forks of different materials will have different resonances. It is clear that most of your statements are not really what is going on.Tosh said:
I used to say "damping," and was told by my boss to say "dampening." Both mean the same thing, but "dampening" also has the additional meaning of "to make moist." I will revert to say "damping."
The two tuning forks of different material but the same dimensions will have *very close* to the same resonant frequency. The difference in the resonant frequencies would be attributable to the slightly different effective lengths of the legs, due to the different densities and inherent damping between the two materials. They would of course also sound different to a keen set of ears because of the differing harmonic signatures, which is how we can tell materials apart. But the *dominant* sound would be the tone of its resonant, or natural, frequency, which is *dominated* by its shape. Not *only* by its shape, but *mostly.*
What is clear, markp, is that you are just nit-picking on an explanation that you don't like...
Tosh
The two tuning forks of different material but the same dimensions will have *very close* to the same resonant frequency. The difference in the resonant frequencies would be attributable to the slightly different effective lengths of the legs, due to the different densities and inherent damping between the two materials. They would of course also sound different to a keen set of ears because of the differing harmonic signatures, which is how we can tell materials apart. But the *dominant* sound would be the tone of its resonant, or natural, frequency, which is *dominated* by its shape. Not *only* by its shape, but *mostly.*
What is clear, markp, is that you are just nit-picking on an explanation that you don't like...
Tosh
We've All Missed The point?
I don't think we've all "missed the point", and I don't think that "enough said."
The "point" was that the originator of this thread was seeking advice on the kind and quantity of materials with which to construct an enclosure and, though the rest of us may not have used terms such as "damping", "dampening", "resonance", etc. in their purest scientific contexts, the advice we gave him was nonetheless sound, practical, and useful.
Isn't that what we're all here for?
I don't think we've all "missed the point", and I don't think that "enough said."
The "point" was that the originator of this thread was seeking advice on the kind and quantity of materials with which to construct an enclosure and, though the rest of us may not have used terms such as "damping", "dampening", "resonance", etc. in their purest scientific contexts, the advice we gave him was nonetheless sound, practical, and useful.
Isn't that what we're all here for?
I have read about 2/3rds of this thread and can not keep up with it but how about-
using old oak wine barrels as enclosures , they are fairly cheap and could be rolled around the house (not lifted) or cut in half to make 2 speakers. Yes I know there are lots of problems like securing the metal rings ( or just remove them and use glue etc)
to stop them vibrating and your living room smelling like a winery - although some people may like that.
Or make small enclosures for the tweeter and mid, then put the base driver on the ceiling and use the roof cavity as an enclosure - only good for people who live in a normal house- not a block of flats.
using old oak wine barrels as enclosures , they are fairly cheap and could be rolled around the house (not lifted) or cut in half to make 2 speakers. Yes I know there are lots of problems like securing the metal rings ( or just remove them and use glue etc)
to stop them vibrating and your living room smelling like a winery - although some people may like that.
Or make small enclosures for the tweeter and mid, then put the base driver on the ceiling and use the roof cavity as an enclosure - only good for people who live in a normal house- not a block of flats.
I once had some MDF and it's density was .87 g/cm^2 I think (around there). Here are some other wood densities http://www.engineeringtoolbox.com/24_40.html You can find some woods denser than MDF. I would expect MDF's good damping properties to come mostly from it's weight.
Important thing is to get dried wood (i believe this is the same as the expression "seasoned" wood). The wood's m.c. or moisture content should be stamped on the wood. 5 to 7 % I think is considered good for building furniture out of wood.
The thing is that, wood expands as it approaches it's FSB (fiber saturation point). It's about 28% on average (mass of water/oven dried wood). Oven dried is suppose to be as close to 0% m.c. as possible. Also denisty is measured in the oven dried state or o.d. state.
Wood expands on average (varies from species, just like fsp) 8% tangentially, 4% radially, and .1% longitudinally as it reaches it's fsb (anything above that doesn't matter). You should be able to figure out those directions I hope; think of a tree. But If you get dried wood with the 5% - 7% m.c. and brace it then it will not expand if you do this correctly. So for example, you get boards glue them side by side. You have 1x6x30" pieces glued together. The 1" tangential potential expansion of 4% would matter much of course (4 hundredths). But in the 6" direction, radially the piece will expand 8%, that's .48". The if you glued 4 pieces together that's 2." This is worst case senario though. M.c. of wood depends apawn relative humity of air. So the higher the relative humity the higher the moisture content of the wood. 100% rh is 28% m.c. in wood, 50% relative humidity m.c. of wood is about 8%. So it's not linear and from 50% to 100% it more than one would think, if you assume m.c. vs. length of expantion is linear. Which I don't know off hand.
But the important thing is to brace the wood radially when it is at this desireable m.c. This is easy, since wood expands .1% longitudinaly. So you would glue some wood with it's longitudinal direction across going across the radial direction of the board you just glued together. This is the one of the reasons old medival doors have battens (I think that's what they're called), also plywood applies this same principle to stop wood expanding. Also bracing should fufil this function, but it has to be across the part that will be expanding.
Oak barrels would be fine if they were constructed when the wood was at a low m.c. Or if you live in an area with a high relative humidity you will be fine. Or if you don't mind watering your speakers along with your plants.
I guess if you live in a place where the relative humidity is always high you don't have to worry about this, but I don't know if such a place exists.
Important thing is to get dried wood (i believe this is the same as the expression "seasoned" wood). The wood's m.c. or moisture content should be stamped on the wood. 5 to 7 % I think is considered good for building furniture out of wood.
The thing is that, wood expands as it approaches it's FSB (fiber saturation point). It's about 28% on average (mass of water/oven dried wood). Oven dried is suppose to be as close to 0% m.c. as possible. Also denisty is measured in the oven dried state or o.d. state.
Wood expands on average (varies from species, just like fsp) 8% tangentially, 4% radially, and .1% longitudinally as it reaches it's fsb (anything above that doesn't matter). You should be able to figure out those directions I hope; think of a tree. But If you get dried wood with the 5% - 7% m.c. and brace it then it will not expand if you do this correctly. So for example, you get boards glue them side by side. You have 1x6x30" pieces glued together. The 1" tangential potential expansion of 4% would matter much of course (4 hundredths). But in the 6" direction, radially the piece will expand 8%, that's .48". The if you glued 4 pieces together that's 2." This is worst case senario though. M.c. of wood depends apawn relative humity of air. So the higher the relative humity the higher the moisture content of the wood. 100% rh is 28% m.c. in wood, 50% relative humidity m.c. of wood is about 8%. So it's not linear and from 50% to 100% it more than one would think, if you assume m.c. vs. length of expantion is linear. Which I don't know off hand.
But the important thing is to brace the wood radially when it is at this desireable m.c. This is easy, since wood expands .1% longitudinaly. So you would glue some wood with it's longitudinal direction across going across the radial direction of the board you just glued together. This is the one of the reasons old medival doors have battens (I think that's what they're called), also plywood applies this same principle to stop wood expanding. Also bracing should fufil this function, but it has to be across the part that will be expanding.
Oak barrels would be fine if they were constructed when the wood was at a low m.c. Or if you live in an area with a high relative humidity you will be fine. Or if you don't mind watering your speakers along with your plants.
I guess if you live in a place where the relative humidity is always high you don't have to worry about this, but I don't know if such a place exists.
I dunno why you guys think hardwoods don't work. Obviously, the rules of joinery and proper sealing have not been followed. All my designs are finished in 19mm thick hardwoods, and not one failure yet.
James
An externally hosted image should be here but it was not working when we last tested it.
James
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