On that same page they list Medite. Back when i was using MDF (Medite actually HDF), Medite is all i used.
It has all the problems Bob mentioned but is heavier and eats tools faster. I often laminated it both sides with plastic laminate.
dave
I might mention that Speakerlab, back in the 70's used 1/2 inch particle board glued to the inside of 3/4 inch plywood on their cabinets to produced a "very" dead cabinet. I suppose that instead of yellow glue it could be "Green Glue" instead, for an even better constrained layer cabinet.
My "Magnum Opus" speaker will certainly use something of this nature.
Best Regards,
TerryO
My "Magnum Opus" speaker will certainly use something of this nature.
Best Regards,
TerryO
I think the laminate/composite is definately the best way to go.
I have used MDF and will probably use it again, its lossy nature is NOT a disadvantage in my opinion. I used to have a very cheap electric guitar, and it sounded dead, and dull. Turned out the solid body was MDF. I bought my first new guitar at 15 and that was some kind of ply. At the time I was a little annoyed because I thought it was solid wood. Even so the tone was better. It had a resonant character, even though the pickups are largely responsible for the sound. Both guitars were Cheap copy stratocasters.
My 'best' guitar, is solid mahogany, and faced with some exotic hardwood. tone is much more apparent.
from this kind of experience whether misguided or not, I believe that MDF is not bad, but perhaps SHOULDNT be used alone. I think that essentially ply or wood shows a much more pronounced resonant signature, due to the tension along fibres as opposed to the adhesion between fibres in MDF, the former which i believe (no real idea tbh) to be greater than the latter.
SO then I think the ply would actually represent a MORE resonant system than the MDF, all else equal, such as mass as opposed to thickness.....and the plys increased tensile strength is good. Also the MDF box with equal mass 'walls' would surely have a far lower fundamental, due to its inferior tensile strength. BUT its lossy nature isnt bad...many a time ive thought of a sand filled cavity type of wall, using the thin bendy scored mdf sheet, bracing rings along the interior, to form the MDF sheet against. add top and bottom and float the whole thing in the exterior shell.
Essentially, im coming to the conclusion (correct or not) that bracing to damp and strengthen a resonant system, is actually very effective, perhaps more so than bracing a less resonant/differently resonating one; I once had some 1½" thick cork and rubber sheeting, and considered trying to make a box with it! The idea of lining a ply box with thin mdf >3mm<6mm, maybe green glue, or just silicone, maybe non hardening pipe gasket sealant(blue stuff© lol) sounds like an experiment worth trying.
I have used MDF and will probably use it again, its lossy nature is NOT a disadvantage in my opinion. I used to have a very cheap electric guitar, and it sounded dead, and dull. Turned out the solid body was MDF. I bought my first new guitar at 15 and that was some kind of ply. At the time I was a little annoyed because I thought it was solid wood. Even so the tone was better. It had a resonant character, even though the pickups are largely responsible for the sound. Both guitars were Cheap copy stratocasters.
My 'best' guitar, is solid mahogany, and faced with some exotic hardwood. tone is much more apparent.
from this kind of experience whether misguided or not, I believe that MDF is not bad, but perhaps SHOULDNT be used alone. I think that essentially ply or wood shows a much more pronounced resonant signature, due to the tension along fibres as opposed to the adhesion between fibres in MDF, the former which i believe (no real idea tbh) to be greater than the latter.
SO then I think the ply would actually represent a MORE resonant system than the MDF, all else equal, such as mass as opposed to thickness.....and the plys increased tensile strength is good. Also the MDF box with equal mass 'walls' would surely have a far lower fundamental, due to its inferior tensile strength. BUT its lossy nature isnt bad...many a time ive thought of a sand filled cavity type of wall, using the thin bendy scored mdf sheet, bracing rings along the interior, to form the MDF sheet against. add top and bottom and float the whole thing in the exterior shell.
Essentially, im coming to the conclusion (correct or not) that bracing to damp and strengthen a resonant system, is actually very effective, perhaps more so than bracing a less resonant/differently resonating one; I once had some 1½" thick cork and rubber sheeting, and considered trying to make a box with it! The idea of lining a ply box with thin mdf >3mm<6mm, maybe green glue, or just silicone, maybe non hardening pipe gasket sealant(blue stuff© lol) sounds like an experiment worth trying.
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Never used Medite, I think I know what it is though, that stuff is solid. The Medex is good, cuts nice, less dust. I worked on a pair of full range mirco towers today and that’s what I’m using (Medex).
The HD/Lowes MDF is pretty cheesy, like old newspaper and glue lol. However I do use it all the time. Obviously it can be covered with, veneer, formica, or simply painted.
The HD/Lowes MDF is pretty cheesy, like old newspaper and glue lol. However I do use it all the time. Obviously it can be covered with, veneer, formica, or simply painted.
Stiffness goes up as the cube of thickness, so in your example MDF would have to be 12 * 2.2^(1/3) = 15.6mm thick, not 40mm.
GM always uses the example of 3/4" BB = 1 1/4" MDFin terms of stiffness. BB being less mass will still have higher reonant frequencies (and therefore less likely to be excited)
dave
Planet,
stiffness is as Ron stated.
Resonant frequency is dependant on both mass and stiffness, just like the strings of a violin. Although this is not a great analogy since in stringed instruments the stiffness is replaced with tension. But in both cases, the panel or the string, changing the mass changes the frequency.
stiffness is as Ron stated.
Resonant frequency is dependant on both mass and stiffness, just like the strings of a violin. Although this is not a great analogy since in stringed instruments the stiffness is replaced with tension. But in both cases, the panel or the string, changing the mass changes the frequency.
as I am no engineer (thankfully)...
I've never looked at the problem of stiffness in terms of beams and plates, nor have I ever had to. All things being equal, it is the reduction in mass (not weight) that is at least partially responsible for the different sounds one hears in MDF vs. BB ply. The speed of sound in the material is another Based on density), and the MOE. The fact that the plywood is glued between layers helps as well.
Anyone have a good derivation of the "stiffness" equation from 1st principles? (I've been online and in my library seeking a source, however I concentrated on quantum mechanics rather than classical mechanics when at uni). Halliday and Resnick? Gianacoli? The only formal exposure I have had in regards to Young's modulus and MOE was in a class in Heat & Thermodynamics, where we discussed the effects of Pressure and Heat to a 3_D object based on the thermal properties of the material used in the object and derived the equation that explained the behaviour of the object as a partial differential equation in 3-D. Even when I took a tech program (Manufacturing Process Technology), I took materials science and rec'd zero instruction on the equations or their derivations regarding beam loading. I guess that was for a class that I was never expected to take.
I think that one must also consider the boundary conditions of any physical problem. That much I do recall (particularly in QM). An enclosure is not as simple as it first appears.
Now having said all of that, I think one often overlooked material for loudspeakers are "medite" or hardboard (paper) cylinders. Those are dominated by their behaviour as a Helmholtz resonator (and), that is something that I am very familiar with. PVC pipes could also be used, if treated (again), in an appropriate manner. My "wannabees" are similar to the toobz loudspeaker and to Linkwitz's Pluto loudspeakers. However I've always wanted to try the basic setup in a 4" paper tube" (or perhaps sonotube?). In PVC there is some significant ringing, but it is relatively easy to reduce it below the audible level, with dampening material glued to the interior and with appropriate stuffing. Mine sound startling good, considering total cost was about $50 complete.
I have contacted a friend (JRWilling) who is a mechanical designer that may be able to point me in the right direction regarding some self-education in non-static beam loading and plate behaviour. I won't make anymore comments about Young's Modulus until I do that.
My comments still stand. There is what I think is a sonic advantage to using BB ply vs MDF. Perhaps my presentation of the technical aspects have been lacking. I'll try to mend that. I also did not want to post further about the relations until after I educate myself (or get educated), so if I don't post here for a bit, it's because I am concentrating on that.
I've never looked at the problem of stiffness in terms of beams and plates, nor have I ever had to. All things being equal, it is the reduction in mass (not weight) that is at least partially responsible for the different sounds one hears in MDF vs. BB ply. The speed of sound in the material is another Based on density), and the MOE. The fact that the plywood is glued between layers helps as well.
Anyone have a good derivation of the "stiffness" equation from 1st principles? (I've been online and in my library seeking a source, however I concentrated on quantum mechanics rather than classical mechanics when at uni). Halliday and Resnick? Gianacoli? The only formal exposure I have had in regards to Young's modulus and MOE was in a class in Heat & Thermodynamics, where we discussed the effects of Pressure and Heat to a 3_D object based on the thermal properties of the material used in the object and derived the equation that explained the behaviour of the object as a partial differential equation in 3-D. Even when I took a tech program (Manufacturing Process Technology), I took materials science and rec'd zero instruction on the equations or their derivations regarding beam loading. I guess that was for a class that I was never expected to take.
I think that one must also consider the boundary conditions of any physical problem. That much I do recall (particularly in QM). An enclosure is not as simple as it first appears.
Now having said all of that, I think one often overlooked material for loudspeakers are "medite" or hardboard (paper) cylinders. Those are dominated by their behaviour as a Helmholtz resonator (and), that is something that I am very familiar with. PVC pipes could also be used, if treated (again), in an appropriate manner. My "wannabees" are similar to the toobz loudspeaker and to Linkwitz's Pluto loudspeakers. However I've always wanted to try the basic setup in a 4" paper tube" (or perhaps sonotube?). In PVC there is some significant ringing, but it is relatively easy to reduce it below the audible level, with dampening material glued to the interior and with appropriate stuffing. Mine sound startling good, considering total cost was about $50 complete.
I have contacted a friend (JRWilling) who is a mechanical designer that may be able to point me in the right direction regarding some self-education in non-static beam loading and plate behaviour. I won't make anymore comments about Young's Modulus until I do that.
My comments still stand. There is what I think is a sonic advantage to using BB ply vs MDF. Perhaps my presentation of the technical aspects have been lacking. I'll try to mend that. I also did not want to post further about the relations until after I educate myself (or get educated), so if I don't post here for a bit, it's because I am concentrating on that.
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