That name is one of those trademarked brand names that have come to describe generic types - and like all generalization, not always correctly. (e.g. others are "Formica", "Arborite", "Corian", "Medite", etc.)
Appleply is indeed a much higher quality product than shop grade (C-face) Baltic Birch, both in terms of the integrity of core laminations and most particularly the selections and quality of face veneer species.
The last project my commercial employer used this material for was over 10yrs ago, and at that time the product was over 3 times the cost per sheet of BB, but certainly still less than half that of the current trendy upscale material - laminated bamboo. So, aside from careful cut-planning, particularly in terms of grain sequence matching, and gentle handling of off-cuts, there's no particular difference between working with Appleply and Baltic Birch.
It's also "available" in larger sizes for architectural work (i.e. 4x10ft) than the 5x5ft which is common for BB.
"availability" of sizes and species can mean special factory order, minimum quantities and lead times of up to several months - don't go looking for it at your local Windsor, Rona or Home Depot.
Chris,
>don't go looking for it at your local Windsor, Rona or Home Depot.<
!
If things are like over here (Germany) you allegedly only pay for what you carry home, cut to half a millimeter - but you pay for someone trained to sell cat litter using a clapped out saw and throwing away half the sheet as cutoffs.
Maybe things are ~like that in CAN/US - standard pro sheets here are 2m07x2m80, a friendly carpenter will share the wholesale %%% he gets, as long as you give him a cutz plan and pay him for the ripping.
I have ended up with paying ~half what I would have paid at Bauhaus, plus the cuts were done by a pro.
Pit
>don't go looking for it at your local Windsor, Rona or Home Depot.<
!If things are like over here (Germany) you allegedly only pay for what you carry home, cut to half a millimeter - but you pay for someone trained to sell cat litter using a clapped out saw and throwing away half the sheet as cutoffs.
Maybe things are ~like that in CAN/US - standard pro sheets here are 2m07x2m80, a friendly carpenter will share the wholesale %%% he gets, as long as you give him a cutz plan and pay him for the ripping.
I have ended up with paying ~half what I would have paid at Bauhaus, plus the cuts were done by a pro.
Pit
Hi All,
Read all 583 posts on the 59 pages over the past few days and i got say mybrain hurts a bit. Still trying to digest all the great info. If I can recap the main points I've pulled out from what I've read :
1) the speaker enclosure should be designed and built to prevent the panels from vibrating (most important near panel resonance)
2) the speaker enclosure should be designed and built to prevent the panels from transmitting sound
3) the speaker enclosure should be designed and built to prevent the panels from deflecting under internal loading (most important for sealed cabinets)
Based on these points and some references in the threads I looked up some technical papers and setup a spreadsheet to calculate the resonant frequency for panels. I found the modulus of elasticity for numerous materials including BB plywood, regular plywood, MDF, aluminium, steel, granite, corian, OSB and something called Paperwood. These simple calulations show that steel and aluminium allow for the largest panels at a given thickness and a given panel resonance. The next best of the materials I checked out is BB plywood. Based on this BB plywood is a good material to satisfy point #1 above since it allows for the largest distance between braces of the easily available and easily workable materials. Does anyone know how to calculate the resonant frequency when laminating different materials?
Now how do I calculate which materials satisfy points #2 & #3 above ?
Regarding point #2 above, people have mention that the materials should be internal damped. I assume this means that the sound waves (longitudinal and transverse) should be turned into heat as they travel in the material. People have also mentioned that CLD does this as the sound wave travels through the layers. Does anyone know how to compare the internal damping of materials?
Regarding point #3 above, I've found equations for calculating the deflection of a plate under a load and a table that relates pressure to dB for sound. Does anyone have any equations for plates made when you laminate different materials?
Read all 583 posts on the 59 pages over the past few days and i got say mybrain hurts a bit. Still trying to digest all the great info. If I can recap the main points I've pulled out from what I've read :
1) the speaker enclosure should be designed and built to prevent the panels from vibrating (most important near panel resonance)
2) the speaker enclosure should be designed and built to prevent the panels from transmitting sound
3) the speaker enclosure should be designed and built to prevent the panels from deflecting under internal loading (most important for sealed cabinets)
Based on these points and some references in the threads I looked up some technical papers and setup a spreadsheet to calculate the resonant frequency for panels. I found the modulus of elasticity for numerous materials including BB plywood, regular plywood, MDF, aluminium, steel, granite, corian, OSB and something called Paperwood. These simple calulations show that steel and aluminium allow for the largest panels at a given thickness and a given panel resonance. The next best of the materials I checked out is BB plywood. Based on this BB plywood is a good material to satisfy point #1 above since it allows for the largest distance between braces of the easily available and easily workable materials. Does anyone know how to calculate the resonant frequency when laminating different materials?
Now how do I calculate which materials satisfy points #2 & #3 above ?
Regarding point #2 above, people have mention that the materials should be internal damped. I assume this means that the sound waves (longitudinal and transverse) should be turned into heat as they travel in the material. People have also mentioned that CLD does this as the sound wave travels through the layers. Does anyone know how to compare the internal damping of materials?
Regarding point #3 above, I've found equations for calculating the deflection of a plate under a load and a table that relates pressure to dB for sound. Does anyone have any equations for plates made when you laminate different materials?
I can't answer your questions but I have a couple of things to say about your thoughts.
I think CLD really addresses #1. I think the larger motions at resonance create more shear forces and allow this to work.
#2 and #3 seem to be best controlled to the extent possible with increasing stiffness and mass - thicker panels and more bracing.
#4 Isolating the drivers from the canbinet to the extent possible may help also.
I think CLD really addresses #1. I think the larger motions at resonance create more shear forces and allow this to work.
#2 and #3 seem to be best controlled to the extent possible with increasing stiffness and mass - thicker panels and more bracing.
#4 Isolating the drivers from the canbinet to the extent possible may help also.
Thanks for the reply.
I've been wondering about CLD. Some technical papers I've read show CLD to be very effective above 30 Hz so that should help in the woofers and midrange boxes. These papers also state that if you use solid middle layer like rubber, thicker is better but if you use a "liquid" middle layer such as Green Glue thinner (to a point) is better. These papers don't say anything about how relationship between deflection and effectiveness.
Based on further reading, sound transmission seems to have 2 components :
1) How effectively does sound transfer from the air into the solid?
2) How much of the sound in the solid is absorbed (converted to heat as it travels)?
The transfer seems to be related to the critical or coincidence frequency while the absorption of sound depends on the material properties. Found a chart that shows that cork, rubber, certain plastics, and visco-elastic polymers are best.
I'm guessing here, but ideally you'd want to transfer as much of the energy (sound/vibration) into a material that absorbs sound as you can. Finding those materials and using them in a composite layer aproach may be the best way to go.
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Solid Wood Info
For anyone that is thinking of using solid wood this article may be of interest.
http://www.amjbot.org/cgi/reprint/93/10/1439.pdf
For anyone that is thinking of using solid wood this article may be of interest.
http://www.amjbot.org/cgi/reprint/93/10/1439.pdf
Hi All,
After lots of searching and reading, it seems there is no common available material that really good at keeping the sound that is in the speaker enclosure contained within the enclosure ince the frequency of the sound gets low. One article lists the transmission loss at 15 dB for 1/2" plywood at 100 Hz and 12 dB for 1/4" hardboard. Not sure if Balsa or cork are a whole lot better at these low frequencies.
"Sounds" like keeping the designing panels of an enclosure to prevent sound transmission at those low frequencies is going to be downright impossible.
After lots of searching and reading, it seems there is no common available material that really good at keeping the sound that is in the speaker enclosure contained within the enclosure ince the frequency of the sound gets low. One article lists the transmission loss at 15 dB for 1/2" plywood at 100 Hz and 12 dB for 1/4" hardboard. Not sure if Balsa or cork are a whole lot better at these low frequencies.
"Sounds" like keeping the designing panels of an enclosure to prevent sound transmission at those low frequencies is going to be downright impossible.
One More Post Today,
On the positive side, another one of my objectives is going to be darn easy to achieve.
The panels of even poorly built speakers are unlikely to deflect due to the internal pressure. It seems very little pressure is actually generated when creating even loud sounds. 100 dB at 1 meter from the source results in 2 Pa and 168 dB at 1 meter results in 5000 Pa (or less than 1 psi) according to a wikipedia page. another way to look at this is Boyles law (Boyle's Law) which states that Pressure times Volume is a constant (assuming temperature is constant). Using this for a subwoofer I am designing with an internal volume of 115 liters, the movement of the speaker (10 mm at 106 dB) changes the volume by 0.79 liters resulting in a 0.1 psi pressure increase or decrease. Bracing will not be a problem even if we want to keep deflections below 0.01 inches.
On the positive side, another one of my objectives is going to be darn easy to achieve.
The panels of even poorly built speakers are unlikely to deflect due to the internal pressure. It seems very little pressure is actually generated when creating even loud sounds. 100 dB at 1 meter from the source results in 2 Pa and 168 dB at 1 meter results in 5000 Pa (or less than 1 psi) according to a wikipedia page. another way to look at this is Boyles law (Boyle's Law) which states that Pressure times Volume is a constant (assuming temperature is constant). Using this for a subwoofer I am designing with an internal volume of 115 liters, the movement of the speaker (10 mm at 106 dB) changes the volume by 0.79 liters resulting in a 0.1 psi pressure increase or decrease. Bracing will not be a problem even if we want to keep deflections below 0.01 inches.
Ok I read half so far. Planet10,
I don't really see where we differ (with one exception maybe). I think bracing is important. It pushes the resonance where there is less energy to excite it. I don't think adding something to the walls to dampen them is useful for a wood enclosures. I do think that CLD done well is useful as it will lower the energy transmitted at panel resonance (due to energy loss via heat). I do think adding damping material to a box can reduce reflected higher freq. waves (dense material like OW 705 can absorb a bit lower do to density). This does not damp walls per se. You say that the biggest contributor to vibration is mechanical via the driver - so do I. You say that push-push cancels this. I say I don't know but I like the idea of isolation. Last you did not know Fir was a pine and neither did I until I lived in WA state. But I knew what an accelerometer was since I have a degree in Physics.
I don't really see where we differ (with one exception maybe). I think bracing is important. It pushes the resonance where there is less energy to excite it. I don't think adding something to the walls to dampen them is useful for a wood enclosures. I do think that CLD done well is useful as it will lower the energy transmitted at panel resonance (due to energy loss via heat). I do think adding damping material to a box can reduce reflected higher freq. waves (dense material like OW 705 can absorb a bit lower do to density). This does not damp walls per se. You say that the biggest contributor to vibration is mechanical via the driver - so do I. You say that push-push cancels this. I say I don't know but I like the idea of isolation. Last you did not know Fir was a pine and neither did I until I lived in WA state. But I knew what an accelerometer was since I have a degree in Physics.
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Douglas Fir is a pine. I'm sure there are firs that are firs
I like to couple the driver to as much of the box as possible to get the maximum amount of damping for its spurious mechanical energy.
I don't have an accelerometer, but i regularily use a mechanic's stethoscope. CLD has some decided benefits, but using the rationale that is embedded in this thread i can build boxes with no audiable energy exiting the wall panels, so haven't had the need to go the extra mile w CLD anymore.
dave
Well there is more than one way to skin the cat but I can say I like the way you do it.
I am sure that you build them as well as anyone does. When you say "i can build boxes with no audiable energy exiting the wall panels" is that for BB only? If it were for others than you could not hear a difference no matter what the material was.
I am sure that you build them as well as anyone does. When you say "i can build boxes with no audiable energy exiting the wall panels" is that for BB only? If it were for others than you could not hear a difference no matter what the material was.
my 2 pence,
the difference as far as i can see between MDF and decent ply, as far as speaker boxes go, is NOT the stiffness difference between them. Sure good ply is about15% stiffer perpendicular to the (again perpendicular) grains, due to wood grain tension, but weaker in compression. Also this introduces a 'springiness' to the ply that MDF, with its lossy fibrous structure does not possess in equal measure. This is a plus for MDF IMHO. shorter spurious vibration and all that. besides that when weighing up both compression AND tension forces on a board, which will be equal or thereabouts; I dont see any real significant difference between the two. MDF may be better, SLIGHTlY, when used in identical constructions, due to the more damped 'springiness' of the media. This means, to me at least, that MDF exhibits a more wideband lower amplitude vibrational resonance-low Q low F-and if braced well, or used in thr right way should be far better than ply. Real wood would be great to use, i just cant get over the fact that solid wood will always add tone and colouration to the sound. thats fine for music PRODUCTION, but not REPRODUCION, as far as im concerned.
maybe i will use a 'sandwhich' of 5mm MDF/HDF, 10mm sand/cement/concrete/rubber compound, with 20mm MDF on exterior. That should be stiff enough when braced sufficiently, and better damped than either of the two media on its own.
OR....maybe i will go solid wood route, and build oversize thickness, layering with MDF, or perhaps GRPing the whole inside of the constructed box to a good thickness to increase the rigidity....hmmmmmmmmmmm
the difference as far as i can see between MDF and decent ply, as far as speaker boxes go, is NOT the stiffness difference between them. Sure good ply is about15% stiffer perpendicular to the (again perpendicular) grains, due to wood grain tension, but weaker in compression. Also this introduces a 'springiness' to the ply that MDF, with its lossy fibrous structure does not possess in equal measure. This is a plus for MDF IMHO. shorter spurious vibration and all that. besides that when weighing up both compression AND tension forces on a board, which will be equal or thereabouts; I dont see any real significant difference between the two. MDF may be better, SLIGHTlY, when used in identical constructions, due to the more damped 'springiness' of the media. This means, to me at least, that MDF exhibits a more wideband lower amplitude vibrational resonance-low Q low F-and if braced well, or used in thr right way should be far better than ply. Real wood would be great to use, i just cant get over the fact that solid wood will always add tone and colouration to the sound. thats fine for music PRODUCTION, but not REPRODUCION, as far as im concerned.
maybe i will use a 'sandwhich' of 5mm MDF/HDF, 10mm sand/cement/concrete/rubber compound, with 20mm MDF on exterior. That should be stiff enough when braced sufficiently, and better damped than either of the two media on its own.
OR....maybe i will go solid wood route, and build oversize thickness, layering with MDF, or perhaps GRPing the whole inside of the constructed box to a good thickness to increase the rigidity....hmmmmmmmmmmm
MDF is not nearly as stiff (the delta is more than 15% if you use the right stuff). Weaker in compression? I can't see that. MDF -- even HDF is pretty squishy.
Its big deficit is that higher mass, lower stiffness, and less damping means that resonances are lower in frequency, lower in Q (therfore more audible), and has significant energy storage. What you get is a low-level time smeared signal oozing from the panels that buries the low level stuff, limiting the downward dynamic range.
AFAIC, MDF is not a suitable material for building loudspeakers out of.
dave
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