Hi,
I will eventually get around to building my subwoofer but i wanted to know if i should use Plywood or MDF? Also will using a certain type of wood effect sound quality?
The cabinent will be vented and housing a 12" subwoofer with a large port and largish plate amp, dont know if this info will help.
Thanks,
Greg
I will eventually get around to building my subwoofer but i wanted to know if i should use Plywood or MDF? Also will using a certain type of wood effect sound quality?
The cabinent will be vented and housing a 12" subwoofer with a large port and largish plate amp, dont know if this info will help.
Thanks,
Greg
Hi Greg,
There are many threads concerning this here as it is both subjective and controversial.
I use plywood, others MDF. It depends on where you live (humidity) and the difference in cost. Here in BC, plywood is affordable so I use only it unless I need exactly 3/4". The plywood is metric so it measures 23/32"
There are many threads concerning this here as it is both subjective and controversial.
I use plywood, others MDF. It depends on where you live (humidity) and the difference in cost. Here in BC, plywood is affordable so I use only it unless I need exactly 3/4". The plywood is metric so it measures 23/32"
While I disagree that the selection is subjective the threads that discuss them probably are. From what I remember from a while back is that mdf has slightly superior damping properties, so if we assume that the only parameter that matters to you is damping and that humidity, and toxic dust etc. are things that you would deal with then go with mdf.
However, if you are designing a box solely based on the damping and physical properties of the wood then you already have a seriously flawed design, by that I mean flat panels flex and therefore resonate.
I recommend you focus on bracing and damping, where damping is more crucial than bracing (Loudspeaker Cookbook, Dickason).
Bracing only bisects the panel geometrically, shifting the natural frequency upwards (the level is also reduced a little due to the difficulty in rigid panels resonating at high frequencies) whereas damping attacks the vibration itself.
However, if you are designing a box solely based on the damping and physical properties of the wood then you already have a seriously flawed design, by that I mean flat panels flex and therefore resonate.
I recommend you focus on bracing and damping, where damping is more crucial than bracing (Loudspeaker Cookbook, Dickason).
Bracing only bisects the panel geometrically, shifting the natural frequency upwards (the level is also reduced a little due to the difficulty in rigid panels resonating at high frequencies) whereas damping attacks the vibration itself.
nunayafb said:
Fair enough. The reason I chose the term is that I have had the opportunity to listen to identical systems made from both ply and MDF in side by side listening tests. There is a difference and I prefer the sound of plywood. I found the MDF sounded lifeless.
At this point you might say lifeless is the point of the cabinet but in the end it comes down to preference. To me, plywood sounds better and there's no meter in the world that can measure the enjoyment factor.
greg_mcquaid said:
There is a potential here for confusion. There are 2 kinds of damping that can be discussed. Panel damping which was mentioned in respect to the MDF panels. And then there is airspace damping. Whether it is needed in a sub at all is open to debate, i would at least line the walls -- and if you are building a BR that is all you would do. In a TL.quarter-wave design the airspace damping is an essential part of the design. Ina sealed box, dampng can be used to increase the apparent size of the box up to ~25%.
dave
Probably doesn't matter which coloration you choose (MDF or plywood) as the vent will probably provide all the coloration you need.
With due respect to nunayafb, all wood panel selection is subjective. By definition, a panel will vibrate - how much (and what flavor) depends on the type of wood.
Concrete avoids this problem (almost). Using other techniques like Stig Erik Tangen Almighty Subwoofers or Tony Gee's Andromeda will reduce the panel vibration to a very low figure also while still using wood. Even Wilson Audio's 'X' (is it Corian) can't completely get rid of coloration (no matter how much is spent on advertising).
With due respect to nunayafb, all wood panel selection is subjective. By definition, a panel will vibrate - how much (and what flavor) depends on the type of wood.
Concrete avoids this problem (almost). Using other techniques like Stig Erik Tangen Almighty Subwoofers or Tony Gee's Andromeda will reduce the panel vibration to a very low figure also while still using wood. Even Wilson Audio's 'X' (is it Corian) can't completely get rid of coloration (no matter how much is spent on advertising).
MDF or Ply?
I had this discussion with Dan Wiggins many years back, and while MDF is (perhaps) preferable for mids and treble, Ply works great for subs. It's stiffer, so just about any panel resonance will be outside of the bandpass, especially if you have incorporated a shelf brace of some sort.
Back in the 70's Speakerlab, here in Seattle, built their cabinets out of a 3/4 inch ply and 1/2 inch particle board laminate. Ply on the outside of course :^) Solid as a rock, it is heavy though. With long throw Sub drivers that's actually a plus, you don't want them "walking" around anyway.
In fact, the first Shiva Subwoofer Driver ever sold (yeah, I was the buyer) went into a downfiring 85 Liter BR cabinet constructed in this manner. Oak veneer with a marble top and an Apex Jr. plate amp. The owner (an old buddy of mine) is still using it and has never had any complaints.
Just to be clear: it's particle board, not MDF, that I'm talking about.
Best Regards,
TerryO
I had this discussion with Dan Wiggins many years back, and while MDF is (perhaps) preferable for mids and treble, Ply works great for subs. It's stiffer, so just about any panel resonance will be outside of the bandpass, especially if you have incorporated a shelf brace of some sort.
Back in the 70's Speakerlab, here in Seattle, built their cabinets out of a 3/4 inch ply and 1/2 inch particle board laminate. Ply on the outside of course :^) Solid as a rock, it is heavy though. With long throw Sub drivers that's actually a plus, you don't want them "walking" around anyway.
In fact, the first Shiva Subwoofer Driver ever sold (yeah, I was the buyer) went into a downfiring 85 Liter BR cabinet constructed in this manner. Oak veneer with a marble top and an Apex Jr. plate amp. The owner (an old buddy of mine) is still using it and has never had any complaints.
Just to be clear: it's particle board, not MDF, that I'm talking about.
Best Regards,
TerryO
Cloth Ears said:
with due respect... Im not sure why you are saying that when you are agreeing with my original statement.
You are also reiterating my statement that all panels flex and therefore resonate.
To my knowledge there are no reasonable woods that have any significantly greater stiffness than any other woods, so bracing is required by geometry not material. Physical testing has shown that mdf has higher damping than other woods (most?), so based on the ability of a material to dampen vibes mdf has a slight advantage. However, if you add a damping layer to plywood or any wood for that matter it's ability to dampen vibes will far exceed any woods internal damping ability making material selection trivial.
In response to concrete walls Cloth Ears, let me just say this: while it is nice to not have the walls flexing and transmitting sound, where does the sound energy go? In a perfectly rigid enclosure the sound has to be converted to heat by internal damping or it will collide with and transfer energy back to the driver.
That is why I am now a fan of dipole speakers.
nunayafb said:
Only in as far as the wood selection is subjective (you said "I disagree that the selection is subjective"), and I thought it was. I agreed with the rest of your stuff. The other option, to promote conversion to heat, is diffusion. If your inner surface is a mass of different angles and shapes, then the sound will bounce around a fair bit more than if you just have flat bare walls. I tend to do this by having the bracing have varying sizes of holes drilled in them (from about 1-6 inches in diameter).
Fair enough, I guess my problem here is the usage of the word "subjective" which means more of a personal decision, or taste. My thought processes lead me to the question is material A better than material B, and is it enough to base a decision on this, or are the differences trivial.
As far as diffusion converting sound to heat, this cannot happen unless the baffles are absorbing some energy and converting it to heat via internal damping. That pesky little law of conservation of energy is responsible for this, if you don't provide an "out" for the acoustic energy it will bounce around until the molecular friction dissipates the energy as heat. For this to happen though you need perfect reflection inside the box, since this is not possible with thin wood you will have absorption and resonance and this is where I would say that a material with high damping would help.
As far as diffusion converting sound to heat, this cannot happen unless the baffles are absorbing some energy and converting it to heat via internal damping. That pesky little law of conservation of energy is responsible for this, if you don't provide an "out" for the acoustic energy it will bounce around until the molecular friction dissipates the energy as heat. For this to happen though you need perfect reflection inside the box, since this is not possible with thin wood you will have absorption and resonance and this is where I would say that a material with high damping would help.
Does anybody use MDO? It doesn't have the grain appearance of plywood, but it's chemically treated to hold up to weather. I've seen signs that were painted 15 or 20 years ago on MDO and they haven't changed shape despite all those years of rain, sun, and snow.
Curious how it would work for an enclosure. The stuff is cheap, too. (Not as cheap as comparable plywood, but way cheaper than veneers or solid exotics.) You can get it from any sign supplier like Regional Supply or Midwest Supply and many others (obviously US examples given).
- Jon
Curious how it would work for an enclosure. The stuff is cheap, too. (Not as cheap as comparable plywood, but way cheaper than veneers or solid exotics.) You can get it from any sign supplier like Regional Supply or Midwest Supply and many others (obviously US examples given).
- Jon
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