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MDF or plywood?

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plywood?
26K views 73 replies 21 participants last post by  SinCron 
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#1 ·
I want to know what difference fellow members find when the subbox is built in mdf of plywood.
 
#2 ·
Re: mdf or plywood?


MDF is hard to work with and heavy. A properly designed and braced cabinet doesn't have to be heavy. I use plywood exclusively, and 1/2" at that, and my cabs do not vibrate. But bracing entails higher labor costs, so manufacturers prefer to use heavy materials instead, and MDF especially, as it's both heavy and cheap. One benefit of DIY is that you can do a better job on the cabinet and not be concerned about the labor cost.
 
#7 ·
Re: mdf or plywood?

Would you guys still use 1/2" material if you were building an LLT? Say something 4' X 4' X 2' for example?
By LLT you mean EBS right?

I usually stick with 3/4" and add bracing where needed. A box that big I would normally do a double baffle as I usually like to flush mount the drivers. I've found with ply you don't need much bracing since it is structurally superior to MDF to begin with.

Best,
Mark
 
#9 ·
Re: mdf or plywood?

It is very rare for panel resonances to be an issue with subwoofers that have an Fc (crossover point) at or below 100Hz. If you are really worried about resonance in a large design just ensure there is a bracing every 6-8" and panel resonance will be more than fully attenuated in the typical range of a subwoofer.The real issue with panel resonance is in the 150-1000Hz range.

As far as ply vs MDF. No question ply wins, it is lighter, but actually more stiff (if cabinet grade material is used). This means the ply will actually be less resonant than a similarly braced piece of MDF.

-Andrew
 
#11 ·
Re: mdf or plywood?

So with everything said above, is plywood ok for an IB manifold? No way I can get an MDF manifold in the attic, no way I can assemble on up there either. I figure I can do a little bracing as well, it would have to be right down the middle, but I guess it's better than nothing.
 
#12 ·
Re: mdf or plywood?

So with everything said above, is plywood ok for an IB manifold? No way I can get an MDF manifold in the attic, no way I can assemble on up there either. I figure I can do a little bracing as well, it would have to be right down the middle, but I guess it's better than nothing.
Absolutely plywood is ok for that. Which comments thus far have made you think otherwise? :scratch:

I use plywood whenever I can afford it. My current beast of a subwoofer is a real mish-mash of materials - plywood for the outer 'shell', particleboard (yes, not MDF) for the inner front and rear baffles, and hardboard screwed liberally to the particleboard as trim. Internal bracing is a complete frame of 2x2 to hold all the panels together, and front to back bracing using six 2x4s. I had almost no tools at the time of construction, and not much money. I also didn't want a box that weighed 200+ pounds. 130 pounds is enough! Unfortunately now it's more like 147 pounds thanks to the Tempest-X upgrade.
 
#13 · (Edited)
Re: mdf or plywood?

Without A doubt if you have the wood working skills 1"-2" thick MDF will give you the best finnish and (sound quality :hide:) in the end product especialy if you want it painted, just look what all the High end home audio sub manufactures like JL Audio's Fathom subs are made out of and most high end Speakers.... But MDF is very easily marked and makes heaps of fine dust when cuting and routing also MDF is very poisonous so it pays to wear A good quality Dust mask and eye protection.....

Ply is more durable and used alot in the Pro audio industry for speakers and subs, mainly because of its lighter weight and durability.....

Cheers.....
 
#14 ·
Re: mdf or plywood?

Without A doubt if you have the wood working skills 1"-2" thick MDF will give you the best finnish and (sound quality :hide:) in the end product especialy if you want it painted, just look what all the High end home audio sub manufactures like JL Audio's Fathom subs are made out of and most high end Speakers.... But MDF is very easily marked and makes heaps of fine dust when cuting and routing also MDF is very poisonous so it pays to wear A good quality Dust mask and eye protection.....

Ply is more durable and used alot in the Pro audio industry for speakers and subs, mainly because of its lighter weight and durability.....

Cheers.....
This is not really the case. Most mass produced speakers are made from a MDF product because they it is far easier and less expensive to machine than plywood, not because they are superior. The opposite is true, in fact. MDF less stiff than plywood meaning it is likely to be more resonant, but of course MDF is cheaper. Just because the well known brands use the material does not make it good. It just means it is cheap and easy to work with.

Also note, increasing thickness of a material (using 1-2" over 3/4") is an extremely inefficient way to minimize resonances and cabinet flex. Rather, use of a constraint layer and efficient XYZ bracing techniques is a far superior way to mitigate such issues. Now, with the typical passband of subwoofers the differences between ply and MDF are not an issue, but with loudspeakers it is an issue.

Additionally, it requires more than a good dust mask to filter MDF particles due to the use of formaldehyde a chemical rated respirator should be used.
 
#15 ·
Re: mdf or plywood?

Hi avaserfi,
I guess We agree to disagree on which is the better product to use for building A sub or speakers when given the 2 choices MDF or PLY....

I will say IMO that MDF is A better product to work with and gives very good results if you have the wood working skills, design and construct the box correctly...
The down side of MDF is that of course it is very poisonous :yikes:....

I am pretty sure the B&W 800 series speakers are made in part with PLY.....

Cheers....
 
#16 ·
Re: mdf or plywood?

Bill said:
I'd never build a reflex box that large, in the same space a folded horn would work far better
Not really. If one's subwoofer goals are a naturally flat and extended frequency response, low distortion, and ample headroom, there is no alignment that can best a LLT on a driver for driver basis.

mrogowski said:
The term is known, understood and recognized by the engineering community (AES, IEEE, etc). The term 'LLT' is little more than a customized EBS and is known only in forums like this one. Mention LLT outside these forums and you will get a bunch of blank stares..
EBS is an extremely generic and vague alignment description that doesn't ensure any level of performance and has very limited characteristics. From diysubwoofers.org:

diysubwoofers.org said:
The volume of the box is larger (sometimes significantly larger) than that of a maximally flat ported system using the same driver.
The tuning frequency of the enclosure is at or close to Fs, the driver's resonance frequency
The power handling of the EBS is lower in the midbass frequencies when compared to the maximally flat systems. However, the power handling at lower frequencies is usually better.
As with the standard ported systems, almost any driver can be used. However, the best results will be obtained with drivers of Qts <0.35.
Based on those "guidelines", an EBS can be a 50 liter enclosure tuned to 35hz using a 1" diameter port :gulp:

LLT is an alignment that meets a certain set of guidelines that ensure a subwoofer that achieves the best balance of linear FR, non linear FR, and headroom for a given, acceptable driver for the dollar. Is LLT a recognized, audio community term? Who cares :daydream:
 
#17 ·
Re: mdf or plywood?

I just finished building my second IB manifold. My first was IB was built from MDF, this one from ply. They were both very strong. I could stand on either without issue. I can pick up the new manifold which will house 4 18's with one hand, I had to have help picking up the 2 15" manifold. Very important to me as this will be an attic mount. I did give the wood a coat or two of paint to act as a moisture barrier. Next weekend it should go up.
 
#19 ·
Re: mdf or plywood?

Sure. All of the pictures are over in the IB area in the thread IB II, but here are a few. As far as design, there really is not one. It needed to hold 4 18's and fit between 24" on center ceiling joists. I'm not a very good wood worker, but, this box is solid. I've stood on it and it did not even creek.... I'm 6'3 and weigh quite a bit. I sat the twins on top of it, it held up for that too.

Like I said, it's just an ugly box...


Mock up



Glued and Screwed


Holes are cut


Like I said, I can stand on it


The other 2 drivers should be here on Thursday


I wanted them to all be innies,but, it just did not work. I'll have to do all of them as outties now, that's ok.. I think. I hope the rafters don't get in the way once I get it in the attic. If so, I can mount the 2 rafter side drivers from the inside, but, they will lose some of the extra support, No way i can fit back in there to install from the attic side, it'll all be done from the floor except for running wires.

Oh, I painted the inside black as you can see, just so there is no distracting contrast between the drivers and the wood. The drivers are MJ18's, i got a of a deal on them from Otto. I also gave the outside of the box a coat of enamel spray paint I had left over... Not to make it pretty, but, to help as a moisture barrier.

Before the install, I plan to caulk the joints, maybe add a few glue blocks to the inner joints and touch up the spray paint. Still need to cut the hole and get the grill cover figured out, but, I think I'm just going to make a basic frame out of 1x2 and then mount an air return vent to that. The biggest size I can find at Lowes is 20x20 and the hole is going to be an bit larger than that as the box is 21x19
 
#21 ·
Re: mdf or plywood?

This is my first post on this forum but have been building speakers and furniture for years. It amazes me that there is this growing consensus that plywood is a better building material for speakers than MDF. While it might be lighter and structuaraly stronger, I can't see getting the same accustics from it. The test for me is simple, pound on the side of a plywood box and a MDF box. MDF is ten times denser, hence the reason why it is used for speakers.

People seem to think that because plywood costs more, it is a better building material for speakers and I don't think that is true. To suggest that high end speaker companies use it because it is cheaper is just crazy. 1" MDF is about $50 a sheet and 1" ply is about $100 a sheet, that would easily make a set of speakers. I can't confirm this, but every high end speaker I have seen is MDF.

Now, using if for the reasons of easier to work with, that is a very good reason.

FYI- Almost all MDF is now made without formaldehyde making it not as dangerous as it use to be.

A picture of my Seas thor... BTW- they call for MDF in the building instructions.
 

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#25 · (Edited)
Re: mdf or plywood?

...
People seem to think that because plywood costs more, it is a better building material for speakers and I don't think that is true. To suggest that high end speaker companies use it because it is cheaper is just crazy. 1" MDF is about $50 a sheet and 1" ply is about $100 a sheet, that would easily make a set of speakers. I can't confirm this, but every high end speaker I have seen is MDF.

Now, using if for the reasons of easier to work with, that is a very good reason.
...
I certainly wouldn't say that manufacturers use MDF only because it's cheaper. That's only one factor - though one of vastly more importance to a high production manufacturer than a home builder. I would say of equal importance are it's ease and stability of machining, and uniformity for applying a veneer.

I have seen several high end speakers that do not use MDF, at least for the primary shell of the cabinet. Although true enough, the overwhelming majority do.

I use plywood myself because of the lighter weight and the fact that it comes with a ready to stain exterior. Either plywood or MDF can make a fine cabinet. I believe the cabinet shape, as well as the internal structure, bracing, and stuffing, can all play a larger role in the final sound, than the wall material does.
 
#23 ·
Re: mdf or plywood?

You are right MDF is far more dense, but cabinet grade ply being more stiff allows for a less resonant cabinet. That is why ply is superior, of course, if MDF is properly used a completely inert cabinet can result.
By cabinet grade do you mean A-1? This is not what you find at your local home depot and basically it is the same wood, just better veneer on it. If you are going for superior, why not recommend 1" ply?

I will still disagree that is is superior.... Maybe I will do a test and build myself a sub box out of ply and compare them...
 
#26 ·
The Danish factory where the High End B&W 800 series are made use's A 35mm thick sheet of PLY wood pressed into shape + real wood veneer for the outer skin for the main cabinet body that hold the Larger woofer Drivers and Matrix internal bracing made from MDF....

But I Agree with Wickedrx7 that 1"-2" thick MDF is the superior product in many ways for Speaker Building,
IMO the biggest + for MDF is the finnish that can be obtained and ease to work with if you posses the Gear and wood working Skills as compared to PLY....

Cheers...
 
#27 ·
I'd use MDF for sealed enclosures and plywood for ported. The possibility of "voids" in ply makes perfect sealing difficult. For ported enclosures the perfect sealing quality is not as important.
The mechanical linear strength properties of (either) material can be braced to reduce spurious vibrations to meet design minimums.
Over sized sub enclosure designs IE: LLT, IB, EBS, Reflex, folded horn, etc. would benefit from weight reduction using ply. Some of the over sized sub enclosure designs are able to use "sonotube", a cardboard like material shaped into tubes of various diameters, used in the construction industry to form concrete piers. No one that I've read yet has tested and determined the vibration or inert characteristics and quality of sonotube.
 
#28 ·
Ive found that mdf seems to sound better and the walls of the box vibrate less. I have found that plywood is a lot more durable, finishes nicer if you do a stain, and is a lot safer on the lungs. Ideally I would do oak or birch plywood and just reinforce with cross braces on the inside. MDF dust is some nasty stuff (Formaldehyde).
 
#36 ·
Sort of, and it has to do with your second post about dampening factor. Dampening factor is basically the resistance to the mechanical motion from other forces. Think of it as drag. In the case of a speaker cabinet the primary source of dampening would be the internal resistance of the material. In an ideal spring mass sytem with zero dampening, amplitude would gradually work it's way to infinity at a rate proportional to energy input. Of course this can never happen in real life due to the mechanical limitations of the 'spring' and dampening.

For the debate of MDF vs Ply, dampening needs to be considered as the amplitude of frequencies near resonance will be dependent on this factor. Regardless, moving the resonant mode outside the bandwidth of the system will be the most effective method of reducing cabinet vibration.
 
#38 ·
Right. Outside of natural resonance, vibration drops off but does not disapear completely and the natural mode can be excited by harmonics, though at much lower levels. The amplitude of these vibrations is controlled by the dampening factor of the material but can more directly reduced through the use of bracing.

A cross brace running the full length of 2 opposing surfaces serves two purposes. For one, it cuts the cross section in half, and thus it's fundamental mode of resonance is doubled. For another, it couples two opposing surfaces which are each trying to move in opposite directions, thus cancelling any vibration less the elasticity in the brace (for all intensive purposes this can be assumed to be zero).

The major source of cabinet resonance in most speakers usually occurs around a few frequencies and is a result of cabinet construction that allows a natural resonance to be excited. Removing cabinet resonance has less to do with whether it is constructed from MDF or Ply than is does from proper sizing, bracing and shaping.
 
#39 ·
Dampening factor is basically the resistance to the mechanical motion from other forces.
Duh. OK, makes sense. I didn't quite think it through the other night. I suspect you can increase resistance to vibration by coupling two materials of different resonant properties and stiffness together.

A cross brace running the full length of 2 opposing surfaces serves two purposes. For one, it cuts the cross section in half, and thus it's fundamental mode of resonance is doubled. For another, it couples two opposing surfaces which are each trying to move in opposite directions, thus cancelling any vibration less the elasticity in the brace (for all intensive purposes this can be assumed to be zero).
That leads to questions on the effective use of the material you have chosen. I know its ouside of the thread topic, but these two things are very closely related and should both be considered.

I have often wondered if, when given the choice of 1x1/2" brace vs 2x1/4 braces, if we would not be better served by multiple thinner braces.

That leads to another question. If you add mass via MDF to reduce a modal resonance by half, and then add a brace cutting the sheet in half thus doubling the modal resonance, are you not back to where you started (but a lot heavier)? I suspect not given that a greater mass will require greater energy to excite, but I wonder if you are limiting the effectiveness of your design because you would still have a modal resonance that will be excited by frequencies being produced by the driver.
 
#40 ·
I have often wondered if, when given the choice of 1x1/2" brace vs 2x1/4 braces, if we would not be better served by multiple thinner braces.

That leads to another question. If you add mass via MDF to reduce a modal resonance by half, and then add a brace cutting the sheet in half thus doubling the modal resonance, are you not back to where you started (but a lot heavier)?

Good questions... Now that you've got me thinking about this some more I don't think adding a brace would halve the resonant frequency. Even though it makes sense from traditional wave propogation it doesn't fit nicely into the root(k/m) equation. Changing these distances would have to change the spring constant. Adding mass would alter the frequency according to that equation so doubling the mass wouldn't exactly halve resonance.

The more I've been thinking about this the more I think that a single point brace could be nearly as effective as one running the full length of the surface like what is traditionally done, giving back valuable internal volume and reducing weight and building complexity. In your statement, it would certainly be better to spread the braces out vs one thicker one.
 
#41 ·
Ask enough questions and sooner or later you're bound to ask a good one. :devil:

Some of this stuff is not as strait forward as it would seem at a glance. Given the size and weight of some of the subs built here, it would be nice to know what has maximum effect for minumum weight penalty. I wish I had taken more math and physics in school. It would have been useful. Confusing, but useful.
 
#42 ·
The more I've been thinking about this the more I think that a single point brace could be nearly as effective as one running the full length
If I understand damping properly, it is the process of converting energy stored as momentum to energy stored as heat through friction.

In order for the single point brace to be effective, enough energy being applied to the mass, the side of the box, has to be transfered to the single point brace rather than vibrating the mass (which transfers energy to the surrounding air as sound waves). Something tells me that dosn't happen.
 
#43 ·
In order for the single point brace to be effective, enough energy being applied to the mass, the side of the box, has to be transfered to the single point brace rather than vibrating the mass (which transfers energy to the surrounding air as sound waves).
The brace serves as a point on the surface which is constrained and cannot move. The material could still flex between the brace and the next point of constraint.
 
#46 ·
It seems one important aspect of resonance is being forgotten, quality factor (Q). Audibility of resonances has been established based on Q, frequency, source material and acoustic environment all related to transducer output level.

One example where understanding this situation is vital would be a tower speaker which has each set of drivers divided into their own sub chambers using typical bracing techniques. Such a technique would seem to be superior in terms of minimizing resonances due to added bracing, but as the panels are divided out the panel Q is likely lowered causing more easily excited resonances that will be more audible over a larger range.
 
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