Plywood or MDF?

[greg_mcquaid]

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

[Cal Weldon]

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"

[nunayafb]

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.

[Bare]

For a Sub?? double layers of MDF is would be a good choice.
Significantly superior to even one layer MDF which in turn is a whole league ahead of Plywood unless it's baltic birch in which case a single layer of MDF is only 'better' rather than significantly better

[Cal Weldon]

Originally posted by nunayafb
While I disagree that the selection is subjective

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.

[planet10]

I'd use nothing but well-braced BB plywood. If i was building a push-push woofer (as i usually do), i'd use 15 mm for a small one, 18mm for a larger one.

dave

[moray james]

making a composite panel from two thin wall sheets where the panels are seperated at a central point by a disk (of equal thickness) and the edges are then glued and clamped? This then tensions the panel. The void can be filled with sand after assembly.

[planet10]

Originally posted by moray james
making a composite panel from two thin wall sheets where the panels are seperated at a central point by a disk (of equal thickness) and the edges are then glued and clamped? This then tensions the panel. The void can be filled with sand after assembly.

That is a very interesting idea... very simple, very clever.

dave

[greg_mcquaid]

On the subject of damping do all subwoofer designs need to have damping inside? What affect does damping have on the overall sound of the subwoofer?

Sorry for all the questions but i want to make sure i get it all correct before i go ahead and build.

Thanks,
Greg

[planet10]

Originally posted by greg_mcquaid
On the subject of damping do all subwoofer designs need to have damping inside? What affect does damping have on the overall sound of the subwoofer?

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