Background:

For many years I have used MDF for construction of speaker enclosures. A long time ago I accepted this as gold standard and best practice. The argument was made(by someone else and I accepted this info) that the density of the material was the asset that made it most desirable for speaker enclosure construction. From memory I recall that the higher density disposed MDF to a higher resonance frequency. I took this info and really never questioned it.....

In discussing this with another member It appears an important part of the this behavior may have been overlooked by myself and whoever suggested this to me. The Elastic modulus does in fact play a part in most equations that I find determining panel resonance. Normally depending on the application it is some derivation that includes but not limited to the following:

E E= the elastic modulus of the material

M M= the mass of the material

By this relationship one would conclude that as you increase (E) so would the resonant frequency. Also, as mass increases the resonant frequency decreases. This document shows that the modulus of elasticity of regular plywood is at least 2X MDF's.

Is there a formula to calculate a panel resonance of say a speaker enclosure panel? This should be out there somewthere. We should be able to plug in the material's properties for a given panel size and calculate its resonance right? I'm still assuming the goal would be to push the panel resonance high enough to be outside of the bandwidth of the speaker.

Another aspect which I havent heard discussed much is the Damping Ratio of the material or how long it continues to oscillate after the excitation is removed.

So which Is it? MDF or Plywood?

For many years I have used MDF for construction of speaker enclosures. A long time ago I accepted this as gold standard and best practice. The argument was made(by someone else and I accepted this info) that the density of the material was the asset that made it most desirable for speaker enclosure construction. From memory I recall that the higher density disposed MDF to a higher resonance frequency. I took this info and really never questioned it.....

In discussing this with another member It appears an important part of the this behavior may have been overlooked by myself and whoever suggested this to me. The Elastic modulus does in fact play a part in most equations that I find determining panel resonance. Normally depending on the application it is some derivation that includes but not limited to the following:

E E= the elastic modulus of the material

M M= the mass of the material

By this relationship one would conclude that as you increase (E) so would the resonant frequency. Also, as mass increases the resonant frequency decreases. This document shows that the modulus of elasticity of regular plywood is at least 2X MDF's.

Is there a formula to calculate a panel resonance of say a speaker enclosure panel? This should be out there somewthere. We should be able to plug in the material's properties for a given panel size and calculate its resonance right? I'm still assuming the goal would be to push the panel resonance high enough to be outside of the bandwidth of the speaker.

Another aspect which I havent heard discussed much is the Damping Ratio of the material or how long it continues to oscillate after the excitation is removed.

So which Is it? MDF or Plywood?