Hello everyone,
I know enclosure bracing is a topic that has been discussed quite often but I wanted to take my own tour of the topic by simulating different Bracing types to compare them to each other. Sadly I ran in to some problems which requier experience that I am lacking and, as here are many people that can be considered experts, decided to discuss them further before publishng them in a single post.
This is where I currently stand...
...I have made several Models with the same external dimensions and implemented different Bracing strategies, like single ring Braces:
Simple diagonal Braces:
And even full out B&W Matrix Bracing:
Over all there are 15 differnet Bracing strategies implemented and compared using a Matlab script. Sadly, the results seem to be counter intuitive:
The First plot is a comparison of the maximum wall Flexing at 1 Hz to compare the overall stiffness of the different Enclosure types. The 10 to 25 mm "Braces" are just thicker Walls. And here the confusion starts. I Expected a thicker wall to be more resistent to flexing but this does not seem to be the case, which I highly doubt. And the Matrix enclosure seems to be one of the worst in the field....
The second plot is the displacement above 100 Hz vs Frequency to show the modal region of the different braces. There is not much damping going on but that may be subjective due to the presentation. Does annyone know of a method to "Rate" such modes which would make it more subjective to compare? My first Idea would be to calculate the derivative of the excursion and the sum it up as less modes mean less change in the derivative and would therefore be better, leaving psychoacoustics out of the picture for now.
Also, some comparison between real worls data and my simulations show differences as well.... just not some I would expect.... Juul[1] did some simulations and measurements, here are his results:
and here are mine:
While the Frequencys of the resonances seem to be in the same area, the amplitude is way of( be aware of the 2 dB Scale!). This is schown with the driver radiating in to the same space as the enclosure. For this Plot I replicated his Model and used his material Values. I tried to contact him but I have not recived an answer in over a month.
As for my Simulations. The bottom of the cabinet is assumed to be fixed. The Material Values for the wood parts are:
Youngs Modulus: 4 GPa
Piossons Ratio: 0.18
Density: 700 kg/m³
Bulk Modulus: 1e10 N/m²
Shear Modulus: 5.8e10 N/m²
Material damping is modeled via Rayleigh Damping with alpha = 0.251 1/s and beta = 6.35e-6 s
The driver is assumed to exert 10 N Driving Force on a 0.1 kg Membrane and is modeled as a lumped system and coupled to the enclosure via a prescribed acceleration at the mounting ring of the chassis basket. The Front of the driver radiates in to an acoustically sound hard chamber while the enclosure can radiate sound in to a free air enviroment.
Has annyone an Idea if these Values can be correct? Are there similar studys out ther which I did not find? My intuition says I have done something wrong but my expertise is limited and I would like to hear some opinions.
Have a nice weekend and I am looking forward to what I can learn.
PS: I hope I did post this right in the DIY section.
[1]https://www.google.com/url?sa=i&url...2ahUKEwiD8obgoPHvAhULahoKHeihCXAQr4kDegQIARBo
I know enclosure bracing is a topic that has been discussed quite often but I wanted to take my own tour of the topic by simulating different Bracing types to compare them to each other. Sadly I ran in to some problems which requier experience that I am lacking and, as here are many people that can be considered experts, decided to discuss them further before publishng them in a single post.
This is where I currently stand...
...I have made several Models with the same external dimensions and implemented different Bracing strategies, like single ring Braces:
Simple diagonal Braces:
And even full out B&W Matrix Bracing:
Over all there are 15 differnet Bracing strategies implemented and compared using a Matlab script. Sadly, the results seem to be counter intuitive:
The First plot is a comparison of the maximum wall Flexing at 1 Hz to compare the overall stiffness of the different Enclosure types. The 10 to 25 mm "Braces" are just thicker Walls. And here the confusion starts. I Expected a thicker wall to be more resistent to flexing but this does not seem to be the case, which I highly doubt. And the Matrix enclosure seems to be one of the worst in the field....
The second plot is the displacement above 100 Hz vs Frequency to show the modal region of the different braces. There is not much damping going on but that may be subjective due to the presentation. Does annyone know of a method to "Rate" such modes which would make it more subjective to compare? My first Idea would be to calculate the derivative of the excursion and the sum it up as less modes mean less change in the derivative and would therefore be better, leaving psychoacoustics out of the picture for now.
Also, some comparison between real worls data and my simulations show differences as well.... just not some I would expect.... Juul[1] did some simulations and measurements, here are his results:
and here are mine:
While the Frequencys of the resonances seem to be in the same area, the amplitude is way of( be aware of the 2 dB Scale!). This is schown with the driver radiating in to the same space as the enclosure. For this Plot I replicated his Model and used his material Values. I tried to contact him but I have not recived an answer in over a month.
As for my Simulations. The bottom of the cabinet is assumed to be fixed. The Material Values for the wood parts are:
Youngs Modulus: 4 GPa
Piossons Ratio: 0.18
Density: 700 kg/m³
Bulk Modulus: 1e10 N/m²
Shear Modulus: 5.8e10 N/m²
Material damping is modeled via Rayleigh Damping with alpha = 0.251 1/s and beta = 6.35e-6 s
The driver is assumed to exert 10 N Driving Force on a 0.1 kg Membrane and is modeled as a lumped system and coupled to the enclosure via a prescribed acceleration at the mounting ring of the chassis basket. The Front of the driver radiates in to an acoustically sound hard chamber while the enclosure can radiate sound in to a free air enviroment.
Has annyone an Idea if these Values can be correct? Are there similar studys out ther which I did not find? My intuition says I have done something wrong but my expertise is limited and I would like to hear some opinions.
Have a nice weekend and I am looking forward to what I can learn.
PS: I hope I did post this right in the DIY section.
[1]https://www.google.com/url?sa=i&url...2ahUKEwiD8obgoPHvAhULahoKHeihCXAQr4kDegQIARBo