Box Vibration Simulation Needed

Taco

Member
2002-11-06 11:32 am
lowlands
Any structural mechanics finite element code is capable of a modal analysis. That's the place where I would look first. With that kind of analysis you find out at which frequencies you can await problems.
This analysis is relatively straight-forward. However, you need proper material properties (density and stiffness).

If you also want the coupled acoustic-mechanical coupling, a computational fluid dynamic analysis coupled to a structural code could be interesting (air is also a fluid). Of course this is far more complicated, not only involving physics, but also the difficulties and problems of finite element analysis in general (models, element properties, numerical stability issues).

In both cases you need FE software, the commercial stuff is too expensive but well documented and validated. The free stuff is badly documented and hardly validated (results can be faulty). Look for an academic code which is most times freely available.
 
elvischan917 said:
Hello!

I would like to see how each wall of a box vibrate when the woofer is working on it. Can you suggest some softwares?

:confused:

You can look for more information from svante/DIY forum or on this website with email (go to Contact Tolvan Data). http://www.tolvan.com/

You can entertain yourself in here
Kirchner Elektronik Braunschweig.

Feel free to post your feedback, elvischan.
 
WOW! What Taco said is complicated to me, but I really appreciate your fast feedback. THANKS!

I have taken a brief look at tolvan.com but I did not see any program which can sim. the wall vibration. However, I found this website full of useful information and BIG THANKS to your suggestion, INDUCTOR.

Let me tell you my story here first. I bought an AR centre speaker for my home 5.1 system in 1999. Amony these years, I was constructing my DIY loudspeakers and discover that: despite whatever tunning I made to the passive filter and box filling, the sound/the harmonics cannot be reproduced as nice as that AR speaker. I suspect it is the problem of the box dimension, bracing and plywood material.

I'm from the field of electronic so I don't know too much on mechanic and acoustic. I just want a program that can show me the vibration pattern and frequency harmonic in difference type of box, with different box structure.

Someone may remind me to consider the room condition and loudspeaker dispersion characteristic in this case. However, my focus is on the box this time. That's what information I lack of.

Oh, go back to the subject. Is there any user friendly program can reach my goal? Thanks!

Alvis
 
The most user friendly FEA program I've come across is COSMOS, the FEA add-on to Solidworks. I know it will do both fluid and vibration calculations, however I don't have enough experience with it to know if it will be able to couple the two accurately. User friendliness is relative however... even COSMOS can be a pain in the A$$ to set up correctly and obtain a vaild result... or even a result at all.
 
What makes you suspect the sound differences between the AR speaker and your DIY speaker are due to enclosure characteristics? If your DIY speaker isn't an exact copy of the AR you're comparing apples to oranges.

What is the design of your DIY speaker? What drivers are you using? What is the crossover design and how did you come up with it? How is the enclosure constructed?
 
Re: Re: Box Vibration Simulation Needed

elvischan917 said:

I would like to see how each wall of a box vibrate when the woofer is working on it. Can you suggest some softwares?



Inductor said:

You can entertain yourself in here
Kirchner Elektronik Braunschweig.



elvischan917 said:

...However, I found this website full of useful information and BIG THANKS to your suggestion, INDUCTOR.

...I suspect it is the problem of the box dimension, bracing and plywood material.

I'm from the field of electronic so I don't know too much on mechanic and acoustic. I just want a program that can show me the vibration pattern and frequency harmonic in difference type of box, with different box structure.

...Oh, go back to the subject. Is there any user friendly program can reach my goal? Thanks!

Alvis

Yes, go to "Kirchner Elektronik Braunschweig". :yes:

The ATB PC Pro has an optional accelerator sensor (12,00€) for gauging resonance suppressions.

Connection:
The sensor is connected to the microphone input of the soundcard. Here the sensitivity has to be increased by turning on the Mic-boost or microphone amplifier in the system control. :µphone:
Enjoy Alvis.
 
What makes you suspect the sound differences between the AR speaker and your DIY speaker are due to enclosure characteristics? If your DIY speaker isn't an exact copy of the AR you're comparing apples to oranges.

Yes, I know the drivers, box material and design all are affecting the sound. So what I said is to make it "as nice as" but not "as same as". The difference triggered my interest to investigate what is the role of box in a speaker system. As the most popular programs on box simulation can just simulate the performance in ideal case, which does not satisfy my need. When a speaker produce sound, each wall of the box also produce sound which is similar to a diaphram. While most of the programs does not consider the sound radiated by each wall, e.g. WinISD, LspCAD, SpeakerWorkshop and etc. That's why "I would like to see how each wall of a box vibrate when the woofer is working on it"