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MultiWay Conventional loudspeakers with crossovers 

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7th October 2018, 08:47 AM  #11 
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Join Date: Aug 2005

Hi Juhazi,
Yes, I knew his software. 
7th October 2018, 10:40 AM  #12  
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Join Date: Apr 2005
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Quote:
There are a range of damping models for materials but the more realistic ones are often not implemented in general FEA codes. The adopted model will determine the number and kind of coefficients needed to represent the stress/strain/rate of strain/... relationship. It will also determine how much larger and slower the simulation will become. Which dynamic models does your FEA code support? 

8th October 2018, 11:16 AM  #13  
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Join Date: Aug 2005

Quote:
To my knowledge, damping seems to be geometry dependent too. I measured stiffness and damping by means of bending (fixedfree cantilever) test of rectangular beam of the surround rubber. Damping obtained from the bending test and damping of the complete conesurround are not the same. The FEA tool supports typical proportional damping model and structural damping. It supports creep as well. Are these answers of your question? 

8th October 2018, 11:27 AM  #14 
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Join Date: Aug 2005

Hi guys,
Let me update the driver type being studied. I don't have parts for the one with rubber surround, but for another 6" woofer with foam surround. Luckily, they are essentially identical except the surround material. I don't need to make changes to the already created models and just need to update the material properties. Please see photos of the driver and its soft parts. 
8th October 2018, 12:32 PM  #15 
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Join Date: Aug 2005

A rectangular beam was cut from the outer flange of the surround part. The beam was fixed a one end and free at the other end for bending test. Laser sensor measured the displacement of the free end. Vibration level was kept small in order to use EulerBernoullis (simple) bending theory to correlate elastic modulus to measured resonance frequency. The beam resonance frequency obtained is 55.7 Hz.
Vibration analysis package written by Tom Irvine was used to get elastic modulus. The GUI of the script is shown in the graph. Elastic modulus obtained is 5.5 MPa where mass density is 350 kg/m^3. 
8th October 2018, 04:09 PM  #16 
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Yes those are two of the simpler models. They tend to need experimental input to produce something reasonable for small deflections over a modest frequency range. It will be interesting to see how you get on.

9th October 2018, 03:41 AM  #17 
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Join Date: Aug 2005

Paper cone mass density estimated is 910 kg/m^3. A quarter solid model was created to perform modal simulation. Together with the mass of dust cap and voice coil former, the mode 1 (piston mode) frequency is 33.4 Hz as shown in the graph.
We can verify this result later with the actual driver (spider removed). The complete driver TS parameters are FS 40.8715 Hz VAS 11.3314 L RE 3.9000 Ohms QMS 9.7463, QES 0.8307, QTS 0.7655 BL 6.3000 T×m dBSPL 81.7136 SD 1.327E2 m2 CMS 0.4606 mm/N, MMS 32.9206 g, RMS 0.8674 L1kHz 1.3019 mH 
10th October 2018, 05:03 AM  #18 
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Join Date: Aug 2005

Using shell (plate) elements for complete conedust capsurround modal analysis. Simulation can run much faster even with higher mesh density (not the one shown).

10th October 2018, 05:58 AM  #19 
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Join Date: Aug 2005

Without the dust cap, the cone bends at 1.474 kHz as shown. It would not bend like that in the presence of voice coil. At this frequency, elastic modulus of the surround would be higher than that measured by lowfreq. test.
Last edited by panson_hk; 10th October 2018 at 06:08 AM. 
10th October 2018, 10:21 AM  #20  
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Quote:
If you are not experienced using these elements it may be wise after you have built a full model to run a few checks to prove that you have not suppressed important degrees of freedom and have used sufficient resolution. That is, setup a representative simulation and repeat it using several levels of grid refinement everywhere, low and high order elements, elements that suppress no degrees of freedom and those that suppress ones considered unimportant,... and compare the results looking for differences. 

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