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Get familiar with the reaction system: Introducing the Reaction System
Easy ZMA & T/S Parameters Using the LIMP Module in ARTA - An Illustrated Guide
This modest contribution is for newcomers to this great hobby who have
done kits, but wish to go deep (football pun intended) and design their
own. We often read about budget constraints and especially about where
to start. Well, here's one way to start determining the parameters of
any speaker driver, and produce accurate ZMA files without breaking the
bank. Here we go:
1. Download ARTA software (current version is 1.90) from http://artalabs.hr/download.htm.
Total cost: Free
2. Hardware Requirements:
a. Laptop or desktop running Windows 7 or 10.
b. Duplex soundcard – I suggest you experiment with your current duplex soundcard to see if there are incompatibilities before investing in a new card.
More info here: http://artalabs.hr/requirements.htm
c. Digital Multimeter (DMM).
d. Appropriate audio cables to connect jig, soundcard and speaker driver.
e. Weight for added mass method (explained below).
f. Double-sided scotch tape.
3. Measurement Jig Bill of Materials:
a. 6X3X2 project box:
http://www.parts-express.com/hammond...1-x-2--320-714
b. Dual binding post:
http://www.parts-express.com/parts-e...black--090-475
c. 2 pairs of RCA jacks:
http://www.parts-express.com/parts-e...-pair--090-278
d. One 100ohm resistor:
http://www.parts-express.com/100-ohm...rance--015-100
Total parts cost: $15.31
1. Download ARTA software (current version is 1.90) from http://artalabs.hr/download.htm.
Total cost: Free
2. Hardware Requirements:
a. Laptop or desktop running Windows 7 or 10.
b. Duplex soundcard – I suggest you experiment with your current duplex soundcard to see if there are incompatibilities before investing in a new card.
More info here: http://artalabs.hr/requirements.htm
c. Digital Multimeter (DMM).
d. Appropriate audio cables to connect jig, soundcard and speaker driver.
e. Weight for added mass method (explained below).
f. Double-sided scotch tape.
3. Measurement Jig Bill of Materials:
a. 6X3X2 project box:
http://www.parts-express.com/hammond...1-x-2--320-714
b. Dual binding post:
http://www.parts-express.com/parts-e...black--090-475
c. 2 pairs of RCA jacks:
http://www.parts-express.com/parts-e...-pair--090-278
d. One 100ohm resistor:
http://www.parts-express.com/100-ohm...rance--015-100
Total parts cost: $15.31
Comments
1. Connect the finished jig to the computer soundcard using the appropriate cables.
2. Start the LIMP module. Click Continue in Demo Mode. LIMP is fully functional in demo mode, except for the Save function.
3. Change the starting frequency to 10Hz, since the graphs of both PCD and WinPCD start at this same frequency.
4. Right-click on the program to bring up the Graph Setup dialog box, change the Low frequency to 10Hz and click on Update. This will extend the graph from 20 to 10Hz (see lower left corner).
5. Go to the Setup menu to select the drivers for your particular soundcard:
6. My soundcard is a Creative EMU 0204, so my setup looks like this:
7. Next, calibrate the soundcard:
a. Click on the CAL icon to bring up the Calibrate Input Channels box.
b. Click on Calibrate in the Dialog Box to calibrate both channels. LIMP will alert if there’s a significant difference between the 2 channels. In the Status box, the channel difference is only 0.11dB, so the calibration process is successful.
Note: Do not connect your speaker driver to the jig during the calibration process.
8. After calibration:
a. Position the driver on a hard, flat surface while ensuring that the venting hole is not blocked, and connect the speaker driver to the jig.
b. Select Pink PN (Pink Periodic Noise) as the generator.
c. Select the M+P icon (Magnitude and Phase).
e. In the Measurement Setup box, change Averaging to Linear, and Max averages to 10.
f. Click OK to accept these changes.
9. Now click Record to start the measurement process.
10. After about 8 seconds, the recording stops, and the below plot is displayed:
12. Save the file on a hard drive location, and load into PCD to test. You should see the ZMA file appear on the driver impedance box as shown below. As you can see, PCD’s graphs start at 10Hz, so should measurements in LIMP.
To Obtain T/S Parameters:
1. Save the graph in Section 10 as an overlay by selecting Set as overlay curve in the Overlay menu.
2. Add about 20g of weight to the woofer, using double-sided tape to secure the weight to the cone. Four nickels can be used as each weighs about 5g, or enough weight to shift the resonance frequency (Fs) lower by at least 20% to 50%.
3. Click Record again. When the recording stops, you should see the plot below. The first impedance graph (blue) is the original measurement, the second one (black) is with the added weight.
4. Next, click on the Analyze menu and select Loudspeaker parameters – Added mass method.
5. In the Loudspeaker Parameters – Added Mass Method dialog box:
a. The frequency shift is 30% with the 20g, so within the recommended limit. Add or subtract weight as required to ensure the shift is correct and re-measure if necessary.
b. Use the DMM to measure the Voice Coil Resistance (Ω) of the speaker and enter the value in this box.
c. Enter the piston diameter in cm by measuring from mid-surround to mid-surround.
d. Enter the value of the mass used.
e. Click on Calculate Parameters.
6. Select Copy to copy the T/S Parameters to Notepad or a word processor to be saved, or enter the values into your favorite box design program.
https://www.google.com/url?sa=t&rct=...tTYmRDHMCrTtUw