by Hong Nguyen
Total cost: Free
Laptop or desktop running Windows 7 or 10.
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
Digital Multimeter (DMM).
Appropriate audio cables
to connect jig, soundcard and speaker driver.
Weight for added mass method (explained below).
Double-sided scotch tape to secure weight to cone.
Jig Bill of Materials:
6X3X2 project box:
Dual binding post:
2 pairs of RCA jacks:
One 100ohm resistor:
Connect the finished jig to the computer soundcard
using the appropriate cables.
LIMP module. Click Continue in Demo Mode. LIMP is fully functional in demo mode, except for the Save function.
the starting frequency to 10Hz, since the graphs of both PCD and WinPCD start at this same frequency.
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).
to the Setup menu to select the drivers for your particular soundcard:
My soundcard is a Creative EMU 0204, so my setup looks like this:
calibrate the soundcard:
on the CAL icon to bring up the Calibrate Input Channels box.
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.
driver on a hard, flat surface while ensuring that the venting hole is not blocked, and connect the speaker driver to the jig.
Pink PN (Pink Periodic Noise) as the generator.
M+P icon (Magnitude and Phase).
Setup menu, select Measurement.
Measurement Setup box, change Averaging to Linear, and Max averages to 10.
OK to accept these changes.