PE #269-469 "69 cent wonders" T/S data:
I have spent a week measuring 300+ of these drivers and have discovered some lot differences, particularly in Fs, as is apparent in the graphs below.  I used the Woofer Tester to measure the parameters of at least a case of each lot.  Lot K1SJG has the lowest average Fs of all 8 lots I measured (over 2 cases of these examined, all consistently low Fs).  The T/S values over all 300+ drivers are: (average followed by standard deviation in parentheses)

Fs =  108 ( 7)        Qts =  .620 (.040)       Qes =  .703 (.046)       Qms =  5.260 (.385)        Re =  7.830 (.120)
Le =  .300 (.036)   Vas(L) =  3.02 (.60)     Mm(g) =  3.12 (.32)     cms(mm/N) =  .705 (.150)
Rm(mechanical ohms) =  .40 (.05)          Efficiency(db/watt/m) =  89.0 (.29)        Measured area(sq. m) = .0054
Xmax (measured by cutting a driver open!) =  1.1 mm

Fs is closer to 111 Hz if I normalize data to reflect equal numbers of each lot number.  No significant adjustment to the other parameters is necessary after normalization.  Vas was measured by delta mass (dime with double-sided tape attached to dustcap) measured to nearest mg on analytical balance.  All measurements were made at 24 degrees Celsius.  I have already observed before that these numbers depend on temperature.  None of the drivers was "broken in" before testing (except possibly by UPS).  Prior experimentation has shown these drivers drop in Fs and the Qs when broken in.  Typical Fs drop is 3 - 5 Hz.  Easiest break-in is achieved by hand massage (100 full inward presses followed by 100 full outward presses) as was pointed out on the Full-Range Driver Forum.  I have since determined that the hand break-in approach is not advised for these drivers, as can be seen in data presented in the following link:

Spectral waterfall decay data and MLS plots
BACK to driver projects
BACK to page index