For all measurements, the plots show the LAUD program settings used to acquire the data. The test set-ups and procedures are described below in more detail for each measurement.
Each DX series driver was placed horizontal on a bench with the magnet resting in the foam packaging. The backs of the cones were elevated approximately six inches above the bench surface and clear of any obstructions. The delta mass method was used in the LAUD measurement program. The program settings can be seen on the plots and ten measurements were made and averaged to calculate the final T/S parameters.
The impedance of each DX series driver was measured, using 10 averages, over the frequency range from 10 Hz to 20 kHz. This measurement was performed at the same time as the SPL measurements using the same test set-up.
Each DX series driver was mounted in the center of a 24" by 24", 3/4" thick, plywood baffle with two reinforcing ribs attached to the back of the baffle. A 1 m wooden rod was clamped onto the front of the baffle for repeatable positioning of the mic at 1 m on axis and at 1 m 30 degrees off axis. The baffle was clamped to the end of a bench and positioned in a large basement, pointing diagonally across the longest dimension, about 1/4 of the way along the diagonal. Based on this set-up, I estimated that accurate data would be measured above 200 Hz. While the measurements were taken over the frequency range from 10 Hz to 20 kHz, only the data above 200 Hz is displayed. Reflections from the fiber-glass insulated walls were probably minimal. Floor bounce, ceiling bounce, and baffle edge defractions are present in the test data. But without a special chamber, this is the best that could be done. A few near field measurements were made, to check the validity of the 1 m results, and the correlation was good.
Averages of 20 measurements were used to produce the final SPL frequency response measurements. The raw data was post processed using 1/12 octave smoothing and then the Hilbert Transform was applied to remove the linearly increasing phase shift associated with the 1 m measurement distance. This is the format of all the SPL response data presented for the Lowther drivers.
T/S Parameter Measurement :
Impedance Measurement :
SPL Measurements :