Paraflex 2x12 Type O Measurements

Written By John White

Measurement Conditions

  • Ambient Temperature - 22° C

  • Barometric Pressure - 1024mb

  • Humidity - 74%

  • Background Noise - 56dBA averaged over 1 minute

Location

Measurements were taken in a flat, empty parking lot with the nearest obstruction being a grove of trees approximately 55 meters from the microphone. The microphone was placed on the ground at 10 meters distance from the center of the subwoofer.

Hardware

  • Paraflex Type O 2x12 version 2 loaded with B&C 12NBX100-8 drivers wired in parallel

  • Dayton Audio EMM-6 Calibrated with factory file

  • Focusrite Scarlett 2i2 Interface calibrated using REW loopback

  • Admark ADP1500 Class D Plate Amplifier

  • REW v5.31.2

Measurements - .mdat file download here

  • Note that the because the sweeps were taken at 10 meters in half space, a correction is needed for calculating the equivalent 1m readings (add +20dB) unless otherwise noted in the image description.

  • A 1w/1m calculation is not provided as I did not bring my multimeter with me to measure voltage, so the purpose of the below measurements is more to examine the overall curves of the response, group delay, distortion, etc. rather than sensitivity.

  • The raw & processed on axis responses were measured with a 20-2,000hz 1m sweep length with 2 repetitions. The remainder were measured with a 20-500hz 1m sweep length with no repetitions.

  • All graphs are shown with a 500ms left/right window applied and no smoothing

The below graph shows the same response with an 80hz LR4 high pass filter applied - no further processing.

NOTE - the distortion graph has been adjusted for 1m SPL for readability

Rear Rejection Testing

The next few measurements were taken to determine if this cabinet exhibits any rear rejection. The measurement setup was the same, with the subwoofer being rotated in an upright position on it’s centroid axis from 0-180 degrees in 45 degree increments.

Note that for this type of measurement to produce accurate reliable data, the speaker needs to be rotated on the axis that corresponds with it’s acoustic center. Because this is not known for this particular cabinet, there is a degree of error involved. The 10 meter mic distance means that this maximum error is +-0.3dB (see below formula)

maximum error = 20*log[R/(R + D)]

Where:

R = Distance in meters from microphone to centroid of subwoofer (10)

D = Distance in meters from front/rear of subwoofer to centroid (0.338)

The subwoofer exhibited between 2-3dB overall rear rejection

Linearity Testing

The next measurements were taken to observe any nonlinearity in the magnitude response as the drive level increased. The final sweep at approximately 129dB showed THD exceeding 10% @45Hz, so further increased levels were not tested. A gradual softening of the 40hz knee was observed as the drive levels were increased.

NOTE - the linearity testing graph has been adjusted for 1m SPL for readability

John White