I decided to measure the frequency response of my Acoustic Audio HD-Sub 12 subwoofer. Unfortunately, a home theater room is not the best place for this type of measurements. The frequency response changes quite a bit in different locations in the room. I am also aware that the Audyssey calibration program has tweaked the subwoofer's frequency, but I am not trying to win the Nobel prize. Who wants to live in an anechoic chamber?
I took a few measurements and finally decided to take the readings about a meter (≈3.2 ft) directly in front of the subwoofer.
I turned the volume on the back of the subwoofer to the middle (50% point) and turned the subwoofer’s gain in the receiver to zero. The receiver's volume was intentionally set high in the 90dB range so that the measurements are calculated more accurately in case of weak sound output at some frequencies. All the other speakers and subwoofers in the room were turned off.
I played Rives Audio’s Test CD-2 test tones and measured the levels of the sound outputs at different frequencies with my Radio Shack Digital SPL Meter. I recorded the numbers and then plotted SPL in dB’s versus frequency in Hertz using Microsoft Excel. The following graph demonstrates the results.
The subwoofer performs very well in the low and middle frequencies up to 130Hz. After this point, the sound output begins to drop significantly. The reason is because the maximum level on the crossover network on the back of the subwoofer is set at 130Hz.
