- Written by John E. Johnson, Jr.
- Published on 21 March 2011
On the Bench
Distortion measurements were performed within an 80 kHz bandwidth. I did the measurements using the default preset, which is Preset 3 - Jazz. The contour was turned off (set to 0) and the Theater/Music setting was 8, for maximum servo-feedback (the least amount of distortion).
At 15 Hz and 100 dB output, at 2 meters, distortion was less than 5%, which is pretty amazing. This is a very tough frequency for any subwoofer, and far below the limits of audibility. The only time you will ever get this frequency passing through your home theater system is with an occasional movie special effect, or the lowest pedal tone on a pipe organ. Again, though, you won't hear it; you will simply feel it.
At 20 Hz, on the other hand, now we are seeing what the DD+ could really do. Less than 2% THD+N at 100 dB. And the 2nd order harmonic was the predominant distortion peak. That is very impressive for this frequency and high output volume.
At 25 Hz, even less distortion. Taking into account that some of this is noise, we are probably talking about less than 1% THD. The 2nd and 3rd harmonics were about the same level. This is the lowest distortion I have ever measured in a subwoofer at this frequency and volume level from 2 meters.
Wow! At 31.5 Hz, still less. And, the 2nd harmonic was 10 dB higher than the 3rd. This means there is still a lot of steam left in this baby to produce higher volume.
At 40 Hz, only 1.22% distortion. What can I say that the graph doesn't?
And, at 50 Hz, we went below the 1% THD+N level at 100 dB and 2 meters for the first time in a Secrets subwoofer bench test (at 50 Hz).
I could easily get 110 dB output at 20 Hz and 2 meters from this subwoofer, and that was as loud as I was prepared to test. Research suggests that intense low frequencies can affect internal body organs, so be judicious with that volume control.