I measured the effects of Sonarworks’ True-Fi processing using a G.R.A.S. Model 43AG ear/cheek simulator (including the RA040X high-resolution ear simulator and KB5000 pinna), a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface, and a Musical Fidelity V-CAN amplifier. Because the test files had to be processed through the Sonarworks app, I had to play a pink-noise file as the stimulus and use TrueRTA, instead of generating and analyzing signals using my usual Audiomatica Clio 10 FW analyzer. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed.
This chart shows the frequency response of the Audeze LCD-X headphones measured with and without True-Fi processing. True-Fi introduces a bass boost of about 7dB centered at 35Hz, and a treble boost of about 5dB maximum and centered at 3kHz, as well as a 4dB boost centered at 7.5kHz.
This chart shows the frequency response of the Bose QC20 earphones with noise canceling on, measured with and without True-Fi processing. True-Fi cuts the bass by about 7dB centered at 40Hz, and introduces treble cuts of about 4dB maximum centered at 3.1kHz, and 9dB centered at 8kHz.
This chart shows the frequency response of the Sony MDR-7506 headphones, measured with and without True-Fi processing. Here the effect is more subtle than with the above headphones and earphones. True-Fi cuts the bass by about 2dB centered at 60Hz, boosts the lower mids by about 4dB centered at 200Hz, and reduces the treble response by about 2dB on average between 4 and 7kHz.
Here you can compare the responses of the Audeze LCD-4, Sony MDR-7506, and Status Audio CB-1 headphones after True-Fi processing. It seems the target response is different for each design; if it were the same, the traces would overlap except for a few spurious variances caused by differences in the physical design of the headphones and the fit of their earpieces on the ear/cheek simulator.
In this chart you can see the effects of True-Fi’s Adjust for Age feature, with the intensity set to 50%, and the correction set for 55-year-old males and females and a 35-year-old man. Interestingly, this control introduces not only a treble rolloff, but also some effects on the bass and on the overall listening level.
What constitutes a “correct” measurement for the results above is very much a matter of debate, but these measurements do indicate that True-Fi’s corrections are not (at least in the cases of these headphone models) extreme or unexpected, and that Sonarworks does seem to have put some serious thought and work into each of the correction curves, rather than merely making each headphone model conform to the same curve.
. . . Brent Butterworth
brentb@soundstagenetwork.com