I measured the Phiaton MS 100 BAs using a G.R.A.S. Model RA0045 ear simulator, a Clio 10 FW audio analyzer, a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface, and a Musical Fidelity V-Can headphone amplifier. Measurements were calibrated for drum reference point (DRP), roughly the point at the center of the eardrum (in this case, the center of the measurement mike). I used the Phiatons’ medium-size eartips because those best fit the RA0045. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed.
This chart shows the frequency response of the MS 100 BAs. It’s surprisingly flat -- most earphones have a larger dip in the midrange and a bigger bump in the bass -- which suggests that the Phiatons may sound smoother, but less vivid and less exciting, than many of their competitors.
As with most headphones using balanced-armature drivers, adding 70 ohms output impedance to the V-Can’s 5 ohms, to simulate the effects of using a typical low-quality headphone amp, has a large effect on the MS 100 BAs’ tonal balance. If you connect it to a high-quality source device, it has a flat response; if you connect it to a high-impedance source device (such as the headphone amps built into most laptops), the treble will be boosted a couple dB and the bass reduced by about 5dB -- easily audible differences.
The MS 100 BAs’ departure from the norm is visible in this comparison with NAD’s HP20 dynamic earphones and Sony’s XBA-H1 hybrid dynamic/balanced-armature earphones. The midrange dip visible in the NADs’ and Sonys’ responses is usually thought to produce a subjectively flatter response and a more spacious sound. However, the science here is still developing.
The Phiaton MS 100 BAs show no significant resonances above 800Hz, which is excellent performance.
The MS 100 BAs’ total harmonic distortion (THD) is relatively high; at 100Hz, it’s 2% at 90dBA and 7.5% at 100dBA. Competitors such as the Marshall Mode EQs post numbers more in the range of 1-2%. However, note that 100dBA (level measured with pink noise) is an extremely high listening level; I include it here mainly because some headphones can handle it and some can’t. Also note that research has shown that headphone distortion is rarely audible except when it’s very high.
In this chart, the external noise is at an SPL of 75dB; the numbers below that indicate the Phiatons’ attenuation of outside sounds. Their isolation is very good for earphones, reducing noise by 20dB at 100Hz (the middle of the “airplane cabin-noise band”) and by up to 32dB in the treble. Note that your results may not be as good, depending on the size and shape of your ear canals and on the size of eartips you choose.
This is the biggest impedance swing I can remember measuring in a passive headphone model: from 24 ohms in the bass to about 460 ohms at 20kHz. This is why the Phiatons’ tonal response changes so much when they’re used with a high-impedance source device.
The Phiatons’ sensitivity, measured between 300Hz and 3kHz with a 1mW signal and calculated for the rated 24 ohms impedance, is 110.8dB, which is exceptionally high. This means that the MS 100 BAs will be able to deliver high playback levels from practically any source device.
. . . Brent Butterworth
brentb@soundstagenetwork.com