Sony XBA-H1 Earphones

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I measured the Sony XBA-H1s using a G.R.A.S. RA0045 ear simulator, a Clio 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): the equivalent of a headphone’s response at the surface of your eardrum. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed. Except as noted, I used the XBA-H1s’ medium standard tips. I experimented with the fit of the tips/earpieces by inserting and reinserting them in the RA0045, settling on the positions that gave the best bass response and the most characteristic result overall.

For an earphone, the XBA-H1s’ frequency response looks pretty flat overall, with perhaps a slight excess of energy between 3 and 5kHz. (Almost all headphones have a peak or two somewhere in this region.)

Adding 70 ohms output impedance to the V-CAN’s 5-ohm output impedance, to simulate the effects of using a typical low-quality headphone amp, tilts up the XBA-H1s’ response, dropping their bass output -1dB at 80Hz and kicking up the treble +5dB at 10kHz. Given my perception that the XBA-H1s sounded ever-so-slightly bright, even with the low-impedance output of my iPod Touch, I’d recommend using these headphones only with Apple or higher-end Android products, or with a separate headphone amplifier that has a low output impedance, preferably under 20 ohms.

Above 500Hz the XBA-H1s are fairly similar to the Audiofly AF78 hybrid and the RBH EP1 dynamic earphones, but the Sonys’ bass response looks much more neutral.

The spectral-decay (waterfall) plot looks very clean, with no notable resonances.

Total harmonic distortion (THD) at 100dBA is quite moderate overall, but with a little 10% peak centered near 3kHz; this drops to 3% at 90dBA. Considering that the first and second distortion harmonics of 3kHz are at 6 and 9kHz, respectively, your sensitivity to this distortion will vary inversely with your age, and more so if you’re male. (Translation: Your ability to hear higher frequencies decreases with age, especially in males.)

The spectrum of a 500Hz sinewave shows that the second and third distortion harmonics are nearly equal in level. It’d be nicer to see more second and less third, because odd-order harmonics are more objectionable, but the distortion is moderate anyway, so no big deal.

There’s not much isolation in the bass — only about -8dB at 100Hz — but it improves dramatically as the frequency rises: to -20dB at 1kHz, and about -30dB from 2.5 to 8kHz. That’s with the standard tips. The noise-isolating tip didn’t make a big difference, at least not when used in the cold-steel cone of the RA0045 ear simulator. It gave me an improvement of -8 to -15dB, but only at high frequencies: from 3 to 14kHz. I wonder how the results vary when the tips are inserted into a soft, warm ear canal.

The XBA-H1s’ impedance rises dramatically with frequency, running about 32 ohms below 1kHz, then rising to 186 ohms at 20kHz. The impedance phase rises similarly; it’s right near 0° at low frequencies, but jumps to +65° at 20kHz. Impedance swings at high frequencies are common in balanced-armature drivers, but I’d never before seen one so extreme. This causes the shift in tonal balance when the XBA-H1s are used with source devices that have a high output impedance.

The Sony XBA-H1s’ average sensitivity from 300Hz to 3kHz at the rated 40 ohms was very high, at 109.3dB.

. . . Brent Butterworth
brentb@soundstagenetwork.com

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