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Reviewed on: SoundStage! Solo, January 2020

I measured the Rai Penta earphones using laboratory-grade equipment: a G.R.A.S. Model 43AG ear/cheek simulator/RA0402 ear simulator with KB5000/KB5001 simulated pinnae, and a Clio 10 FW audio analyzer. The earphones were amplified using a Musical Fidelity V-CAN. Except as noted, all measurements were made using medium-sized, single-flange silicone eartips, as these fit the ear/cheek simulator best. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed. If you’d like to learn more about what our measurements mean, click here.

Frequency response

The above chart shows the Rai Penta earphones’ frequency response, which in terms of the shape of the curve is fairly typical. The peak between 1.5 and 4.5kHz is much broader than the usual narrow peak centered at about 3kHz. The broad hump between about 20Hz and 600Hz is typical of earphones, but has a little more upper-bass/lower-midrange content than I typically see in high-end earphones.

Frequency response

This chart shows how the Rai Pentas’ tonal balance changes when they’re used with a high-impedance (75 ohms) source, such as a cheap laptop or some cheap professional headphone amps, or some exotic tube amps. As I usually see with earphones employing balanced armatures, there’s a change in tonal balance with high-impedance and low-impedance sources; with a high-impedance source, you’ll hear about 1.5dB more bass and about 2dB less treble. That’s a fairly large tilt that will mellow out the sound of the earphones.

Frequency response

This chart shows the Rai Pentas’ right-channel response compared with the Campfire Solaris and the AKG N5005 earphones. The N5005s, when used with their reference filter, are the earphones said to best conform to the Harman curve, the response that research shows delivers what most listeners consider the most natural sound. The Rai Pentas seem to mostly strike a balance between the two other earphones, although they have more upper-bass/lower-midrange output than either.

Waterfall

The Rai Pentas’ spectral decay (waterfall) chart looks very clean above 400Hz, but there’s a lot of resonance below 400Hz. I wonder if this is part of why I perceived the upper bass and lower mids to be overly rich at times, and I wonder if the ports on the dynamic-driver enclosure have anything to do with it.

THD

The Rai Pentas’ distortion is low; we see a rise to about 2% in the range of 500Hz to 1.4kHz, as the balanced armatures take over from the dynamic driver, but it’s only at the extremely loud listening level of 100dBA.

Impedance

The impedance magnitude of the Rai Pentas is typical of a hybrid earphone design: mostly flat in the bandwidth of the dynamic driver, but fluctuating with frequency as the balanced armatures take over. This is why the tonal balance shifts when a high-output-impedance source device is used. Phase stays fairly flat, though.

Sensitivity of the Rai Penta earphones, measured between 300Hz and 3kHz, using a 1mW signal calculated for 20 ohms rated impedance, is 112.4dB, thus the Rai Pentas will deliver ample volume from any source device.

. . . Brent Butterworth
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