Reviewed on: SoundStage! Solo, March 2022
I measured the Monoprice Monolith M1570C headphones using laboratory-grade equipment: a GRAS Model 43AG ear/cheek simulator/RA0402 ear simulator with KB5000/KB5001 simulated pinnae, and an Audiomatica Clio 12 QC audio analyzer. For isolation measurements, I used a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface. For most measurements, the headphones were amplified using a Musical Fidelity V-CAN amplifier; I used a Schiit Magnius amplifier for distortion measurements. 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.
This chart shows the M1570Cs’ frequency response with the lambskin pads. If that 3kHz peak were about 3dB lower, and the bass about 5dB higher, these would look not too far off the Harman curve. But that’s a big 3kHz peak.
Here’s the difference between the lambskin and velour pads. You can see that despite the extra 2dB or so of energy at 3kHz with the lambskin pads, the 5dB reduction in bass output with the velour pads makes the velour pads sound brighter.
Here we can see the difference in the headphones’ response when a high-impedance (75 ohms) source is substituted for a typical low-impedance source (5 ohms). As with most planar-magnetic headphones, the difference is negligible and probably inaudible.
This measurement shows how sensitive the headphones’ response is to their position on the ears, using the lambskin pads. The black line shows the curve I used above, which is the curve I got most often with the headphones optimally positioned on the ear/cheek simulator. For the other curves, I reseated the headphones a few times, and also shifted them about 5mm up, down, forward, and back on the cheek plate. There’s not much variance, so the sound isn’t all that fit-dependent. Results with the velour pads, which don’t create a tight seal, should be even more consistent.
This chart shows the M1570Cs’ right-channel response with the lambskin pads, compared with a few other closed-back models and the open-back M1570s. It’s clear that the M1570Cs’ ~3kHz peak is unusually strong, and that’s likely to make them a little blarey-sounding. It’s also apparent that the M1570s sound substantially different from the M1570Cs, which is disappointing to me—I’d have hoped the M1570Cs would basically be just the M1570s with closed backs, but they’re really a different set of headphones.
The spectral-decay (waterfall) response of the M1570Cs (measured with the velour pads) looks clean except for an unusual and strong, but narrow (i.e., high-Q), resonance at about 2.5kHz, which corresponds to that zig-zaggy peak/dip in the frequency response in this range. I’d guess it’s audible if whatever you’re listening to has significant content at that frequency. There’s also a smaller resonance at about 4.5kHz.
This chart shows the total harmonic distortion, measured at 90dBA and 100dBA (both levels set with pink noise, using the velour pads). It’s near zero—one of the best results I’ve seen for this measurement. Very crankable if used with an amp.
In this chart, the external noise level is 85dB SPL (the red trace), and numbers below that indicate the degree of attenuation of outside sounds. The lower the lines, the better the isolation. The M1570Cs’ isolation is typical for headphones in its class, and it’s a few dB better with the lambskin pads.
As with most planar-magnetic headphones, electrical impedance magnitude is dead-flat (in this case at 62 ohms) and impedance phase shift is close to zero.
Sensitivity of the M1570Cs, calculated for 60 ohms rated impedance and averaged from 300Hz to 3kHz, is 97.1dB with the velour pads, 96.8dB with the lambskin pads, so using some kind of an external amp, DAC-amp, or high-quality portable music player with these is a good idea.
Bottom line: These seem well-engineered, but that’s a big 3kHz peak. Those looking for headphones with a familial sonic relationship to the excellent M1570s better look elsewhere.
. . . Brent Butterworth