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I measured the Massdrop x NuForce EDC3 in-ear headphones using a G.R.A.S. Model 43AG ear/cheek simulator (including the RA0402 high-resolution 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 amplifier. On the Model 43AG, I used the original KB0065 simulated pinna for most measurements as well as the new KB5000 pinna for certain measurements, as noted. These measurements used the medium-sized silicon eartips; for isolation measurements, I tried both the silicon tips and the largest of the included foam tips. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed.

Frequency response

I can’t recall measuring a set of earphones with a response like that of the EDC3s. It looks more like the response of a set of large, open-back, planar-magnetic headphones: essentially flat up to about 1kHz, then rising to a broad peak between 1.4 and 3.2kHz, then to a couple of smaller peaks between 4 and 10kHz. That’s not necessarily to say that the EDC3s will sound like big planar-magnetic headphones -- they’re inserted into the ear canals, and thus bypass the acoustical effects of the pinna and the outer portion of the ear canal, which of course affect the sound quality of over-ear headphones.

Frequency response

This chart shows the EDC3s’ right-channel frequency response measured using only the RA0402 coupler (which has a stainless-steel tube into which an earphone fits), and measured using the Model 43AG ear/cheek simulator with G.R.A.S.’s new KB5000 pinna (which I’ll eventually switch to for my earphone measurements because it’s a more realistic representation of the acoustical environment presented by the human ear). I include this for future reference; I intend to show both measurements until I begin using only the new pinna.

Frequency response

This chart shows the results of 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. As with every set of balanced-armature earphones I’ve measured, the EDC3s’ large swings in impedance (see impedance graph below) interact with the output impedance of the source device to change the response. Here, however, the effect is more subtle than I usually see -- you’ll get just a little less bass and a little more treble if you use a lower-quality headphone amp with a relatively high output impedance.

Frequency response

This chart compares the EDC3s’ measured right-channel frequency response with that of three other multidriver earphones: the 1More Quad Drivers, the PSB M4U 4s, and the Shure SE215s. Note how, compared with the EDC3s, all three competitors exhibit a large bump in the bass and a higher, more pronounced peak in the lower treble.

Waterfall

The ECD3s’ spectral-decay (waterfall) chart shows very low resonance overall.

THD

The ECD3s’ total harmonic distortion (THD) is pretty low, and a bit unusual. At the testing levels I use (both are high relative to normal listening levels), there seems to be a flat 1% THD below 1kHz -- yet even at the very high testing level of 100dBA, the distortion doesn’t significantly rise. THD of 1% is common in transducers and generally not noticeable, but this test provides yet another indication that something a bit different is going on in the EDC3s.

Isolation

In this chart, the external noise level is 85dB SPL; the numbers below that indicate the degree of attenuation of outside sounds. (Note that I recently switched to measuring at a level of 85dB instead of 75dB; this doesn’t change the way the isolation curves look, but an 85dB level lets me get better measurements of noise-canceling headphones, which demand a lower noise floor.) The EDC3s deliver excellent isolation, especially when their included foam eartips are used. Even by the generally high standards of earphones with over-ear cable routing, this is an excellent result.

Impedance

The EDC3s’ impedance, like that of all the balanced-armature earphones I can remember measuring, has a large swing, rising from 16 ohms in the bass to 53 ohms in the treble. The phase shift, too, is considerable, going from 0° in the bass to +72° at 20kHz. This is the reason for the change in sound quality when you switch from a low-impedance source (such as an iPhone or a typical good headphone amp) to a high-impedance source (e.g., the headphone amps built into most cheap laptops).

The sensitivity of the Massdrop x NuForce EDC3s, measured between 300Hz and 3kHz with a 1mW signal at their specified impedance of 20 ohms, is 109.1dB. This means that you should get plenty of volume from any source device.

. . . Brent Butterworth
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