Tuesday, September 26, 2017

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I measured the performance of the Audeze LCD-3 headphones using a G.R.A.S. 43AG ear/cheek 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 ear reference point (ERP), which is roughly the point in space where your palm intersects with the axis of your ear canal when you press your hand against your ear, and the place where the front of the headphones’ driver grilles will sit when you wear them. This is a “flat” measurement: no diffuse-field or free-field compensation curve was used. I experimented with the position of the earpads by moving them around slightly on the ear/cheek simulator, and settled on the positions that gave the best bass response and the most characteristic result overall.

Frequency response

The LCD-3’s frequency response is textbook for planar-magnetic headphones, with essentially flat response below 1kHz, a strong response peak at 2.8kHz, and minor response peaks at 6 and 8.5kHz. This generally conforms to the typical diffuse-field equalization used in many headphones.

Frequency response

Thanks to the resistive impedance of the planar-magnetic driver, 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 had zero audible effect. I could measure a difference only below 20Hz.

Frequency response

This chart compares the LCD-3 with another highly regarded planar-magnetic headphone, the HiFiMan HE-6, and a respected, new dynamic open-back headphone, the AKG K712. The responses of all three are similar below 1kHz, but between 3.3 and 6.5kHz the HE-6 has a lot more output than the LCD-3, which should make it sound brighter than the Audeze. The K712 should sound substantially different from its planar-magnetic competitors, with less output in the octave between 2.5 and 5kHz.

Waterfall

The spectral-decay (waterfall) plot shows a series of strong but narrow resonances between 2 and 4kHz.

THD

For logistical reasons, I was unable to run a 90dB SPL distortion measurement on the LCD-3, but considering that the 100dB measurement shows near-zero distortion, the 90dB result could only be better.

Isolation

The LCD-3 being an open-back planar-magnetic headphone, it provides almost no isolation from outside sounds. There is no significant attenuation below 2kHz, and only -5dB of isolation at 5kHz.

Impedance

The impedance magnitude is essentially flat at 47 ohms, and the impedance phase is at 0 degrees through almost the entire audioband, rising to +5 degrees at 20kHz.

At its claimed impedance of 45 ohms, the LCD-3’s average sensitivity from 300Hz to 3kHz measured 94.5dB.

. . . Brent Butterworth
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