Hidizs' new MD4 IEM is also a quad driver like its predecessor - the Mermaid MS4 - but the MD4 is an all BA (balanced armature) IEM with four balanced armature drivers per earphone and on-board EQ via a nifty 2-switch tuning filter mechanism!

Despite the lack of dynamic drivers, the Hidizs MD4 balanced armature drivers have been tuned to handle all the frequencies, including bass. Two of those balanced armature drivers handle bass, and the other two balanced armature drivers handle the midrange and treble respectively. To accomplish this, the Hidizs MD4 uses a 3-way audio cross over (just like most multi-driver IEMs and stereo speakers) to split and send the right frequency to the correct BA driver. A 3 way cross over is basically a filter circuitry with three filters (low-pass filter, band-pass filter and high-pass filter).

 

The Hidizs MD4 earphones have very low impedance (8 ohms) and high sensitivity (102 dB), which means you can get plenty of volume without the need of an external DAC Amp. As far as sound/audio quality, it is an interesting one because of the tuning modes. 

 

Despite the name, the "Warm" tuning mode is actually more balanced than the "Balanced" mode and the best all-rounder out of all 4 tuning modes. The bass is clean (not dynamic) and midbass focused; hence very little sub-bass thump/slam. The sound stage is very wide and frequency layering very good naturally separating vocals, instruments and treble, letting you retrieve details very easily.

The MD4 earphones weigh 7 grams each, while the cable weighs 15 grams bringing the total combined weight to 27 grams. The Hidizs MD4 body shell is made of smooth anodized CNC machined aluminum alloy and rose gold accents, while the glossy faceplate is made of celluloid (plastic) - same type of material most vintage snooker (billiard) balls are made of. 

 

Hidizs branding on the faceplate is embedded within the celluloid. The 2 pin socket connection has a plastic guard reinforcement, while the tips of the long nozzle body are guarded with metal mesh.

 

On the side of the MD4 body shell, there are the tuning filter switches (white switches with number 1 and 2 markings). The tuning filters give you a 4-band tone control to EQ the sound. It works by flicking the switches up or down in 4 combinations: 1 up/ 2 down = balanced, 1 up/2 up = bass and 1 down/2 up = warm and 1 down/ 2 down = treble.

The Hidizs MD4 IEM come with a detachable 1.2 meters long IEM cable with gold plated 2 pin (0.78mm) connectors (hard plastic enclosure), 3.5mm straight plug and mixed internal wiring (2-core high purity silver wiring and 2-core OFC wiring). Like most IEMs, the Hidizs MD4 audio cable wearing style is around the ears via pre-shaped ear hooks that you loop over the top of the ears. The square y-splitter is located 36cm down the cable.  

 

The included storage case is the same square case you get with the Hidizs Mermaid MS4. The storage case is very fancy (reminds of a cufflink box), has magnetic closing, it's padded on top and bottom and covered with distress leather material for a vintage look. The storage case lid can open clamshell via a fabric hinge and features a small internal netted pocket for storage. The dimensions of the MD4 case are 7cm long, 7cm wide and 3cm internal height. On top of the case lid, there is a lovely Hidizs branding laser engraved onto the leather. 

 

The included custom silicone ear tips (bowl shape) that you get with the MD4 IEM have a soft flange and thick bore, which maximizes in-ear isolation. The ear tips are made with smaller and wider bore, which slightly alters the sound. The MD4 IEM is part of the Mermaid Series earphones so, it has the same basic design style. 

 

Potential deal breakers facing the MD4 include the tuning filter switches which can be confusing to use. There are no foam tips included, the website branding (hidizs.com) printed on the earphones is unnecessary and cheapens the design. The 2 pin connectors extruded design means they stick out more than recessed 2 pins, which are better at preventing bending/breaking the pins. 

The pre-shaped earhooks have very thin silicone wrapping, which is nice as it makes them flexible but can potentially cause some discomfort during long use when rubbing against the top of the ear. The on-board EQ tuning switches are a neat design and work but they are essentially preset sound modes. They don't give you as much control as a proper digital graphic EQ like the ones you get built-in to some wireless earbuds mobile app. For bass lovers, the MD4 won't likely be as fun to listen. The MS2 IEM do a better job in that regard.

Selling points for the MD4 include superb passive noise isolation, quality quad core IEM audio cable with metal 3.5mm plug that matches the smooth anodized aluminum alloy of the earphones. The audio cable has a twist rope steampunk design that does not tangle easily and has a copper cinch inline for cable management. The included accessories are premium. 

 

The 2 pin connectors have red/blue dot markings, which help quickly identify the right and left earphone. You get an ear tip holder and gift box packaging presentation. The MD4 is available in different colorways and come with a total of 9 pairs of silicone tips, storage case (weighs 102 grams), cleaning brush and velcro strap for cable management. You can buy the MD4 IEM from Hidizs website. Check out the review of the Hidizs AP80 MP3 player and DH80S portable DAC Amp

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