Review: SOL Republic Master Tracks

Two years ago, not a soul had heard of SOL Republic. Last summer, that all changed as everyone watching the Summer Olympics frantically googled to see what brand of headphones were seemingly permanently attached to swimmer Michael Phelps' head whenever he was out of the water. Overnight, SOL Republic went from "what's that?" to "must have." Can their latest design keep up with the hype?

The SOL Republic Master Tracks ($199.99) are their over-ear headphone model. Like previous on-ear versions, this one has completely interchangeable components. The cable, headband and X3 Sound Engines (cups) can all be mixed and matched to create your own look. Right now, it's available in gunmetal gray, electro-blue or white, but more colors should be available shortly.

The design is somewhat unique. SOL Republic claims that the headband is virtually indestructible. I didn't test this. The "sound engines" (earpieces) simply slide onto the headband. There's nothing attaching them except friction, making them infinitely adjustable. To adjust them, just slide them up or down. Surprisingly, they stay where you put them. This design is clever, but because the cups don't swivel at all, getting a snug fit might be difficult, although they are slightly articulated. Perhaps to make up for this, the cups are extremely cushioned, and they're remarkably comfortable. Who needs a travel pillow when you can rest your head in these little cushions of SonicSoft delight? All that cushioning also helps with noise isolation. They're not noise-cancelling, but they block out significant amounts of ambient noise.  They weigh 243 grams.

The interchangeable cable has a built-in three-button volume control, playback control and mic. I was surprised that I could skip or jump back to tracks using the pause button on the cable with my iPod nano. The cable is said to be extremely durable. I did not test this either, but if something bad happens, it's nice to know that it can be easily swapped out. I did notice that the portion of the cable between the jack and the controller is very resistant to touch noise. The split cable from the controller up to the sound engines wasn't as impervious to this.  The cables have small channel indications, and the sound engines also have a tiny indication. I actually have a gripe that this is so faintly marked. It was impossible to read without sliding off the headband.

Performance

The Master Tracks use SOL Republic's X3 Sound Engine speakers.  They are designed to deliver powerful bass, clear highs and vocal accuracy. There's an inherent problem with headphones that are voiced and tuned to a certain quality – in this case, pushing the bass. These days, most music is already mixed that way – most likely to compensate for crappy little earbuds. This is a perfect example of that situation. These headphones are tuned to have a really heavy bass-response – a hip-hop heavy, club-like sound. The problem is that songs in that genre already have a huge bass response. With these headphones, the bass just sounds tubby and loose. Instead of a tight, impactful bass, you get a mushy, undefined sound. It just doesn't work for me.

In listening to F.U.N.'s "Some Nights", the stacked vocals in the intro were already showing a problem – the baritone voices were artificially boosted although the falsetto vocals in the upper ranges had a pleasant brightness. But when the drums and bass kick in, the sound just falls apart. I usually love the low-end of this song, but it becomes an undefined wash of tonality.  Same thing with Macklemore & Ryan Lewis' "Can't Hold Us" – the bass completely overwhelms the vocals.

Other tracks that were more pop-oriented suffered the same problem, country-oriented songs too. I checked them out with Darius Rucker's "Wagon Wheel." His voice should have a rich, luscious tone, and here it's just tubby and boomy. The high-end is clean, but it is masked by the artificial sound of the low-end.  Female vocals also sound unnaturally colored. There is a good high-end sound when it can shine above the lows, but the midrange is underwhelming.

Ken Pohlmann, contributing tech editor: I loved the style of these. They're so comfortable – I really wanted to love them because I wanted to keep wearing them. Listening to "Run" by Kill It Kid, I could appreciate what the SOL Republic designers were trying to pull off, but they should let music engineers do what they do – balance the sound at the mix. This song has massively deep acoustic sounds, and they become a blur instead of having the impact they should. Instead of wanting to hear more, I couldn't wait to take them off. On less bass-heavy tracks, it still feels artificially colored.  I normally seek out a dark, warm sound, but this is too far gone.

Will Huff, L.A. jazz musician and frequent West Coast listening panelist: The design is great. They're extremely comfortable. However, the sound didn't work for me. It's muffled and there's no imaging, so it's hard to tell what sound is coming from where. When I listened to the Eagles' studio version of "Hotel California," the mids and lows didn't jell. It was like a choir where someone is singing out of tune.

Brent Butterworth, contributing tech editor: I do love the SOL Republic design concept with the interchangeable bands, and the super-soft earpads made these a joy to wear -- I was able to go for a couple of hours straight with no discomfort. That said, the sound is a mushy as the earpads. The bass is bloated and undefined; it overwhelms everything else and makes the headphone sound dull and muffled. I have heard other headphones voiced similarly, so SOL Republic isn't the only culprit, but still, I cannot understand why manufacturers ruin great industrial designs with these totally unmusical and unrealistic voicings.

Measurements

I measured the performance of the Master Tracks HD 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), roughly the point in space where your palm intersects with the axis of your ear canal when you press your hand against your ear. 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.

This is one of those cases where the frequency response curves do not square well with our panelists' subjective impressions. (Hey, it happens.) The only anomalous features I see in the curves is are less deep bass output (below 50 Hz) than expected, and more output in the midrange around 1 kHz than expected. (Many headphones have a midrange dip between about 500 Hz and 2 or 3 kHz.) 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 has almost no effect, merely boosting bass by about +1 dB in a narrow band centered at 75 Hz.

The spectral decay plot (a new and somewhat experimental feature of our headphone measurements) shows very little resonance. There's less resonance in the bass compared to most of the headphones we've measured this way, and that resonance indicated by the blue band around 1.8 kHz is almost certainly too narrow to be audible.

Total harmonic distortion (THD) at 100 dBA is somewhat high: 3% at 100 Hz, rising to 8% at 20 Hz. Isolation is about the norm for an over-ear headphone: -8 dB at 1 kHz, dropping to -20 to -30 dB above 2 kHz. Impedance averages 34 ohms, while average sensitivity from 300 Hz to 6 kHz at the rated 33 ohms is 108.4 dB. –Brent Butterworth

Bottom Line

The SOL Republic Master Tracks have a fabulous design. Anyone who is hard on their headphones should consider these with their indestructible headband and completely replaceable components. If you do care for a big, bass-heavy sound, these are just what you are looking for. However, their clean, unadorned look is no match for the colored sound.  I will give them huge props for comfort. I finished my listening test about an hour ago, and realized that I still have them on. Nice. 

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