Back in May, British headphone maker Reid Heath Audio (RHA) announced a new pair of in-ear headphones that debuted something called DualCoil dynamic driver technology. The company had managed to install two independently-powered dynamic voice coils on a micro ring magnet, one to handle lower audio frequencies and the other to take care of the higher end. The T20s promised a true-to-life reproduction and support for high resolution audio. We got to plug in for some hi-res, and lo-res, listening.

At first glance, the T20s seem pretty familiar. They sport the same injection-molded stainless steel driver housings as the earlier T10i and T10 models, have the same patent-pending over-ear hooks, run the same length of oxygen-free copper cable and come supplied with the same frequency-tweaking screw-in tuning filters. They're also every bit as comfortable plugged in, even for long-haul listening. In the box you'll also find the same impressive selection of soft silicone and foam buds and a quality carry case. But the T20s are a different animal.

Sure, the cable color is black rather than gray, and the ear hooks are covered instead of exposed, but RHA has been also messing around with magnets and copper-clad aluminum wire since releasing its previous high-end flagships.

"Our research and development team reengineered the traditional dynamic driver, using a small annular (or ring) magnet in place of a solid one," the company's Emma Dixon told us. "This allowed them to experiment with using an additional voice coil operating independently to manipulate the same diaphragm. It is the first time this configuration has been used, our DualCoil driver is totally unique."

As you can see from the exploded view above, a voice coil is positioned around the magnet within the housing – much the same as with conventional earphone drivers. But RHA selected an annular magnet for its new driver, and also placed another voice coil within its ring. And the company redesigned the diaphragm to have both an outer and an inner apex to match the new coil setup.

"The frequency range signal is divided by a crossover, into high and low frequency bands," Dixon revealed to us. "Frequencies below 2.2 kHz (bass and lower midtones) are generated by the inner coil, while the outer coil handles frequencies above the crossover point (upper mids and treble) for an ultra efficient, high resolution performance."

The upshot is a pair of earphones claimed "capable of outperforming conventional drivers in levels of resolution, clarity and detail." So how do they stack up?

Vive la résolution

Both the packaging and the product page proudly display the Hi-Res symbol, meaning that the T20s conform to high resolution audio standards laid out by the Japan Audio Society – so it only seemed right and proper to head for some high resolution FLAC and WAV files. The following outlines the different listening experiences encountered with various formats, including MP3s, spinning plastic discs and 24-bit digital audio files.

A 256 kbps MP3 version of Blue Train by John Coltrane proved a vibrant and enjoyable, if a little cramped, affair through the musical and entertaining, rather than neutral, Reference filters. The T20s didn't appear to punish this lower quality audio format too severely, though where detail had been stripped out of the source track, these earphones picked that up as a reminder that higher resolution audio files really are worth the effort and money.

The T20s responded to the higher quality of a CD of the same track by widening and deepening the stereo image and offering a more detailed rendition of some fine blowing from Coltrane, Morgan and Fuller. They breathed more life into the energetic percussive prowess of Philly Joe Jones, the walking bass had more impact and the piano had more color to it. At the risk of being branded quite, quite mad, the reproduction of this digital format seemed almost vinyl-like.

The performance of RHA's new flagship bumped up a notch again when a high resolution WAV file (24-bit/192 kHz) was driven through them via a laptop and external DAC. The T20s offered a vivid and quite expansive stage with the image pushed out beyond, and a little behind, the ears and arcing round in front of the nose.

Even at low volume levels, the clarity and attention to detail were impressive. Where distortion did start to creep in at higher, ill-advised, volume levels when listening to the MP3 version of this track, none could be detected here. This is definitely the format for folks who like the opulent sound of the wind blowing though the reeds.

Elsewhere, there was natural decay to snare and cymbals, attention-grabbing definition to the slightly warm upper mids and a nice airy feel to the instrumentation. Though criticism at this resolution could force us into the realm of ultra pickiness, the bass did feel a little more laid back in the high resolution mix than we're used to hearing through earphones. On the plus side, the T20s gave Drew's piano-playing gymnastics a little more room to shine.

Earphones weren't really designed for sitting in a favorite armchair with a glass of single malt in one hand and the hi-fi remote in the other, they were made for music on the move. An MP3 of Woke up Dreaming from Joe Bonamassa via a Galaxy Note 8.0 running the music player that came as default with the tablet, for example, was a little less forceful at the bottom end through the T20s than with the T10s, but nonetheless full-bodied and lively in an intimate small room kind of way.

With some cheaper earphones, the vocals on this nippy little number can come through a little lacking around the edges and the acoustic guitar can sound like its strings haven't been changed in a while, but despite the limitations of the lossy format, the T20s managed to smooth out the rough edges and offered up a surprisingly well rounded presentation of the guitarist's voice positioned front and center. And, as they should, the strings responding to Bonamassa's fast-fretting pick-trickery had a refreshing lively pop to them.

Presenting the bass on some tracks with less presence than earphones designed by 50 Cent, for instance, doesn't mean that the T20s are lacking in that department, as a listen to full band rock music using the Reference filters – such as Seether's explosive, and a little twisted, Gasoline on an iPhone – testified. The combination of pounding kick, relentless bass and some thick, dark and dirty crunch from the main guitar rhythm ensured that there was thunder-a-plenty.

There was no sign of the "fighting for air" issues that can sometimes trouble plug-in audio throwers when dealing with a lot of power play. The T20s produced a tight, full-bodied bass that dug way down below and a tantalizing edge to hot-running distorted guitars. Morgan's throaty growl punched through clean and clear and the drum kit definitely gained more space across the stage.

If even more bass is desired, then a quick swap over to the bass filter will put a little more emphasis on the lower registers, without stripping away definition from elsewhere or overpowering the lower mids.

Our final example of the kind of music played through the T20s over the past few weeks is quite a mixed bag musically. Child of a blind man by Hazmat Modine (in FLAC format on a portable music player) features soothing, laid back vocal harmony punctuated by arresting sassy brass fills from instruments such as trombone, flugelhorn and saxophone. The former can feel like they're locked in a small cupboard with some less capable earphones, but the T20s allowed them to fill out their rightful positions slightly behind each ear, ever so slightly forward and also out to the left and right.

The various representatives of the horn section were fat and boisterous, with a live performance feel to them, and a multi-voiced Fon chant from members of the Gangbé Brass Band proved powerful, well paced and well placed as it powered through the middle of the track. And, rather bizarrely, there was a nicely rounded punchy rasp to the low end thanks to a tuba doing a very good impersonation of a bass guitar.

The bottom line

As you might expect, the new driver technology and fine-tuned signature of the T20s offer a somewhat different listening experience to the T10s that came before. We found them to have a forgiving nature when it came to lossy audio formats, and very capable indeed when the resolution was dialed up. Hi-Res WAV and FLAC files were detailed, immersive and lively.

There may not be quite enough lower end out of the box to satisfy those used to Beats tuning, but the bonus is a distinct lack of bleed and distortion. What the T20s lack in midbass, however, they make up for in sub bass. And RHA has provided a means to further tweak the sound by swapping out the filters. As with the T10s we reviewed back in April, the black Bass filters give the lower frequencies a bit of a boost, while the copper-colored Treble filters bring out the higher reaches.

For much of our time with the T20s, though, we found the clean, clear and rather jolly lines taken by the silver Reference filters more than sufficient for most genres, but the other filters were always ready for deployment from their own metal holder if needed. It can be a bit of a fiddle to swap out filters for just one or two tracks though, so some forward planning is beneficial.

Music found to be worth the effort of changing to the bass filters included tracks by Nero, Massive Attack and, surprisingly, Ed Alleyne-Johnson. As for the treble filters, they brought out the best from artists like Jorma Kaukonen, Carlos García Montoya and Leo Kottke, though we did find them a little harsh with some selections, such as Tim Buckley's Dolphins and T-Bone Walker's Midnight Blues.

Though earphones are ideal for listening to music on the move, they're generally a bit lacking when it comes to home hi-fi, computer audio or TV/gaming entertainment. Not so the T20s. We found the stage wide enough, the image detailed enough, the sound quality high enough and being plugged in comfortable enough to leave the closed back circumaural headphones in the drawer for pretty much the whole of the review period.

At a suggested retail price of US$239.95, the T20s are clearly not going to be in everyone's budget. But if sound quality, comfort and durability are what float your boat, then RHA's new DualCoil-packing in-ear headphones are worth saving up for. They're available now.

A slightly pricier version with inline controls will follow in September, to be called the T20i.

Product page: RHA T20

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