Radius HP-TWF21 “W N°2” aka “DDM 2” Review

ddm2 main Radius HP TWF21 “W N°2” aka “DDM 2” ReviewRadius Co. Ltd. are from Japan, but unlike fellow countrymen such as Audio Technica or Denon, Radius mostly relies on rebranding Chinese OEM in-ear phones rather than creating original designs. Most of their products are found in the lower price segment, usually competing with fashion brands such as Skullcandy or JBuds.

This however changed when Radius introduced the HP-TWF11 “DDM” phone some time ago. They were priced at around $200 and featured a seldom seen construction that uses two dynamic drivers; a big one for bass and midrange next to the ear and a smaller one for treble behind it – hence the “DDM” nickname that stands for “Dual Driver Matrix”. While these DDM couldn’t quite compete with top-tier dynamic driver IEMs such as the JVC FX700 or Sennheiser IE8, they pulled off a gigantic in-your-face bass while still retaining some very nice stereo imaging, timbre, and good dynamic range.

Now Radius revised their DDM concept and released the HP-TWF21 “W N°2”. Compared to the old DDM, the new DDM2 (as I call them) have an infinitely better form factor, somewhat more tamed bass quantity, better clarity… and of course a somewhat higher price tag than the old ones.

Read on to find out more about them.

  • Radius HP-TWF21 “W N°2” DDM 2 Specs:
  • Driver: Dual dynamic diaphragm (15mm/7mm)
  • Sensitivity: 107dB/mW
  • Impedance: 24 Ohm
  • Frequency response: 10Hz – 20kHz
  • Cable: 125cm, fabric covered, Y-style, straight gold plated 3.5mm plug
  • Accessories: 6 pairs of silicone ear tips (2x small, 2x medium, 2x large), right-angle converter cable, leather carrying case with silicone winding puck

Design, Build, Accessories

It’s nice that Radius packs two pairs of silicone tips of each size with the DDM2, so you don’t have to order new ones when you lose one of the size that fits your ears – but I’d rather have seen some higher quality tips for a phone in this price range than the usual generic ones. They’re rather thin, flimsy, and they have injection mold ridges – they’re basically the same you get with no-brand $5 phones. Needless to say, I didn’t really bother with those tips, and went for my trusty high quality Ultimate Ears Super.Fi tips straight away.

The included right-angle converter plug/cable sure could come in very handy – especially with players that have their headphone jack in awkward places, such as the Cowon X5. This is a very nice addition, and I can see myself using that add-on for other phones than the DDM2 as well.

As amusing as it sounds, the leather carrying case is actually the item with the highest build quality of the whole bundle – including the phones themselves. It looks and feels like real leather (but it probably isn’t), it’s very hard and sturdy. This thing oozes quality and sophistication – the material, polished to a luster, the stitches, the zipper, and of course the soft, heavy rubber puck inside. Truth be told: I won’t use the puck since it’s too much hassle winding the cable around it, but I like the way it looks and feels. Good thing the puck is removable, so one can still use the leather case without it.

On to the phones themselves. Well, they sure don’t look very Japanese. To put things in perspective: the Panasonic HJE900 are made of zirconium dioxide, the Sony EX1000 are made of magnesium alloy, the JVC FX700 are made of various metals and quality wood, varnished to perfection. There’s a history of nifty and exotic high-quality materials used in Japanese IEMs – the Radius DDM2 on the other hand use cheap plastic. It’s thin, glossy, and slightly creaky. To add insult to injury, the ostentatious gold-colored accents on the DDM2 don’t help either. They really don’t make them look any classier – as usual with such tactics, if it’s fake it often achieves the opposite effect. If the DDM2 were at least matte black without gold accents, they would look a lot more sophisticated than cheap glossy plastic and needless bling. It seems Radius has a lot to learn about design cues that work outside of dime stores, to convey a real sense of quality… but let’s see how they fare in their main application – sound quality – before condemning them for being rather cheap looking and feeling.

To their defense, the DDM2 have much better ergonomics, a highly improved form factor over their older siblings, the DDM1. While the old DDM were as ostentatious as the new ones, they also had the disadvantage of barely fitting any human’s ears. On par with the Sony EX1000 or Ultimate Ears Super/Triple.Fi, the DDM1 have the dubious honor of being some of the least comfortable IEMs ever made. The only way I could get a proper fit and seal with the DDM1 was by wearing them… Mickey Mouse style, ear pieces turned inside out and upside down, sticking out of my ears. The new DDM2 are much easier to insert into one’s ears and give a much better fit. They are as hassle free to wear and as comfortable as the next dynamic driver IEM. Radius did a great job of addressing these shortcomings of the older model.

However, the DDM2 are made to be worn with the cables hanging down, which is not the optimal way to wear any IEM. To reduce cable noise and give a more secure fit, nearly every professional IEM is made to be worn with the cables over the ears. To achieve that with the DDM2, one has to swap the left and right ear buds – there is no way around that. Swapping the channels is no issue with a Rockboxed MP3 player or a professional sound card, where changing the left and right channels is easy – for other sources however one has to solder a left/right inverter cable, or solder a new, inverted jack onto the DDM2. If swapped channels are no issue, then all is fine – but if you’re as picky as me, then prepare for some DIY tinkering. Of course, wearing them with the cables hanging down is no major issue, but since they work even better as an over-the-ear phone when one swaps the buds, I find it a bit sad that Radius chose to configure them in a less optimal way.

Speaking of the cable: I sure don’t like it much. It’s a fabric covered cable, style over substance. Same as the gold accents on the phones’ housings, cloth sleeving on the cable doesn’t do anything besides making it look more ostentatious. It makes the cable stiffer, more susceptible to grime, often more microphonic (which fortunately isn’t the case with the DDM2). I wish the DDM2 had a soft quality PVC cable like on the Sennheiser IE8 or Panasonic HJE900. It’s not an awful cable though, it certainly is OK. It could be better though without the cover, and it would even save a few cents in manufacturing.

Strain reliefs on the cable seem fine. While the 3.5mm connector is the classic generic aluminum tube that is found on any $2.50 Dealextreme phone, it has a better rubber strain relief than average. The same goes for the Y-splitter and the connectors where the cables enter the ear pieces. I don’t see any weak points where any connector meets the cable, so I’d assume it should last for a long time. The rather long strain reliefs on the ear buds might be the reason that cable noise/microphonics are rather well behaved, even when wearing them with the cables hanging down.

The flared bass ports on the back of the phones and the vent holes on the inside should make the DDM2 somewhat susceptible to wind noise, but they’re surprisingly well behaved in that aspect. I’ve heard fully closed IEMs that are much noisier in windy weather. These openings however do prevent the DDM2 from being overly isolating. Depending on the application, this might be a good or bad thing. While they should be on the safer side to use while jogging or biking, they sure don’t isolate enough to be used at safe listening levels on a bus or the subway. As for noise rejection, I’d say they do isolate a tad more than the FX700 or EX1000, but a bit less than the IE8 or HJE900.

Sensitivity is fine on the DDM2. They go loud enough with any portable player, and they don’t hiss much either with sub-par sources. They work well with anything I tried them with, ranging from a Sansa Clip+ to an Asus EEE netbook to a Nintendo DS.

To conclude this chapter: while I’m not a big fan of their looks and the materials used in their construction, there’s nothing that would stick out as a really negative point or overly big issue. They work well, they are comfortable – I think that’s what really matters. There are other expensive phones that use cheap materials as well , like the Earsonics SM3, so the DDM2 aren’t alone.


Describing the older DDM as utterly insane brain-smashing basshead phones would be an understatement. They even best the Hippo VB in bass quantity (but not in quality). It is good that Radius toned the DDM2 down a notch – they’re just very bass heavy phones, comparable to the likes of the JVC FX700, but they’re no complete overkill anymore.

Besides the tamed bass response, many other things have been improved in the new DDM2 as well, compared to the older one. Their treble is more refined (although a bit more recessed), they are less veiled, they aren’t ‘nasal’ like the old DDM, their stereo imaging seems wider, they are more ‘natural’ sounding in general. For some reason the old DDM appear to have a somewhat larger dynamic range, but only by a bit. Dynamics on the DDM2 is still way above average; they can definitely be called ‘exciting’ sounding.

One sure notices that a large 15mm driver is at work in the lower frequency registers. Bass goes very deep on the DDM2; it’s punchy, rich, and full, with nice texture and sense of space. It is an excellent bass for any type of electronic music, for movies, but also for several types of classical music that might need a bit of added oomph. However, the frequency response is tuned in a way that the bass bleeds a bit into the midrange; there sure is a noticeable midbass hump. This makes them appear a slight bit veiled, but not as much as the old DDM.

Said midrange can be described as ‘relaxed’ and ‘natural’, very palpable, not recessed at all. One thing the DDM2 are not is being analytical sounding in any way. They are fun sounding phones, made for the enjoyment of music, not for counting sine waves, so to speak. Despite being a bit veiled by the bass, instrument separation is still good. Usually a veil caused by overly much bass manifests itself in mudded male or female vocals, or unclear guitars, saxophones, and the like. Luckily, this isn’t the case with the DDM2. Maybe it’s better describing their midrange as ‘full’ and ‘forward’ than calling it ‘veiled’. It might not be everyone’s cup of tea, but after getting used to its special signature, I’m thoroughly enjoying it.

The treble is where one notices the most difference between the DDM2 and other, less refined bass-heavy phones. Having a second dynamic driver just for the high frequencies sure pays off in their design. It does sound and feel like a dedicated tweeter – in a good way, with a well tuned crossover, not in a tacked-on way. Treble on the DDM2 is very clear, not overly bright, but ‘sparkling’ while never being sibilant at all. It’s treble done right – at least for my taste. Some people might find it a bit recessed (but not as much as, say, the old Future Sonics Atrio), especially when coming from brighter sounding phones. I experienced it the same when I wasn’t accustomed to the DDM2′s sound, but now I really can’t say I find a flaw with it. Well, it’s not quite as fast and detailed as some top-tier balanced armature treble, but for a dynamic driver it’s at the very top of the food chain. Again, same as before: very musical and enjoyable, but not meant to be analytical.

As for stereo imaging, it is very well done. Due to the aforementioned vents and the bass port that gives the drivers room to breathe, the sound stage appears vast and expansive. Actually, closing the bass ports with one’s fingers totally collapses the stereo image, and also robs the DDM2 of all their dynamics. If you want the DDM2 to sound like Etymotic MC5 – you know what you have to do. Now that was uncalled for… but you catch my drift.

All in all, the DDM2 have excellent overall timbre, a sort of roomy, spacious reverb/decay that makes most music sound more engaging. They are perfect for relaxed listening, for watching movies, for making anything that might reach one’s ear drums more enjoyable. If you allow me to get a bit sappy here: at the moment I’m typing this review into my netbook, sitting on my terrace, surrounded by plants and birds. The DDM2 are plugged into the not-so-bad onboard soundcard, and Audacious on Ubuntu is delivering some quality tunes. This is the kind of ambiance where these IEMs truly bring a smile on my face. Nice and easy.

In my experience, the closest match to their sound signature is actually a full-sized phone, the AIAIAI TMA-1, not an in-ear phone. Those two phones share most of their sonic signature – with the difference that the DDM2 beats the TMA-1 in treble detail and refinement.


How to summarize that? Well, the DDM2 have something cinematic, larger-than-life to their sound. They can make most anything sound enjoyable, but some of their sonic traits might be detrimental to some people’s tastes. They’re not for purists who want a ruler flat frequency response, they’re not the be-all-end-all in clarity, but it sure seems that Radius didn’t aim for that demographic when creating the DDM2. It seems their goal was placing the listener in a concert hall, not a recording studio – and they managed to pull that feeling off very well.

I started to call the DMM2 my ‘Hans Zimmer’ phones. Listening to soundtracks from movies like Inception, Dark Knight, or Sherlock Holmes with the Radius gives them a whole new meaning for me, and enough goosebumps to match. For me the DDM2 can convey emotions that no technically more advanced phones like the Earsonics SM3 or Phonak PFE can do. Of course the DDM2 aren’t the right choice for every kind of music I listen to, or for every mood I’m in – but I sure keep grabbing them for listening sessions more often than I thought I would.

This just leaves one issue to discuss – their price. At around $250 they sure aren’t overly cheap. You pay for the emotions conveyed while listening to them, not for any fancy materials or build quality. If that asking price is worth it for anyone besides me I cannot say. In any case they’re certainly worth the $50 over the old DDM1. Of course no ‘high-end’ audio device is worth its sticker price, law of diminishing returns and all that… if you’re looking for a very engaging, grand sounding, ‘musical’ phone I would certainly recommend the DDM2. I truly like what they do to my ears.


  • Warm, bass-driven sound, euphonic and lush
  • Good, clear (albeit a bit recessed) treble due to second driver
  • Surprisingly low cable noise and wind noise
  • Comfortable to wear


  • Low isolation


  • Design and materials used do not reflect the price of the phones
  • Midrange clarity could be a bit better


The Radius HP-TWF21 “W N°2” aka “DDM2” can be bought from Musica Acoustics Japan, currently for $298 (incl. worldwide shipping). UPDATE: Musica Acoustics offers them now for $250 incl. shipping.


Justin on May 23, 2011 11:30 PM

I really like the looks on those.

confispect on May 24, 2011 12:38 AM


will on May 25, 2011 12:38 PM

Apart from the greater bass, how do these compare to the e-q5?

Arashi on June 1, 2011 12:23 PM

The old DDMs fit my ears just fine cables down, so perhaps they fit better in Asian ears. =3

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