[General Accessories] vectron:
This is a review of Superlux HD668B studio semi-open headphones. Manufacturer website: Superlux. Seems that the best prices for these are on Mod Edit: Affiliate referral sales link removed. where you can find it on sale between $30-$35.

It has been awhile since I posted my audio reviews in android communities. But I finally have a new discovery to share with everybody. Even so I have been focusing lately on testing and reviewing flagship IEMs and CIEMs, majority of which cost north of $1k, in this write-up I’m going back to my roots and will talk about sone of the cheapest pairs of headphones I’ve tested to date. Keep in mind these are full size semi-open cans, not another budget pair of in-ears or earbuds where I have seen even lower prices ($5 Monk being the prime example). But still, at $35 or sometime even down to $30, I haven’t heard full size headphones that cheap with a sound that good! Don’t mistake this level of excitement for “OMG, this kills any $500-$1k pair of headphones”, let’s be realistic. But I have no problem saying these $30-$35 headphones have a build quality of other $60-$70 pairs and sound quality that can go head-to-head with a number of full size cans up to $200.

3+ years ago when I started writing my audio gear reviews, my focus was solely on budget earphones, trying to find the next Giant Killer. But you can’t judge something to be a “giant killer” without experience of testing more expensive mid-tier and flagship “giants”. Now, I made a full circle which gives me a more objective point of reference for comparison. I also made an interesting observation about this HD668B model while reading various impressions since its release in 2011. Many of the negative comments I read about it are no longer applicable to this 2016 version, which makes me wonder if Superlux already implemented some of the fixes and improvements based on the received feedback.

The ironic part of this write-up is that I wasn’t even planning to review these headphones and was asked to take a listen to them in addition to something else I requested to review from Gearbest. I probably would have dismissed them just on the basis of how much they cost, expecting the usual of “you get what you paid for”. But I was proven wrong, and now would like to share with you about my experience with Superlux HD668B after spending the last few weeks testing them.

Unboxing and accessories.

Unboxing experience of HD668B didn’t feel at all like I was dealing with a cheap pair of budget headphones. A sturdy cardboard box with a nice cover image, a very detailed spec and a description of the design, and a complete list of accessories with corresponding pictures – the packaging box exterior already carried a message of the product being too good to be true for $35 price tag. But as you know, the writing on the box could be just a part of the overhyped marketing, so without further hesitation I proceeded to lift the cover.

I was greeted with a set of full size cans neatly packed inside of a cardboard insert and other accessories around it. With everything out, I was looking at a generous size soft nylon carrying pouch/bag, two extension cables, 6.3mm adapter, a peculiar cable clip, and a printed manual/guide. The nylon pouch felt neat and durable, branded with Superlux name. I consider adapter to be a filler, but it could come handy with full size headphones when used in a desktop setup. The clip made sense once I attached the cable to HD668B, realizing it does a great job securing the joint if you pull on the wires.

Regarding the cable, it was actually an extension cord. First of all, the whole idea of a removable cable in $35 pair of full size headphones is impressive. But it’s not a traditional cable with 3.5mm male plug on each side. To keep HD668B earcups slim, Superlux brought out the connector to the outside with a male 3.5mm plug and a very short extension cable. As a result, you attach the provided “extension” cable to this external connector. Included was 1m short cable, perfect for a portable use, and 3m long cable for other applications. You can also combine them together to form 4m extra long cable to give you more traveling room around the desk.

This "extension" cable idea was quite unique, though it would not be easy to find an extension cable with in-line remote if you need to. But you can also argue that majority of people would prefer not to carry a phone conversation with these on. With connector placed on outside, the earcup housing was definitely slimmer. Also, the attached earcup connector cable is very short with a heavy duty shielding and impressive strain relief. Not 100% sure if the cable clip was really necessary since the mating of the cable was already secure, but it never hurts to add another level of protection.

Design & build.

The first look at HD668B brought back the memory of my recent review of ATH-A2000Z with a similar wire-headband design and 3D-wings. Honestly, I was expecting a flimsy plastic construction, but surprisingly found it to be not bad at all. Starting with a headband, you have minimalistic design with a support of 2 steel spring-wires, assuming one carries a cable going to the connector on the left side. I have an average size head, and it was a bit tight at first but loosened up after a short time of being stretched over the soccer ball.

There is no height adjustment like in traditional full size headphones, and instead you have soft foam “wings” on a spring metal wire which self-adjusts as you put headphones on. This could be hit-or-miss with some people who have big head or curly hair (the last comment actually came from my wife). For me personally, it works quite well since I’m already accustomed to ATH-R70x and ATH-A2000Z, both of which have a similar “wings” headband support.

HD668B next to ATH-A2000Z

Though the headband spring-wire felt solid, these wings felt a bit flimsy in comparison, especially a thinner wire attachment - just have to be more careful when taking these headphones off you head. Closer to earcups, the headband wires are held together with a plastic joint piece on each side, kind of reminding me of “y-splitter”. These pieces look to be replaceable, if needed, and made of a solid plastic material. I found HD668B to be relatively comfortable to wear, and with evenly distributed 220g of weight it felt feather light.

Moving on to earcups, here Superlux took a page right out of AKG240. I have no doubt that Superlux engineers were inspired by AKG design, even bringing the connector to outside, though keeping a standard 3.5mm TRS plug for “extension” cable attachment. The back of earcups also has a similar to AKG circular vents, intended for a semi-open back performance. The inner middle part of earcups does pivots to adjust around your head, and it works quite well. The pleather earpads are easy to remove and to replace, especially if you want something softer. Since the earpads look universal and stretch over the top of earcups, I’m sure replacement alternatives won’t be hard to find.

The included original pleather pads are OK, but they do get a little hot after extended use. It definitely makes sense to experiment with different earpads to hear how they affect the sound. Just like eartips of in-ear monitors, you can fine tune the level of low end extension and impact as well as being able to control the top end. In addition, once you remove the earpads, you can also experiment with different dampening foam materials to figure out how it affects the sound. Here you will find plenty of room for modding experiments.

The fit.

Sound analysis.

Before jumping into sound analysis, I left HD668B on burn in for about 100hrs, making sure their dynamic drivers are properly conditioned. Honestly, I didn’t have too high expectations for these, still being a bit skeptical due to the low price. As a result, my surprise was more shocking when I discovered HD668B to be tuned with a tasteful V-shaped full body sound signature and warm detailed tonality.

In more details, I hear a deep low end impact, down to a textured sub-bass rumble and a tight mid-bass which has a bit of a hollow punch. The bass is rather well controlled, articulate, and there is no spillage into lower mids. The lower mids have a nice full body, but there is no muddiness or congestion, while upper mids are clear and detailed with an organic presentation of vocals - not too much upfront, just pushed a little back due to an elevated low end. Treble is surprisingly crisp and detailed, with a good extension, and some nice airiness which helps with layering and separation of instruments and vocals and contributes to higher resolution of the sound. If I have to nitpick, perhaps upper frequencies have a little shade of metallic sheen, but it wasn’t that bad especially when you pair up with different sources.

Soundstage has a good expansion in width, not super wide but definitely way above the average. The depth is not too far out, but you still feel like a few rows in front of the stage, giving a soundstage perception of spreading left/right around you without going too deep. Layering and separation was surprisingly good due to well controlled low end which keeps the sound clean from muddiness without spilling into mids and extra sparkle in treble which adds some air between the layers of the sound.

If you are looking for a good isolation, these are definitely not the best for listening on the bus or in the library, after all - this is a semi-open design. But it wasn’t leaking as bad when you step away 2-3ft. I’m sure some will find this semi-open design even beneficial since it could raise the surround awareness without losing too much of the sound details.

Sound comparison.

Considering 98dB sensitivity and 56 ohm impedance, I found HD668B to be a little less efficient in comparison to my other headphones, and as a result I had to push the volume a little higher. Also, it’s clear that more expensive headphones have an edge in build quality and material selection.

HD668B vs ATH-MSR7 - HD soundstage is wider, while MSR7 has more depth. HD has a deeper sub-bass and a little stronger mid-bass, while MSR7 has a more balanced low end. I also noticed that HD has a little faster attack of the mid-bass while MSR7 is a tad slower. Lower mids are similar, while MSR7 upper mids are more forward, balanced, and a little brighter in comparison to HD. I hear treble as being similarly crisp and well defined, though MSR7 has a little more airiness and a better extension. Overall, the biggest difference here is a more balanced signature of MSR7 versus lifted low end and slightly recessed mids of HD.

HD668B vs ATH-M50x - HD soundstage is wider, while M50x has more depth. HD has a deeper sub-bass while mid-bass is similar, perhaps with HD having a bit stronger impact. Mid-bass speed is also similar. Lower mids are very similar, while upper mids in M50x are more balanced and more forward in comparison. Also, M50x upper mids are a little smoother and a touch warmer. HD treble is crispier and has more airiness in comparison to a smoother M50x treble. While I enjoy M50x comfortable fit for extended listening on my laptop, here I actually preferred the sound of HD.

HD668B vs SoundMagic HP150 - HP150 soundstage comes closer to HD width, but not quite there, and HP150 has a little more depth. Also, HP150 sub-bass reaches deeper to the same level as HD, but a little shy of HD quantity, and mid-bass in HP150 is a bit lower in quantity as well. HP150 lower mids are leaner and upper mids are a little more upfront and brighter with an advantage of slightly improved retrieval of details. Treble is rather similar, being crisp, bright, snappy, and with enough extension and airiness to make the sound more resolving and layered. Actually, after closer listening I hear HP150 being a little brighter in upper mids/treble.

HD668B vs Oppo PM3 - HD has more width and both have a similar depth. HD has a deeper sub-bass extension and faster mid-bass punch with more impact. PM3 mids sound more congested in comparison to HD, though they are more forward in presentation. Actually HD upper mids are brighter and more detailed and the treble is crisper, better defined, and with more airiness. PM3 has a very smooth laid back sound while HD has a faster punchier brighter and more detailed sound.

Conclusion.

I’m starting to notice a pattern where many of my “giant killer” discoveries happen by accident, when I’m not even looking for another budget pair of headphones and instead just asked to try something new for fun. Did I get spoiled by flagships? It’s hard not to, and I’m being honest about it. But sometime it’s refreshing to take a step back and to listen to these amazing gems that cost so little. From $5 Monks to $10 KZs and now $35 HD668B – these are all amazing discoveries that show you how creative a manufacture can get by challenging themselves to squeeze every ounce of performance and sound tuning on such a small budget. HD668B is a real deal Giant Killer, and either if you are on a budget or just want to humor yourself with another budget discovery – I have no problem recommending these semi-open full size headphones because they don’t just look cool and ready for modding, but they also sound great!