[Listening test] Superlux HD681 - semi-open dynamic circumaural monitoring headphone

Product: Superlux HD681 - dynamic semi-open wired headphone
Approx. price: ∼25€
Manufacturer: Superlux - Taiwan
Reviewer: Lucio Cadeddu - TNT-Audio Italy
Reviewed: March, 2024

Foreword

After the comparison test of three headphone amps under €100 and the clash between three headphones under €10 published recently, following the suggestion of several TNT-Audio readers whom I thank, I decided to submit to a listening test of an entry-level headphone that has gained an almost legendary reputation for sound quality in relation to the price (∼€25): the Taiwanese Superlux HD681.

Superlux is a manufacturer of headphones, microphones and audio accessories, both in the consumer and professional field, with a truly vast catalogue. The model under test is the HD681, called Professional Monitoring Headphone, and is very similar to a classic studio monitor headphone, the AKG K240. I wouldn't be surprised if AKG had this headphone made directly by Superlux. I have not had the opportunity to carry out a direct comparison, which I will postpone to a possible subsequent article.

The HD681 is a traditional semi-open dynamic headphone, with connection cable. It is available in three different versions: this one being tested, simply branded HD681, the HD681F and the HD681B. As can be seen from the graph below, the three versions should, in the manufacturer's intentions, satisfy different needs: the HD681 should be more suitable for classical music (and has the most extended and powerful bass response), the HD681F should be designed for pop, with the F standing for “Front Row”, while the HD681B should be more suitable for rock. As can be seen from the frequency response graphs, the most evident differences are in the low range and above 10kHz.

This headphone is quite comfortable to wear, the cable which has a single exit from the left ear-cup adding a pinch of extra comfort; the finish and packaging in no way suggest the very low cost of this headphone. A very elegant fabric bag is also included.

Claimed tech specs

Listening

The tests were carried out in different ways: with or without a dedicated headphone amplifier, and in comparison with the three inexpensive headphones of the previous test, plus a comparison with headphones of higher price classes: Grado SR80 and Grado SR225, the latter costing over 10 times more, at €350.

As expected, the headphone amplifier always makes a big difference, even with such cheap headphones. It's not just about the maximum achievable sound pressure, but about cleanliness, detail, dynamics and bass response. However, with the sensitivity of 98dB at 1mW and the low impedance of 32Ω, this HD681 proves to be adequate even for qualitatively and electrically modest sources such as PCs and smartphones. The sound pressure is always quite high.

The headphones from the previous test, all around ten euros each, were defeated without mercy. Not only does the HD681 sound louder, but it has a significantly wider frequency response, decidedly incomparable dynamics and greater spatiality. The impulsive sounds, not very incisive with the other headphones under test, are reproduced with an unexpected verve, considering the entry-level price class. The difference in cost (€10 versus €25) is negligible: I would say that there is no need to ask the question as the HD681 wins hands down from all points of view. The comparisons were therefore stopped quickly and without any doubts. The difference is so evident that you can hear it even without using headphone amplifiers, your smartphone or notebook are sufficient to highlight the sound quality gap.

The comparison with the two more expensive headphones turns out to be more interesting, because while the Grado SR225 sounds significantly better on all parameters, especially in terms of cleanliness and detail in the mid-high range and control and extension in the low range, the SR80 struggles a little more to make the difference. At first casual listening, the excellent low range of the HD681 almost seems to shift the balance of comparison in its favour, but in the long term other characteristics begin to emerge, which make the Grado SR80 more faithful and enjoyable overall. The Superlux HD681 has an important bass and a quite powerful high range, which can become edgy at times. It is not easy to notice this limit in a quick listen, but after some time some traces of listening fatigue inexorably emerge. The sibilants, especially of female voices, and some harmonics of the drum cymbals sometimes exceed in terms of presence and, in the long term, can generate listening fatigue.

The spatiality is also very good, and the semi-open typology helps to limit the annoying sensation of that “inside the head” sound. For this price it is difficult to expect anything more, and the overall performance of this Superlux HD681 brings the quality/price ratio to very high levels. It doesn't have the sound of much more expensive headphones but, without a direct comparison, it is really a pleasure to listen to. Despite having a hefty bass range, this does not mask the mid range. However, I wouldn't define its sound either warm or soft. Fans of soft and warm tones may find the HD681 too bright or edgy.

Complaints

The pavilions are very large and the padding is thick, this contributes to a mass that is not exactly featherweight. In the long run, you can definitely “feel” the headphone on your head and over your ears. The Grado phones I tested are significantly lighter and more comfortable. The eco-leather of the pavilions and the large headband, in case of high temperatures, is certainly more annoying than the sponge. A less wide headband and sponge pavilions would have increased comfort, especially in summer. From a sound point of view I would have preferred a slightly less strong presence in the mid-high range; I would be curious to try if the F and B versions of this headphone are more balanced.

Conclusions

This Superlux HD681 has been a nice surprise: for €25 you purchase a headphone that not only sounds loud even without a dedicated amplifier, but offers a very wide frequency response, excellent dynamics and a truly presence effect on voices. Remarkable, to say the least. Obviously, it can rival headphones costing 10 times as much, but it certainly makes a mockery of the entry-level headphones from the previous round of tests. Superlux HD681, a cool headphone with simply stellar quality/price ratio.

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Superlux HD681 headphone

Very good sound for peanuts

Foreword

Claimed tech specs

Listening

Complaints

Conclusions