PerformanceWe left the headphones to burn in for over 100 hours to make sure they were at their peak performance. The headphones were tested on our faithful O2+ODAC combination manufactured by JDSLabs and modded to 1x and 2.5x gain, and our Samsung Galaxy S3 International Edition. The obvious headphones for a comparison are KRK Systems' KNS-8400s and 6400s, and the Sennheiser PX 200-IIs which have been our go-to on-ear headphones for a while now.
To start off with, the HM9s feature a very laid back sound signature, which makes new, poorly mastered tracks listenable. There is not a hint of sibilance even though it is there in the recording. This, along with the sound stage being quite deep, makes the HM9s very pleasant to listen to over extended periods of time, though they are far from as engaging and interesting to listen to as the KRK KNS-8400s. The HM9s are not totally comparable to the 8400s because they are supra-aural, but the truth is that the HM9s are somewhere in-between because their pads seal up your ears quite well. Noise attenuation levels with the HM9s are comparable to what you can get from a set of KRK KNS-8400s.
Where the KNS-8400s offer a close-to-neutral sound signature, the HM9s provide you with a very warm, bassy sound signature, which is great if you are after a bass monster. The HM9s have a less precise bass that is more boomy and not as textured as the KNS-6400 and KNS-8400s. Compared to the Sennheiser PX 200-IIs, the HM9s are of course more bassy, but bass definition is actually better on the PX 200-IIs, which surprised me a bit. When it comes to portability, the PX-200s and KRK Systems headphones come out on top as they are lighter and have a slightly better wearing comfort on European-sized heads. The clamping force on the HM9s is a bit over the top, which is good if you are into headbanging, but bad for the rest of us as it is a bit of a nuisance. They are very heavy, which is an issue under normal circumstances.
What is great about the HM9s is their extensive bundle. You get three different types of cables—one for at-home, one for portable use, and one with a microphone. This is a stroke of genius as it basically gives you three headphones in one, which is a perfect example of a bundle done right; we could have only wished for a pair of velour pads to complement the pleathers. Velour pads usually reduce bass and bring forward the mids and highs, which would suit the HM9s well. At $149, the HM9s are not that brilliant in value; that is, compared to the KRK Systems KNS-8400 offering a more neutral sound and much improved wearing comfort at only $140. The KRK headphones obviously lack the microphone and extensive bundle, but still seem to be the better choice. The HM9s then seem much more competitive at their pre-order price of $119.