Let me start off by saying that I did not expect to find the following results as I was comparing the Ultrasone HFI-2400s to my Proline 2500s and Beyerdynamic DT-770 Pros. I had preconceived notions of the Ultrasone sound signature because I use the 2500s almost daily, but the HFIs are truly something different. The sources utilized were a 2nd gen Ipod touch and an RME ADI-2. I will be as specific as possible as I attempt to describe their sound signature.
This is truly where the HFI 2400s shine. The low end on these headphones rivals that of the 2500s, but there is a difference when powering these with varying sources. Take for example the Ipod touch. The iPod will drive these headphones with enough volume to please listeners, but this is only when the volume is at maximum output. When the volume is turned down to 75% or 80%, it affects the signal immensely, to the point where volume decreases dramatically.
I would not recommend using these outside or while commuting, mainly because they are open-back headphones and because their sound will lose its presence as it mixes with the outside noises of trains, cars, or people –although to be fair, this is true of all open-back headphones. On the other hand, if you are looking to use these indoors, their low-end does not disappoint, as it requires less juice than the DT-770s to provide excellent low-end response. It actually has better controlled bass than the beyers, and it goes deep to the point of providing a nice vibrating feeling around your ears that I really enjoy
As stated in some impressions of these headphones, they sound great with clean gain from a high quality source. As I listen to these headphones through my RME ADI-2, I notice that their sweet spot lies with the gain knob at 12PM. The maximum gain they can take before distorting lies between 1PM and 2PM. Anything after that is painful to listen to and may damage your ears.
The mids of the HFI 2400s as they are driven by my Ipod compare to the mids of the DT-770s as they are driven by my RME. This sounds odd, but I get the feeling that the HFI 2400s were made with the general consumer in mind. The mids on the 2400s sound recessed when given clean gain through my RME DAC, but have a sweet and light presence when connected to my Ipod at max volume. Although many reviews online state that these headphones will allow you to hear things you “never heard before”, I personally found this not to be the case with mid frequencies.
Although the low-end of these headphones benefits from clean gain and can handle its own when compared to the Proline 2500s, the mids take a step back to the low frequencies. Because of this, the HFI 2400s might not be the headphones you’re looking for if you seek cans that provide in-your-face mids. This affects snares and vocals within songs. This was noticeable while listening to Track #4 "All Good In The Hood" of Jamiroquai’s Rock Dust Light Star Album. Although the bassline was punchy and in your face, the vocals hid behind the low end and failed to impress. On the other hand, while listening to the same track through my Ipod, the mids sounded like tasting light butter, although not powerful or in-your-face, they were VERY MUSICAL and I can see how regular consumers could enjoy these headphones. Their signature is very pleasant and will not fatigue your ears as it provides you with musical goodness.
NOTE: As I used my Blue Robbie Pre-amps to color the sound of the music I was listening to, I noticed that the vocals took a bit of a step forward and sounded sweet and creamy. I am beginning to think that the HFI 2400s might benefit from TUBE based amplifiers.
This is where the HFI 2400s fall short. The highs on these headphones have a completely different signature than that of other Ultrasone headphones. Most people describe the highs of Ultrasone headphones to be exaggerated or painful, and I think that Ultrasone might have listened to them when designing the HFI 2400s.
The highs are a bit rolled off on these headphones. Instead of providing extended highs, they fall short when attempting to reproduce certain instruments that require high frequencies to extend across the audio spectrum. On the positive side, anyone hesitating from buying Ultrasone headphones will definitely enjoy these, the reason being that because highs are noticibly rolled off, harsh vocals are non-existant and there is no need to pray for the headphone gods to de-ess the vocals on certain music tracks.
The HFI 2400s provide extended low end to satisfy bass-heads without losing tightness. This also makes them good candidates for users who seek controlled and punchy low end –this is the first headphone I have used that can do this. These require less juice than my DT-770s while providing even better low end, but sound less open than my Proline 2500s because they lack in mids and have rolled off highs.
The rolled off highs and recessed mids of the HFI 2400s when using a clean and powerful source will leave users who seek a detailed and open sound, wanting for something more. This is not the case when using an Ipod or MP3 player though, as I personally feel that the HFI 2400s were made to be used by these devices –although I would not recommend using these to commute or in noisy places. The mids have a bit more presence when being powered by my Ipod touch, and pretty much taste like light butter. These headphones might also benefit from a TUBE based amplifier, as my Blue Robbies pushed vocals a little-bit forward and made them sound creamy, never becoming fatiguing or sibilant.
I hope my review can help people considering these headphones and anyone that might be interested in adding another pair of headphones to their arsenal to make an informed decision.
Edited by kesslerjesus - 11/8/10 at 8:01pm