Short answer: the Austrian Audio Hi-X55, though neither ranks well in its class. It ranks #178 of 216 over-ear headphones by sound quality, rated 2.9/5, at $315.71; the KLH Ultimate One ranks #197, rated 2.5/5, and costs $325.11, so there is little reason to consider the other one. Both are rated below 3.0/5 among the 216 over-ear headphones, and the HIFIMAN Ananda Nano, ranked #4 at $319, is a better place to start if sound quality matters.
The Austrian Audio Hi-X55 is the better-sounding choice. The closed back blocks outside noise and keeps sound from leaking, so it works in shared rooms and studios. The tradeoff: oratory1990’s measurement shows a deep 9.9 dB dip near 2.3 kHz and presence about 3.9 dB below target, so vocals and guitars sound recessed and distant.
What the KLH Ultimate One does well: Bass from 60 to 200 Hz runs about 8.5 dB above target with sub-bass 5 dB up, so bass lovers get heavy, rumbling lows from an open headphone. Watch for: In oratory1990’s measurement the treble also sits about 5 dB above target from 3 to 16 kHz with a 9.6 dB peak near 6 kHz, which can make vocals and cymbals sound sharp and tiring at volume.
Buy the Austrian Audio Hi-X55. It is rated higher for sound quality than the KLH Ultimate One and costs less, which makes it the one to get unless you need something the other one does better.
Still deciding? The full Headphones rankings cover every ranked option.
Specifications Side By Side
| Austrian Audio Hi-X55 | KLH Ultimate One | |
|---|---|---|
| Price | $315.71 | $325.11 |
| Ranked | #178 of 216 in Over-Ear Headphones | #197 of 216 in Over-Ear Headphones |
| Form Factor | Over-ear | Over-ear |
| Harman Preference Score | 56 (measured by oratory1990, via AutoEQ) | 49 (measured by oratory1990, via AutoEQ) |
| Deviation From Target | 3.63 dB standard deviation | 3.96 dB standard deviation |
| Tonal Tilt | -0.79 (negative is warmer, positive brighter) | -1.03 (negative is warmer, positive brighter) |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (-2.7 dB at 30 Hz) | Within 6 dB of target down to 20 Hz (+2.6 dB at 30 Hz) |
| Connection | Wired | Wired |
| Back | Closed | Open |
| Driver Type | Dynamic | Dynamic |
| Drivers | 1 x 44mm dynamic | 1 x 50mm dynamic |
| Impedance | 25 ohms | 32 ohms |
| Sensitivity | 118 dB SPL/V | 97 dB/mW |
| Weight | 0.7 lbs (305 g) | 0.7 lbs (340 g) |
| Frequency Response | 5Hz - 28kHz (Manufacturer specified) | 18Hz - 22kHz (Manufacturer specified) |
| Built-in Microphone | No | No |
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- Focal Listen Professional vs KLH Ultimate One
Prices on this page were last checked October 11, 2026 at 4:59 PM UTC. Product prices and availability are accurate as of that date/time and are subject to change; the price and availability shown on Amazon at the time of purchase will apply to the purchase of this product.
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The Two Headphones In Full
Austrian Audio Hi-X55: $315.71 Amazon eBay
Pros: The closed back blocks outside noise and keeps sound from leaking, so it works in shared rooms and studios. A 25 ohm load and 118 dB/V sensitivity let it run loudly from a phone or laptop, and it weighs a moderate 305 g. Bass sits about 1.1 dB above target with sub-bass still within 6 dB down to 20 Hz, which suits listeners after a warm, bass-leaning balance.
Cons: oratory1990’s measurement shows a deep 9.9 dB dip near 2.3 kHz and presence about 3.9 dB below target, so vocals and guitars sound recessed and distant. Sub-bass averages 4.1 dB below target, so the deepest rumble is lighter than the midbass suggests. Its preference score of 56 sits far from the Harman target.
Full Austrian Audio Hi-X55 review and specifications →
| Released | 2020 (6 years ago) |
|---|---|
| Back | Closed |
| Built-in Microphone | No |
| Connection | Wired |
| Deviation From Target | 3.63 dB standard deviation |
| Driver Type | Dynamic |
| Drivers | 1 x 44mm dynamic |
| Form Factor | Over-ear |
| Frequency Response | 5Hz - 28kHz (Manufacturer specified) |
| Harman Preference Score | 56 (measured by oratory1990, via AutoEQ) |
| Impedance | 25 ohms |
| Sensitivity | 118 dB SPL/V |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (-2.7 dB at 30 Hz) |
| Tonal Tilt | -0.79 (negative is warmer, positive brighter) |
| Weight | 0.7 lbs (305 g) |
EQ preset to match the Harman target
Set a preamp of -6.7 dB, then add these filters in any parametric equalizer (Wavelet, Equalizer APO, Peace, or a player with parametric EQ). Calculated by AutoEQ from its measured frequency response.
| Filter | Frequency | Gain | Q |
|---|---|---|---|
| Low shelf | 105 Hz | +1.6 dB | 0.70 |
| Peak | 138 Hz | -7.0 dB | 1.32 |
| Peak | 2,373 Hz | +7.7 dB | 1.17 |
| Peak | 1,284 Hz | -7.8 dB | 2.01 |
| Peak | 53 Hz | +2.7 dB | 0.80 |
| High shelf | 10,000 Hz | -0.9 dB | 0.70 |
| Peak | 472 Hz | +2.6 dB | 1.22 |
| Peak | 234 Hz | -1.7 dB | 2.33 |
| Peak | 946 Hz | -1.7 dB | 3.22 |
| Peak | 6,612 Hz | -1.8 dB | 6.00 |
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KLH Ultimate One: $325.11 Amazon eBay
Pros: Bass from 60 to 200 Hz runs about 8.5 dB above target with sub-bass 5 dB up, so bass lovers get heavy, rumbling lows from an open headphone. At 32 ohms and 97 dB/mW it plays at moderate volume from a phone or laptop without an amp, and it rates level with the Audio-Technica ATH-AD900X and AKG K271 MKII.
Cons: In oratory1990’s measurement the treble also sits about 5 dB above target from 3 to 16 kHz with a 9.6 dB peak near 6 kHz, which can make vocals and cymbals sound sharp and tiring at volume. A deviation of nearly 4 dB and a preference score of 49 mean most listeners will hear a heavily colored sound, and the open back leaks noise both ways. The Neumann NDH20 rates slightly higher.
Full KLH Ultimate One review and specifications →
| Released | 2020 (6 years ago) |
|---|---|
| Back | Open |
| Built-in Microphone | No |
| Connection | Wired |
| Deviation From Target | 3.96 dB standard deviation |
| Driver Type | Dynamic |
| Drivers | 1 x 50mm dynamic |
| Form Factor | Over-ear |
| Frequency Response | 18Hz - 22kHz (Manufacturer specified) |
| Harman Preference Score | 49 (measured by oratory1990, via AutoEQ) |
| Impedance | 32 ohms |
| Sensitivity | 97 dB/mW |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (+2.6 dB at 30 Hz) |
| Tonal Tilt | -1.03 (negative is warmer, positive brighter) |
| Weight | 0.7 lbs (340 g) |
EQ preset to match the Harman target
Set a preamp of -6.1 dB, then add these filters in any parametric equalizer (Wavelet, Equalizer APO, Peace, or a player with parametric EQ). Calculated by AutoEQ from its measured frequency response.
| Filter | Frequency | Gain | Q |
|---|---|---|---|
| Low shelf | 105 Hz | +0.6 dB | 0.70 |
| Peak | 1,122 Hz | +6.6 dB | 0.74 |
| Peak | 206 Hz | -7.1 dB | 0.57 |
| Peak | 478 Hz | +3.3 dB | 1.24 |
| Peak | 2,632 Hz | -5.8 dB | 2.57 |
| High shelf | 10,000 Hz | -3.4 dB | 0.70 |
| Peak | 6,143 Hz | -4.3 dB | 6.00 |
| Peak | 4,905 Hz | +2.7 dB | 2.64 |
| Peak | 43 Hz | -0.6 dB | 2.14 |
| Peak | 5,841 Hz | -1.7 dB | 6.00 |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons