KLH Ultimate One – Steam with draught up to both ears

In the test, the KLH Ultimate One has to show today what influence it can have on my eardrums. For this purpose, I put clean and high-quality processed material over my ears and enjoy the use of sustainable materials that promise extraordinary comfort. In the first impression, the American can already convince with fundamental bass and rich highs. Whether the good first impression also withstands a longer music session, I clarify in this article.

KLH wants to combine build quality and comfort with rich bass and fine treble with the Ultimate One.

First of all, I wonder who KLH actually is, because I had never heard of this company before. Wrongly, as it turns out, because the company founded by Henry Kloss, Malcolm S. Low and Josef Anton Hofmann in Massachusetts has existed since 1957. With over 30,000 loudspeakers annually, it was once the largest manufacturer of loudspeakers in the world. According to the magazine Stereophile, the Model Nine is one of the twelve best speakers ever built. With the model Forty, the first tape recorder with Dolby noise reduction was introduced. With the Model Five, Model Six and Model Seventeen, the best-selling loudspeaker models were launched on the market for many years. Since 2017, KLH has been under the umbrella of Kelly Global Brands and the headquarters have been moved to Noblesville, Indiana, where the KLH Ultimate One is also manufactured.

In its home market of the USA, KLH devices have been in demand since 1957. With the Ultimate One, the name should also grow in Europe.

A solid package

The KLH Ultimate One comes in a robust slipcase. The cardboard slot is equipped with a fluted cover, which together with the silver embossed logo leaves a high-quality impression. Magnets hold the folding mechanism in position so that the carton always retains its shape. Inside is a leather case with zipper, which stores the headphones shockproof when traveling. In addition, the case comes with a carrying bag made of soft velour, in which you can store the headphones. Of course, the scope of delivery also includes a separate two-meter-long connection cable with 3.5-millimeter jack plug and an adapter for sockets with a diameter of 6.3 millimeters. In addition, there is an insert that describes individual components of the music converter and the properties. So you can listen to his music in all possible constellations and always safely accommodate the KLH Ultimate One in all situations without it being damaged.

The two-metre-long connection cable features high-quality silver strands and a fine textile cover. In addition to a hard case and cloth bag, a 6.3-millimeter adapter is also included.


The KLH Ultimate One cuts a very good figure when unpacking. The earcups are made of zebra wood. A metal bracket holds them in position and the shells can be rotated 180 degrees in it. The metal bracket has space in its solid hinge 90 degrees to the front and 90 degrees to the rear. The headband leaves a very solid impression and lies on my head with layers of cowhide, lambskin and two-layer memory foam. That’s how the cushions that wrap around my ears are designed. It is noticeable that the headphones weigh just 340 grams despite the high-quality materials and its robust design. Of course, this accommodates the wearing comfort. The open design also provides a certain relaxation, as you are not completely disconnected from the outside world. However, the auricle will be too small for wearers with protruding shaped ears.

Thanks to pads with a mixture of cowhide and lambskin, in combination with memory foam, the headphones offer great wearing comfort.

Technical features

Of course, the technical details also play a central role in a test, because they ultimately determine what I hear. The KLH Ultimate One uses drivers with a diameter of 50 millimeters and thus offers plenty of space for stately bass. This is also reflected in the data sheet, because KLH attests to the Ultimate One a frequency range of 18 heart to 22 kilohertz. With a sound pressure of 108 decibels, it causes a lot of rumbling on the eardrum, but remains in an area that does not harm health. With the impedance of 32 ohms, it is in the upper range, which demands a certain power from pocket-sized players. Naturally, my amplifier has no problems vibrating the driver. The smartphone has to work much harder to play against the outside world due to the open design.

The large 50-millimeter widebands combine rich deep bass with clearly defined treble.

The wearing comfort

Due to the first-class choice of materials, the KLH Ultimate One feels extremely high-quality and can also compete with models from other manufacturers such as the Sendy Audio, which plays in a significantly higher price range. Headphones in the same price range are clearly beaten off in terms of material selection and visual appearance. On the head, the soft padding pleases. The leather is comfortable on the skin and feels soft and natural. Even with prolonged listening pleasure, I do not sweat here. I find the open construction of the auricles very pleasant. So a few ambient sounds as well as fresh air come to my ears and I am not completely cut off from the outside world. The contact pressure of the bracket is a bit tight, but this may be due to the brand new specimen. The earcups just fit over my ears, who has already made large ears while reading, wears here rather an on-ear headphone.

Thanks to beautifully crafted zebra wood and soft padding, the Ultimate One offers pleasant wearing comfort and high-quality haptics. For larger ears, however, the earcups could be a bit too small.

Proper fuss

Yes, how does the visually impressive piece sound now? What is striking at first is the incredibly deep bass that the KLH Ultimate One delivers. The 50 millimeter diaphragm can vibrate very slowly and powerfully. “Play” by David Grohl starts right at the beginning with a deep bass carpet that lays a solid foundation. But that’s not all, really deep it goes down with the drums into the frequency cellar, because Grohl has tuned the bass drum extremely dry, rich and deep. And the Ultimate One is happy about every impulse in this area. It gives the impression that you have built a subwoofer into the headphones, so powerfully the beryllium diaphragm pushes the bass into my ear canals. Especially at low volumes, a very voluminous and tidy sound image is created. If you then turn into the range of, I call it pleasure volume, the bass also delivers a decent rumble.

With dynamics and pressure, KLH’s over-ear is a lot of fun. On the other hand, his demands on the service provided are quite high.

Accentuated tips

There is no doubt that the KLH Ultimate One can deliver its 18 hearts. 22 kilos are no longer perceptible to my elderly ears, but it is noticeable that the chassis are emphasized and precise here. So I continue to listen to the piece and will not be disappointed in the treble range. The beryllium driver precisely works out fine structures from Grohl’s drums. I can clearly perceive the dynamic differences on the basins and also the staggering of the different brass discs in the room is finely divided. Sharp and determined, the membrane articulates the accentuated tips on high-hat and ride cymbals. The steel strings of Hellyeah’s guitar in the track “I Don’t Care Anymore” get the necessary hardness and crispness to give the piece the necessary note on the way. The driver places the instruments very precisely on the targeted places and thus creates a pleasant plasticity.

The connection cable with 3.5 mm jack is connected to the headphones on one side. The Ultimate One cannot be operated symmetrically.

KLH Ultimate One – Modernly tuned

As the next title I chose “Anima” by Angela Puxi. The chilled title captivates with countless sounds, to which the KLH Ultimate One pulls a wide stage and distributes it finely from left to right. Again, the excellent treble reproduction and the incredibly deep bass are striking. Due to this V-like, modern tuning of the driver, however, the mids are a little underemphasized. The singer sounds as if she was a little too close to the microphone during the recording. The bass also loses some precision, because it is powerful, but due to the size of the diaphragm also a bit more sedate and gets a more comfortable character. But he is really fun in the “Flight of the Cosmic Hippo” by Béla Fleck and the Flecktones. The deeply tuned bass guitar drills into such deep climes that you can hardly believe your ears.

Stable pegs always keep the rotatable earcups in the correct position. With a weight of only 340 grams, the Ultimate One offers good long-term suitability.

Club Machine

But if you stay in the corresponding modern genre, the KLH Ultimate One does not miss out on fun. I certainly don’t have to introduce the title “No Sanctuary Here” by Chris Jones anymore, it runs up and down at every hi-fi fair. However, Marian Herzog has taken on the number again and lifted it to a modern level. A rich “Four on the Floor” beat massages the eardrums in the sub-bass range that it is a real joy. At the same time, the highs tear a groovy high-hat into the upbeat. The song has picked up a bit in tempo and thus gains even more grooviness, which you can hardly resist thanks to this club machine. Once you get used to this tuning, you can also enjoy “Liberty” by Anette Askvik. It appears sonically with a little too much belly, but the round bass and the finely worked highs in the piece fit in perfectly.


The KLH Ultimate One is super processed and also the accessories, such as the great leather hard case, definitely bring points. The materials used fit into the next higher price level. The separate connection cable is not only super processed and makes no noise when worn. You can also simply exchange it, should it break at some point. The wearing comfort is pretty good. I had the headphones on my ears for several hours while writing this test. The sound can definitely be captivating. The tuning of the beryllium chassis is modern and geared to current tracks. The incredibly deep bass plays in a league of its own and also the crisp highs are really fun. Nevertheless, the inclined buyer should try the good piece, because the sound could polarize. For use on mobile players, an external DAC is recommended for stronger volumes.

Test & Text: Dieter Pfeil
Photos: Branislav Ćakić



Overall score: 87/90
Class: Upper class
Price/performance: good


86th of 90


90th of 90


88th of 90


Ultimate One
Device category:Over-ear headphones
Price:EUR 429
Warranty:2 years
Executions:– Zebrawood
Marketing:Bellevue Audio, Unna
02303 3050178
Weight:340 g
Design:Over-ear, open
Impedance:32 ohms
Band:18 Hz – 22 kHz (manufacturer specification)
Placement:2 x 50 mm widebands
Connection:3.5 mm jack
Scope of delivery:1 x Ultimate One
1 x Travel Case 1 x Cloth Bag 1 x Connection Cable

1 x Adapter 6.3 mm
Pros & cons:+ noble workmanship
+ high-quality connection cable
+ leather hard case + potent bass range
+ defined tweeter

+/- modern tuning can polarize

– no symmetrical connection option
– very power-hungry on the smartphone
Sound (60%):86/90
Practice (20%):90/90
Equipment (20%):88/90
Overall grade:87/90
Class:Upper class
Value for moneygood

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