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In-Akustik Referenz 4004 Air

In-Akustik Referenz LS-4004 Air

Helix to Heaven

For its 40th anniversary, In-Akustik is crowning its cable lineup with the impressive top model In-Akustik Referenz LS-4004 Air.

In-Akustik Referenz 4004 Air

Get ready to save the stereo. With a cable. A crazy idea, but hey: Cables do make a difference, so why not? The power strip for the black background, the NF cable for the space, and with the right speaker wire we can also take care of our thunderous bass.


No cable can save a system that’s been poorly set up. Or iron out a twisted frequency response. A cable is not an equalizer. It has just one job: to take an output signal to the receiver without damaging it. A cable is very good if it can brighten the qualities of a fundamentally harmonious system. Under the right circumstances, an excellent cable can work a small miracle. And speaking of miracles: The spotlight is on the In-Akustik Referenz LS-4004 Air, a low inductance and low capacitance speaker cable in the presence of a high-class electronic component. It’s the top model from the manufacturer based in southwest Germany and marks the next step in the clever AIR design first introduced with the LS-2404 Air.

In-Akustik Referenz 4004 Air

As with that model, this one features the company’s “Cross Link Super Speed waveguide” in the form of lacquer-insulated copper wires in a double layer without insulating sheath braided around a PE core, the main component of the cable. In the case of the LS-4004 Air, 16 of these strands are threaded through perforated discs, or clips — twice as many as with the little brother LS-2404 — resulting in 19.2 square millimeters of copper. Twisting the clips against one another gives the cable its final helix form. A semitransparent PE sheath lets the observer appreciate the significant amount of craftsmanship that goes into its assembly.

The design of the LS-4004 Air draws from the fact that, just as the conductor material influences the transmission properties with its profile and purity, the immediate environment of the cable does this as well. The nonconductive material located in the direct area of influence of the electromagnetic field around the conductor is the dielectric. Every dielectric, regardless of whether it’s solid, liquid, or gas, interacts with the useful signal. The lowest dielectric losses are exhibited by a conductor that’s freely suspended in the air. In the LS-4004 Air, the sheerest layer of lacquer insulating the fine copper wires forms the only effective dielectric layer. Apart from that, the main element is: Air. The Air cable is assembled using crimping technology and specially designed rhodium-plated terminals made of tellurium copper (the alloy produces mechanical properties favorable for milling) that can optionally be finished with cable lugs or banana plugs. The user can individually adjust the angle at which the banana or lug protrudes from the cable. It’s a great idea, but the torque needed to get a firm hold is asking too much of the slim Torx key included with delivery, so it’s best to find a proper tool for this task.

In-Akustik Referenz 4004 Air

The hinge design with the thickness of a fire hose is visually imposing, but it proves to be lightweight and gentle on the socket when in use. The clever clips also provide welcome flexibility. When space is tight, it’s easy to reposition and it most definitely won’t pull the compact speakers or amplifier off the shelf.

Right from the start, the LS-4004 Air was astonishing. Once integrated into the system, it wasn’t so much its presence that was noted, but the absence of the sound signature of the familiar connector. We weren’t suddenly greeted with clearly identifiable qualities, no frequency bands, spatial dimensions, or subtle shades that warrant explicit praise. In a nutshell, the LS-4004 Air lets users see what’s lacking in their standard cables — and the potential still lying dormant in the system itself. Because cables represent passive electric components with a complex mix of properties (keyword: equivalent circuit; each cable has a resistance, a capacity, an inductance and impedance), I intended to put the test object through its paces in the most varied environments as possible. At home, I put my Naim power amp (an old school transistor with low damping factor) and the Silbatone integrated amplifier JI­300B Mk III complete with 300B triodes to work. Outside of my own four walls, I selected a powerful integrated amp from Accuphase, fine three-way compact speakers from KEF, and, as a more exotic choice, a high-efficiency chain equipped with tubes.

In-Akustik Referenz 4004 Air

The Silbatone was surprisingly calm when it came to having its familiar speaker cable replaced. Not that my standard cabling from Fadel has a bad pedigree. But I was hoping for a little more of a wow factor. Great, the sound did seem more relaxed. And more open, unfettered. I let some time pass and listened to music a little longer each day. Without any significant split testing I found the amp with the in-akustik to be more commanding and to play a bit louder. The music flowed effortlessly into my ear and from there coursed right into my stomach. My goodness — that was fun! The LS-4004 AIR blended in with my Naim and the Ayon speakers as if it had been made for just this combination. The music buoyantly poured from the speakers, clearing the way for all the sentiments stored on the recording. I couldn’t identify any preferences in sound quality, whether darker or brighter. The deepest bass — not the best event for the Naim — seemed to own the room with previously unheard-of confidence. Not in the sense of “more bass,” but as a more extensive spectrum. Then on top there were the overtone subtleties, three-dimensionality, sound displacement, and the finest in dynamics. This cable has what it takes to lift the performance of my chain into the next higher class!

Use of it in the harmonious Accuphase-KEF chain almost created a touchstone for a friendship. The difference between the not-too-bad entry-level strip of the system owner and the super-cable from the Black Forest was so great that it prompted me, with some cursing, to seriously go and check the balance of my bank account. In listening, the in-akustik practically liberated the music from a corset — the test was a true wow experience! The “carte blanche” tube chain was also good for a surprise. Once again I was treated to more as I listened — more air, more plasticity, more information — but the “house” cable also demonstrated explicit synergies with its accompanying equipment. It was logical to assume the designers of the system specifically harmonized the amplifier and speaker load and selected an appropriate “collaborative connector.” A very interesting encounter that conclusively complemented past experiences.

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As visually imposing as the In-Akustik Referenz LS-4004 Air appears, it remains a team player of utmost seriousness. There’s no spectacle with this cable; no manufacturer statement calling for blind faith. Everything about it is visible and comprehensible: from the copper conductor material to the woven pattern of the individual conductors that suppresses the formation of eddy currents and the open structure with no mysterious correction I heard consistently sounded more exciting and more emotive with the in-akustik than with any other connector. Let’s just forget the price tag: The LS-4004 Air is a phenomenal speaker cable. Period.

Accompanying Equipment

Turntable: Bauer Audio dps 3 | Tonearm: Bauer Audio Tonarm | Cartridge: Lyra Kleos | Phono amplifier: Bauer Audio Phono | CD player: Electrocompaniet EMC 1 UP | Integrated amplifier: Silbatone JI-300B Mk III | Pre- and power amplifiers: Naim NAC 202/NAPSC, NAP 200 | Loudspeakers: Ayon Seagull/c | Cables: Chord Company, Fadel, Naim, Nordost, Sun Audio | Power supply: Music Line Powerigel | Accessories: Bauer Audio Rack

Speaker cable

In-Akustik Referenz 4004 Air

In-Akustik Referenz LS-4004 Air

Setup: Air-Helix, 16 Cross Link Super Speed waveguide, each 1.2 mm2 | Special features: directly crimped connectors made of Tellurium copper with adjustable angle; bi-wiring option (€300 surcharge) | Warranty period: two years | Price: €5,600 (2x 3m, single-wire assembly)

in‑akustik GmbH & Co. KG

Untermatten 12–14
79282 Ballrechten-Dottingen
Phone: +49 7634 5610-0



The stated retail price of the reviewed device is valid as of the time of the review and is subject to change.