Seventour KL-10 under-seat subwoofer: features, specs and who it suits

The Seventour KL-10 is a slim 10-inch subwoofer with its own amplifier built in, made to sit under a car seat. It adds low bass to a factory or aftermarket stereo without taking over the trunk or cargo area. Here is what its specifications mean and what to check before fitting one.

Why an under-seat powered subwoofer

Most car door speakers are small and fade out well before the deepest notes in music. A subwoofer handles only the low frequencies, which also takes some of the load off the other speakers. A powered (or active) subwoofer has the amplifier inside the same enclosure, so there is no separate amp to mount and wire.

Under-seat models trade some depth of enclosure for a much smaller footprint. The KL-10 measures about 13.5 x 10.2 inches (34 x 26 cm), Seventour gives its thickness as 3.1 inches (about 8 cm), and it weighs about 10.8 lb (4.9 kg). The enclosure is cast aluminum, which Seventour says helps the amplifier shed heat.

What the power and sound figures mean

Seventour lists 1200 watts of peak power into a 4-ohm load. Peak figures describe short bursts rather than steady output, so they say less about everyday loudness than continuous (RMS) figures, which tend to be much lower for any amplifier.

The listed frequency response runs from 20 Hz to 500 Hz. In practice the crossover (below) decides how high the subwoofer actually plays, so the useful part is the low end. Seventour also lists total harmonic distortion below 0.4% and a signal-to-noise ratio above 90 dB. Lower distortion means the output follows the input more closely, and a higher signal-to-noise ratio means less background hiss when the music is quiet.

Controls: gain, crossover and bass boost

The control panel sits on the side of the unit:

• Gain matches the amplifier to the strength of the signal coming from your stereo. Set too high, it typically causes distortion before it adds useful volume.
• Low-pass filter (crossover), adjustable from 50 Hz to 150 Hz. The subwoofer plays below the frequency you set and fades out above it, so it blends with the door speakers.
• Bass boost adds 0 to 12 dB centred on 45 Hz.
• Sub-acoustic filter at 20 Hz, built in. Filters like this typically trim content below what a speaker can usefully reproduce.
• Wired bass remote, so you can turn the bass up or down from the driver's seat.

Connecting it to your stereo

The KL-10 accepts low-level RCA inputs (300 mV sensitivity) and high-level inputs (0.9 V), with adjustable input sensitivity. RCA inputs suit aftermarket head units with preamp outputs. High-level inputs take the signal from speaker wires, which is how a subwoofer is usually added to a factory stereo that has no RCA outputs.

A wiring kit is included: a 12V power cord with a fuse, a ground cable, a remote turn-on cable, an RCA cable, a high-to-low level converter, connection terminals and mounting screws. The listed fuse is 25 A. Thermal, short-circuit and overload protection circuits are built in, with a green power LED and a red protection LED.

The light ring and grille

A spider-style grille covers the speaker, and an RGB LED ring around it lights up when the car starts. It is a bold look, so it suits owners who want the subwoofer to be seen.

Who it suits

The KL-10 suits drivers of cars, pickups and SUVs who want more low bass but have no room for a conventional subwoofer box. With the amplifier built in and a wiring kit in the box, it is a single-unit addition rather than a set of separate parts. Seventour offers a replacement within 12 months for quality issues and repair within 2 years.

What to check before you buy

• Space under the seat: measure length, width and height, and allow for seat rails, wiring and seat adjustment.
• Your stereo's outputs: check whether it has RCA preamp outputs or only speaker wires.
• Power wiring: plan the route for the power cable and fuse, and follow the included instructions or use a professional installer.
• Foot room: in some vehicles, rear passengers' feet go under the front seats.
• Looks: the lit grille is meant to be noticed; decide whether that fits your interior.

The short version

• A slim 10-inch powered subwoofer with a built-in amplifier, sized to fit under a seat.
• Seventour's figures: 1200W peak at 4 ohms, 20-500 Hz, THD below 0.4%, signal-to-noise above 90 dB.
• Gain, bass boost (0-12 dB at 45 Hz), a 50-150 Hz low-pass filter and a wired bass remote.
• RCA and high-level inputs, a wiring kit, and thermal, short-circuit and overload protection.
• An RGB LED ring and spider-style grille; replacement within 12 months and repair within 2 years.

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