Seventour ST-800 10-inch Under-Seat Car Subwoofer: specs and who it suits

The Seventour ST-800 is a slim, powered 10-inch subwoofer for cars and trucks. The amplifier is built into the enclosure, so there is no separate amp to mount and wire. It is aimed at drivers who want more low-end weight than factory speakers deliver, without giving up the boot or cargo area to a large box.

What "powered" and "under seat" mean

A powered (or active) subwoofer combines the driver, enclosure and amplifier in one unit. That simplifies an upgrade: you supply power, a ground, a remote turn-on signal and an audio input. Seventour describes the ST-800 as an ultra-slim under-seat design, and lists it at roughly 13.5 x 10.2 inches with a thickness of about 3 inches (listed variously as 2.7 and 3.1 inches) and a weight of 10.7 lb. Whether it fits under a given seat depends on the clearance beneath yours, so measure first.

The enclosure is cast aluminum, which Seventour says helps with heat dissipation. An amplifier in a sealed, slim case has to shed heat somewhere, so a metal shell is a sensible choice.

Reading the power figures

The listing gives two numbers: 800 watts peak and 220 watts RMS, at 4 ohms. RMS is the figure that describes what the unit can handle continuously, while peak power describes short bursts. When comparing any subwoofers, RMS is generally the more meaningful number.

Other listed specs include:

• Frequency response of 20Hz to 500Hz.
• Total harmonic distortion under 0.4%.
• Signal-to-noise ratio above 90dB.
• A rated fuse of 25A.

Controls and tuning

Seventour includes a wired bass volume remote, so the level can be adjusted from the driver's seat. On the unit itself there are controls for:

• Gain: matches the amplifier's input level to your head unit's output.
• Low-pass filter: adjustable from 50Hz to 150Hz. It sets the highest frequency the subwoofer plays, so the speakers in the doors handle everything above it.
• Bass boost: 0 to 12dB at 45Hz, which adds emphasis to the deepest notes.

The listing also mentions a built-in sub-acoustic filter at 20Hz, which cuts frequencies below that point that add strain without much audible benefit.

Inputs and protection

The ST-800 accepts low-level RCA inputs, with a listed sensitivity of 300mV, and also supports high-level (speaker-wire) inputs at 0.9V, which is useful when a factory stereo has no RCA outputs. Input sensitivity is adjustable. Seventour lists thermal, short-circuit and overload protection circuits, with a green power LED and a red protection LED to show status.

The look

The 2024 version has a spider-style speaker protector and a blue LED ring that lights when the car starts. It is a cosmetic feature; it doesn't change how the unit sounds.

Who it suits

It suits drivers of cars, pickups and similar vehicles with limited space, who want a simple add-on to improve bass. Seventour also states a one-year warranty, with replacement for quality issues within six months.

What to check before you buy

• Space: measure the clearance under the seat and where the unit will sit.
• Wiring: you'll need a suitable power cable, ground and fuse; follow the manual and local rules for installation.
• Inputs: confirm whether your stereo has RCA outputs or only speaker-level outputs.
• Electrical load: check that your vehicle's electrical system can support the extra draw.
• Fixing: make sure the unit is secured so it can't slide in braking.
• What's in the box: confirm the remote and wiring kit contents as listed.

The short version

• A slim 10-inch powered car subwoofer with a built-in amplifier.
• 800W peak, 220W RMS, 4 ohms; frequency response 20Hz to 500Hz.
• Gain, bass boost, adjustable low-pass filter and a wired bass remote.
• RCA and high-level inputs, plus protection circuits.
• Cast aluminum enclosure and a blue LED ring.

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