Zapco ST-2000XM III — Mono Class D Subwoofer Amplifier

Zapco ST-2000XM III — Mono Class D Subwoofer Amplifier

The ST-2000XM III is a true mono Class D amplifier and the highest-output model in Zapco's ST-X Mono III series, rated 1,000 watts RMS at 4 ohms, 1,450 watts at 2 ohms, and 2,000 watts at 1 ohm. Signal-to-noise is 100dB with THD under 0.1%, across a 10Hz to 150Hz bandwidth.

Two units can be strapped together to drive a single voice coil at double the output.

Power and Impedance

A kilowatt at 4 ohms is the figure worth noting. Across the range the amplifier delivers 1,000 watts at 4 ohms, 1,450 at 2, and 2,000 at 1 — a doubling from top to bottom rather than a steep dependence on reaching 1 ohm.

That keeps woofer selection open. A driver that wires to 4 ohms still receives a kilowatt, so the enclosure and driver can be chosen on their own merits rather than to satisfy the amplifier.

Strapping Two Amplifiers

Two ST-2000XM III units can be strapped for double the output, following Zapco's procedure:

• Decide which amplifier is master and which is slave
• Connect the head unit's bass or full-range RCA output to the R and L inputs of the master
• Connect the master's Bridge Out to the slave's Bridge In with a single RCA cable
• Connect nothing to the slave's regular R and L inputs
• Connect the bass remote to the master's Remote In

The master controls both amplifiers. The slave drives the negative side of the signal and has no control functions of its own.

Each amplifier must see a minimum load of 2 ohms when strapped.

System Application

Multiple subwoofers on a common load, or a single competition-grade driver rated to take the output. This is the bass amplifier for a system where the subwoofer stage is the most demanding part of the build.

Bandwidth is 10Hz to 150Hz — bass duty only, with the low-frequency extension needed to stay in control below port tuning on a ported enclosure.

Installation Considerations

At this output the electrical system is part of the specification, not an afterthought. Sustained operation near 2,000 watts requires charging capacity, battery capacity, and cable sized to match. An amplifier starved of voltage under load goes into protection rather than simply playing quieter.

Add up the fuse values, size power and ground wire from that total and the run distance from the battery, use the same gauge for ground as power, keep the ground short, and secure it to clean bare metal on the vehicle frame.

A remote control port is provided for the bass remote, which becomes the single control point in a strapped pair.

Specifications

• Configuration: Mono, Class D
• Power: 1,000W RMS @ 4Ω
• Power: 1,450W RMS @ 2Ω
• Power: 2,000W RMS @ 1Ω
• Minimum load per amplifier when strapped: 2Ω
• Frequency response: 10Hz–150Hz
• THD: <0.1%
• Signal-to-noise ratio: 100dB
• Bridge In / Bridge Out for strapping
• Remote control port for bass remote

HF Audio Perspective

The ST-2000XM III is built for bass sections with the woofer count or power handling to use two kilowatts, and it should be selected after that section is designed rather than before.

What makes it worth the step up from the ST-1500XM III is not the headline number so much as the 4-ohm rating — a full kilowatt without needing to engineer the wiring down to 1 ohm. Once the drivers, voice coil configuration, and final impedance are settled, the rating at that impedance tells you whether this is the right amplifier or whether one lower in the line already covers the job.