Harmony HB 154D II — 4-Channel Class D Car Amplifier

Harmony HB 154D II — 4-Channel Class D Car Amplifier

The HB 154D II is a four-channel Class D amplifier rated 150 watts RMS per channel at 4 ohms, 200 watts per channel at 2 ohms, and 350 watts bridged into 4 ohms per bridged pair. Signal-to-noise is better than 90dB with THD under 0.1%, across a 20Hz to 20kHz bandwidth.

Input impedance is 22 kilohms, and the chassis measures 180mm in length — ten millimetres longer than the HB 104D II for roughly 50% more output per channel.

More Output, Same Footprint Class

The difference between this and the HB 104D II is power, not capability. Both are four-channel Class D designs with the same measurements, the same input impedance, and the same load requirements.

What the extra 50 watts per channel buys is headroom for drivers that can use it — higher power-handling components, or a bridged pair asked to drive a subwoofer harder. Where the speakers are rated near 100 watts, the HB 104D II already covers them.

Load Requirements

Each channel is rated for 2 to 4 ohms, and bridged pairs for 4 to 8 ohms. Wiring within those ranges is what keeps the amplifier delivering rated output.

A 22-kilohm input impedance suits any standard line-level source.

System Application

One hundred fifty watts per channel into 4 ohms drives a component front stage with real reserve, or a two-way active front stage across all four channels.

At 2 ohms each channel produces 200 watts, and a bridged pair delivers 350 watts into 4 ohms — enough for a subwoofer alongside a front stage from one 180mm chassis.

Installation Considerations

Bridged loads should be 4 to 8 ohms. Each channel sees half the load when bridged.

Class D keeps heat manageable, but a compact chassis in an enclosed location still benefits from airflow. Avoid sealing it into an unventilated cavity.

Size power and ground wire from the fuse rating 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 frame.

Specifications

• Configuration: 4-Channel, Class D
• Power: 150W RMS × 4 @ 4Ω
• Power: 200W RMS × 4 @ 2Ω
• Power: 350W RMS × 2 bridged @ 4Ω
• Speaker load: 2–4Ω per channel, 4–8Ω bridged
• Frequency response: 20Hz–20kHz
• THD: <0.1%
• Signal-to-noise ratio: >90dB
• Input impedance: 22 kΩ
• Length: 180 mm

HF Audio Perspective

The choice between this and the HB 104D II comes down to the speakers, not the budget.

Since both amplifiers share their measurements, load requirements, and compact format, the only variable is output. Check what your components are rated to handle: if 150 watts a channel is within their range and a bridged pair is being asked to drive bass, the HB 154D II gives the system room to work. If the drivers top out closer to 100 watts, the extra power sits unused and ten millimetres of chassis length buys nothing.