Compact 4-channel powersports amplifier — 50 watts RMS x 4 HMP 4D

$379.99

Small Size. Big Splash. Serious Sound.

Don’t let its size fool you — the Hertz HMP 4D 4-channel amplifier delivers impressive power and clarity whether you're cruising on the road or cutting through waves. Designed for tight spaces, this compact yet rugged amp brings your sound system to life with 50 watts RMS per channel, easily outclassing most factory stereo or marine head units. Need more punch? You can bridge it for up to 130 watts RMS per channel to drive subs or high-performance speakers.

Built for the Harshest Environments

The HMP 4D doesn’t just sound great — it's engineered to survive. Housed in a durable cast-aluminum chassis, it’s rated IP64 for resistance to water spray, and meets ASTM-D4329 for UV protection and ASTM-B117 for salt fog endurance. Whether it’s sunlight or saltwater, this amp is built to take a beating and keep performing.

Clean, Customizable Sound

With balanced high- and low-level inputs, the HMP 4D integrates cleanly into almost any system — without introducing noise or distortion. Selectable high-pass and low-pass filters give you the flexibility to tune your setup for your exact speaker configuration, delivering tighter bass and smoother highs.

[ user’s manual ]

Small Size. Big Splash. Serious Sound.

Don’t let its size fool you — the Hertz HMP 4D 4-channel amplifier delivers impressive power and clarity whether you're cruising on the road or cutting through waves. Designed for tight spaces, this compact yet rugged amp brings your sound system to life with 50 watts RMS per channel, easily outclassing most factory stereo or marine head units. Need more punch? You can bridge it for up to 130 watts RMS per channel to drive subs or high-performance speakers.

Built for the Harshest Environments

The HMP 4D doesn’t just sound great — it's engineered to survive. Housed in a durable cast-aluminum chassis, it’s rated IP64 for resistance to water spray, and meets ASTM-D4329 for UV protection and ASTM-B117 for salt fog endurance. Whether it’s sunlight or saltwater, this amp is built to take a beating and keep performing.

Clean, Customizable Sound

With balanced high- and low-level inputs, the HMP 4D integrates cleanly into almost any system — without introducing noise or distortion. Selectable high-pass and low-pass filters give you the flexibility to tune your setup for your exact speaker configuration, delivering tighter bass and smoother highs.

[ user’s manual ]

  • Product highlights:

    • compact 4-channel amplifier for ATV, motorcycle, boat, or car

      • 50 watts RMS x 4 at 4 ohms

      • 65 watts RMS x 4 at 2 ohms

      • 130 watts RMS x 2 bridged at 4 ohms

    • Class D amp technology

    • selectable high-pass filter on front channels (full, 65, 85, 115 Hz at 12 dB/octave)

    • selectable high- or low-pass filter on rear channels (full, 65, 85, 115 Hz at 12 dB/octave)

    • IP64 grade protection against water spray, ASTM-D4329 standards for UV resistance, and ASTM-B117 for salt fog operability

    More Info:

    • preamp and speaker-level inputs

      • speaker wire to RCA adapters required for speaker-level input

      • signal-sensing turn-on on speaker-level inputs eliminate need for a separate remote lead

    • nature-proof connection cable included

    • wiring and hardware not included with amplifier

      • 10-gauge power and ground leads recommended

    • fuse rating: 15A x 1

    • dimensions: 9"W x 1-3/4"H x 4"D

    • Power Output: at 14.4 volts and 1% THD

      • 4Ω: 50 watts RMS x 4

      • 2Ω: 65 watts RMS x 4

      • Bridged: 130 watts RMS x 2 into 4Ω

    • Additional Specs: Hertz also published the power output at 14.4 volts and 10% THD; 60 watts RMS x 4 into 4Ω and 75 watts RMS x 4 into 2Ω

    • Signal to Noise Ratio: 95 dB

    • THD: 0.2% (at 100 Hz into 4Ω)

    • 4-Channel powersport amplifier

    • Two 15-amp ATM fuses (one installed/one spare)

    • 2.5mm Allen wrench

    • Four 5/8" Screws

    • User's manual