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Hertz HMP4D — Compact 4-Channel Class-D Motorcycle Amplifier (260W RMS / 65W x4 @ 2Ω)
$595.00 AUD
SKU: HMP4D
| Channels | 4 Channel |
| Power | 4x50W RMS |
| Year Range | 1998-2013, 2014-2023, 2024+ |
Hertz HMP 4D — Compact 4-Channel Amplifier for Everyday Harley Audio Upgrades
The Hertz HMP 4D is a compact, weather-resistant 4-channel amplifier designed for riders who want a clean, reliable power upgrade without stepping into high-output SPL territory. With an IP64-rated chassis, flexible crossovers, and efficient Class-D power, it pairs perfectly with high-sensitivity speakers and budget-conscious Harley Touring builds.
Key Features
- 50 W x 4 RMS @ 4 Ω (@ 14.4 VDC, 1% THD) — ideal for efficient coaxials and midranges.
- 65 W x 4 RMS @ 2 Ω (@ 14.4 VDC, 1% THD) for added headroom when needed.
- Bridged Output: 130 W x 2 @ 4 Ω (@ 14.4 VDC, 1% THD) for 2-channel systems.
- IP64 weatherproof chassis protects against rain, washdowns, and dust.
- Ultra-compact size (223 × 100.5 × 43.6 mm) ideal for tight Harley fairings.
- Selectable crossovers for HPF, LPF, or full-range operation, with Hi-Pass and Lo-Pass both switchable at 65 / 85 / 115 Hz, 12 dB/oct.
- High and low level inputs for compatibility with OEM and aftermarket radios.
Why It Works on Harleys
- Perfect match for high-efficiency speakers (95–100 dB sensitivity).
- Compact chassis fits easily into Street Glide and Road Glide fairings.
- Weather-resistant build ideal for open-air motorcycle use.
- Efficient power draw works well with stock charging systems.
Recommended System Use
- Front + Rear Speakers: Drive all four speakers with moderate power.
- Entry-Level Front Stage: Clean upgrade over factory amp or radio power.
- Bridge Mode: Power a pair of coaxials or midranges with 130 W x 2 for added authority.
Fitment
- Designed for Harley-Davidson Touring motorcycles
- Fits most amp trays, fairings, and under-OEM radio cavities
- Works with factory head units and aftermarket radios
Specifications
| Channels | 4 |
| RMS Power @ 4 Ω | 50 W × 4 (@ 14.4 VDC, 1% THD) |
| RMS Power @ 2 Ω | 65 W × 4 (@ 14.4 VDC, 1% THD) |
| RMS Power (Bridged @ 4 Ω) | 130 W × 2 (@ 14.4 VDC, 1% THD) |
| Maximum Power (10% THD) | 60 W × 4 @ 4 Ω / 75 W × 4 @ 2 Ω / 150 W × 2 bridged |
| Minimum Stable Impedance | 2 Ω (4-channel) / 4 Ω (bridged) |
| Frequency Response | 10–30,000 Hz |
| Crossovers | Hi-Pass 65 / 85 / 115 Hz, 12 dB/oct — Lo-Pass 65 / 85 / 115 Hz, 12 dB/oct — Full-Range |
| Input Sensitivity | Low level 0.2–5 V, high level 0.8–20 V |
| S/N Ratio | 95 dB (A-weighted @ 1 V) |
| THD | 0.2% (100 Hz @ 4 Ω) |
| Damping Factor | 45 |
| Supply Voltage | 11–15 VDC |
| Fuse | 1 × 15 A |
| Dimensions | 223 × 100.5 × 43.6 mm |
| Weight | 1.35 kg |
| IP Rating | IP64 |
Specifications per Hertz published technical documentation.
Need Help Choosing?
If you're building a clean, budget-friendly Harley system with high-efficiency speakers, the HMP 4D is a perfect fit. We can help you match it with the right speaker and wiring configuration.
Australia Shipping:
- Under $500 → $19.95
- $500–$2,500 → $14.95
- Over $2,500 → FREE
- Bulky items → +$24.95 surcharge (waived over $2,500)
Fast dispatch from Brisbane. Same-day shipping on in-stock orders before 1pm AEST.
Change-of-mind returns: We accept returns within 7 days of delivery on unused, unopened products in original sealed packaging. Restocking fees apply (20–30%). Return shipping is the customer's responsibility.
No returns on opened audio gear, installed items, custom orders, or special-order products. Please check fitment carefully before installing.
Faulty or incorrect items: If you experience an issue, contact us with photos/video and your order number. We'll assess the claim and arrange repair, replacement, or refund for verified faults under the Australian Consumer Law.
Fitment assistance: If you're unsure about compatibility, reach out before ordering—we're happy to help.